Developing New Solutions for Metallic Airframe Parts
P. Lassince1, T. Warner2, F. Eberl2, J. C. Ehrstrom2, P. Lequeu3, H. Ribes3, (1)Kaiser Aluminum, Spokane, WA, (2)Alcan, Voreppe, France, (3)ALCAN Pechiney Rhenalu, Issoire, France
Meeting ambitious airframer targets for weight and cost reduction will require both materials’ development efforts and innovative processing and design solutions. Alcan Aerospace is actively pursuing both routes.
To achieve optimum weight and cost benefits when developing new solutions for airframe parts, it is necessary to consider concomitantly their design, the corresponding materials, as well as appropriate joining/forming techniques. This multidisciplinary approach implies the development of concepts optimised at the level of the part: e.g. consider wing covers rather than the wing panel and wing stringer separately. It also involves developing solutions that enable the tailoring of materials’ properties to local requirements at an acceptable cost: in this context welding (both FSW and LBW) has great potential, but other innovative approaches are possible.
Within such a holistic approach, there is still significant potential for materials’ development, not least to optimise property balances for the chosen design/joining/forming solutions. Even in apparently well-explored alloy systems such as the 7xxx family, products with improved damage tolerance-strength balances have recently been developed: 7056-T7951 (for high strength, high damage tolerance upper wing skins) and 7140-T7651 (for thick plate applications). Higher performance Al-Cu-Mg alloys are also available, such as 2139-T8 (Al-Cu-Mg-Ag alloy) and 2023-T3x (Al-Cu-Mg-Zr-Sc). More damage tolerant variants of another family of alloys, the so-called “third generation Al-Li alloys” initially largely developed for military and space applications, are also in the final stages of development.
Examples of solutions combining design-materials-joining technique will be presented, with particular emphasis on the corresponding implications for material and processing optimisation.
Innovative High Performance Wing Concepts
P. Lequeu1, A. Danielou2, B. Commet3, D. Dumont3, (1)ALCAN Pechiney Rhenalu, Issoire, France, (2)Alcan, Voreppe, France, (3)ALCAN CRV, Voreppe, France
Aircraft manufacturers are challenging material suppliers for solutions to increase performance of their airframe structures. Advanced alloys are one straightforward way to decrease weight and thus increase structural performance. This can be done through higher strength and/or improved toughness and fatigue, with additional benefits coming from the reduced density and higher stiffness of the recently introduced third generation of Al-Li alloys.
Analysis of Aircraft Structures Using New Aluminium Alloys Developed for the Next Generation Aircraft
M. Miermeister1, J. J. M. De Rijck2, (1)Aleris Aluminum Koblenz GmbH, Koblenz, Germany, (2)Corus Research Development & Technology, IJmuiden, Netherlands
Current developments in the field of aerospace applications, such as the application of composites in primary aircraft structures, are continuous drivers for new and derivative aluminum aerospace alloys. Continuous effort between Corus Aluminum Rolled Products (CARP) and Corus Research, Development & Technology (CRD&T) resulted in several improved and newly developed aluminium alloys to compete with the rising application of composites in primary aircraft structures. New aluminium alloy developments are showing better weldability, static strength, damage tolerance and corrosion properties compared to existing alloys. To investigate the applicability of these aluminum alloys developed in the cooperation between CARP and CRD&T several numerical, analytical and finite element tools have been developed. Tools focused on dealing with specific loading conditions inherent to fuselage and wing structure, both tension and compression dominated. For fuselage structures a scheme has been developed that allows extraction of both geometrical data and loading conditions from a full-scale finite element analysis. Dependent on the loading condition, tensile dominated or compression, a fatigue crack growth analysis or static strength analysis can be performed. The data extracted from the finite element model is transferred to a refined mesh that a crack growth analysis in both longitudinal and circumferential direction can be performed. Once the performance of the baseline structure is established the performance of an improved or target alloy specification can be assessed. Compression dominated fuselage structures can be analyzed for static strength, and subsequently be analyzed for fatigue crack growth performance. These structural analysis capabilities within Corus allow for a more controlled development of existing and new aluminium alloy types.
PROFORGE - Teamed Supply Network Management at Sikorsky
W. Harris1, J. D. Tirpak2, D. Gearing3, (1)Sikorsky Aircraft, Stratford, CT, (2)Advanced Technology Institute, North Charleston, SC, (3)Industrial Capabilities Division, Fort Belvoir, VA
Introduction PROFORGE is the name for a cross-functional, cross-departmental procurement led team that has re-engineered the way that we design and acquire forgings. Directly supported by the Forging Defense Manufacturing Consortium, and partnered with the Advanced Technology Institute, the PROFORGE Team has participated in lean events, benchmarking activities, training seminars, and on product/process improvement activities which have led to reductions in lead times and costs for this strategic material form. While science and technology have been an element of the team’s activities, the most significant advances have occurred by increased communication and cooperation internally between departments and externally between customers and suppliers in an integrated value-stream approach. PROFORGE – Teamed Supply Network Management at Sikorsky The Sikorsky PROFORGE Team has been in existence since June 2003. This team, sponsored by the senior management of Purchasing and Research & Engineering departments, has promoted partnerships and collaborations with Sikorsky forging suppliers to improve cost and lead-time as well as responsiveness and customer satisfaction. Tangible savings to the UH60M program and the Defense Logistics Agency have exceeded the initial investment in resources. In addition to these “hard” savings, Sikorsky has realized many so-called “soft” benefits, especially during the product development process. As strategic materials such as titanium become increasingly difficult to obtain, the PROFORGE Team has been instrumental in supplier down selection, tooling procurement, and material aquisition concurrent with design development. The team has tackled quality issues, using simulation technology to understand root causes and test corrective measures. Additionally, the team is working with suppliers to promote the use of forging and heat treatment simulation to optimize processes prior to insertion on the production floor. Summary This paper describes how Sikorsky has grasped the power of cross-functional chartered teams in working enterprise issues with complex business and technical requirements.
Advanced Metallic Lower Wing Stiffened Panel Concepts: Results of Large Panel Validation Test Program
M. Kulak, J. Liu, G. Dixon, W. H. Grassel, R. L. Brazill, M. B. Heinimann, R. J. Bucci, H. R. Zonker, J. Scheuring, Alcoa, Inc., Alcoa Center, PA
Metallic structural solutions are mistakenly perceived to be near the top of the "S" curve with regard to providing significant weight savings for the next generation commercial transport aircraft wing structure. Alcoa believes that the combination of advanced alloys, new innovative structural concepts, and novel manufacturing techniques can result in greater than 20% weight savings for the wing covers and provide significant airframe cost reductions over current state of the art wing structures. Alcoa is in the second year of an ambitious R&D initiative to develop product/design solutions that achieve these goals. Using generic structural sizing methods and custom developed software design tools, studies have been conducted to identify the most promising structural concepts for lower wing skin/stiffener panels. Currently, large scale articles are being tested to validate the feasibility of these lower wing concepts for further scale-up and optimization. In phase 1 twenty six panels were designed, built ,and tested. Additional panels are planned for Phase 2 (2nd half 2006) including new concepts. The 30 in.(762 mm) wide by 90 in. (2286 mm) long stiffened panel test tests simulate a Damage Tolerance repeat inspection interval scenario and a Two Bay Crack Residual Strength design scenario. Supplementary static strength and fatigue tests are also being conducted. Comparison of static strength, fatigue,damage tolerance, and residual strength of the baseline structure to the advanced concept will demonstrate the weight saving potential. This presentation will include an overview of the testing program and the Phase 1 results. Panel concepts include advanced aluminum and aluminum-lithium alloys, hybrid concepts which utilize fiber metal laminates for selective reinforcement, and friction stir welded integral panels (reinforced and non-reinforced with) as a means to reduce cost.
Improvements in Corrosion Resistance Offered By Newer Generation Aluminum Alloys for Aerospace Applications
J. Moran, R. Rioja, E. L. Colvin, Alcoa Incorporated, Alcoa Center, PA
Over the past decade, the Aging Aircraft Community has invested heavily into research and development for the characterization, prediction, remediation, and prevention of aircraft corrosion. The vast majority of this work has been geared toward military aircraft; hence most of the focus has been on the so-called "legacy alloys", e.g., 2024 and 7075. Over the past few decades, the alloys used for aircraft construction have evolved considerably from a corrosion perspective. Alloys in the 7x5x family, 7085, and new-generation Al-Li alloys offer improved corrosion resistance relative to the "legacy alloys". This paper will provide a summary of the corrosion improvements offered by these newer-generation alloy systems, and will highlight applications for these newer-generation alloys on newer-generation aircraft structures.
Advanced AlMgSc Sheet Products for High Performance Aircraft Structures
A. Bürger1, S. Spangel1, A. Heinz1, N. Telioui2, G. Tempus3, K. Juhl3, J. Schumacher3, (1)Corus Aluminium Rolled Products, Koblenz, Germany, (2)CORUS Research Development & Technology, IJumuiden, The Netherlands, (3)Airbus, Bremen, Germany
The aircraft industry requires improved aluminium alloy sheet material that enables higher performance while simultaneously delivering reduced costs. The property profile of AlMgSc alloys permits a beneficial application in terms of weight and costs for e.g. high lift components of Airbus aircrafts. Reduced density in the range of today’s Al-Lithium alloys, good fatigue and damage tolerance properties, excellent corrosion resistance, good weldability as well as an adequate static performance are the key properties of these alloys. The application of advanced manufacturing technologies such as Laser Beam and Friction Stir Welding in combination with a following creep forming process simplifies further integration of structural components and offers additional weight and cost reduction potential. This presentation will provide an overview of the overall process chain, comprising the design concepts, the production of AlMgSc sheet and the following manufacturing steps and will show the weight reduction potential of these alloys based on trade study results.
Affordable Fsw Structures Using Advanced Alloys
P. Lequeu1, R. Muzzolini1, J. C. Ehrstrom2, F. Lemaitre2, H. Gerard2, (1)ALCAN Pechiney Rhenalu, Issoire, France, (2)Alcan, Voreppe, France
Monolithic structures are generally attractive to aircraft manufacturers since they allow for simpler processing sequences: integral machining replaces in such a case fastening and associated preparation processes. Such structures however display some drawbacks: on the metallurgical point of view, higher gauges lead to lower properties due to the quench sensitivity of the 7xxx alloys generally used; on the costing point of view, generation of a lot of chips can jeopardize the overall economics of the considered part, specially when dealing with high value alloys, like Al-Li. There are various ways to improve the cost-weight trade-off of such monolithic structures. One of them consists in developing medium to high gauge alloys better suited to integral machining. For example, 2050 Al-Li solution displays overall better properties than incumbent 7050-T7451 alloy, which, added to its lower density and higher modulus, can allow for weight savings. Usage of such an alloy can however be limited by the higher price of the material. Other cost-weight balance can be achieved through friction stir welding (FSW). In such a case, the final part can indeed be manufactured by welding two or three pieces of lower gauges. Weight performance is thus a balance between the better alloys performances due to the lower material thickness, and the loss of properties in the heat-affected zone. The cost performance is also a balance between the better material usage and the relative manufacturing costs of welding versus machining. The presentation will highlight some of the key points leading to optimised FSW structures using new advanced conventional and Al-Li alloys.
Low Cost Metal Fabrication Processes for Aerospace Systems
R. Cochran1, H. N. Chou2, (1)Boeing-St. Louis, Maryland Heights, MO, (2)Boeing Phantom Works, St. Louis, MO
Low cost fabrication and assembly processes are the primary driving force for weapon systems such as Small Diameter Bomb (SDB) and Joint Direct Attack Munition (JDAM). Both of these programs have taken a more commercial approach in defining the requirements of the weapon components to become more cost effective. JDAM started this acquisition reform by virtually elimination military and Boeing specific process specification which drove up costs without adding value to the product.
SDB recently has followed this model as well as looking at processes and suppliers that were traditionally non-aerospace to take advantage of processes that were better fit for the higher rates of production for weapons. Automotive, Marine, and Recreational vehicle industries have been sought out for proven cost competitive processes.
Some of the processes that have been qualified and are being used on SDB and JDAM are as follows:
Aluminum Die Castings - Structural and Nonstructural
Inertia Welded Steel Warhead Case
Permanent Mold Aluminum Castings
17-4PH Metal Injection Molding
Shape Memory Alloys
Other processes under development with Phantom Works
Semi-Solid Metal (SSM) Aluminum Castings
Lost Foam Aluminum Castings
V-process Aluminum Castings
Spinduction solid state welding without flash
An overview of these processes and qualification and finishing processes will be discussed.
Advanced Waterjet Applications for Turbine Components
W. R. Thompson, Huffman Corporation, Greenville, SC
Aerospace components, specifically gas turbine superalloys, require advanced machining techniques to fabricate complex shapes and to generate flow patterns for part cooling during operation. To meet these needs, water jet machining has evolved into a highly controlled process utilizing multiaxis machining technology to generate shapes in any materials. This process is impervious to inhomogeneities of structure or imperfections in the base material. In the aftermarket arena, the process removes coatings and oxidized material formed when the environmental coatings are subjected to high operational temperatures. The coatings are removed uniformly with no damage to the substrate. The process is ecologically superior to conventional coating removal processes since no toxic waste is produced by the waterjet process. Surface finishes are pristine and there are no imperfections such as recast layer, intergranular attack, or alloy depletion common in many nontraditional machining processes.
Corrosion Monitoring of Lap Joints Using MWM-Array Sensors
H. Weiland1, J. Moran1, F. Bovard1, D. Grundy2, V. Zilberstein3, I. Lorilla3, D. Schlicker3, N. Goldfine3, (1)Alcoa Incorporated, Alcoa Center, PA, (2)Jentek Sensors, Inc., Waltham, MA, (3)JENTEK Sensors, Inc, Waltham, MA
Joints of electrochemically similar and dissimilar materials are susceptible to hidden corrosion that is detectable only with
Brazing of Ti Alloys by Ti-Cu-Ni Foils
C. S. Chang1, C. T. Chang2, R. K. Shiue3, (1)Engineered Materials Solutions, Attleboro, MA, (2)National Dong Hwa University, Shoufeng, Hualien, Taiwan, (3)National Taiwan University, Taipei, Taiwan
Microstructural observations of infrared brazed Ti-15-3 joint using Ti-15Cu-15Ni and Ti-15Cu-25Ni braze alloys have been performed. Ti-rich phase alloyed with higher Cu, Ni contents, Ti-rich phase alloyed with lower contents of Cu and Ni, eutectic and eutectoid structure are observed in the as brazed specimen. Interdiffusion among V, Cr, Cu and Ni is preceded during annealing the joint at different temperatures and/or time periods. Accordingly, it is preferred to apply appropriate brazing cycle in order to reduce or eliminate the presence of residual Cu-Ni rich Ti phase in brazing titanium alloys using Ti-Cu-Ni filler metals.
Machining Distortion of Specially Processed Low Residual Stress Aluminium Alloy Plates
K. Brown1, G. Trilling2, I. Kröpfl2, A. Heinz2, A. Philips3, D. Chellman3, (1)Corus Aluminum Rolled Products, USA, Corpus Christi, TX, (2)Corus Aluminium Rolled Products, Koblenz, Germany, (3)Lockheed Martin Aeronautics Company, Fort Worth, TX
A comparison was made of the machining behavior of conventional and special process plates of 7050 T7451 aluminium alloy plates. The residual stresses in these plates were characterized by ultrasonic scans and standard machining deflection tests. The differences in the residual stress levels resulting from the different production processes were then verified by machining actual aircraft parts. The special processing yielded measured residual stresses approximately half of those in conventional processed material, and the actual machined parts showed over 30% smaller deflections
Advanced Machining of Aluminum Alloys
A. M. Helvey, The Boeing Company, St. Louis, MO
Current aerospace structure requirements are not just focusing on thin aluminum machinings, but monolithic as well to reduce weight, part count, and part cost. Therefore, monolithic machinings need to be more accurate in order to fit into aerospace assemblies with ease. Several modeling and machining techniques are being evaluated, demonstrated, and transitioned to production aircraft programs to meet the new accuracy requirements. This presentation will discuss the modeling techniques being used and the overall results of the evaluation and demonstration of these techniques.
Modeling Capabilities to Part Distortion Management for Machined Components
A. Grevstad, Third Wave Systems, Minneapolis, MN
Residual stresses and part distortion are major cost cutting obstacles with respect to time-to-market, reduced scrap, and high part quality in the metal machining community. Aerospace monolithic structures suffer from distortions that hamper assembly operations. Automotive powertrain components have high flatness-tolerance surfaces that maintain fuel efficiency and component life while lowering emissions. These problems persist because industry lacks a capability to predict machining induced residual stresses and part distortion. Part Distortion prediction and management needs to address the following essential components:
The intent is to reduce testing as:
Simulations of Fatigue Crack Growth and Fracture Behavior for Large Panels Based on Small Panel Test Data
M. A. James, J. Brockenbrough, R. J. Bucci, M. Kulak, R. Brazill, Alcoa, Inc., Alcoa Center, PA
Under ideal circumstances fatigue crack growth and fracture data would be generated using large laboratory test specimens with characteristic dimensions that are representative of the final application domain. Often this means that the preferred test configuration requires a significant investment in material and testing resources. However, cost, time and material availability may preclude wide panel testing, especially during early trade studies that guide the material selection process. These cost, time and availability trade-offs can lead to preliminary design curves from much smaller specimens, leading to associated compromises in the form of specimen size effects for the design curves used for trade studies and preliminary design. Examples of specimen size effects include: (1) fatigue crack growth, where region-III data from smaller specimens typically have higher growth rates than wide panels at the same applied driving force; (2) spectrum, where fatigue lives of small specimens are not consistent with wide integral structures, and (3) fracture, where smaller specimens fail at much lower toughness values than wide panels. In each of these cases the small specimens lead to design curves that are unrealistically conservative. However, advanced simulation and design tools are often able to overcome these limitations, leading to more realistic estimates for preliminary design curves and ultimately to better preliminary designs. This talk will: (1) contain examples of test data that demonstrate the size effects described above; (2) include analysis results that account for the size effects; (3) present simple corrections where possible to account for size effects; (4) and demonstrate the importance of understanding and accounting for these effects through trade study examples with fatigue crack growth life and residual strength predictions. Finally, this talk will outline areas that standard test methods can be modified to account for or guard against these limitations when testing small specimens.
Advances in Testing and Analytical Simulation Methodologies to Support Design and Structural Integrity Assessment of Large, Monolithic Parts
R. J. Bucci1, M. A. James1, H. Sklyut1, D. Ball2, J. K. Donald3, (1)Alcoa, Inc., Alcoa Center, PA, (2)Lockheed Martin Aeronautics Company, Fort Worth, TX, (3)Fracture Technology Associates, Bethlehem, PA
The quest for lighter and more affordable airframes has accelerated demand for thicker/wider/shaped alloy products (plate, extrusions, forgings, castings) and manufacturing technologies (e.g., high-speed machining, weld-joining) to grow applications of unitized structure. Capturing full benefit of these technologies requires that residual stress effects be accounted for in both material characterization and final part design. In the case of thick or shaped metallic products, residual stresses from thermo-mechanical processing can introduce bias and large scatter effects into coupon-based durability and damage tolerance property determinations, which in turn confounds the ensuing transfer to final design.
The presentation describes efforts of Alcoa and others directed to developing improved fatigue crack growth rate data analysis methods and modeling tools that may be used to account for residual stress effects in testing and analysis. Two fundamental principles will be discussed at this seminar: advancements in fracture toughness and fatigue crack growth rate testing and analysis; and the way forward to account for the residual stress effect(s) in analysis and design of fatigue and fracture critical structures. Case study examples are presented to validate the recommended approach, and the presentation concludes with a vision for virtual design support to large monolithic part applications.
Advanced Aluminum Aerostructures Initiative: Progress on F-22A Nose Landing Gear Door Redesign
J. McMichael1, N. Cawley2, J. Barnes2, (1)Alcoa Technical Center, Alcoa Center, PA, (2)Lockheed Martin Aeronautics Company, Marietta, GA
Under the auspices of the Advanced Aluminum Aerostructures Initiative (A3I), a DoD contract administered by the US Air Force, Lockheed Martin and Alcoa have worked together to redesign the F-22A Nose Landing Gear Doors (NLGD). The present doors are comprised of a glass/phenolic honeycomb core sandwiched between two carbon epoxy skins. The redesign consists of a two piece aluminum bi-grid structure that significantly reduces cost, fit up problems, and Interchangability and Replaceability (I&R) issues. The redesigned doors consist of an outer mold line skin with an integral grid, joined to an inner mold line skin by way of a ConnexSysTM snap geometry specifically dimensioned to accommodate adhesive for this application.
July 2006 is the anticipated production implementation date for the redesigned doors. This presentation will provide a summary of the NLGD design and manufacturing development work performed over the past three years, as well as the results of joint, sub-element, and full-scale testing programs.
Lightweight Ramps for Cargo Airlifters
J. McMichael1, J. E. Barnes2, R. Olliffe2, J. Walker2, (1)Alcoa Technical Center, Alcoa Center, PA, (2)Lockheed Martin Aeronautics, Marietta, GA
The main objective of the Advanced Aluminum Aerostructure Initiative (A3I) program is to achieve cost and weight reductions in aerospace components through an integrated team of the material producer and OEM. Alcoa and Lockheed Martin Aerospace are teamed in A3I to optimize incumbent designs of the Lockheed Martin C-130 Hercules tactical airlifter. Through analytical and materials fabrication approaches, the C-130 Ramp Extensions have been re-designed 15-20% lighter than the baseline. Concept trade studies were performed before choosing the best combination of weight reduction and manufacturability for low cost. Detailed analysis determined material and manufacturing limitations. While the re-design was mainly driven analytically for weight, manufacturability was a constant theme. Analyses, test results and manufacturing options, including friction stir welding, will be presented.
Re-Qualification of 2098 F16 Fuselage Plate at Alcan Issoire Facility
H. Ribes1, M. Niedzinski2, J. Amin3, J. Padrul2, B. Bes4, (1)Alcan Aerospace Transportation and Industry, Issoire Cedex, France, (2)Alcan Aerospace, Chicago, IL, (3)Lockheed Martin, Fort Worth, TX, (4)Pechiney CRV, Voreppe, France
During the past five years, several critical components of the F-16 fuselage were redesigned using 2098-T82 plate. Enhanced damage tolerance and fatigue performance compared to the incumbent 2024-T62 plate were the main drivers for the replacement. In addition, 2098 provides higher static properties and significantly improved spectrum fatigue crack growth rate performance. Also a 3% weight reduction was achieved due to lower density inherent to Al-Li alloys.
Following the shutdown of McCook (Illinois) operations, Pechiney (now Alcan) made the decision to produce 2098 plate in Issoire, France. Working in close cooperation with Lockheed Martin Aeronautics, Alcan demonstrated the ability to reproduce and improve upon previous fabrication practices necessary to exceed specifications requirements.
Qualification was successfully completed in mid 2004. To date about 130 lots of the material were delivered to subcontractors, for production of F-16 fuselage components. Improved consistency in the Issoire thermo-mechanical practice translated into more robust fracture toughness and static properties.
Recent registration of 2098 under AMS 4327 and inclusion in MMPDS provides additional application opportunities. With the help Alcan's Voreppe Research Centre 2098 is currently being optimised for commercial aircraft applications offering an optimised balance between strength (controlled reduction) and toughness (significant increase).
Affordability Process Implementation at Northrop Grumman
R. Keele1, J. Ornato1, P. E. Smith2, J. Fields2, F. DiCocco2, M. Falugi3, (1)Northrop Grumman Corporation, El Segundo, CA, (2)Alcoa inc., Alcoa Center, PA, (3)Airforce Research Laboratory, Wright-Patterson AFB, OH
Northrop Grumman and Alcoa teamed together under the auspices of the Advanced Aluminum Aerostructures Initiative (A3I), a DoD contract administered by the US Air Force. The main goal of this program is to demonstrate that close cooperation between material producers and airframers through all stages of product development could significantly reduce the cost of installed aerostructure while maintaining or improving performance. The presentation will outline the Northrop Grumman Corporation’s Affordability process; discuss the importance of A3I methodologies used in developing improved designs and reducing Unit Recurring Flyway (URF) and Unit Life Cycle Cost (ULCC).
Advanced Aluminum Aerostructures Initiative: Progress Report on an Unnamed Aircraft
P. E. Smith1, J. Fields1, F. DiCocco1, J. F. Ornato2, R. Keele2, M. Falugi3, (1)Alcoa inc., Alcoa Center, PA, (2)Northrop Grumman Corporation, El Segundo, CA, (3)Airforce Research Laboratory, Wright-Patterson AFB, OH
Alcoa and Northrop Grumman teamed together under the auspices of the Advanced Aluminum Aerostructures Initiative (A3I), a DoD contract administered by the US Air Force. The main goal of this program is to demonstrate that close cooperation between material producers and airframers through all stages of product development could significantly reduce the cost of installed aerostructure while maintaining or improving performance. The presentation will be a continuation of last year’s presentation. It will provide a summary of how A3I worked in the advancement of a design and manufacturing of an aluminum prototype aft inlet duct assembly. The aluminum design provides an alternative to the incumbent composite structure. The part and fastener count of the current composite aft duct structure was reduced while decreasing the recurring unit cost. The new monolithic forged duct and cast superstructure utilizes high speed machined, stress relieved forged and cast aluminum technology for maximized part consolidation. Structural qualification was achieved by analysis and by comparison to the original built-up structure.
Validation of Advanced Fuselage Concepts Integrating Materials, Design and Manufacturing
M. Kulak, J. Scheuring, B. Bodily, B. Bucci, G. Dixon, M. Ripepi, J. Newman, Alcoa, Inc., Alcoa Center, PA
Metallic structural solutions are mistakenly perceived to be near the top of the "S" curve with regard to providing significant weight savings for the next generation commercial transport aircraft fuselage structure. Alcoa believes that the combination of advanced alloys, innovative structural concepts, and novel manufacturing techniques can result in greater than 20% weight savings and provide significant airframe cost reductions over current state of the art fuselage structures. Alcoa is well into the third year of an advanced fuselage R&D initiative to develop solutions that achieve these goals. Using generic structural sizing methods and custom developed software design tools, studies have been conducted to identify the most promising structural concepts for fuselage skin/stringer/frame panels.
The fuselage concepts tested demonstrate performance improvements for both longitudinal and circumferential crack directions. Damage tolerance and residual strength are demonstrated via large stiffened panel testing, while other structural improvements are demonstrated through coupon to sub-component level tests. Results from testing completed to date are presented.
Large stiffened panels (762 mm wide and 2032 mm long with 5 extruded stiffeners at 178 mm pitch) are tested with circumferential cracks to simulate skin panels with stringers for various configurations. Mechanically fastened built-up structure, built-up structure with fiber metal laminate reinforcement, laser welded structure, and laser welded structure with fiber metal laminate reinforcement are tested for crack growth and residual strength. Baseline alloy configurations are compared to advanced alloys developed at Alcoa for both the built-up and laser welded structures.
Frame configurations are simulated in panels (762 mm wide by 1905mm long) via a load controlling methodology designed to simulate skin panels stiffened with frames. Additionally, wide (760mm) center crack panels are tested to provide supplementary crack growth data at the high Stress Intensity Factor ranges that are found in today’s high performance structures.
Advanced Aluminum Aerostructures Initiative: Progress Report on the C-17 Program
C. O. Standish1, R. Talwar2, J. Inouye3, T. W. Williams3, M. Novak4, F. A. DiCocco5, M. Kulak5, (1)Boeing, Huntington Beach, CA, (2)Advanced Manufacturing R&D, Boeing – Phantom Works, St. Louis, MO, (3)Boeing IDS, C-17, Long Beach, CA, (4)Alcoa Inc., Alcoa Center, PA, (5)Alcoa, Inc., Alcoa Center, PA
In close cooperation, Alcoa and Boeing redesigned and developed the Emergency Exit Door and three Aft Fuselage Frames for the C-17 Globemaster. This program was covered by Advanced Aluminum Aerostructures Initiative (A3I), a DoD contract administered by the US Air Force. The main goal of this program is to demonstrate that close cooperation between material producers and airframers through all stages of product development could significantly reduce the cost of installed aerostructure while maintaining or improving its performance. This presentation will provide a summary of the design and manufacturing of the production monolithic frame for the pressurized C-17 Emergency Exit Door that was introduced in production in 2005. The part and fastener count of the current conventionally build-up door was significantly reduced while significantly decreasing the recurring unit cost. The new monolithic door frame utilized the high speed machined stress relieved forged aluminum technology for maximized part consolidation. Structural qualification was performed by analysis and by similarity to the original build-up structure. This presentation will also outline potential benefits of monolithic redesign of some other primary structures in the C-17 aircraft as well as technology spin offs considered for the future commercial jets. As such, a conversion of conventionally build-up Aft Fuselage Frames into more integrated structure and a business case for the large semi-monolithic Vertical Stabilizer Skins will also be discussed.
An End-to-End Materials Information Management System Meeting the Needs of Materials and Engineering Workflow Aerospace, Defense and Energy
W. Marsden, Granta Design Limited, Cambridge, United Kingdom
Materials are the bedrock of all products and structures. Their influence within the aerospace sector is particularly significant as they govern performance and drive innovation.
An influential group of commercial and government groups (including OEM’s, Tier-1 suppliers, materials suppliers, DoD, DoE, NASA, UK MOD, ASM International…) recognized this and have focused on creating a toolset for managing this vital resource within their organizations. Together they have influenced the development of a system to streamline and manage their materials workflow – meeting their own individual requirement with a common platform.
This group, collectively known as the Materials Data Management Consortium is in the second three-year phase and has a growing collective understanding of the problems they face, how the tool they developed continues to solve them and where further development is necessary.
The system allows all forms of materials data (text, numerical and pictorial) to be easily and automatically loaded into an environment for its storage where it is automatically linked to other pertinent data using in-house business rules and made accessible for further manipulation or comparison using toolsets specifically aimed at the different audiences and their workflows with the different organizations.
Ultimately, the information is used in the design and analysis of new components and structures. Deployment of data to these groups is the final stage in materials workflow. These groups use complex business and computational tools which can access the information within the system directly.
The new tool integrates directly with an organization’s existing practice. It allows organizations to realize efficiency benefits in the generation of design data, increase the quality and traceability of all materials information and reduces the risk of failure.
The results of the discussions within the MDMC, the software and future development will be discussed, in addition to some demonstration of the capabilities of the tool.
Data Management for MMPDS at Battelle
J. Jackson, Battelle Columbus Labs, Columbus, OH
Battelle has been involved with data acquisition and analysis for design allowables for metallic materials used by the aerospace industry since the 1950’s starting with ANC-5, which became MIL-HDBK-5, and has been superceded by the current MMPDS (Metallic Materials Properties Development and Standardization) Handbook. Data is acquired from various producers and users. Battelle provides an un-biased analysis result. Data types include both static and dynamic properties such as; tensile, compression, bearing, shear, effect of temperature, stress-strain curves, creep-rupture, and fatigue. Several tools have been and are being prepared for analysis use. These tools incorporate the analysis guidelines of MMPDS (and former MIL-HDBK-5). A recent project with Boeing, ASM and others showed the feasibility of using electronic data transmittal using MatML language for greater efficiency of data transmittal to the software tools. Use of a common data transmittal form or language will increase the efficiency of data analysis process and data storage. This also provides a single method to transmit data in the handbook to the licensees which may have different input formats. Two of the tools will be demonstrated; ISG software analysis for static design allowables and an ISG stress-strain analysis tool. These tools have been created in conjunction with ISG (Industry Steering Group) funds and are available to ISG members on the MMPDS website. More information on membership may be obtained at http://www.mmpds.org .
Materials Data Management Business Challenges
E. J. Sharp1, R. J. Weiss2, (1)Boeing Phantom Works, Seattle, WA, (2)Boeing, Auburn, WA
There is a large push in the aerospace industry to create a system that allows for electronic submittal and analysis of cerification data to the final customer from a supplier or test house. Analysis of this data is expected to be automated to look for trends and assignable cause variation within a process. However, one can not always expect a current and uninterrupted database from which to derive knowledge on how to control the process. Engineers would then rely on the real-time data to identify shifts or trends, but with some products, such as titanium forgings or castings, the amount of variation can be quite large, which can inflate control limits for processes with only a small number of data points. This work is aimed at using existing production data to test how control calculations for small pieces of a larger production run compare the the control calculations for the overall set of data. Randomizing this "tested occurrence" to happen at any given point within a historical data set will simulate the beginning of tracking a process. Comparing the results of these random beginning points to the overall results will help to show what kind of accuracy and control abiltiy is to be expected once an electronic data submittal system is brought online. Further, using a known problematic data set can help to also test the possibility that a marked process deviation can be deciphered during the early stages of process monitoring.
Materials Properties Thesaurus/Glossary Development for Use with Materials Markup Language: A Project Report on a Key Enabler for Materials Properties Data Exchange
S. Fahrenholz-Mann, ASM International, Materials Park, OH
ASM International, with input from industry leaders and members, is developing a materials properties thesaurus for use with MatML. the Materials Markup Language, to be used for tagging materials properties information. This presentation will detail the objectives and key issues involved with developing and using a set of commonly understood terms for materials properties. A project update with key milestones will also be presented.
2006 Update on MatML, the Extensible Markup Language for Electronic Materials Information Exchange
L. M. Bartolo1, G. Kaufman2, (1)Kent State University, Kent, OH, (2)Kaufman Associates, Columbus, OH
The background, status of development, and current applications of MatML, the extensible materials markup language, will be discussed. Coverage will be provided on how MatML can be utilized and its advantages in ease of use, understandability, efficiency, and cost-effectiveness. An update on the activities of the ASM MatML Coordination Committee will also be provided, including the activity to produce an OASIS specification for MatML.
ComeldTM- Challenges for Industrial Application of this Novel Composite to Metal Technology
R. Freeman, F. Smith, B. Dance, TWI Limited, Cambridge, United Kingdom
Fibre reinforced polymers offer high strength and low weight, but their use in engineering invariably demands that they are joined to other materials, usually metals. A deep mistrust of the joint’s repeatability and integrity have, until now, coerced designers into over-conservatism regarding design and weight savings.
The composite to metal joining world could be changed as a result of the Comeld™ invention. Using a novel metal pre-treatment process, called Surfi-Sculpt™, composite materials can be joined to metals with excellent load displacement results. Surfi-Sculpt™ involves texturing of a metallic surface utilising a power beam technique e.g. electron beam, before the treated surface is joined to a composite material using standard processing techniques such as autoclave (when prepreg materials are used), and vacuum infusion for dry fabrics.
This presentation will explain the pre-treatment of stainless steels, aluminium and titanium alloys and the method of joining the pre-treated metals to glass and carbon fibre reinforced composite materials. Mechanical property data for glass to stainless steel and carbon to titanium will be shown, including video clips of the tests, to allow the failure mechanism of the joint to be clearly seen.. Finally the challenges that need to be faced in adopting this technology in industry will be presented to the audience.
Weight Minimization of Laminated Composite Plates with Deflection Constraint
U. Topal, Karadeniz Technical University, Trabzon, Turkey
Laminated composite structures are made up of two or more layers bonded together to achieve the best properties of the constituent layers. An advantage of laminated composite materials over conventional ones is the possibility of tailoring their properties to the specific requirements of a given application. The tailoring can be achieved by optimising the material properties with regard to design objectives. Optimum design of fiber composite plates presents one of the most interesting and yet intricate problems of structural mechanics. This is chiefly due to the increase in the number of the variables and levels of interrelation as compared to the case of isotropic materials. Recently, one of the most important reasons for using composite materials in mechanical/aerospace engineering applications is for reducing structural weight due to the high specific stiffness/strength of the composites. The current work deals with optimal design of simply supported laminated composite plate structures subject to uniform pressure loading. The composite laminate design process typically involves optimization of the laminate thickness. The structural weight is considered as the objective function (minimizing weight). Constraints are imposed on deflection design. The laminated composite plate is constructed of four layers of equal thickness. The finite element method, based on Mindlin plate and shell theory, is used the application in conjuction with the Modified Feasible Direction mathematical programming approach in order to obtain the optimal design. Numerical examples are performed for investigating the effect of different plate aspect ratios, boundary conditions, ply angles and number of plies on the results.
The Production of SiC/Al Ceramic Matrix Composites by Directed Melt Oxidation (DIMOX)
A. Z. -, I. F. -, Faculty of Engineering, University of Indonesia, Depok, Indonesia
This research is to study the effects of firing temperature and holding time on production of SiC/Al Ceramic Matrix Composites (CMC) and characterization of this materials produced by Directed Metal Oxidation (DIMOX). The firing temperature and holding time used are varied from 900oC to 1300oC with holding time for 10 and 20 hours respectively. The characterizations of composites are examined such as density, porosity, hardness, and microstructure analysis.
The results showed that SiC perform has been infiltrated by Al liquid occurred optimally on firing temperature of 1100oC with holding time for 20 hours. Ceramic composites produced have highest density of 3,54 gram/cm3 can be obtained at this condition, while porosity tents to increase with increasing firing temperature. Porosity within the channels is associated primarily with insufficient Al flow to feed the solidification shrinkage. The highest hardness can be obtained on firing temperature 1300oC with holding time for 10 hours i.e. 1820 VHN. Distribution of SiC particles spread over SiC/Al composites product., and around SiC particles can be found Al, spinel (MgAl2O4), Al2O3 and Mg2Si analysed by EDS.
Key Words : DIMOX process, SiC/Al composites, Firing Temperature, Holding time
Metal Matrix Composites Made from Co-Synthesized Nanoscale Cermet Powders
J. S. Hardy1, K. S. Weil2, N. Canfield2, (1)Pacific Northwest National Laborotory, Richland, WA, (2)Pacific Northwest National Laboratory, Richland, WA
A method of co-synthesizing ceramic/metal (cermet) composite powders by combustion techniques has been developed. The resulting powder is an intimate mixture of particles of the two materials that are on the order of 10 nm in size. A model system consisting of 30 vol% CeO2 and 70 vol% copper metal has been co-synthesized in this manner to explore the microstructures of metal matrix composites that can be achieved utilizing a co-synthesized precursor powder with such a fine scale of homogeneity. The microstructures resulting from various milling, compaction, and sintering techniques and parameters will be presented, including the effects of spex milling parameters on powders in which the CuO phase, which is present after combustion synthesis, was reduced to Cu metal either before or after milling. The spex milling parameters were investigated using a 2-level full factorial matrix study and included the milling media composition, the number and size of milling balls, and the milling time.
Additive Repair Using the LENS Process
D. Keicher, R. Grylls, R. Plourde, T. Marchione, Optomec, Inc., Albuquerque, NM
Repairs of high-value metal components can be made in a number of ways. Methods that add material to worn or damaged areas primarily use either wire or powder feed material, and either welding or laser-based power sources. The Laser Engineered Net Shaping (LENS®) process is a laser-powder additive manufacturing system that has been adapted over recent years to be optimized also for repair of metal components. Because of it’s adaptation from an additive manufacturing technique, and it’s use of a Nd:YAG laser, it offers several advantages over other techniques in making various repairs. This paper will describe recent advances in the technology's equipment, controls and capabilities, including the introduction of new fiber-lasers. Several case studies will be described, including demonstration repairs of compressor airfoils, and test results showing the microstructural features and mechanical properties of the added material. Demonstrated Return-on-Investment for repair applications will also be discussed. LENS is a registered trademark of Sandia National Laboratories and Sandia Corporation.
Advances in Micro Manufacturing
S. J. Sam Easley, Boeing, Berkekely, MO
Milling, fabrication, inspection and assembly of parts on the order of 10 to 500 microns (with features smaller than 5 microns) results in particular problems not experienced with larger parts. The purpose of this presentation is to address some of these problems, identify areas that will require further research and to review what Boeing has done in the area of small parts manufacturing research to date. Problems associated with small tools, on the order of 10 to 500 microns, end mills and drills running at speeds of 160,000 RPM's will be discussed. Handling and assembly of micro sized parts will also be discussed. Where a small amount of pressure can serve to make tight parts fit together in large parts, but will deform and destroy micro-scale parts. Inspection of these parts is difficult due to the size of the current inspection tools. Optical inspection techniques will be discussed. Other issues such as workpiece fixturing , assembly and inspection will be presented. Areas for application of small parts and mechanisms within the Boeing Company will be addressed as well.
Emerging Low Temperature Coating Technology - Kinetic MetallizationTM
R. Hanson1, H. Gabel2, (1)Timken Super Precision, Keene, NH, (2)Inovati, Santa Barbara, CA
Kinetic Metallization (KM) coatings can be applied on a variety of materials through solid-state impact consolidation of powder particles using friction-compensated sonic nozzles. The KM Coating Development System permits users with a wide range of backgrounds and experience to explore custom coating applications. The efficiency of the KM sonic nozzle allows operation at low gas pressures and temperatures, and provides optimum particle velocities for highly dense coatings. A wide variety of coatings of metals and metal matrix composites are possible. Technical specifications for the latest model of the KM Coating Development System (the KM-CDS 2.1) are presented, and potential applications discussed. A key feature of the KM-CDS 2.1 system is a new powder-fluidizing unit that permits feeding of nano-sized and ultra-fine powders which are highly agglomerating. Properties of some of the recent coatings produced with the KM process will be summarized.
Fabricating with Nanoparticles via Direct-Write Technology for Industrial Applications
J. W. Sears, South Dakota School of Mines & Technology, Rapid City, SD
Direct Write (or Printing) technologies uses nano-particle inks and pastes to build mesoscale-scale devices. The term mesoscale refers to sizes from approximately 10 microns to 1000 microns, and covers the range between geometries deposited with the more conventional thin film and thick film processes. These processes begins with dispensing of liquid molecular precursors or colloidal suspensions of metal, dielectric, ferrite, or resistor nano-powders. The dispensing is accomplished by either controlling an aerosol stream or bead of thick viscous paste to produce features with dimensions as small as 10 microns. In a typical configuration, the substrate is placed on a platen that is attached to a high precision CAD/CAM stages, so that intricate geometries may be produced. Either laser, photonic or furnace thermal treatments is used to process the deposit to the desired state. Application of these technologies to the production of direct write inductors, capacitors, and resistors is presented, along with electrical characterization of these components.
Potentials of Highly-Developed Laser Base Techniques for Additive Manufacturing and Repair of Complex Shaped Aero Engine Parts out of Nickel and Titanium Base Alloys
I. Kelbassa1, W. Meiners1, K. Wissenbach1, L. Trippe2, (1)Fraunhofer Institute Laser Technology, Aachen, Germany, (2)Chair of Laser Technology, RWTH Aachen, Aachen, Germany
Additive manufacturing and repair techniques like Laser Metal Deposition (LMD) and Selective Laser Melting (SLM) as well as Laser Drilling (LD) are well known applications. The range of processable materials was extended in the last years towards serial aero engine materials like Nickel and Titanium base alloys. Achieved results regarding macro and micro structure, hardness, defects (e. g. cracks, bonding defects, porosity) and contamination with atmospheric elements (e. g. O, N, C and H) are presented for Titanium alloys like Ti-6Al-4V, Ti-6246 and Ti-17 as well as for Nickel base alloys like Inconel 718 and Rene 80. The influences of the process parameters on the achieved results are discussed. Suitable process parameter windows are presented. Achieved static (tensile) and dynamic mechanical properties (HCF) are shown and compared to those of heat treated forged raw materials. Implemented applications are demonstrated and discussed in detail. Based on the results, technological and economical (low-cost manufacturing and repair) potentials of the Laser based techniques are estimated for specific manufacturing and repair cases occurring in the near future in the aero engine field of application. One innovative solution proposal (manufacturing case) is to use a mould for a rotationally symmetrical casing without any geometrical elements on the surface and to fabricate the small and filigrane complex shaped geometrical elements by LMD (Laser Metal Deposition) and / or SLM (Selective Laser Melting). By LMD these elements are built-up directly on the large parts. With SLM the elements are manufactured separately in the SLM machine and connected by a subsequent joining technique with the large parts. With SLM also small complex shaped parts like combustor swirlers, HPT blades and vanes with internal cooling channels can be manufactured completely also in combination with subsequent Laser Drilling (LD).
Characterization of Mechanical Properties of Cold Spray Aluminum Alloy Coatings via a Taguchi Experimental Design
E. Sansoucy, B. Jodoin, L. Ajdelsztajn, University of Ottawa, Ottawa, ON, Canada
The Cold Spray (CS) process is an emerging and promising coating technology that can produce conventional and nanocrystalline coatings. In CS, solid particles are accelerated above a critical velocity in a supersonic gas flow. Upon impact on a substrate, the particles deform plastically and bond to the substrate to form a coating. CS aluminum coatings have demonstrated an increased surface hardness and improved corrosion resistance. Although the CS process is mainly governed by the particle impact velocity, other process parameters, that do not change the particle impact velocity, might influence the coatings quality. Accordingly, it becomes important to identify and evaluate the effects of these parameters. The influence of four spray parameters including substrate surface conditions, powder feed rate, spray distance and traverse speed on the mechanical properties of CS aluminum alloy coatings will be examined. Coatings were produced at a constant particle velocity and experiments were conducted using a Taguchi fractional factorial design parametric study. The coatings microstructures are observed and the coatings are characterized by adhesive strength tests, hardness tests, porosity, and thickness. In particular, this presentation describes the testing and the particle in-flight diagnostic methods, and attempts to correlate the mechanical properties of the coatings to the process parameters.
Methodology for the Selection of Optimized Cold Spray Process Parameters
A. DeBiccari1, C. Vargas1, H. Berek2, A. Koehler2, S. Marx2, A. Paul2, (1)Pratt & Whitney, East Hartford, CT, (2)FNE Forschungsinstitut fur Nichteisen-Metalle, Freiberg, Germany
Cold Spray is an emerging solid-state material deposition process in which coatings are applied by exposing a substrate to a high velocity jet of particles accelerated by a supersonic jet of compressed gas. The process is considered "cold" because of the relatively low temperatures of the expanded gas and particle stream impacting the substrate. Using this process, researchers have successfully deposited stainless steel, nickel, copper, aluminum, and many other alloys.
By using gas jet and particle temperatures well below material melting temperatures, cold spray offers many advantages over conventional gas-thermal spray methods. These include compressive rather than tensile residual stresses, wrought like microstructure, near theoretical density, and freedom from oxides and other inclusions. Moreover, with a narrow particle stream footprint, fast growth rates of coating thickness with better shape control, often eliminating the need for masking, are possible.
To aid in the transition of cold spray from the laboratory into production, a method to determine optimized spray parameters is required. Process variables such as carrier gas pressure and temperature, nozzle travel speed, nozzle design, and powder feed rate all influence the coating quality and its properties. Depending on the application, users may be interested in optimizing coating density, bond strength, deposition efficiency, etc., or a combination of these and/or other properties.
This talk describes one such methodology. A design of experiments test plan was established, based on selected independent processing variables. Coating trials were performed and the dependent variables of interest measured for each test condition. Influence coefficients were then determined, including higher order cross-coupling terms, to assess the effect of the processing parameters on the properties of interest. Based on these influence coefficients, process parameters yielding the optimized predicted properties of the coating were selected. Finally, coatings were produced using this optimized parameter set to validate the model predictions.
Effect of CP Al Cold Spray Deposition on 7075 Substrate
J. E. Barnes1, V. K. Champagne2, D. L. Ballard3, T. Eden4, J. Kleek5, B. Shoffner4, (1)Lockheed Martin Aeronautics, Marietta, GA, (2)U.S. Army Research Laboratory, Aberdeen Proving Ground, MD, (3)Air Force Research Laboratory, Wright-Patterson AFB, OH, (4)The Pennsylvania State University, University Park, PA, (5)Air Force Research Laboratory, Wright Patterson AFB, OH
The objective of this study was to examine how the deposition of a thin layer of Commercially Pure (CP) Al on thin plates of Al-7075 T6 affects the tensile properties of the substrate. The CP Al was deposited using both Cold Spray and Kinetic Metallization™. Cold Spray utilizes both He and N2 as the carrier gas and a supersonic nozzle while Kinetic Metallization™ uses only He as the carrier gas and a sonic or friction compensated nozzle. A test matrix was established to evaluate the coatings applied by both methods. Characterization of the coatings included microstructural analysis, hardness measurements, and tensile, S-N fatigue and bend tests. Results of the characterization are presented.
Rolling Element Bearing Performance in Jet Fuel vs. Turbine Oil
T. Y. Hui1, F. Sadeghi1, R. G. Rateick Jr.2, (1)Purdue University, West Lafayette, IN, (2)Honeywell Aerospace, South Bend, IN
Jet fuel, designed primarily to burn, is not commonly thought of as a good lubricant, yet many existing and emerging aerospace propulsion system component designs rely on the fuel to lubricate things such as rolling element bearings. However, compared with oil, little data exists for bearing life and performance prediction in jet fuel. This research compares the rolling contact fatigue behavior of metal (AISI 52100 on M50) bearing couples and silicon nitride (NBD-200) on metal (M50 and BG42) hybrid bearing couples in fuel (JP8+100) and turbine oil (MIL-PRF-23699). Additional results show the running torque and thermal behavior for tapered roller bearings and angular contact ball bearings in fuel and oil lubricants and the friction coefficient of fuel under various loads and slide to roll ratios.
Weibull analysis of rolling contact fatigue results showed lives of hybrid bearings in fuel were not as good as in oil, as would be expected. The lower viscosity and the attendant reduction in film thickness give rise to higher stresses in the fuel vs. oil lubricated bearings. The torque and thermal characteristics of bearings operating in fuel vs. oil show that in general, the fuel lubricated bearings run significantly cooler and with less parasitic torque. This is thought to be largely the result of the lower viscosity. The friction coefficient of fuel is also similar in magnitude to other oils.
Thus, fuel is not as poor of a bearing lubricant as might be expected. Rolling contact fatigue resistance is not as good as in oil, but the reduced parasitic bearing torque losses in fuel contribute to greater component operating efficiency and incrementally reduced weight. Also, lower operating temperatures for the fuel lubricated bearing may allow use of lighter weight structural materials for the housings.
Ultra High-Strength, Corrosion Resistant, Secondary Hardened Landing Gear Steel
B. Tufts1, C. Kuehmann1, P. Trester2, (1)QuesTek Innovations LLC, Evanston, IL, (2)General Atomics, San Diego, CA
QuesTek Innovations has applied its Materials by Design® methodology to computationally design a new high strength corrosion resistant steel, Ferrium® S53, that eliminates the need for toxic cadmium coatings currently used on conventional steels in landing gear systems. S53 exhibits the strength level of 300M steel, yet with corrosion resistance similar to 15-5PH steel. QuesTek is currently in the 3rd year of a certification and test program to qualify S53 for applications on US Air Force aircraft. The program will submit an Aerospace Material Specification in mid-2006 and begin flight-testing in late 2006. Data will be presented from characterization and process studies. Alloy characterization has focused on strength, toughness, corrosion resistance, fatigue, and stress corrosion cracking. Processing studies completed to date include forging, welding, and machining. DARPA “Accelerated Insertion of Materials” techniques are being used to estimate design allowables from the limited data generated for the AMS specification. Plans to generate MMPDS properties will be discussed. Although S53 was developed as a drop-in replacement for 300M in landing gear systems, many additional applications are anticipated for this 290ksi UTS corrosion resistant steel. S53 is currently available for qualification testing in a number of product sizes.
Development of Niobium / Niobium-Silicide Based Alloys for Ultra High Temperature Applications
R. P. Dicks1, X. Wu2, (1)IRC in Materials Processing, University of Birmingham, Birmingham, United Kingdom, (2)University of Birmingham, Birmingham, United Kingdom
Materials based on niobium / niobium-silicides have been identified as candidates for use in gas-turbine engines. This is due to their high temperature capability and low density, around 6.6 g/cm3, in comparison to nickel-base superalloys. There are, however, a number of undesirable properties that must be addressed if their implementation within the industry is to be achieved. These are primarily a low ductility at room temperature and poor oxidation behaviour at intermediate and high temperatures. In this study, a large range of compositions based on the Nb / Nb-silicide system are screened in order to identify those that offer the best combination of oxidation resistance at both intermediate and high temperatures as well as ductility at room temperature. Samples, 20mm x 20mm x 3mm, were manufactured using the Direct Laser Fabrication (DLF) technique, by feeding a mixture of pre-alloyed and elemental powders into the laser focal point, and controlling its movement via a CAD file to build the desired geometry layer by layer. This method allows a large range of compositions to be produced more efficiently than using button melting. Nb-25Ti-16Si-8Hf-2Cr-1.9Al at% was used as a base composition and other elements, such as Cr and Si, were added in different amounts to individual samples. The laser fabricated Nb-silicide based samples were tested for oxidation resistance at 800 and 1200°C. The oxidised samples were sectioned to understand the oxidation mechanisms and the influence of added elements. The compositions of phases present in the material and those formed during oxidation were measured using EDX. The hardness and fracture surface topography of the samples tested at room temperature have also been assessed.
Evaluation of the Oxidation Resistance of Nickel and Cobalt Alloy Thin Sheet for Aircraft Engine Applications
J. R. Crum, B. A. Baker, R. S. Parsons, Special Metals Corporation, Huntington, WV
Examples of important nickel alloy thin sheet applications for aircraft engines include exhaust ducting and abradable honeycomb seals. These components may operate at very high temperatures, resulting in possible severe oxidation attack. In thin sheet the oxidation rate can be the critical factor in determining useful life of the material. Measuring oxidation rate by mass loss alone can be misleading, while total depth of attack measurements are much more meaningful. Oxidation testing of several stainless steels, nickel alloys and cobalt alloys has been conducted for up to 2000 hours at temperatures up to 1100° C with periodic mass loss and depth of attack measurements. In some cases depth of attack measurements reveal poor performance while corresponding mass loss results indicate only moderate attack. Beneficial effects of minor additions of aluminum, silicon and rare earth elements and detrimental effects of niobium, as well as the need for a substantial "chromium reservoir" for continuous oxide repair are demonstrated. Effects of high temperature fatigue are also addressed and data for a new lower cost nickel alloy are presented. Finally, overall high temperature performance relative to alloy cost is evaluated.
3-D Modeling of Machining Distortions of Aerospace Components
S. K. Srivatsa1, K. Ma2, K. Young3, Y. L. Yin4, W. T. Wu4, (1)GE Aircraft Engines, Cincinnati, OH, (2)Rolls-Royce Corporation, Indianapolis, IN, (3)Boeing Phantom Works, St. Louis, MO, (4)Scientific Forming Technologies Corporation, Columbus, OH
Aircraft engine and airframe structural components that are machined from forgings represent a significant cost of both military and commercial aircraft. Typical component applications are rotating disks in aircraft engines and structural components in airframes. The buy-to-fly weight ratio, which is the ratio of the forged material weight to the finished part weight, is typically between 4 and 10 for such components. The excess material is removed by various machining operations, which are a major contributor to the cost of forged components. Machining distortions are a problem with most forged components which are quenched rapidly in order to generate the required mechanical properties. Distortion can be caused by material bulk stresses resulting from heat-treating operations, or from local near-surface machining-induced stresses. Typically additional machining operations and setups are added in a time-consuming and costly trial-and-error approach to minimize the effects of part distortion. Manufacturing residual stresses can adversely impact the behavior of the components during service. There is a need to understand the effects of heat treating and machining on distortion and to predict, minimize, and control these distortion-related processes. The objective of this project is to establish a modeling method that accurately predicts distortion during machining of 3-D shaped forgings used in aircraft engines and airframe structures. Prediction and validation of machining distortions during broaching and milling operations due to bulk residual stresses will be presented. Future work will involve generation of experimental data under controlled and under production conditions and extensive model validation followed by implementation on production hardware. This program is funded by the USAF Metals Affordability Initiative (MAI).
Counter-Gravity Positive-Pressure Vacuum Casting Process
S. Shendye1, D. Cargill2, (1)Metal Casting Technology, Inc., Milford, NH, (2)Hitchiner Manufacturing Co., Inc., Milford, NH
The Counter-gravity Positive-pressure Vacuum (CPV) casting process is an investment casting process developed and patented by Hitchiner Manufacturing Company, Inc. This process is used to cast high quality components in reactive metals such as Ni and Co-based superalloys. During the CPV process, a hard vacuum is created in the mold and melting chambers. An impermeable fill pipe protrudes from the bottom of the mold chamber and is sealed to the mold. The mold chamber is then moved so that the fill pipe is inserted into the liquid bath which is induction heated and contained in the melt chamber. Pressure is then applied to the melt chamber, thus forcing the metal upward through the fill pipe and into the mold. Typically, pressure is applied on top of the melt surface using an inert gas such as argon. Pressure control over the melt surface results in a controlled rate of filling of the mold which enables casting of extremely thin walled polycrystalline components with walls as thin as 0.015 inch. Chemical composition, NDTE x-ray and fluorescent penetrant inspection (FPI) requirements, mechanical properties, and microstructure specifications are routinely met and exceeded for all the alloys cast. A large number of superalloy components are currently produced using the CPV process by Hitchiner at their manufacturing facility in Milford, NH. Some of these applications along with properties and microstructures, and the specific advantages of the CPV process will be reviewed.
Failure Analysis for Metal Injection Molded 17-4 PH Steel Fatigue Specimens
H. N. Chou, Boeing Phantom Works, St. Louis, MO
Metal Injection Molded (MIM) casting can be used to produce low cost affordable components for aerospace applications. Phantom Works co-worked a MIM development program with Advanced Manufacture Research Center (AMRC) in U.K.
This presentation describes the behavior of MIM specimens in heat treated and hot isostatic pressing (HIP) conditions when they were tested in stress life fatigue test. HIPed and heat treated castings usually exhibited longer fatigue life than those that was not HIPed. However, AMRC reported that the HIPed MIM fatigue specimens had shorter fatigue life than heat treated ones. A failure analysis was initiated to investigate the cause and to solicit ate any recommendations.
The optical and image mapping examinations of the fractured specimens determined the HIPed specimens had less amount of porosity than the heat treated ones. Scanning Electron Microscope examination observed typical fatigue striations in both HIPed and heat treated specimens. Fatigue origins were observed to be close to the internal porosity in the only heat treated specimens. Photomicrographs taken from the prepared etched mounts revealed carbide particles in the grain boundaries, which can serve as stress riser for fatigue initiation.
Further investigation revealed that the HIP process for the specimens was performed at a higher temperature than the solution heat treatment temperature. This HIP process facilitated the formation of carbides in the grain boundaries. So, the damage caused from carbides resulted from HIP contributed more to the fatigue initiations. This damage overrides the benefit from pore closing and shortened the fatigue life for the HIPed specimens. It was decided that new MIM specimens are needed and shall be HIPed at a temperature lower than that used for heat treatment to minimize the carbide formation to correct the problem. The new specimens shall be submitted for tests to validate the process.
Overview of TiAl Implementation at GE Aviation
M. J. Weimer1, T. J. Kelly2, (1)GE Aviation, Cincinnati, PA, (2)GE Aviation, Cincinnati, OR
Realizing the aircraft engine weight and performance promise of titanium aluminides has been a goal of materials engineers for the last thirty years. Numerous alloy systems have been developed, but none have been introduced into full-scale production. Impediments to implementation include the need to establish a complete database of design properties, design methodologies that accommodate the characteristics of titanium aluminides, and a cost effective supply chain. Prior to addressing these items a specification had to be developed that identified a compositional range that could be measured and processed through a specified thermal cycle or cycles to produce repeatable mechanical properties. After this, the first impediment to implementation could be addressed, General Electric has established a complete material database for TiAl alloy 48Al-2CR-2Nb which is currently in use by designers. This presentation compares the properties of TiAl alloy 48Al-2CR-2Nb with competitive nickel base superalloys used in low pressure turbine applications. TiAl alloy 48Al-2Cr-2Nb is very competitive with alternative nickel base materials and designs can be successfully executed within the property database. The remaining challenge is therefore establishment of a cost effective supply chain, which is the subject of considerable effort by our colleagues at PCC.
Characterization of Alloy 718Plus™ for Small Turbine Applications
D. Cameron, B. Chase, W. Baker, Honeywell Aerospace, Phoenix, AZ
Improving C1023 Manufacturability by Two-Step Heat Treatments
I. Hernández, A. Subinas, I. Madariaga, K. Ostolaza, Industria de Turbopropulsores, ITP S.A., Zamudio, Spain
C1023 alloy (Ni – 15.5% Cr – 9.7% Co – 8.3 % Mo – 4.1 % Al) is widely used in the manufacture of equiaxed nozzle guide vanes and seal segment for aero gas turbines. However, in spite of its extensive applications in many different types of engines, C1023 is considered difficult to weld, repair or machine. The high strength of this alloy is mainly due to the presence of a fine distribution of gamma prime precipitates that are formed directly after casting. The quick formation of this precipitates does not allow to process C1023 components with a soft material condition that could be comparable to the solution state of other superalloys. However, it would be desirable to achieve some kind of temporary soft condition that could improve the manufacture of C1023 components.
For this reason, a detailed study on the response of C1023 material to different kind of heat treatments has been conducted. These heat treatments were focused in two opposite directions. First of all, it was necessary to achieve a heat treatment capable to soften the material in order to improve all the aspects related to its manufacturability. After this, it was necessary to develop a second heat treatment that would be introduced at the end of the manufacturing process and that could be able to restore the high resistance of C1023.The results have shown that it is possible to achieve a significant reduction on the hardness of C1023 after 4 hours at 1200ºC followed by a controlled slow cooling. A starting microhardness of 375 HV can be reduced to 341 HV. The subsequent application of a 1190ºC heat treatment for 1 hour followed by a combination of furnace cool and gas fan quench is able to restore the original hardness of the as cast material.
Effect of Heat Treat Process Variables on Alloy 718Plus for Structural Applications
J. R. Groh, General Electric Aircraft Engines, Evandale, OH
Alloy 718Plus™ provides cost, manufacturing, and field service advantages relative to established cast plus wrought superalloy Waspaloy. Achieving the key characteristics needed to successfully replace an established production alloy in gas turbine applications requires an understanding of process variables on the microstructure and mechanical properties. Under a USAF Materials Affordability Initiative contract, a controlled experiment was performed on full-scale forgings to determine the influence of solution temperature, quench rate, and age temperature on microstructure, tensile and combination smooth-notch rupture behavior. The application-integrated project team consisting of engine manufacturers: GE, Honeywell, and Pratt & Whitney; forging suppliers Firth-Rixson and Ladish Company; primary metal producers Allvac and Carpenter Technology; in combination with the Air Force Research Laboratory Materials and Manufacturing Directorate, selected the Allvac-developed 718Plus™ alloy chemistry for scale-up and validation. Results are provided relative to anticipated AMS specification property limits.
Deposition Technologies for High Strength Ni Alloys
A. Wisbey1, J. Segal2, I. Pashby2, S. Jones3, J. Allen4, P. Holdway1, H. S. Ubhi1, (1)QinetiQ, Farnborough, United Kingdom, (2)Nottingham University, Nottingham, United Kingdom, (3)Rolls-Royce, Derby, United Kingdom, (4)Medtronic Vascular, Santa Rosa, CA
Reducing the cost of manufacturing high performance aero-engine components is crucial for the introduction of new high fuel efficiency engine technology and designs. One particular area is that of large wrought nickel alloy components, which have been traditionally produced from oversize wrought products and then machined to final size, with significant wastage. An alternative approach may be to employ conventional welding to assemble pre-formed parts, however, many of the higher strength wrought nickel alloys are considered unweldable. The new additive manufacturing routes now available may offer a solution to some or all of these problems. In the work reported here the high strength nickel alloy, Waspaloy, has been evaluated using various deposition technologies. These have included four different heat sources – GTAW, diode laser, Nd-YAG laser and electron beam, and both wire and powder feed. Simple wall type deposits have been manufactured using these techniques and the deposits have then been examined microstructurally, along with their tensile performance. Some investigation of the role of deposition parameters has been evaluated, especially for the GTAW and diode laser heat source techniques. Large columnar grains were found with most of the processes used, however, the GTAW system gave the largest grain size, with the Nd-YAG the smallest. Some anisotropy in the tensile properties was found with all of the deposition processes. The work reported here has shown that the deposition technology selected is very dependent on the geometry of the target component and the level of subsequent machining tolerable.
Fabrication and Repair with High Temperature Materials by Laser Powder Deposition
J. W. Sears, South Dakota School of Mines & Technology, Rapid City, SD
Laser Powder Deposition (LPD) for component manufacture and repair offers some unique solutions for high temperature aerospace applications. LPD is a CAD/CAM solid freeform fabrication technology that uses metal powder and laser fusion to repair components. Inherent to LPD is the ability to add material for repair of critical gas turbine engine components with minimal heat affect to the under lying material. Also, due to the nature of LPD, hard coatings can be achieved without heat treatment allowing producing durable hard surfaces on soft materials. LPD also provides a mean to transition from low temperature material to high temperature refractory metals. In some cases LPD can be used to replace hard chrome, nitrided or carburized surfaces. Details of several high temperature applications that have been produced will be disclosed.
Properties of Cold Spray Nickel Based Coatings
P. Richer, B. Jodoin, L. Ajdelsztajn, University of Ottawa, Ottawa, ON, Canada
Cold Spray is a relatively new coating process that uses a supersonic gas flow to accelerate fine powder particles above a given critical velocity. Upon impact, the particles plastically deform and adhere to the substrate to form a coating. In recent years, nickel based alloys used in coating applications have been the focus of many studies, particularly in the aerospace industry. Their inherent corrosion and oxidation resistant properties have made them especially attractive for use as the metallic bond coat found in thermal barrier coating systems. The present study examines the properties of nickel based alloy coatings produced by the cold spray deposition process. Evaluation of the coating properties is achieved by means of electron microscopy, porosity measurements and adhesion testing. A correlation between coating properties and in-flight particle velocity measurements is also presented.
BAC 100(TM) Microalloyed Aluminum Casting Alloy
A. P. Druschitz, University of Alabama at Birmingham, Birmingham, AL
BAC 100TM, a family of high strength, high toughness, weldable, microalloyed aluminum casting alloys and a heat treatment process that insures good ductility and good resistance to stress corrosion cracking was recently invented. The goal of this material development program was to produce aluminum alloy castings with properties that meet MIL-DTL-46192C, Aluminum Alloy Armor, Rolled Plate, Weldable.
Currently, only wrought aluminum alloy 2519 processed in accordance with US Patent No. 4,610,733 can meet MIL-DTL-46192C. To meet this specification, wrought aluminum alloy 2519 is “stretched” in excess of 6%; this raises the yield strength of the material. However, to produce a structural component, a plate or billet must be machined. This is time consuming, costly and restricts the use of 2519 to relatively simple shapes. Further, if this material is welded, its high strength and high toughness are lost in the weld and the weld heat affected zone.
Two BAC 100TM variants have been developed: high strength and high toughness. Twenty-four (24) chemistry variations have been cast and evaluated in the T4, T6, T61 and T7 tempers. As the chemistry has been optimized, the heat treatment optimization has occurred in parallel. From this data, mathematical models have been developed to predict the influence of the seven primary elements that give BAC 100TM its unique physical and mechanical properties.
To accelerate the development of the BAC 100TM family of microalloyed aluminum alloy casting alloys, a CRADA was established and is currently in-progress with the US Dept. of Energy, Albany Research Center National Laboratory, Albany, OR.
The Effect of Grain Refinement and Modification on the Mechanical Properties of Al-Si-Mg Alloys
N. Iqbal1, T. Tinga2, L. Katgerman3, (1)Delft University of Technology, Delft, Netherlands, (2)National Aerospace Laboratory Netherlands, Emmeloord, Netherlands, (3)The Netherlands Institute for Metals Research, Delft, Netherlands
The mechanical properties of materials strongly depends on its microscopic structure. During the casting of Al-Si-Mg (A356) alloys, a small amount of grain refiners (TiB2, TiC etc) is added to reduce the aluminum grain size, while small traces of strontium modifies the eutectic silicon particle size and morphology. These changes in microstructure significantly improve the mechanical properties of the alloy. Experiments are conducted on the sand cast test rods using A356 alloy. The effects of grain refiner (Al-5Ti-1B) and modifier (Sr) additions are investigated separately and both together. The microstructural changes associated with additions have been studied by optical microscopy and scanning electron microscopy. The specimens cut from various locations of each cast, are tensile tested. The correlation between the mechanical properties and the microstructural changes due to grain refinement and Sr modification is established. The results indicate that the addition of both grain refiners and modifier have beneficial effects on the mechanical properties of A356 alloy. It is shown that the mechanical properties are affected by the specimen position in the cast bar. The responsible mechanisms are probed in terms of variation in microstructure and macrosegregation along the solidification path during casting.
2198 – Advanced Aluminium-Lithium Alloy for A350 Fuselage Skin Sheet
M. Knuewer1, J. Schumacher2, H. Ribes3, F. Eberl4, B. Bes5, (1)Airbus Deutschland, Bremen, Germany, (2)Airbus, Bremen, Germany, (3)Alcan Pechiney Rhenalu, Issoire, France, (4)Alcan Rhenalu, Issoire Cedex, France, (5)Alcan CRV, Voreppe, Cedex, France
2198 as today’s most advanced Aluminium-Lithium alloy is chosen as the ideal fuselage skin sheet material for world’s most advance twin-engine aircraft A350. 2198 in T8X temper condition shows an outstanding combination of high static strength and high damage tolerance for large damage capability like two frame bay crack. High thermal stability, a “must” for fuselage skin application, is also one of the 2198 main advantages. For today's Airbus fuselage application, an alloy has to show additional features: Laser-Beam- and Friction-Stir-Welding as well as good forming capability. The paper gives a brief history of the 2098 (2198) development, a view on the application of 2198 T8X in the A350 fuselage, the main properties and an overview of the Friction-Stir- and Laser-Beam-Welding application.
Development of 7140 T7651 Thick Plate for Structural Airframe Components
K. P. Smith1, B. Reichlinger2, G. D. Tuss2, (1)Alcan Rolled Products, Ravenswood, WV, (2)The Boeing Company, Seattle, WA
Alcan Aerospace has developed a family of thick plate products offering significant improvements in strength and fracture toughness compared to conventional 7050 products. 7140 T7651 is the latest solution in thick rolled plates offering very high strength combined with a good level fracture toughness and stress corrosion resistance.
These products allow for consolidation of built-up structures and weight savings opportunities for airframe producers. Availability of rolled plates with low residual stress quality in very large cross sections also provides an alternative to forged products when control of machining distortion is critical.
Design data representing over 40 industrial plates is now available. This information will be submitted for MMPDS and AMS specification coverage. Additionally, The Boeing Commercial Airplane Group has performed an extensive testing program using the material. Full scale machining of parts has also been conducted with very positive results and low machining distortion behavior.
Applications for 7140 T7651 may include wing spars and ribs, bulkheads, fuselage frames and various other fittings in aircraft structure. This rolled plate product will be offered from 4 to 10 inches thick.
Generation of Design Data for a New Al-Li Plate Product (2050-T8)
M. J. Philbrook1, K. P. Smith2, M. J. Crill3, E. S. Balmuth3, D. J. Chellman4, J. Amin5, (1)Alcan Aerospace, Ravenswood, WV, (2)Alcan Rolled Products, Ravenswood, WV, (3)Lockheed Martin Aerospace, Fort Worth, TX, (4)Lockheed Martin Aeronautics, Fort Worth, TX, (5)Lockheed Martin, Fort Worth, TX
2050-T8 is the latest development by Alcan Aerospace in lightweight plate products. This product was designed to equal or exceed the static and toughness properties of 7050-T7451. Additionally, the product offers improved fatigue crack growth resistance and thermal resistance as well as lower density. Extensive studies at Alcan Aerospace and Lockheed Martin Aeronautics have shown that the original property targets are being met or exceeded.
Latest test results for the product will be presented including tensile, compression, shear, bearing, fracture toughness, elastic modulus, stress-corrosion cracking, and fatigue. This design data for plate products is being generated for submission to MMPDS and will include plate products up to 6 inches thick.Crack turning behavior can be of interest when dealing with aluminum lithium alloys. Predicting when crack turning will occur is a critical step towards being able to implement these alloys in structural airframe applications. Recent advances in prediction techniques have been made by joint studies between Alcan Aerospace and Lockheed Martin Aeronautics.
Damage Tolerance Capability of 2139 Plate (an Al-Cu-Mg-Ag Based Alloy)
A. Cho1, K. P. Smith1, B. L. Reichlinger2, (1)Alcan Rolled Products, Ravenswood, WV, (2)The Boeing Company, Seattle, WA
Abstract
For damage tolerance dominant applications, 2xxx-T3xxx type products are commonly used for a desired balance of strength and fracture toughness.
However, -T3 type temper products have several inherent limitations. These include poor SCC resistance (Stress Corrosion Cracking Resistance), product gauge limitations, limited product forms and limited manufacturing processes. Therefore, aerospace designers have expressed interest to develop a new 2xxx –T8xx temper product having desirable combination of strength, fracture toughness and fatigue resistance without limitations of -T3 type temper product
Alcan developed Alloy 2139 to meet such requirement. Evaluation of 1 inch gauge 2139-T8 plate demonstrated that damage tolerance capability of 2139 –T8 plate exceeded that of 2xxx-T3xx product without having limitations of –T3xx temper product. Alloy 2139 also demonstrated excellent ballistic performance exceeding other incumbent alloys. To explore the potential applications for thicker gauge plate, Alcan produced additional plate with gauges up to 6 inches. This paper will discuss damage tolerance capability of 2139-T8xx (an Al-Cu-Mg-Ag based alloy) plate product at various gauges by presenting combined properties of strength, fracture toughness and fatigue resistance. Comparisons to incumbent alloy products will be discussed.
Application for 2139-T8 alloy product may include lower wing skin plate, wings and spas and armor plate. 2139 plate product would be especially suitable for damage tolerant applications in thermally affected areas where 2xxx-T3xx and 7xxx-T7xxx type products are not suitable.
Microstructure and Properties of Spraycast and Forged Al-Li-Mg-Zr-(Sc) Alloys for Airframe Applications
P. S. Grant, S. C. Hogg, I. G. Palmer, University of Oxford, Oxford, United Kingdom
This work describes the microstructure and properties of a range of spraycast Al-(4-6)Mg-(1.2-1.6)Li-(0.3-0.4)Zr-(0-0.2)Sc alloys. Spraycasting provided refined microstructures, extended solid solubility and a reduction in the concentration of embrittling impurity elements such as H, Na and K. Billets of 20-25kg were produced with as-spraycast grain sizes in 5-15µm range using an Osprey spraycasting plant installed at Oxford University. Following hot isostatic pressing to close any porosity and to precipitate a fine, coherent Al3Zr or Al3(Zr,Sc) dispersoid population, forging of 1kg samples at 250 and 400°C led to a substantial refinement of the microstructure with grain sizes in the range 0.8 to 5µm. A large intra-granular orientation gradient with distance measured using Electron Backscattered Diffraction showed that at 250°C, partial dynamic recrystallisation by progressive lattice rotation led to a ‘necklace’ structure of very fine grains surrounding larger deformed grains. At 400°C, dynamic recrystallisation occurred by nucleation and growth of new grains at prior grain boundaries and triple points. The strength of as-forged alloys was 200-350MPa, with high ductilities of up to 30% that rendered the alloys amenable to post-forging cold work. A proof strength of 460MPa with 9.5% elongation was achieved in a non-heat-treatable Al-6Mg-1.3Li-0.4Zr alloy forged at 250°C and cold worked 20%, matching the best properties of similar mechanically alloyed AA5091, and exceeding the properties of AA7010-T74. The as-forged alloys showed excellent thermal stability up to ~0.9Tm, with no abnormal grain growth after 7 days at 500°C and grain size stagnation in the 4-6µm range due to Zener pinning. Strain rate sensitivity testing revealed an m value of ~0.45 at 400 and 500°C and strain rates of 0.001-0.05s-1 and indicated strongly the potential for superplasticity.
New Developments in Extruded Integrally Stiffened Panels
C. Giummarra1, L. Yocum2, (1)Alcoa Technical Center, Alcoa Center, PA, (2)Alcoa Engineered Products, Lafayette, IN
Integrally stiffened extruded panels (ISPs) are aerospace structural components which are composed of both the skin and stiffeners in a continuous part made from the same piece of raw stock and are an effective way of obtaining high strength, lightweight structures. Renewed focus on the use of extruded ISPs for the wings and wing box of larger commercial planes has been growing over the past few years due to improved extrusion techniques, advances in joining technology and the benefits of new aluminum alloys. Extruded ISPs offer cost saving opportunities for original equipment manufacturers (OEMs) as they can provide improved buy-to-fly ratios and can significantly reduce the number of fasteners required compared to a built-up structure, which reduces the time and cost of manufacturing. The overall result of using ISPs is a reduction in cost and lower part count. This presentation summarizes the recent developments in extruded aluminum ISPs including the high performance new aluminum-lithium alloys, results of fatigue crack growth retardation design concepts and the outcome of joining evaluations, all of which provide beneficial options when tailoring an ISP to the customer’s application.
Magnesium Alloy Elektron 21- a Light-Weight Solution up to 2000C (4000F)
P. Lyon, Magnesium Elektron, Manchester, United Kingdom
Magnesium alloys offer the opportunity to reduce weight due to their low density (2/3rds that of Aluminium). For this reason, Magnesium alloys are used in numerous aerospace applications including Helicopter transmissions and jet engine components.
Over the years, there has been a desire to improve the strength, temperature capabilities and corrosion performance of these alloys in line with the demands of ever onerous operating conditions. These objectives have been met by various alloys systems, most notably the Mg-Y-Nd-HRE-Zr alloy system, allowing operation at upto 2500C (4800F).
In more recent times, cost of components has become an increasingly important requirement. This has been addressed by the development of a new alloy from the Mg-Gd-Nd-Zr alloy system and is known as Elektron 21.This alloy maintains most of the property benefits of the Mg-Y-Nd-HRE-Zr alloy system (including corrosion performance, elevated temperature properties) however has been designed to have improved castability. A consequence of improved castability is reduced processing costs at the foundry. Interest by aerospace end users in this alloy has allowed the alloy to achieve AMS approval (AMS4429) and inclusion in the MMPDS design guideline. Consistency of properties is notable in both of these approvals.
The majority of work done with Elektron 21 has been for sand cast applications. Investment casting, is a means of reducing wall thickness (and hence weight) of complex components. This process is generally restricted to small components for Magnesium due to metal mould reaction. Use of low reactivity Elektron 21 gave successful results during investment casting (using plaster and shell moulds). Using improved processing technology, it has been shown that large components can be made successfully in this alloy with out reaction. This opens new opportunities for further weight reduction in weight sensitive applications.
Ballistic Performance of the Magnesium Alloy AZ31B
T. L. Jones1, M. Burkins1, W. A. Gooch1, R. DeLorme2, (1)US Army Research Laboratory, APG, MD, (2)Magnesium Elektron North America, Inc., Madison, IL
Wrought magnesium alloys, which maintain various niche market applications due to their unique properties, have been the subject of a heightened level of research and development for potential application in the automotive market. However, little data is available on their ballistic properties. In order to fill this gap, the US Army Research Laboratory (ARL) and Magnesium Elektron North America, Incorporated (MENA) conducted a cooperative effort to evaluate magnesium alloy AZ31B, which was commercially available in a wrought form. MENA produced the rolled product and conducted the mechanical testing, while ARL performed the ballistic testing. Some limited ballistic data is provided for this alloy in both the H24 and O tempers.
Effect of Temperature on Behavior of Magnesium Alloys during Backward Can Extrusion
C. Margam, J. Y. M. Shyan, Singapore Institute of Manufacturing Technology, Singapore, Singapore
Aluminum Alloy 2040 for Demanding Aircraft Wheel Applications
L. S. Steele1, L. Mueller2, R. Sawtell3, (1)Goodrich Corporation Aircraft Wheels and Brakes, Troy, OH, (2)Alcoa, Inc., Alcoa Center, PA, (3)Alcoa Inc. Alloy Technology and Materials Research, Alcoa Center, PA
Aluminum aircraft wheels experience harsh and demanding operating conditions during service, including heat, carbon dust, runway and aircraft fluids, and high-energy braking events. Wheel alloy property design drivers include strength at ambient and elevated temperature, corrosion resistance, density, fatigue behavior, and fracture resistance. The combination of these material properties present in conventional wheel alloys such as 2014 and 7050 naturally drives the structural design of the wheel. A new wrought aluminum alloy, 2040, possesses an enhanced combination of these properties relative to 2014 and 7050 which results in reduced weight wheel designs. Alloy 2040 is targeted for its first commercial aircraft use in the near future. This presentation will review and compare the material property drivers of 2040 with both 2014 and 7050, including wheel roll-on-rim performance.
High Performance and Low Cost Fuselage Panels: LBW and FSW Solutions
F. Eberl1, I. Bordesoules2, S. Kempa3, S. Jambu4, J. Hackius5, (1)Alcan Rhenalu, Issoire Cedex, France, (2)Alcan CRV, Voreppe, France, (3)Alcan Technology & Management Ltd., Neuhausen, Switzerland, (4)PECHINEY Aviatube, Montreuil-Juigné, France, (5)AIRBUS Deutschland GmbH, Bremen, Germany
In current aircraft programs as Airbus A318, A340 or A380 laser beam welded panels are already assembled in the fuselage belly area by using high strength 6xxx alloys as 6056 or 6013.
Optimized design concepts and advanced weldable materials allow significant weight savings for future metallic fuselage structures. Thanks to new manufacturing technologies on top of weight savings major cost savings can be reached due to increased joining speed for skin-stringer joints.New Al-Cu-Li fusion weldable alloys show improved strength-toughness balances by decreased density compared to the 6056 baseline. The so-called WeldaliteÓ alloys allow dissimilar material combinations, so that new assembling concepts can be introduced for even higher weight savings for welded fuselage panels without any supplemental cost compared to similar material combinations. Thanks to metallurgical modeling, very low hot cracking sensitivity can be reached for industrial set-ups.
Alloys as 2198 produced as fuselage sheet or 2196 elaborated as extruded section will be presented in welded configurations typical for welded fuselage shells. These materials will be compared to the 6056 sheet + 6056 stringer baseline and other high performance materials as 2022 or 2139. All materials tested have artificially aged final tempers, so that welding in T3 or T6/T8 is possible. Final properties of different processing routes will be compared.
In order to reduce cost, longitudinal friction stir welded joints (skin-skin butt joint) are of great interest. The previously mentioned materials developed for fusion welded applications have been friction stir welded. In order to define the best cost/performance balance, different processing routes have been evaluated.
In summary, the potential weight saving for welded monolithic fuselage structures thanks to optimized design concepts will be reminded. Different welded material combinations using Al-Li-Cu or other high performance materials as 2022 or 2139 will be discussed for fusion and friction stir welded processes.
High Performance Aluminium Sheet and Plate Products for Aircraft Fuselage, Wing and Integrated Structures
S. Spangel1, A. Bürger1, R. Nash2, J. Vd. Langkruis3, (1)Corus Aluminium Rolled Products, Koblenz, Germany, (2)Corus Aluminium Rolled Products, USA, Kent, WA, (3)Corus Research Development & Technology, IJmuiden, Netherlands
The aircraft industry requires improved aluminium alloy sheet and plate that enables higher performance while simultaneously delivering reduced costs. Extreme cost and performance pressures on the Aircraft Original Equipment Manufacturers by the airline customers requires that the performance capability of aluminium sheet and plate is fully utilized in order to be competitive against other materials such as fiber reinforced composites or other high performance metals. Corus has developed new alloys for fuselage, wing structures and for use in general or integrated structures. This presentation covers the recent high performance aluminium sheet and plate developments by Corus Aluminium Rolled Products together with Corus Research, Development & Technology to support the design and manufacture of new aircraft structures.
New High Strength AlMgSc Type Profile Materials for Future Metallic Aircraft Structures
F. Palm, EADS Deutschland GmbH, Munich, AR, Germany
Future metallic aircraft structures are competing with increased applications of carbon fibre composite materials (CFRP). The successful implementation of Boeing´s 787 Dreamliner, a CFRP intensive airliner put metallic Aluminium materials solutions into a difficult position as those technologies are meanwhile stigmatised as old fashioned with no future. Taking into account well known classical shortcomings of Al alloys applications like corrosion and fatigue at the time being Al material technology offers only limited solutions which might be promising enough to become a vital alternative to compete with CFRP. Beside the permanent optimisation of established 6xxx, 2xxx and 7xxx alloy technology coupled with improved structure design (differential and integral (+ welded)) AlMgSc type alloys seem to be very interesting as they are known as very good weldable, long lasting and inherent free of corrosion related damages.
In the mid 90ties EADS Corporate Research Centre Germany started a successful research programme to develop AlMgSc sheet material. Now we are focussing on higher strength (500 – 700 MPa) profile alloys in order to be able to fulfil all relevant requirements for new integral fuselage applications in welded and/or riveted-bonded configurations. Additionally to this, airframe elements like floor beams or seat tracks are envisaged as well. The presentation will address the metallurgical fundamentals necessary to enable higher strength AlMgSc materials, the manufacturing of profiles and the related processing.
Prediction of Aluminum Alloy's Ductile Fracture in Blanking Process
A. Farshidianfar, S. Abbasion, A. Rafsanjani, Ferdowsi University of Mashhad, mashhad, Iran
The present work is dedicated to the study of Aluminum Alloy blanking process. A methodology is proposed to predict the ductile fracture of Aluminum Alloy in this process. Attention is paid to the interaction between parameters influence on blanking process such as punch-die clearance, punch diameter, sheet metal thickness and contact with friction in order to predict the optimum punch–die clearance during sheet metal blanking processes. The Finite element simulation of blanking process obtained and the properties of the cut edge were examined. The explicit time integration method with failure criteria have been used to simulate the process. The comparative study between the numerical results and the experimental ones shows the good agreement.
New Flat Rolled Products from Alcoa – A Progress Report
G. B. Venema1, T. Morales1, R. Ramage1, P. Magnusen2, D. Mooy3, A. Wilson3, C. Giummarra1, R. J. Rioja1, (1)Alcoa, Inc., Alcoa Center, PA, (2)Alcoa Incorporated, Alcoa Center, PA, (3)Alcoa, Inc., Davenport, IA
The development of Al-Li 2199 sheet products for use in fuselage applications is presented. This product is being brought to commercial status at an unprecedented rate because of the significant weight savings that it offers. Weight savings are ealized via lower density, and lower fatigue crack growth rates than the incumbent. The status of development for a high strength temper and a high damage tolerance temper are reported. Major performance attributes such as fatigue crack growth, fracture toughness and static properties used for design are discussed. The corrosion characteristics are examined under several types of tests. Differences in availability in terms of width and gauge are discussed as a function of different flow-paths.
Bare 2199 sheet in conjunction with 2099 extruded products, offer opportunities for significant performance improvements in fuselage applications.
The status of development of 2199 plate for use in lower wings is also presented in the context of the above criteria.
Direct Metal Deposition: An Innovative Way to Produce Near Net Shape Parts and Remanufacture In-Service Components
B. Dutta, J. D'Souza, J. Mazumder, POM Group, Inc., Auburn Hills, MI
Due to the high performance requirements often at high temperature, aerospace industry uses particularly expensive materials, for example, Co-alloys, Ni-base super alloys and Ti-alloys. All these materials are used extensively in the turbine engine components and/or landing gears etc. Due to normal wear or accidental damage the components require remanufacturing. However, most of these materials are difficult to weld and thus, remanufacturing is a challenge. Laser Aided Manufacturing (LAM) has played a key role for repair of aerospace components for more than a decade. Recent developments in Direct Metal Deposition (DMD), a proprietary LAM process originated at University of Michigan and further developed and commercialized by POM Group, Inc. offers a great promise of better microstructure and near net shape control with possibility of significant reduction in cost and lead time. The DMD process controls the deposition through its close loop system and allows control of heat input and dimension of the part. This effective thermal management system keeps the HAZ to a minimum and also does not recrystalize the parent material, thus maintain fatigue strength as per OEM specifications. This coupled with a five-axis deposition capability of DMD505 machine allows the system to deposit almost any NEAR NET geometry. This reduces the post machining/grinding time and saves material and cost. Besides remanufacturing, DMD allows building of special parts with complicated details such as lattice structures, mirror bases etc. It has been observed that DMD can save up to 70% in material, 90% in process time and 20% in process energy for some of these components. The present work will present an overview of the DMD process and properties of DMD materials. It will then elaborate on the merits and demerits of the process with respect to aerospace industry requirements and illustrate with case studies of some components.
High Strength Copper Alloys for Rocket Engine Applications
A. B. Pandey, Pratt & Whitney Rocketdyne, West Palm Beach, FL
There has been increasing interest to develop high strength copper alloys to improve performance of rocket engines. Typically, copper alloys are used for thrust chamber applications in rocket engines for efficient heat transfer capability. Copper alloys are currently limited in their ambient and high temperature strengths. The purpose of this presentation is to provide a comparison of properties for commercially available high strength copper alloys with reference to the requirements of rocket engines. The data are analyzed to provide insight into the strengthening mechanisms for these copper alloys. Most copper alloys derive strengthening from precipitation hardening and dispersion hardening. The basis for dispersion strengthening materials is the individual dislocation-particle interaction mechanism. Narloy-Z is currently used for thrust chamber application that is based on precipitation strengthening mechanism. Cu-Cr alloy (also known as Anaconda) is another precipitation strengthening material that is considered for comparison. Two materials based on dispersion strengthening mechanisms are considered: (a) GRCop-84 and (b) GlidCop. GRCop-84 is a NASA material that contains Cr and Nb and derives strengthening primarily from the Cr2Nb particles. GlidCop material contains fine Al2O3 particles to provide oxide dispersion strengthening (ODS). While GRCop84 is one of the best materials available today, it would be required to develop newer copper alloys with higher strength and creep resistance to improve performance of rocket engines.
Design Readiness Update for 2099 Al-Li Plate
H. W. Babel, The Boeing Company, Huntington Beach, CA
Described is the approach and results used to define expected design allowables for cryotanks for 2099 Al-Li plate in the T6 and T8 temper. These design values were used to develop cryotank designs from which weight savings were established, 20% for upper-stage tanks, a weight savings that was very attractive to the program. As program judgments are made based on the projected weight saving, the expected allowables should not change when the allowables are established. As the designs were being developed, work continued to develop additional information leading to the establishment of allowables.
Lower than targeted strengths were measured on one lot of plate; the approach used to resolve this question is discussed and the results obtained.
The properties that control the design were given the highest priority. Several of the ASTM standards did not provide the precision and reproducibility required, particularly elongation and modulus determination at cryogenic temperatures. The procedure selected to provide the required measurements are described.
Development of Materials for Service in High Pressure, High Temperature Oxygen Environments
D. Hardwick1, M. A. Jacinto2, R. Perez2, (1)AFRL Materials Directorate, Wright Patterson Air Force Base, OH, (2)Boeing North American, Canoga Park, CA
High pressure oxygen is the oxidizer of choice for high performance liquid rocket engine applications. Metallic materials are compatible with liquid oxygen, but high pressure, high temperature gaseous oxygen is a very demanding environment; full flow staged combustion engine cycles will require materials that can operate in that environment. This talk will cover the challenges inherent in designing materials for use in the high pressure high temperature oxygen environment and provide insight into how these challenges can be overcome.
Material Processing Challenges Associated wtih Core Material Consolidation for Nuclear Rocket Engines
B. Panda, NASA Marshall Space Flight Center, Huntsville, AL
In-space propulsion concepts utilize liquid hydrogen as propellant in nuclear rocket engines. In order to maximize the thrust obtained from a unit weight of propellant, the nuclear core of the engine would have to be operated at extremely high temperatures. High melting point uranium compounds are generally used as the core materials for this application. While earlier NASA/DOE efforts utilized graphite base materials containing uranium compounds, in large part, for ease of fabrication, current efforts at Marshall Space Flight Center are assessing the utility of tungsten matrix cermet and carbide materials for such purpose. Processing these materials is difficult due to the inherently high-temperature melting points of these materials. The paper describes earlier processing and test efforts for graphite base materials as well as the current techniques and their associated challenges.
Space Materials Intellectual Property Management: Rules and A Roadmap of Rising Relevance
W. N. Hulsey, HULSEY Intellectual Property Lawyers/IC2 Institute, University of Texas at Austin, Austin, TX
Space Materials Intellectual Property Management:
Rules and A Roadmap of Rising Relevance
William N. Hulsey III
Principal, HULSEYIP Intellectual Property Lawyers, P.C.
Senior Research Fellow, IC2 Institute, University of Texas at Austin
1250 S. Capital of Texas Highway, Building 3,
New Magnesium High Strength Wrought and Cast Alloys
P. Lyon, Magnesium Elektron, Manchester, United Kingdom
Currently available wrought Magnesium alloys are predominantly based upon the strengthening effects of Aluminium and or Zinc additions. This provides alloys which have moderate strength compared with many Aluminium alloys. Improvements in Magnesium alloy technology are available and have included alloy development and process development. An example of the latter is Rapid solidification technology whereby >600Mpa tensile strengths can be achieved. These alloys have however not found application because of poor elevated temperature performance and poor fracture toughness.
Recent activities have concentrated on alloy development to improve properties, combined with conventional wrought production technology. A new alloy currently in the development launch phase is Elektron 675. This alloy offers a step change in mechanical properties which are accentuated as temperature of application increases. Above 1200C for example, Elektron 675 can exceed the properties of high strength Aluminium alloy 7075 T6 at only a fraction of the weight. Properties of wrought products often vary with extrusion ratio; this new alloy is no exception. Data is supplied upon the effect of extrusion profile and heat treatment variations.
Summary data is also provided on the latest elevated temperature cast alloys
Influence Of Tool Geometry of High Speed Steel On Machining Pure Commercial Aluminium Alloy
V. Ananthanarayanan1, M. Nambi2, (1)Hyundai Motor India Limited, Chennai, India, (2)Sri Venkateswara College of Engineering, Chennai, India
Machining of metal involves forcing a cutting tool through excess material of the work piece. Tool geometry plays a major role in machining of metals.Aluminium alloys can be machined economically and rapidly. Because of their complex metallurgical structure,their machining characteristics are superior to those of pure aluminium.Aluminium and alloyed aluminium are important material used for housing and structural parts in automotive and aerospace industries. Machining of aluminium and its alloys require cutting tool with sharp edges either PCD or HSS tool. Only limited investigations on high speed machining of aluminium with HSS tool over the period of several years have been reported.The present work gives the findings of machining commercial aluminium alloy with high speed steel tools of various tool geometry under different cutting parameters in the medium duty lathe,which represents a great challenge for the metal working industries. The result provides some useful information. The main focus on the paper was off-line surface finish measurements, power developed, heat generated and material removal rate(MRR) for the different types of tool geometry of high speed steel (HSS) tools.Keywords: Machining, Aluminium alloy, High Speed Steel, Tool geometry.
Electrical Discharge Machining of Hybrid Metal Matrix Composites
R. Ahamed1, S. Aravindan2, P. Asokan3, (1)Edayathangudy G. S. Pillay Engineering College, Nagapattinam, India, (2)National Institute of Technology, Tiruchirapalli, India, (3)National Institute of Technology, Trichy, India
Metal matrix composites refer to a material system composed of discrete constituent(s) called reinforcement(s) dispersed in a continuous phase of the metal called the metal matrix. The advantages of metal matrix composites over unreinforced metals are high specific strength, high Young’s modulus, high temperature strength, good conductivity, and good abrasion and wear resistance etc. By virtue of their superior properties, not seen in monolithic materials, they are used in structural and functional components for high performance applications such as aerospace vehicles and racing automobiles.
However their machining has been an impediment to their widespread application The inclusion of the ceramic reinforcement in the composite causes excessive tool wear. The dominant wear mechanism is impact at the cutting edge and thermal stresses For these reasons non-conventional machining techniques such as EDM are employed to machine mmcs to guarantee dimensional stability and economic machining.
EDM is a thermal process whereby material is removed by the action of high-energy electrical sparks. The spark melts and vaporizes a small area on the electrode surface. At the end of the pulse-on time, a small amount of molten material is ejected from the surface. The main advantage of this process is that complex shapes can be machined on very hard materials as mmcs without any contact between the tool and work piece.
The present work reports on the experimental investigation into the electrical discharge machining of Al-B4C-SiC hybrid metal matrix composite. The composite is developed through powder metallurgy route. The effects of EDM parameters namely current (C) and pulse on time (P) on the metal removal rate (MRR) and surface roughness (SR) are analyzed. Taguchi’s and ANOVA (Analysis of Variance) are used to analyze the effects of machining characteristics such as MRR and SR. The machined surface characteristics are studied using Scanning Electron Microscopy (SEM).
Thermodynamic Modeling of Titanium Alloys Using CALPHAD Approach
F. Zhang1, S. -. L. Chen1, Y. A. Chang2, D. U. Furrer3, V. Venkatesh4, (1)CompuTherm, LLC, Madison, WI, (2)University of Wisconsin, Madison, WI, (3)Pratt & Whitney, East Hartford, CT, (4)TIMET-R&D,, Henderson, NV
Computational approach has been recognized as a very useful tool in accelerating the development of new materials and improvement of the existing ones. Traditional labor intensive series of experiments are greatly reduced due to the use of computational modeling tools. Implementation of such tools to improve titanium processing via parameter optimization has the potential for cost savings through the elimination of shop/laboratory trials and tests. Thermodynamic modeling tool can be used to predict phase equilibrium information given alloy chemistry, which is essential in understanding the chemical effect on the final microstructure and mechanical properties of a material. In this presentation, we will demonstrate how we can use CALPHAD approach to develop a thermodynamic modeling tool for titanium alloys. Two essentials for the successful application of CALPHAD approach: robust computer software and reliable thermodynamic databases will be discussed. The application of thermodynamic modeling tool to commercial titanium alloys, such as Ti64, Ti6242, Ti6246, Ti17 and so on, will be discussed. Some calculated examples will be presented.
Application of Thermodynamic and Kinetic Modeling to Diffusion Simulations in Nickel-Base Superalloy Systems
P. Mason1, A. Engstrom2, H. Larsson3, L. Höglund4, (1)Thermo-Calc Software Inc, McMurray, PA, (2)Thermo-Calc Software AB, Stockholm, Sweden, (3)KTH (Royal Institute of Technology), Stockholm, Sweden, (4)The Royal Institute of Technology (KTH), Stockholm, Sweden
This paper presents a brief review and some new results on simulation of interdiffusion in Ni-base superalloy diffusion couples, by means of a thermodynamic and kinetic modelling approach as taken in the commercial finite-difference code, DICTRA[1]. This code solves the multi-component diffusion equations, combining assessed thermodynamic and kinetic data in order to determine the full composition dependent interdiffusion matrix. As will be discussed, this approach limits the amount of parameters that needs to be stored in a kinetic database, and additionally allows different types of kinetic information to be considered and accounted for during the assessment procedure. A procedure to directly assess and determine these kinetic parameters from concentration profiles measured in diffusion couples will be demonstrated. Simulation results on interdiffusion in a complex Ni-base superalloy diffusion couple including multiphase regions, obtained using a dispersed phase model[2] in DICTRA will be presented and discussed. In the dispersed phase model all diffusion is assumed to occur in a continuous matrix phase (e.g. γ-phase), and the applicability of this model is limited by the fact that this assumption is not valid for the high volume fractions of secondary phases (e.g. γ’, β and MC carbide) typically present in Ni-base superalloy systems. Hence, there is a strong need for an alternative approach, and a recently developed homogenization approach to diffusion in multi-phase systems[3] that doesn’t suffer this particular limitation will also be presented and its application to the same problem will be discussed.
References:
1. J.O. Andersson, T. Helander, L. Höglund, P.F. Shi, and B. Sundman, Calphad, 26(2002), pp. 273-312.
2. A. Engström, L. Höglund and J. Ågren, Metallurgical and Materials Transactions A, 25A (1994), pp. 1127-1134.
3. H. Larsson and A. Engström, submitted for publication.
Models for Microstructure Evolution during TMP of Alpha/Beta Titanium Alloys
S. L. Semiatin, Air Force Research Laboratory, Wright-Patterson AFB, OH
Models have been developed and applied to predict the evolution of microstructure and texture during the thermomechanical processing of alpha/beta titanium alloys in both the alpha/beta and beta phase fields. The present talk focuses specifically on microstructure models for alpha/beta processing of Ti-6Al-4V. This includes methods to describe static and dynamic coarsening of colony and equiaxed alpha, static and dynamic spheroidization of colony alpha, and the growth of primary alpha and formation of secondary alpha during cool-down following final alpha-beta heat treatment. Many of the models are based on quantitative descriptions of diffusional processes that lead to a reduction of alpha-beta interface area (e.g., coarsening and spheroidization) or a reduction of beta matrix supersaturation (e.g., microstructure evolution during cool-down). The suite of analytical and numerical tools will be summarized for these processes. The importance of appropriate material parameters (e.g., diffusivity, alpha/beta interface energies) for assessing the accuracy of the models will be underscored. The validation of models under both laboratory and production-scale conditions will be summarized.
Texture Modeling for Industrial Forging of Ti-6Al-4V with an Equiaxed-Alpha Microstructure
M. G. Glavicic1, D. R. Barker2, R. Goetz3, S. L. Semiatin4, (1)Rolls-Royce Corporation, Indianapolis, IN, (2)UES, Inc., Wright-Patterson AFB, OH, (3)Rolls-Royce Corporation, Indianapolis, OH, (4)Air Force Research Laboratory, Wright-Patterson AFB, OH
Software was developed to model texture development during the high temperature forging of Ti-6Al-4V with an equiaxed-alpha microstructure. The software makes use of the Los Alamos Polycrystalline Plasticity (LApp) code in conjunction with the finite-element-modeling routine DEFORMä. The software indirectly couples DEFORMä with LApp and quantifies texture evolution at specific points in complex forgings whose metal flow has been characterized with DEFORMä. The methodology also takes into account partitioning of the imposed strain between the alpha and beta phases, models texture evolution for the alpha and beta phases separately, and allows for variant selection rules to be applied to describe the formation of secondary-alpha texture.
Quantitative Phase Field Modeling of Microstructural Evolution in Titanium Alloy
N. Ma1, Y. Wang2, (1)Center for Accelerated Maturation of Materials, Columbus, OH, (2)The Ohio State University, Columbus, OH
Microstructural evolution in commercial titanium alloys is extremely complex. In this presentation we discuss our recent efforts in integrating thermodynamic modeling and phase field simulation to develop computational tools for quantitative prediction of spatiotemporal evolution of microstructures during thermal processing for two alloy systems: Ti64 and Ti6242. The models account explicitly for precipitate morphology, spatial arrangement and anisotropy. The models developed were validated against experimental observations with microstructural features quantified by a set of rigorous procedures based on stereology. The development of multi-component titanium alloy diffusivity database and integration of phase field model with Pandat, a computer software program for thermodynamic calculations, will be emphasized.
Prediction of Microstructure Evolution and Mechanical Properties of Forged Titanium Components for Aerospace Applications
G. Shen1, D. U. Furrer2, J. Meudt1, V. S. Saraf1, (1)Ladish Co., Inc., Cudahy, WI, (2)Roll-Royce Corporation, Indianapolis, IN
Modeling tools have been developed for the prediction of microstructure evolution and mechanical properties of forged titanium components. These tools include (1) beta grain growth model for the heating of Ti-6-4, (2) beta grain size evolution model for beta forging of Ti-6246, (3) alpha growth model for the grain size evolution during heat treatment of Ti-6-4; and (4) Neural network mechanical property model for selected titanium alloys. The application of modeling tools in forging and heat treatment process design made it possible for the selection of the optimum process for the manufacturing of titanium components for aerospace applications.
Simulations of Virtual Microstructures for Design and Development of Light Alloys and Their Composites
A. Gokhale1, H. Singh2, Y. Mao1, A. Sreeranganathan1, S. Lieberman3, J. Harris4, (1)Georgia Institute of Technology, Atlanta, GA, (2)BBSB Engineering College, FATEHGARH SAHIB, India, (3)Exponent Failure Analysis Associates, Menlo Park, CA, (4)Stanford University, Stanford, CA
Current methodologies for microstructure simulations mostly involve idealized simple particle/feature shapes; uniform-random spatial distribution of microstructural features; and isotropic feature orientations. However, the corresponding “real” microstructures often have complex feature shapes/morphologies; non-random/non-uniform spatial distributions; and partially anisotropic feature orientations. Consequently, such simulations do not capture these aspects of microstructural reality. In this contribution, we present a methodology that enables simulations of “realistic” microstructures where feature shapes/morphologies, spatial arrangement, and feature orientations are statistically similar to those in the corresponding real microstructures. The methodology is applied for simulations of microstructures of TiB whiskers in Boron modified Ti-alloys, discontinuously reinforced Al-alloy composites, and coarse constituent particles in wrought Al-alloys. In each case a small set of simulation parameters is used for the generation of these microstructures. The methodology enables the generation of a set of “virtual” microstructures that cover a wide range of process conditions. These virtual microstructures are then implemented in finite element (FE) based computations to simulate local stress distributions and stress-strain curves of the corresponding virtual materials. The methodology can provide useful input for materials design and can decrease the number of experiments needed for material development.
Integrated Process Modeling Applications
R. Shankar, J. Walters, W. T. Wu, Scientific Forming Technologies Corporation, Columbus, OH
DEFORM™ is a finite element based process modeling system that is widely used in the design and development of forging, heat treatment and machining processes. DEFORM™ is widely used in various industries during the development cycle to reduce design iterations, troubleshoot problems and optimize processes.
Process modeling is used in the forging industry to predict metal flow in the die cavity, flow defects and underfill conditions. Modeling plays an integral role in the optimal design of forging process including preform and die tooling design, analyzing die stresses and extending die life. Metal forming processes such as extrusion, rolling, drawing and cogging can also be modeled.
Modeling heat treatment process helps to predict residual stresses and resulting heat-treat distortion and microstructural evolution. The diffusion mechanisms and phase transformations can be modeled. Inverse heat transfer optimization method has been successfully implemented to characterize the heat transfer boundary conditions accurately. A variety of heat treatment processes such as austenizing, carburizing, quenching, tempering and stress relieving can be modeled.
Machining simulation can be used to predict the influence of cutting parameters such as cutting speed, feed and depth of cut on chip morphology, temperature, tool wear, and cutting force. The effect of redistribution of residual stresses during machining on part distortion can be analyzed. A variety of turning, milling and drilling operations can be modeled.
The wide-ranging use of process modeling in industry is instrumental in the improvement of cost, quality and delivery for nearly two decades. Examples of DEFORM™ capabilities will be presented, along with the case studies that highlight applications covering forging, heat treatment and machining process design and analysis.
Integrated Modeling of Process, Microstructure and Performance: An Application to the Study of Weld-Cracking in Nickel Base Superalloys
S. Babu, Y. Yang, W. Zhang, S. Khurana, Edison Welding Institute, Columbus, OH
The enhanced performance of high-temperature nickel base superalloys depend on the underlying microstructure that is achieved during fabrication and its stability during service. With the recent focus on repairing of these alloys after service, there is an increased need to understand the microstructure evolution during welding. This microstructure evolution during weld solidification and cooling controls the weld cracking tendency. Since the weld microstructure evolution is controlled by composition of the alloy and also cooling conditions, the development of repair welding procedure is complicated for each and every geometry and alloy specification. In fact, the development of crack-free welds becomes an expensive and time-consuming development process. To address this critical need an integrated weld modeling framework has been developed.
In this integrated model, a finite-element model predicts the spatial variation of temperature and strain as a function of process parameters and restraint conditions. This model also captures weld solidification conditions, as well as, the repeated heating and cooling during multiple passes. The spatial variations of thermal cycles are then given as an input to the microstructure model. The microstructure model, based on computational thermodynamic and kinetic theories, allows for the prediction of various phases including gamma-prime precipitation. This microstructure information is then qualitatively related to metallurgical susceptibility for weld cracking. By coupling these results, weld-cracking tendency can be evaluated as a function of process, process parameters, filler metal composition, base metal composition and welding geometry. Some example calculations for repair welding of polycrystalline nickel base superalloys will be discussed.
The talk also will highlight some of the innovative approaches to deliver these modeling tools to industry by using automated calculation techniques and web-based interfaces. The enhanced performance of high-temperature nickel base superalloys depend on the underlying microstructure that is achieved during fabrication and its stability during service. With the recent focus on repairing of these alloys after service, there is an increased need to understand the microstructure evolution during welding. This microstructure evolution during weld solidification and cooling controls the weld cracking tendency. Since the weld microstructure evolution is controlled by composition of the alloy and also cooling conditions, the development of repair welding procedure is complicated for each and every geometry and alloy specification. In fact, the development of crack-free welds becomes an expensive and time-consuming development process. To address this critical need an integrated weld modeling framework has been developed.
In this integrated model, a finite-element model predicts the spatial variation of temperature and strain as a function of process parameters and restraint conditions. This model also captures weld solidification conditions, as well as, the repeated heating and cooling during multiple passes. The spatial variations of thermal cycles are then given as an input to the microstructure model. The microstructure model, based on computational thermodynamic and kinetic theories, allows for the prediction of various phases including γ’ precipitation. This microstructure information is then qualitatively related to metallurgical susceptibility for weld cracking. By coupling these results, weld-cracking tendency can be evaluated as a function of process, process parameters, filler metal composition, base metal composition and welding geometry. Some example calculations for repair welding of polycrystalline nickel base superalloys will be discussed.
The talk also will highlight some of the innovative approaches to deliver these modeling tools to industry by using automated calculation techniques and web-based interfaces.
Design Optimization of Tipped Milling Cutter for High Performance Cutting of Aluminum Alloys
A. Javali1, D. S. Ramakrishna2, (1)JNNCE, Shimoga, India,, SHIMOGA, India, (2)JNNCE, SHIMOGA, India
ABSTRACT
This paper deals with the mathematical modeling and optimization of design of tipped milling cutters for high performance machining of Aluminum alloys.
In the present day context, proprietary designs are becoming common, as they are tailor made to application specific. Use of interchangeable cutters, which are manufactured as per the I.S.O standards are restricted to general purpose milling with medium performance. Now a days milling of silicon-aluminum alloys with high Metal Removal Rate is becoming common practice and posing challenges for the tool design engineer. Aluminum alloys are lighter in weight and posses good heat transfer property. Hence these products find their place in aircrafts and automotives. Possibly Aluminum alloys may be the future material.
During the present work, it is aimed to design and develop a mathematical model for the design of milling cutter. Optimal and post optimal solutions are then obtained.
Keywords: optimization, post-optimal solution, performance.
optimization, post-optimal solution, performance.
Modeling Tool Development and the AIM Tool-Box Paradigm
D. D. Whitis1, R. Maffeo1, S. Schrantz1, D. Mourer2, D. Wei2, P. Finnigan3, D. Backman4, (1)GE Aviation, Evendale, OH, (2)GE Aviation - Lynn, Lynn, MA, (3)GE Global Research Center, Niskayuna, NY, (4)Worchester Polytechnic Institute, Worchester, MA
Addressing Critical Air Force Issues Using Multi-Disciplinary Material Modeling
J. Calcaterra, Air Force Research Laboratory, Wright-Patterson AFB, OH
Modern military aircraft are some of the most complex systems ever created. To meet constantly increasing performance goals, aerospace materials are pushed to near their physical limits. Air Force research in the area of material modeling is focused on reducing the risk of using materials in aggressive environments by increasing our understanding of the underlying physics. Research into these models has led to tremendous scientific advances in the areas of life prediction, material processing and material development, to name a few. Invariably, when the newest models are applied to actual engineering problems, the science outpaces the application. In many instances, the models must be extremely simplified in order to be applied to the engineering need. In other cases, the science underlying the model is so new that there is not the confidence needed to utilize the model. Finally, there are some times when the newly developed model completely misses the problem need by the engineering application. This presentation will address three separate applications of relatively new materials and processes models to meet Air Force needs. The first case is the successful application of a machining model to rectify a fabrication problem. The second instance is the development of a titanium heat treating model to meet industrial concerns. The final example is the application of both processing and life prediction models to address a problem in service. This presentation will address the difficulty with linking models to address multidisciplinary concerns and the steps necessary to ensure that the models are pertinent to real world applications.
Challenges in Assessing Residual Stress Depth Profile on Engine Components
R. T. Ko1, S. Sathish1, R. S. Reibel1, M. P. Blodgett2, (1)University of Dayton Research Institute, Dayton, OH, (2)US Air Force Research Laboratory, Wright-Patterson AFB, OH
Eddy current methodology has been shown feasibility of measuring residual stress depth profile in engine materials in a nondestructive way. In general, the changes in an eddy current signal, due to the residual stress variation, are known to be at least an order of magnitude smaller as compared to defect signals. These feasibility measurements were performed in ideal laboratory conditions on controlled samples. In order to extend the eddy current based methodology to engine components, both probe design and instrumentation capability have to be optimized and controlled. This presentation will address the following:
Further, it will also provide possible solutions to successfully implement eddy current methodology for residual stress profile measurement. USAF Contract Number: F33615-03-C-5219
High-Frequency Eddy Current Conductivity Spectroscopy for Residual Stress Profiling in Surface-Treated Nickel-Base Superalloys
B. Abu-Nabah1, P. B. Nagy2, (1)University of Cincinnati, Cincinnati, OH, (2)University of Cincinniti, Cincinnati, OH
Shot peening and other mechanical surface enhancement methods significantly improve the fatigue resistance and foreign-object damage tolerance of metallic components by introducing beneficial near-surface compressive residual stresses and hardening the surface. However, the fatigue life improvement gained via surface enhancement is not explicitly accounted for in current engine component life prediction models because of the lack of accurate and reliable nondestructive methods that could verify the presence of compressive near-surface residual stresses in shot-peened hardware. In light of its frequency-dependent penetration depth, the measurement of eddy current conductivity has been suggested as a possible means to allow the nondestructive evaluation of subsurface residual stresses in surface-treated components. This technique is based on the so-called piezoresistive effect, i.e., the stress-dependence of electrical conductivity. Previous experimental studies were conducted on excessively peened (Almen 10-16A) nickel-base superalloy specimens that exhibited harmful cold work in excess of 30% plastic strain. Such high level of cold work causes thermo-mechanical relaxation at relatively modest operational temperatures; therefore the obtained results were not directly relevant to engine manufacturers and end users. The main reason for choosing peening intensities in excess of recommended normal levels was that the eddy current penetration depth could not be decreased below 0.2 mm without conducting accurate measurements above 10 MHz, i.e., beyond the operational range of most commercially available eddy current instruments. In this presentation we will report the development of a new high-frequency eddy current conductivity measuring system that offers an extended inspection frequency range up to 80 MHz with a single spiral coil. In addition, the new system offers better reproducibility, accuracy, and measurement speed than the previously used conventional system.
Development of a Residual Stress Depth Profile Measurement Instrument
D. Stubbs, J. D. Hoeffel, W. C. Hoppe, R. T. Ko, J. R. Sebastian, University of Dayton Research Institute, Dayton, OH
The U.S. Air Force has a strong strategic and economic interest in extending the safe life of the gas turbine engines in its inventory. In the past few years experimental programs have investigated the relationship between near surface residual stresses, introduced during manufacturing by processes such as shot peening, and the fatigue life of engine components. At the present, there is interest in enhancing engine life by taking credit for these residual stresses that extend fatigue life, however, the stresses must be accurately measured in order to be of benefit.
Recent research programs have established that residual stresses in some nickel-based engine alloys can be accurately and repeatably calculated from electrical conductivity measurements acquired using eddy current (EC) nondestructive testing (NDT) methods. This work has also shown that, under laboratory conditions, conductivity measurements as a function of frequency can be used to calculate residual stress as a function of depth in the material.
The Air Force has recently awarded a competitively-bid contract to the University of Dayton to demonstrate the feasibility of incorporating the EC NDT residual stress measurement technique into a working instrument. The program goals are to create an EC instrument that can reliably and repeatably measure electrical conductivities which allow calculation of residual stress as a function of depth in nickel alloys. Key performance requirements include:
1) Electrical conductivity measurements accurate to within 0.1 percent relative to the nominal alloy conductivity,
2) Measurement times of less than 5 minutes,
3) EC frequencies from 100 kHz to 50 MHz.
This presentation will describe the program goals, approaches, and expected results. Information about the current state of research in using EC NDT for residual stress measurement will be presented including limitations of the technology. The potential for quickly moving the technology to the depot floor will also be discussed.
Characterization of Cold Work in Nickel-Base Superalloys by Instrumented Nanoindentation
S. I. Rokhlin1, E. Kahana1, L. Wang1, X. Bin1, P. B. Nagy2, M. P. Blodgett3, (1)The Ohio State University, Columbus, OH, (2)University of Cincinnati, Cincinnati, OH, (3)US Air Force Research Laboratory, Wright-Patterson AFB, OH
Nondestructive evaluation of residual stresses and of residual stress relief in service conditions has great significance for reliability of turbine engine components. It is important to achieve better fundamental understanding of relations between nondestructive signature and material properties such as hardness, plasticity, cold-work and residual stress. In this work a nanoindentation technique is explored to determine the micromechanical properties and their relation to different levels of cold work in Ni based superalloys. It is shown that cold work has some effect on elastic modulus, in particular texture induced elastic anisotropy appear at plastic deformation above 20%. Cold work has strong effect on hardness and yield stress. Significant size effect has been observed in indentation responses. Nanoindentation measurements are also performed on shot peened Ni based superalloy samples. Local mechanical properties (Young’s modulus E, yield stress ƒnand strain hardening exponent n) are determined from nanoindentation tests based on the inverse scaling functions. The nanoindentation results are compared with non contact measurements of electrical conductivity.
Characterization of Residual Stress in Nickel-Based Superalloys Using High-Frequency Eddy Currents
C. Lee, Y. Shen, C. Lo, N. Nakagawa, Iowa State University, Ames, IA
This paper reports on development of an electromagnetic method for residual stress characterization in shot-peened aerospace materials. The residual stress improves crack-initiation resistance of aerospace components, thus prolonging their service life. Due to possible in-service stress relaxation, component life extension can only be realized if the residual stress profile, which typically extends to about 200 μm, can be characterized nondestructively. X-ray diffraction measurement is limited to about 20 μm thick surface layer. Detection of sub-surface stress requires removal of surface layer, rendering the technique destructive. In this paper, we present the work on an eddy current (EC) technique that combines sweep-frequency EC measurement and model-based inversion for assessing residual stress in nickel-based superalloys. We have developed a high-frequency EC measurement system and proprietary probes fabricated by the PCB technology that can operate up to 50 MHz with the smallest penetration depth of 80 mm. An experimental procedure was devised to extract from EC data the horizontal component reflecting lift-off effects, and the vertical component which is lift-off free and is related to conductivity change. A numerical simulation based on the Born approximation shows that surface roughness affects the horizontal component somewhat, but has virtually no effects on the vertical component. Measurements on Inconel 718 specimens have shown a clear difference before and after shot-peening in the vertical component. The EC signals were then inverted via a multi-layer model to yield conductivity depth profile, from which residual stress and cold work profiles can be determined when a material-based profile model is assumed. The forward and inverse models themselves were validated with simulated layer specimens.
This work was performed at the Center for NDE at Iowa State University with funding from the Air Force Research Laboratory through S&K Technologies, Inc. on delivery order number 5007-IOWA-001 of the prime contract F09650-00-D-0018.
Jet Engine High Temperature Sensing in Harsh Environments
M. Austin, Pratt and Whitney, East Hartford, CT
Abstract: Jet Engine High Temperature Sensing in Harsh Environments
The aerospace industry wishes to sense many real-time high temperature areas throughout the jet engine. Fan, compressor, turbine, augmentor design groups would love to instrument every inch of the engine so they gain an understanding of the engine’s behavior and performance, especially in the hot sections. There can be over 3,000 installed sensors with miles of wire on one test engine! Counting the sheer number of sensors that are installed on an engine during a test, there are a number of questions that come to mind: What parameters, conditions and engine components should be monitored? What components have the highest rate of field replacement and are these components candidates for high temperature sensing? Are there any big paybacks for high temperature sensing in harsh environments?
Pratt and Whitney conducted a trade study to answer these questions. This talk will give a general overview of what was learned from the trade study and discuss how Pratt and Whitney is addressing the future visions of high temperature sensing in harsh environments.
High-Temperature Diagnostic and Environmental Sensors
J. Brogan, C. Gouldstone, J. Gutleber, R. Greenalw, B. Keyes, MesoScribe Technologies, Inc., Stony Brook, NY
Direct-write (DW) technology has been applied to fabrication of strain gages, thermocouples and humidity sensors. The advantages of Direct-Write for harsh-environments include: superior adhesion to substrates without polymer adhesives; flexibility to select temperature-tolerant and substrate-compatible materials; ability to produce low-mass, low-profile multi-layers for rotating and wetted components; ability to embed devices within functional coatings; and batch reproducibility through automated processing to minimize cost and reject rate. Resistive direct-write strain gages exhibit consistent and repeatable strain-reporting. Through a ceramic device-substrate interface, the device tracks longitudinal and transverse deformation of the component being monitored. Automated, integrated alignment and deposition processes simplify sensor installation and improve accuracy. Direct-write thermocouple junctions are innately suited to surface temperature measurements, offering higher fidelity thermal interfaces than conventional contact thermocouples. NIST-standard thermo-element compositions are used, for compatibility with legacy infrastructures e.g., extension leads, junctions and readers. Capacitance-based humidity sensors, applied using Direct-Write, are being developed for use within graphite reinforced epoxy substrates (GrEp). Since GrEp degradation is particularly sensitive to moisture, a hygrothermal suite combining direct-write humidity, temperature and strain sensors will be a valuable prognostic tool for composite structures in the field. This paper will provide an overview of the performance properties for embedded environmental sensors made by Direct Write for health monitoring applications.
High Temperature LGS SAW Sensors and Applications
M. Pereira da Cunha, University of Maine, Orono, ME
Devices capable of operating up to 1000°C are in high demand as harsh environment temperature, pressure, strain and gas sensors. Potential applications include: (i) aerospace vehicle health management of military and civil aircraft; (ii) monitoring of jet fuel combustion targeting economy for increased flight range, and pollution reduction; (iii) detection of gas leaks for both operational and safety purposes in the space shuttle program and space exploration; (iv) early detection and mitigation of hazardous fire situations; and (v) gas and oil well exploration. Semiconductor, magnetic, fiber optic and acoustic wave (AW) technologies have been used for high temperature applications with limited success in terms of reliability and life span, mostly due to temperature limitations in electronic performance or structural properties of the materials available. Recent work by several groups around the world on AW devices using gallium orthophosphate (GaPO4) and the langasite family of crystals (LGX) have indicated that these materials can be used in high temperature sensor applications.
This work reports on recent progress by the author’s group on the design, fabrication, test, and packaging of high temperature langasite (LGS) surface acoustic wave (SAW) sensors using platinum (Pt) and palladium (Pd) thin film technology. The reported temperature and gas sensors have been tested between 250°C and 750°C over periods up to six weeks, with device degradation smaller than 7 dB in the magnitude of the transmission coefficient, |S21|, with respect to room temperature. Single and dual configurations have been used as frequency control elements in oscillator circuitry. Present work is targeting tests up to 1000 ºC and package improvements for Air Force applications. The results obtained so far and that will be presented in this conference qualify Pt and Pd LGS SAW sensors for consideration for the above listed harsh environment applications.Devices capable of operating up to 1000°C are in high demand as harsh environment temperature, pressure, strain and gas sensors. Potential applications include: (i) aerospace vehicle health management of military and civil aircraft; (ii) monitoring of jet fuel combustion targeting economy for increased flight range, and pollution reduction; (iii) detection of gas leaks for both operational and safety purposes in the space shuttle program and space exploration; (iv) early detection and mitigation of hazardous fire situations; and (v) gas and oil well exploration. Semiconductor, magnetic, fiber optic and acoustic wave (AW) technologies have been used for high temperature applications with limited success in terms of reliability and life span, mostly due to temperature limitations in electronic performance or structural properties of the materials available. Recent work by several groups around the world on AW devices using gallium orthophosphate (GaPO4) and the langasite family of crystals (LGX) have indicated that these materials can be used in high temperature sensor applications.
This work reports on recent progress by the author’s group on the design, fabrication, test, and packaging of high temperature langasite (LGS) surface acoustic wave (SAW) sensors using platinum (Pt) and palladium (Pd) thin film technology. The reported temperature and gas sensors have been tested between 250°C and 750°C over periods up to six weeks, with device degradation smaller than 7 dB in the magnitude of the transmission coefficient, |S21|, with respect to room temperature. Single and dual configurations have been used as frequency control elements in oscillator circuitry. Present work is targeting tests up to 1000 ºC and package improvements for Air Force applications. The results obtained so far and that will be presented in this conference qualify Pt and Pd LGS SAW sensors for consideration for the above listed harsh environment applications.Devices capable of operating up to 1000°C are in high demand as harsh environment temperature, pressure, strain and gas sensors. Potential applications include: (i) aerospace vehicle health management of military and civil aircraft; (ii) monitoring of jet fuel combustion targeting economy for increased flight range, and pollution reduction; (iii) detection of gas leaks for both operational and safety purposes in the space shuttle program and space exploration; (iv) early detection and mitigation of hazardous fire situations; and (v) gas and oil well exploration. Semiconductor, magnetic, fiber optic and acoustic wave (AW) technologies have been used for high temperature applications with limited success in terms of reliability and life span, mostly due to temperature limitations in electronic performance or structural properties of the materials available. Recent work by several groups around the world on AW devices using gallium orthophosphate (GaPO4) and the langasite family of crystals (LGX) have indicated that these materials can be used in high temperature sensor applications.
This work reports on recent progress by the author’s group on the design, fabrication, test, and packaging of high temperature langasite (LGS) surface acoustic wave (SAW) sensors using platinum (Pt) and palladium (Pd) thin film technology. The reported temperature and gas sensors have been tested between 250°C and 750°C over periods up to six weeks, with device degradation smaller than 7 dB in the magnitude of the transmission coefficient, |S21|, with respect to room temperature. Single and dual configurations have been used as frequency control elements in oscillator circuitry. Present work is targeting tests up to 1000 ºC and package improvements for Air Force applications. The results obtained so far and that will be presented in this conference qualify Pt and Pd LGS SAW sensors for consideration for the above listed harsh environment applications.
High-Temperature Fiber Optic Sensors for Integrated Systems Health Management
R. J. Black, K. Chau, L. K. Good, D. B. Moslehi, Intelligent Fiber Optic Systems Corporation, Santa Clara, CA
Multipoint strain sensing is crucial to Integrated Systems Health Management (ISHM) for aerospace structures. Strain sensing with commonly used resistive foil gages is typically restricted to less than 400°C, is subject to electromagnetic interference and installation is labor intensive. By contrast, light-weight fiber optic sensors have the potential for noise-free measurement to much higher temperatures with electromagnetic interference immunity, electrical passivity and thus safety in explosive environments, and remote access. Fiber optic grating sensors are also multiplexable and precise, but standard gratings are subject to high-temperature degradation. However, IFOS is developing special fiber grating based strain sensors that significantly extend the maximum temperature at which accurate strain sensing is achievable to 800°C and beyond, thus filling a particular need for users of high-temperature health monitoring of (a) jet and other high temperature engines, (b) thermal protection systems – including those on leading and trailing edges of aircraft and in re-entry protection for shuttle and other space vehicles, and (c) satellite space vehicles. Further applications include instrumentation for fire warning systems, furnaces, nuclear power plants, high-temperature automotive engine sensors, oil refinery and drilling, chemical sensors, and homeland security sensor systems. While our focus is on reliable high-temperature strain measurements, the system will also have the potential for extension to simultaneous measurement of strain, vibration, acceleration, and temperature, and, with appropriately coated gratings, sensitivity to various chemicals and biochemicals, and applicable to gases in combustion environments and high temperature spectroscopy.
Piezoelectric Active Structural Diagnostic Method Development for Structural Health Monitoring in High Temperature Aggressive Environments
J. Kendall1, V. Giurgiutiu1, B. Xu1, J. Laskis1, J. Chung2, (1)University of S. Carolina, Columbia, SC, (2)Global Contour Ltd., Rockwall, TX
Structural health monitoring (SHM) research using piezoelectric wafer active sensors (PWAS) has made considerable progress in recent years. By using guided waves and electro-mechanical standing waves, PWAS have demonstrated successful detection of delaminations, cracks, disbonds, and corrosion. Of considerable interest is the extension of this technology to high temperature applications such as space reentry vehicle thermal protection systems (TPS), jet engine turbine blades and engine exhaust washed structures (EEWS), etc. This paper presents the conceptual architecture of high-temperature piezoelectric wafer active sensors (HT-PWAS). In this initial effort, several essential aspects have been investigated: (a) identification of piezoelectric materials that can survive in harsh and aggressive environment; (b) development of active SHM (i.e., pitch-catch, pulse-echo, phased-array, electromechanical impedance) that can be applied to TPS tiles and engine parts monitoring; and (c) development of self-powered low-power consumption electronics with wireless capability for implementing the active SHM principles, and transmiting the diagnostic results. In initial tests conducted, we created HT-PWAS from x-cut Gallium orthophosphate (GaPO4) single crystal discs with sputtered platinum (Pt) 100 nm electrodes. A HT-PWAS of 7mm diameter and 0.2mm thickness successfully maintained piezo-functionality at 700°C (1300°F). The small HT-PWAS was also capable of transceiving (transmit and receive) ultrasonic waves in ultralight TPS tiles during the test. The test results provided the potential application to SHM of the TPS tile and jet engine parts operating in harsh and aggressive environments. In the TPS SHM study, a technique to detect the disbond between the TPS tile and the airframe structure was researched. In the engine SHM study, we developed a coupled field finite element method (FEM) modeling technique that allows the prediction of the SHM reading for different levels of damage. Our planned future research includes in-depth piezoelectric material formulation research and HT-PWAS installation/wiring technique development.
Advanced Multifunctional Coatings with Embedded Sensors for Insitu Assessment of Operational State and Structural Health
S. Sampath, S.U.N.Y at Stony Brook, Stony Brook, NY
Assessing the operational state of engineering systems and health monitoring of vital engineering components in-situ and in real-time is a important capability that is required for modern engineering designs to be fully utilized. Such active monitoring can minimize maintenance costs, provide real-time system status, and allow for scheduling of major repairs at opportune times. In particular, sensors and sensor systems that are seamlessly integrated into the structural and functional components, and are capable of withstanding harsh environments, will be the key to the successful implementation of actively monitored system components.
Central to this task is the fact that these state awareness sensors must—ideally—not disturb or alter any aspect of the system it is interrogating. After-market sensors, even if attached during the manufacturing process, can be unreliable, difficult to install, and may adversely affect component operation. A sensor that is directly embedded into the component (written on the structure itself), in a coordinated manner has substantial advantages in terms of reliability, longevity, and minimal disturbance of component function. Coatings provide an ideal platform for integration of such sensors with structures.
This presentation will focus on the integration of sensors into thermal spray coatings using a newly developed methodolodgy. Sensors for physical phenomena including temperature, heat flux, strain, humidity, magnetics have been successfully demonstrated. In addition, it is possible to incorporate thick film electronics through patterning and multilayering strategy. This presentation will provide a description of the capability and salient results
Fatigue Damage and Overload Detection and Monitoring in Landing Gear Steel Components Using Scanning and Mounted Sensor Arrays
N. Goldfine1, D. Grundy2, V. Zilberstein1, D. Schlicker3, (1)JENTEK Sensors, Inc., Waltham, MA, (2)Jentek Sensors, Inc., Waltham, MA, (3)JENTEK Sensors, Inc, Waltham, MA
Early detection of fatigue damage and overload events in landing gear components are critical to avoid in-service failures. Conventional eddy current testing (ET), magnetic particle inspection (MPI), and ultrasonic testing (UT) are limited in capability for complex shape components that are shot peened and cadmium plated. This limitation can be overcome by model-based flexible MWM-Array eddy current sensors. Fatigue tests on coupons and components using both permanently mounted and scanning MWM-Array eddy current sensors are described. This presentation will include results demonstrating (1) rapid permeability mapping with correction for variations in cadmium plating thickness on complex surfaces of landing gear components, (2) overload event detection using scanning arrays and on-board monitoring with permanently mounted sensors, and (3) fatigue damage imaging/monitoring with scanning and permanently mounted sensors. The presentation will also describe adaptive damage tolerance concepts for landing gear life management. This work has been funded in part by JENTEK Sensors, Inc., a USAF SBIR Office and a U.S. Navy SBIR Office.
Application of an Optimal Sensor Placement Algorithm for Structural Health Monitoring of Complex Geometries
W. G. Frazier, Radiance Technologies, Inc., Oxford, MS
While considerable effort has been and continues to be invested in the development of sensor technologies and signal processing algorithms for structural health monitoring, much less effort has been made in the area of how these systems should be configured in terms of how many and what type of sensors are required in order to achieve desired levels of system performance. In general, using as few sensors as possible is desirable, but care must be taken that they are located in positions that provide adequate coverage for detection of undesirable structural changes. This presentation will present a formal design strategy that uses engineering design optimization algorithms and the system theory principles of controllability and observability and finite element models of the structure in question to obtain optimal to obtain an optimal sensor configuration. The presentation will include analysis of the performance of a design produced by this algorithm when applied to a complex three dimensional geometry that undergoes simulated structural changes.
Health Monitoring and Remaining Life Determination in Aircraft Components Using Induced Positron Annihilation
C. Rideout, A. Denison, S. J. Ritchie, Positron Systems, Inc, Pocatello, ID
The Induced Positron Annihilation (IPA) nondestructive evaluation technologies offer the potential to significantly advance the ability to assess component quality level from initial manufacture through failure and the effects of operational damage from a range of mechanisms on critical engine and structural components. The IPA technologies nondestructively and very precisely (~0.1% measurement uncertainty) quantify changes in the actual atomic microstructure of material induced by various damage mechanisms. The IPA technology produces a unique “positron signature” for a material or component. Comparing the IPA responses for new, mid-life, and highly damaged components to operational components with unknown damage levels allows an accurate assessment of current damage and estimates of remaining life to be developed. The IPA technologies have demonstrated the capability to quantify near-surface (1-3 mm sensitivity) damage and the effects of material treatments such as shot peening or thermal barrier coatings and the capability to detect buried damage (2-4 inches sensitivity) in thick multi-layer structures.
The behavior of positrons in materials, and the subsequent measurement and analysis techniques used for the quantification of material signatures and operational effects will be discussed. The differences and capabilities of the Induced Positron Annihilation—Volumetric (IPA-V) and the Induced Positron Annihilation—Surface (IPA-S) will be discussed through the examination of specific case study results: 1) Application of the IPA-S technology to characterize surface and subsurface residual stresses/strains induced through mechanical surface treatments and the effects of component operation in single crystal and complex geometry polycrystalline components, which are used in critical hot-section aerospace turbine engines; 2) Application of the IPA-V technology to detect cracks within Taper-Lok fastener holes associated with thick, multilayer wing structures without removing the fasteners; and 3) Applications of both technologies in a fatigue life study of aluminum, titanium and steel materials.
Comparison of Acoustic Sensing Configurations for Quantifying Impact Damage Events in Thermal Protection Systems
S. Kuhr1, K. V. Jata2, (1)University of Dayton Research Institute, Wight Patterson AFB, OH, (2)Air Force Research Laboratory, Wright-Patterson AFB, OH
The Air Force is developing a Space Operations Vehicle (SOV) that will efficiently and cost effectively transport cargo through space. The vehicle requires a robust thermal protection system (TPS) that will endure extreme temperature and acoustic environments on ascent and reentry of the earth’s atmosphere. However, the thermal protection capability of the TPS will be jeopardized if it undergoes impacts from ground handling or micrometeoroids. Therefore, a method for vehicle health monitoring (VHM) is desired to detect such impacts, improve turnaround times on flight takeoffs and increase the overall possibility of condition based maintenance. In this study, impacts were performed on thermal protection materials at various impact energies. The impacts were detected using commercial and polyvinylidene fluoride (PVDF) sensors. Several configurations were attempted to efficiently characterize the damage induced from a hemispherical impactor. Conventional nondestructive techniques as well as fractographic inspections were also performed to further quantify the amount of damage produced in the materials.
“Damage Evaluation and Analysis of Composite Doubler on Fractured Bonded Repair Coupon Using Fiber Bragg Gratings to Determine Structural Health”
N. Ortyl, S. Kreger, F. T. Taylor, Blue Road Research, Gresham, OR
With the augmented use of high performance composite materials in critical structures, it has become increasingly important for ‘smart’ systems to monitor these materials and provide rapid evaluation. Using fiber Bragg gratings embedded into the weave structure of carbon fiber epoxy composites allows the capability to monitor these composites during manufacture, cure, general aging, and damage. Fiber optic sensors allow greater insight into damage progression and can be used to verify analytical models. This paper emphasizes the results of recent work in which multiple arrays of Bragg gratings were placed in the bond line between a composite doubler (repair patch) and an aluminum test coupon that had a crack machined into it. The sensors were monitored as the test coupon was repeatedly load cycled to failure. Based on the response of these sensors, algorithms were developed to identify the location of damage and to monitor both the status of the bondline and the status of the underlying crack.
“Damage Evaluation and Analysis of Composite Pressure Vessels Using Fiber Bragg Gratings to Determine Structural Health”
N. Ortyl, M. Kunzler, F. T. Taylor, Blue Road Research, Gresham, OR
With the augmented use of high performance composite materials in critical structures, it has become increasingly important for ‘smart’ systems to monitor these materials and provide rapid evaluation. Using fiber Bragg gratings embedded into the weave structure of carbon fiber epoxy composites allows the capability to monitor these composites during manufacture, cure, general aging, and damage. Fiber optic sensors allow greater insight into damage progression and can be used to verify analytical models. This paper emphasizes the results of recent work in which multiple arrays of Bragg gratings were wound into composite vessels and monitored while the part was damaged. Based on the response of these sensors, algorithms were developed to identify the location of damage impacts. Results were verified against eddy current and ultrasonic NDE methods.
SIPS, A Structural Integrity Prognosis System*
J. M. Papazian, E. L. Anagnostou, S. Engel, D. Fridline, J. Madsen, J. Nardiello, R. P. Silberstein, G. Welsh, J. B. Whiteside, Northrop Grumman, Bethpage, NY
The Structural Integrity Prognosis System (SIPS) is being designed to provide prompt, informed predictions of the structural viability of individual assets based on tracking of their actual use and modeling of anticipated usage. The prognosis system is founded on a collaboration between sensor systems, advanced reasoning methods for data fusion and signal interpretation, and modeling and simulation systems.
This talk will present recent results of laboraoty testing of fatigue coupons that were representative of a typical aircraft lower wing structure. During the tests, several novel sensor systems were used to detect and quantify fatigue damage. The sensor output was combined with results from several models of fatigue damage. The models were based on the microstructural origins of fatigue, and included statistical distributions of important microstructural parameters. The models and the sensor data were combined in a prognosis system, and used to predict the outcome of the fatigue tests.. Uncertainty in the sensor data and uncertainty in the various models and their microstructural inputs was explicitly dealt with in the prognosis system. The predictions were compared to post-mortem analysis of cracking in the broken samples.
*This work is partially sponsored by the Defense Advanced Research Projects Agency under contract HR0011-04-C-0003. Dr. Leo Christodoulou is the DARPA Program Manger
Assessment of Fatigue Damage to an Aircraft Wing*
G. Welsh, T. Rovere, J. Quevedo, J. M. Papazian, Northrop Grumman, Bethpage, NY
As part of the development of a Structural Integrity Prognosis System (SIPS), two outer wing panels from a retired aircraft have been destructively examined. The results of this examination will be used to compare the actual damage observed with that predicted by the various models being employed in the program.
Two outer wing panels that were recently retired from service were investigated. They had been fabricated in the late 1970’s and were flown until their fatigue life was judged to be expended. The critical area of the panel was the row of fastener holes in the lower wing cover where it was attached to rib 1. This area of the wing cover was cut out, and the fasteners carefully removed. The condition of each hole was documented, and the corrosion protection coatings were characterized and removed using a two-step procedure. The condition of the holes was documented at each phase of the coating removal process. Eventually, all of the fatigue cracks and manufacturing defects were photographed and their sizes and locations documented. Approximately thirty holes in each panel were analyzed. Crack initiation was found to be primarily associated with constituent particles and/or cracks in the anodized coating. Manufacturing defects (e.g. scratches, gouges, grooves, etc.) accounted for only a small fraction of the cracking.
*This work is partially sponsored by the Defense Advanced Research Projects Agency under contract HR0011-04-C-0003. Dr. Leo Christodoulou is the DARPA Program Manger
Prognosis of Electronic Power Supply Fatigue Failure
A. Dey1, M. Curtin1, G. Krishnan1, R. Tryon2, (1)VEXTEC, Brentwood, TN, (2)VEXTEC Corporation, Brentwood, TN
A prognosis framework for prediction of electronic power supply system failure based upon material fatigue is presented. The method uses a reliability simulation algorithm which accounts for individual interconnect and overall product reliability scale-up. The framework is used to evaluate a board with many interconnects, packages, and devices while considering failure interrelationships. The framework can be used to evaluate non-interconnect fatigue failure modes of electronic circuit boards and digital circuitry. The overall prognosis thrust is based on the fact that most electronic failures are material failures – at the board, at interconnects, within the components (i.e., chips). Additionally, most electronic power supply failures are due to fatigue and fracture of interconnects due to high electronic loadings for these systems. At the foundation of this framework is probabilistic microstructural fatigue crack initiation and total life prediction software.
Model-Based Prognosis of Gas Turbine Blade High Cycle Fatigue
R. Tryon1, A. Iyer2, A. Dey2, G. Krishnan2, R. Holmes2, R. Mathews2, (1)VEXTEC Corporation, Brentwood, TN, (2)VEXTEC, Brentwood, TN
Models to simulate gas turbine blade high cycle fatigue (HCF) failure are presented. The models are integrated into a prognosis capability to predict HCF resistance after a foreign object damage (FOD) event. The capability considers the uncertainty in the FOD condition, dynamic loading, material microstructure and diagnostic data. HCF is predicted as the statistical distribution of the number of cycles to failure (cycle counting) or the probability that the fatigue strength has been exceeded (fatigue limit). The statistical confidence bound are also predicted. The technical approach provides a prognosis capability for situations where it is not possible to directly sense the blade damage state with a high degree of certainty.
Empirical and Model-Based Data Fusion Methods for Corrosion Characterization in Multilayer Structures
C. Coughlin1, D. S. Forsyth1, J. C. Aldrin2, H. A. Sabbagh3, Z. Liu4, (1)TRI/Austin, Austin, TX, (2)Computational Tools, Gurnee, IL, (3)Victor Technologies LLC, Bloomington, IL, (4)Institute for Aerospace Research, National Research Council Canada, Ottawa, ON, Canada
There is a need for improved nondestructive evaluation (NDE) capability to characterize corrosion at faying surfaces in multi-layered aircraft structures to better support fleet management decisions and minimize cost and aircraft disassembly. While NDI techniques are capable of detecting thickness loss at multiple interfaces, they have difficulty quantifying material loss in multiple layers for a specific lateral position, and have not readily addressed the problem of characterizing subsurface pitting corrosion and stress corrosion cracking. The use of multiple NDE methods such as ultrasonic and eddy current have demonstrated the potential of acquiring complementary information to benefit corrosion characterization; however, manual interpretation of multiple data sets can be challenging for an inspector. This work presents the development of data fusion methods to combine data acquired at multiple frequency (or time) scales or using multiple NDE methods for improved corrosion characterization. The application of both empirical and model-based approaches are highlighted in this study. Statistical data fusion methods based on Dempster-Shafer (DS) theory are shown to fuse data at the pixel level from both conventional eddy current and pulsed-eddy current techniques for either multiple frequency levels or time scales respectively. Experimental results for the application of this approach to aircraft corrosion material loss quantification are presented. A model-based data fusion method is also presented for incorporating ultrasonic and eddy current data and NDE models to better characterize pits in first and second layers. Ultrasonic data is used to provide data on first layer corrosion to simplify the second layer eddy current inversion problem. Excellent results have been achieved through validation of the methodology with simulated and real pitting corrosion samples. Lastly, a hybrid approach incorporating both empirical and model-based data fusion methods is discussed to ideally address the corrosion characterization problem.
Probabilistic Methods and Software for Assessing Tradeoffs in Maintenance Programs Incorporating Nondestructive Evaluation and Structural Health Monitoring
E. A. Medina1, J. C. Aldrin2, J. S. Knopp3, D. A. Allwine4, M. Qadeer Ahmed4, J. E. Fisher4, (1)Radiance Technologies, Inc., Dayton, OH, (2)Computational Tools, Gurnee, IL, (3)US Air Force Research Laboratory, Wright-Patterson AFB, OH, (4)Austral Engineering & Software, Inc., Athens, OH
Various structural health monitoring (SHM) technologies have recently been proposed for development and possible implementation. Decision support tools are needed that enable tradeoff and cost-benefit analyses for optimizing the value of inserting these SHM technologies into air- and space-vehicle maintenance programs. This work builds upon the development of VNDE, a software platform for integrating NDE design and product life management models. Based on probabilistic models of fatigue crack growth, detection, and repair, previous VNDE demonstration cases showed the ability of the methodology to assess and optimize effects of changes in inspection parameters and scheduling on time-dependent reliability and maintenance cost objectives. While probabilistic risk management models of the type used in the VNDE software have not yet gained widespread use, they are regarded by many in the maintenance community as a means for achieving extended life at reduced costs while maintaining safety, among other benefits. VNDE can provide a convenient platform for applying probabilistic risk management models, value analysis, and decision support tools to facilitate the implementation of improved maintenance technologies. In this work, the VNDE model has been enhanced by probabilistic model components representing SHM systems and their integration into a hybrid life management approach where SHM and NDE are utilized in a complementary fashion. The combined model addresses the use of SHM systems together with secondary in-field and depot inspections, tracking of repairs and removal from service due to SHM indications, and consideration of SHM system degradation over time. Demonstration cases include the analysis of near- and long-term costs and benefits of SHM applications as used in combination with NDE technologies. The presentation will describe the current status and development plans for the software, and results of tradeoff studies on example aircraft maintenance problems that illustrate the value of these decision support tools and models.
Quantitative NDE and SHM Approaches for Sizing Fatigue Cracks in Aircraft Structures Using Computational Methods
J. C. Aldrin1, J. S. Knopp2, (1)Computational Tools, Gurnee, IL, (2)US Air Force Research Laboratory, Wright-Patterson AFB, OH
Accurate knowledge of crack location and size around fastener sites would improve decision-making concerning maintenance actions, reduce unnecessary teardowns, minimize maintenance induced damage, and provide key information for prognostics programs. The primary difficulty for sizing cracks around fastener sites concerns extracting reliable quantitative measures associated with crack location and size that are also insensitive to the vast array of variable conditions concerning part geometry and condition, material properties, flaw morphology, and the measurement system. Several case studies are presented exploring quantitative NDE approaches for sizing fatigue cracks in aircraft structures using computational methods. First, the use of feature extraction and signal classification algorithms is demonstrated for crack characterization with invariance to noise features for eddy current inspection of fastener sites. Using simulated studies, a promising feature extraction method with broad noise invariance is presented associated with changes in the eddy current response in the circumferential direction. Application of this approach to experimental data is also presented demonstrating the ability of this measure to potentially size cracks around fasteners. Second, the problem of sizing cracks using ultrasonic measurements around fastener sites in multilayer structures is explored. Of particular interest toward gaining a better understanding of this complex 3D ultrasonic scattering problem is the spiral creeping wave, which originates from the incident shear wave and propagates around the fastener hole. Numerical models are presented to study the 3D scattering from holes with cracks to evaluate potential features for crack sizing. Lastly, the problem of sizing cracks around fastener sites with limited accessibility relative to an ultrasonic transducer is discussed. Models and signal processing methods are presented providing insight into the potential to size fatigue cracks around fastener holes in vertical riser structures through an angled-beam shear wave inspection. Concepts for extension of this approach to in situ sensors will also be discussed.
A Meshless Boundary Integral Equation Method for Eddy Current Problems
N. Nakagawa1, Z. Chen2, (1)Iowa State University, Ames, IA, (2)Department of Materials Science and technology,, Changzhou, China
Over the past few decades, the finite element method (FEM) has established itself as a powerful numerical technique for solving various electromagnetic problems. Despite great progress in recent years, the FEM has commonly recognized issues such as the laborious and time-consuming task of meshing three-dimensional bodies of complex shapes. Compared to the FEM, the meshing tasks are generally simpler for the boundary element method (BEM) that requires meshing of the bounding surface of the interest domain only. However, even with the dimensionality advantage over the FEM, the BEM still demands significant tasks of meshing or re-meshing of the boundary surfaces for industrial applications, such as eddy current nondestructive inspection simulations, involving complex geometry components and deformations. For such problems, development of advanced methods with simpler meshing requirements is desirable. Various domain-based and boundary-based meshless methods have been proposed to simplify meshing tasks of the FEM and BEM in the field of computational mechanics. The main idea of the meshless methods is to make approximations entirely in terms of distributed nodes rather than using elements. This paper presents a meshless boundary integral equation method for solving eddy current problems. Using the moving least squares approximation, the proposed method adaptively discretizes the boundary integral equations for electromagnetic fields, and hence retains the meshless attribute of the moving least squares approximation and the dimensionality advantage of the BEM. By solving a two-dimensional eddy current problem for non-trivial boundary geometries, we explicitly demonstrate these features, namely that the method has the potential to achieve better accuracy than the conventional BEM, while alleviating meshing tasks and retaining the dimensionality advantage of the BEM over the FEM. It is anticipated that similar computational advantages and accuracies will manifest themselves for three-dimensional electromagnetic problems, including both electromagnetic wave propagation and eddy current phenomena.
Microanalysis of Full-Scale Components with the World's Largest Chamber-Scanning Electron Microscope
J. J. Frafjord, S. J. Dekanich, B. Bolinger, S. S. Turner, Y-12 National Security Complex, Oak Ridge, TN
The Y-12 National Security Complex has recently purchased a new large-chamber scanning electron microscope (LC-SEM), manufactured by VisiTec, that has the largest chamber in the world at eight cubic meters. The instrument can examine specimens measuring up to 1-m in diameter by 1-m tall and weighing as much as 300-kg. This microscope provides high resolution images at magnifications from 10x to 200,000x, while using a column that moves on a four-axis positioning system around the sample. Now large components can be examined without cutting a small section for the conventional SEM.
Not only can this new instrument examine the physical characteristics of large parts, it can also evaluate the chemical and crystalline properties of the material. Unlike most conventional SEM’s that only have one or two associated analytical tools, the new LC-SEM is unique in that it has a variety of analytical tools designed for nondestructive evaluation. The LC-SEM is equipped with backscattered electron imaging, energy dispersive x-ray spectrometry (EDS), electron backscatter diffraction (EBSD), and Fourier-transform infrared spectrometry (FT-IR). The instrument’s variable-pressure mode adds yet another degree of freedom that enables engineers and scientists to perform critical surface characterization studies of both conductive and non-conductive samples, including metals, ceramics, and intermetallics.
This LC-SEM is a one-stop examination and analytical tool for almost any sample, ranging in size from a grain of sand to a diesel engine. A sample can be fully examined with only one instrument, without cutting the sample and introducing new anomalies to the microstructure. The chamber is also large enough for in-situ experiments such as wear and compression studies. The Y-12 National Security Complex is currently using a new large-chamber scanning electron microscope (LC-SEM) to analyze large and unique components of advanced materials. The LC-SEM, manufactured by VisiTec, has the largest chamber in the world at eight cubic meters and can examine specimens measuring up to 1-m in diameter by 1-m tall and weighing as much as 300-kg. This microscope provides high resolution images at magnifications from 10x to 200,000x, while using a column that moves on a four-axis positioning system around the sample. Now large components can be examined without cutting a small section for the conventional SEM.
Not only can this new instrument examine the physical characteristics of large parts, it can also evaluate the chemical and crystalline properties of the material. Unlike a conventional SEM that only have one or two associated analytical tools, the new LC-SEM is unique in that it has a variety of analytical tools designed for nondestructive evaluation. The LC-SEM is equipped with backscattered electron imaging, energy dispersive x-ray spectrometry (EDS), electron backscatter diffraction (EBSD), and Fourier-transform infrared spectrometry (FT-IR). The instrument’s variable-pressure mode adds yet another degree of freedom that enables engineers and scientists to perform critical surface characterization studies of both conductive and non-conductive samples, including metals, ceramics, and intermetallics.
This LC-SEM is a one-stop examination and analytical tool for almost any sample, ranging in size from a grain of sand to a diesel engine. A sample can be fully examined with only one instrument, without cutting the sample and introducing new anomalies to the microstructure. The chamber is also large enough for in-situ experiments such as wear and compression studies. The Y-12 National Security Complex is currently using a new large-chamber scanning electron microscope (LC-SEM) to analyze large and unique components of advanced materials. The LC-SEM, manufactured by VisiTec, has the largest chamber in the world at eight cubic meters and can examine specimens measuring up to 1-m in diameter by 1-m tall and weighing as much as 300-kg. This microscope provides high resolution images at magnifications from 10x to 200,000x, while using a column that moves on a four-axis positioning system around the sample. Now large components can be examined without cutting a small section for the conventional SEM.
Not only can this new instrument examine the physical characteristics of large parts, it can also evaluate the chemical and crystalline properties of the material. Unlike a conventional SEM that only have one or two associated analytical tools, the new LC-SEM is unique in that it has a variety of analytical tools designed for nondestructive evaluation. The LC-SEM is equipped with backscattered electron imaging, energy dispersive x-ray spectrometry (EDS), electron backscatter diffraction (EBSD), and Fourier-transform infrared spectrometry (FT-IR). The instrument’s variable-pressure mode adds yet another degree of freedom that enables engineers and scientists to perform critical surface characterization studies of both conductive and non-conductive samples, including metals, ceramics, and intermetallics.
This LC-SEM is a one-stop examination and analytical tool for almost any sample, ranging in size from a grain of sand to a diesel engine. A sample can be fully examined with only one instrument, without cutting the sample and introducing new anomalies to the microstructure. The chamber is also large enough for in-situ experiments such as wear and compression studies.
Portable XRF Analyzer for Cost-Effective, Nondestructive Evaluation of Metals and Alloys
D. Sackett, K. A. Russell, Innov-X Systems, Inc., Woburn, MA
Portable XRF Analysis is a powerful, cost-effective, and non-destructive metal and alloys evaluation method. Integration of miniature x-ray tubes and power supplies, multiple filter wheels and variable rate kV-mA, pocket PC technology and advanced data analysis software give comprehensive testing results in seconds. This technology allows quick and easy QA/QC, incoming materials screening, stock sorting, critical component verification and validation, confirmation of MIL certs and other specs, and in-process PMI. Portable XRF is a cost-effective solution when everything and anything must be tested, small consumables to large assemblies. Lightweight pistol grip, extended probe head, and removable handle make it easy to test piping, welds, flanges, joints, solder, small or rounded pieces. Novel shock-proof mounting and heat-sink tube compensate for extreme vibration or temp (600-800F) conditions. Tool-belt holster allows easy Analyzer transport. Belt-mounted battery pack is for quick power change outs during long shifts. Pocket PC technology allows off-the-shelf, flexible software and exceptional graphical user interface. Value-added accessories - global positioning, binary storage, multiple language display, and wireless email and data transfer to central computers or portable printers - are commercially available. In seconds and with ease, one can ID and sort high temp alloys, Cu-alloys, electronics, precious metals and exotics. For mixed low Cu-Al loads, one can confidently sort most common wrought Al-alloy grades – including 6061/6063. Ferrous can be sorted by <0.05% Cr content. SmartBeam technology allows accurate analysis of Ti and V (0.05 to 0.5% range) for separation of critical alloys in seconds – 304 & 321, P91 & 9Cr, Ti7 & CPTi. Factory-stored alloy grades – UNS #s, ASME, Mil Specs, common names - and user-specific customized libraries allow for the Fast ID Mode. Portable XRF is a cost-effective solution for the evaluation of standard, specialized and proprietary metals and alloys. Specific applications and performance data will be presented.
Advanced Metallic and Hybrid Structural Concepts for Future Aircraft
J. Liu, Alcoa, Inc., Alcoa Center, PA
There has been a fundamental shift in aerospace R&D programs, with broader scientific and engineering portfolios to create integrated, strategic, long-term initiatives that will redefine the future performance, cost and value of the metallic and hybrid aerostructures that are needed to meet the mission requirements of tomorrow’s aircraft. It is important that we execute internal and collaborative, external programs that will revolutionize materials, structural design and assembly for the coming generations of commercial aircraft. Following intense studies of various structural options, it appears that Hybrid Structural Assembly optimized with a combination of Advanced Metallic and Hybrid Components offer the best opportunities to maximize structural performance; especially when coupled with new alloys that have already resulted in dramatic improvements in corrosion resistance. Even with higher operating stresses, Advanced Metallic and Hybrid design concepts show the potential for multi-fold increase in spectrum fatigue crack growth life. The performance potential of combined Advanced Metallic and Hybrid Structure will create a new S-curve for structural performance – surpassing all of today’s uni-material structures. In this presentation, several advanced structural concepts targeted for wing and fuselage applications and large scale test article results will support optimism for Advanced Metallic and Hybrid Structures. Potentials for structural cost reduction via Advanced Hybrid designs will also be discussed.
Suitable Powders for Kinetic MetallizationTM
R. M. Tapphorn, H. Gabel, J. Henness, Inovati, Santa Barbara, CA
Kinetic Metallization (KM) is an emerging technique for applying metallic and metal-matrix coatings to metallic, ceramic, and polymeric surfaces. This impact consolidation technique provides significant benefits over many other coating technologies which include low temperature (minimizes thermal degradation of the coating or substrate), environmental compliance, and requires no masking. Kinetic Metallization uses friction compensated sonic nozzles that are optimized for accelerating powder particles to velocities sufficient for applying coatings at low operating pressures. Low operating pressures equate to decreased gas consumption, leading to low operating cost. Particles acceleration, via drag force, is inversely proportional to powder particle mass. Therefore, KM requires particle sizes with a maximum upper limit. High quality, low porosity, high deposition efficiency KM coatings are produced with powders of a specific particle size and particle size distribution. This presentation will focus on the relationship between particle size and the velocities required for impact consolidation of powders. In addition, the influence of particle size distribution on the quality of the coatings in terms of density and purity will be presented.
HVOF Alternative: Kinetic MetallizationTM WC-Co Coatings
J. A. Henness, R. Tapphorn, H. Gabel, Inovati, Santa Barbara, CA
Kinetic Metallization (KM) allows deposition of fully dense tungsten carbide-cobalt (WC-Co) coatings with tailorable hardness over an expanded range of 700 - 1400HV. Hardness is functionally related to the concentration of the tungsten carbide in the cobalt matrix, carbide particle size, and carbide grain structure. The enabling technology is a range of Inovati developed KM WC-Co powders with average carbide particle sizes from <1 to 4-5 micron. As a results of these developments, the National Science Foundation (NSF) awarded Inovati a Phase I Small Business Innovation Research (SBIR) grant to develop nano-grain structured WC-Co. We anticipate that KM coatings produced with this powder will exhibit hardness of up to 2000HV. Low temperature Kinetic Metallization is uniquely capable of depositing this powder without decarburization or thermal degradation (i.e. no loss of nano structure). Kinetic Metallization is a low temperature deposition process and offers advantages over the High Velocity OxyFuel (HVOF) thermal spray process including minimal surface pretreatment and no masking. In addition, no pre, post, or in process thermal management is required. Along with these technical advantages, KM is 20-30% less expensive than HVOF and safer to operate.
Kolsterising®: Unique Surface Hardening of Austenitic Stainless Steel
P. T. Dymond, Bodycote Thermal Processing, Santa Fe Springs, CA
The Kolsterising® process is a proven method for the surface hardening of austenitic stainless steel by the diffusion of carbon. Developed in the Netherlands over twenty years ago, the technology is now being further developed in North America. This paper intends to highlight the improvements typically seen in key mechanical properties, including resistance to galling, wear resistance, fatigue life, and resistance to pitting and stress corrosion cracking. Untypically, due to the nature of the process, these properties are generally improved without the usual associated reduction in corrosion resistance. Property improvements will be demonstrated using test data from Europe and North America.
Copper-Nickel-Indium, a Classic Basis for Coating Development
R. K. Betts, Cincinnati Thermal Spray, Inc., Cincinnati, OH
The enigma of fretting as a wear phenomenon with consequences of fatigue-life reduction in machines of many kinds, is well recognized. Incursion of jet engine propulsion into aircraft piston engine realms further raised imperatives for performance and reliability of both military and commercial aircraft. Jets became Fan engines, propelling by-pass air, improving primary thrust efficiency. Engines enlarged, and Ti alloys, with fortuitous strength-weight ratios, were introduced. However, compromised by wear, Ti alloy surfaces may be sensitized to fatigue crack initiation, thus requiring effective coating protection to assure reliability. Thermal spraying has been utilized for this from the earliest days of jet engine service. Review traces origins, testing and adaptation of unique Cu-Ni-In thermally-sprayed wear-resisting coating for aircraft turbine engines. Wear effects upon Ti-6Al-4V alloy and coatings are compiled from patent, contract and unpublished research literature, including dedicated machines built for simulative sliding and fretting modes. Specimens were first subjected to sliding wear at increments up to 10,000 cycles of 0.006 inch stroke, under 50,000 psi contact stress, with friction history continuously monitored. Materials were evaluated by relating friction to surface disruptions such as striations, galling, and debris. In-situ fretting was generated under high-cycle fatigue conditions. Fatigue tests quantified integrity reduction due to wear, providing baselines to specifically qualify wear protection afforded by coatings.
Cu-Ni-In, augmented by MoS2-based dry film lubrication, emerged as the most effective system. Applied to both surfaces, assuring no disruption of Ti surface integrity, it is shown durable for wear cycles up to prescribed limits, with friction coefficients remaining less than 0.06. Fretting fatigue life run-out exceeded 106 cycles. Specialized plasma spray facilitizing is described for production coating of engine components. Attributes of Cu-Ni-In and other materials from contracted research are characterized, providing a basis for ongoing studies toward improved protection methods.
Phase Formation at Condensation of Vapor Stream and Reaction Diffusion
T. Melor, M. Okrosashvili, Georgian State Technical University, Tbilisi, Georgia
The objective of the investigation is to study transition zone and microstructures formed through condensation of titanium stream on the cupper backing and reaction diffusion; development of possible mechanism of phase formation, that can explain regularities of structure formation in transition zone.
Specimens for investigation were obtained in the electron-beam installation. Structure analysis and study of the character of elements distribution over a cross-section area were performed by metallographic and scanning electron microscopes and micro-roentgen spectral analyzer. X-ray structural analysis by means of defractometers.
It has been studied structures of constituents, phase composition and character of relative positions (mutual arrangement) in the Cu-Ti transition zone formed due to condensation of vapour stream and reaction diffusion.
It is shown that constituents of presented phases and structures are formed as continuous and consequently interchangeable zones from the vapour phase according to rising the concentration of the components. It is shone existence of high-temperature phase and non-equilibrium evtectic (ζ+ λ) in the transition zone and possibility of formation of TiCu8 (a new phase) with titanium content of 10,49 atomic percent. Metastable phase exists as stable compound. Two main mechanism of phase formation is suggested that can explain terms of formation of interchangeable zone.
It is ascertained regularity of phase formation in the transition zone at condensation of titanium vapour on the copper backing and reaction diffusion. On the base of generalization of the experimental results it is suggested the mechanism that explains phase formation.
Key words: vapour, condensation, transition zone, phase formation, structure, mutual arrangement, relative position, interchangeable zone, reaction diffusion, copper backing.
Field Repair of IVD Aluminum Coatings on High Strength Steels Using Kinetic MetallizationTM
R. M. Tapphorn, J. A. Henness, D. Arnold, M. Esposito, Inovati, Santa Barbara, CA
Inovati began using Kinetic Metallization commercially 5 years ago. The first commercial application was aluminum composite coatings called Al-Trans® to steel telecommunication equipment racks. These coatings provide electrical conductivity coating for high-frequency grounding of telecommunications equipment. Al-Trans® has demonstrated adhesion strength in excess of 10-ksi with corrosion resistance in excess of 5000 hrs in neutral salt spray per ASTM B117. Recently, the US Navy awarded Inovati a SBIR Phase II contract to develop and qualify methods of IVD aluminum field repair on high strength steels. Performance testing of Al-Trans® (aluminum blended with a transition metal), nano Al-Trans®, and CP aluminum coatings applied to high-strength steels with Kinetic Metallization will be presented in terms of adhesion strength and corrosion resistance. A portable KM system with handheld applicator is used to apply field repair coatings. Inovati is developing techniques for manually rastering the handheld applicator. Acceptance criteria include uniform deposit thickness and a minimum repair thickness of 1 mil.
Kinetic MetallizationTM Coating Development System
H. Gabel1, R. Hanson2, (1)Inovati, Santa Barbara, CA, (2)Timken Super Precision, Keene, NH
Kinetic Metallization (KM) uses friction-compensated sonic nozzles to accelerate fine powder particles to speeds sufficient to create coatings on a variety of materials through solid-state impact consolidation. The efficiency of the KM sonic nozzle allows operation at low gas pressures and temperatures, and provides optimum particle velocities for highly dense coatings. A wide variety of coatings of metals and metal matrix composites are possible. Inovati has developed new technology enabling features for the KM Coating Development System that permits users with a wide range of backgrounds and experience to explore custom coating applications. Technical specifications for the latest model of the KM Coating Development System (the KM-CDS 2.1) are presented, and potential applications discussed. A key feature of the KM-CDS 2.1 system is a new powder-fluidizing unit that permits feeding of nano-sized and ultra-fine powders which are highly agglomerating. Properties of some of the recent coatings produced with the KM process will be summarized.
Fatigue Crack Growth Analysis in Complex Residual Stress Fields
R. C. McClung1, B. M. Gardner1, Y. D. Lee1, J. E. Pillers2, J. O. Bunch3, (1)Southwest Research Institute, San Antonio, TX, (2)The Boeing Company, Seattle, WA, (3)Boeing Integrated Defense Systems, Seattle, WA
Methods for damage tolerance assessment of aerospace structures based on fatigue crack growth analysis are reasonably well established in industrial practice. However, methods to treat the effects of residual stresses on the fatigue behavior of the same structures are not so well established. These residual stresses may arise from surface enhancement processes such as peening or cold expansion of holes, and they can also arise from local plasticity at stress concentrations. While fundamental approaches have been proposed, several significant issues remain unresolved, including three-dimensional spatial variations in residual stress fields, as well as the potential relaxation and redistribution of the residual stresses due to static mechanical load, repeated cyclic loads, thermal exposure, or crack extension.
This technical gap is particularly inconvenient for the development and optimization of new surface enhancement methods such as laser shock peening (LSP). Numerous LSP process parameters can be adjusted to generate different residual stress states in specific component geometries and materials. However, it has not been possible to predict analytically which residual stress states would provide the greatest improvements in fatigue life or damage tolerance capacity in service. Instead, expensive trial-and-error sequences of fatigue experiments have been required.
This presentation describes recent advances in fatigue crack growth analysis methods directed at residual stress effects. The advances include new stress intensity factor solutions that address complex bivariant stress gradients on the crack plane, and elastic-plastic analyses of local material response associated with the formation and modification of residual stress fields. The methodology is implemented in a special version of the NASGRO fracture mechanics analysis software and evaluated by comparison with experimental crack growth data on laboratory coupons containing residual stresses induced by overload plasticity or by surface enhancement methods.
X-Ray Diffraction Technology: The Current State-of-the-Art for Measuring Residual Stress Due to Surface Treatments in Aerospace Structures
M. Brauss, J. Pineault, M. Belassel, R. Drake, Proto Manufacturing Incorporated, Ypsilanti, MI, Canada
Quantitative residual stress characterization of surface treatments in actual aerospace structures and materials is critical to the understanding of structural behavior. Residual stresses due to surface treatments are important in the prediction of fatigue life, in assessing the potential for stress corrosion cracking (SCC), and in the optimization of the surface treatment applied. It has been common practice in the past to assume certain levels of residual stress. However, because of important advances in the state-of-the-art of x-ray diffraction (XRD) and residual stress (RS) measurement technologies this is no longer necessary. More importantly, robust XRD systems and appropriate components are currently available that enable the quantification of RS in aerospace materials and structures in situ, i.e. in the assembled state.
The challenges put forth by aerospace engineers, OEMs, users and maintainers have led to significant developments and numerous advancements in XRD RS technologies. These challenges are best reflected by such equipment characteristics as “smaller, faster, lighter, more accurate, more reliable, more rugged and more portable.” These characteristics have been translated into current technology that exhibits greatly improved accessibility to increasingly tighter and more confined locations in aerospace structures. Evolutionary technological improvements have been applied where appropriate but more revolutionary concepts have also been implemented to achieve the required levels of miniaturization.
Prediction and Experimental Validation of Residual Strees in Turbine Engine Airfoils
M. R. Hill, University of California, Davis, CA
Laser Peening (LP) and Low Plasticity Burnishing (LPB) are two recently emerging surface treatment technologies capable of introducing residual stress deep into a treated surface. While judicious use of these treatments is often of significant benefit to structural component fatigue lives, their misapplication can sometimes lead to excessive component distortion or degrade component fatigue performance through compensating tensile residual stress. Also, during development, there can be a disconnect between successful laboratory treatments and in-field component trials, where slight changes in geometry, loading, and surface treatment application can interact to wreak havoc. Applications of these treatments, therefore, have relied on carefully implemented empirical approaches to provide intended benefits. A computational design tool for residual stress and fatigue analysis could eliminate much of the costly empirical burden imposed by such difficulties. This paper describes a computational design tool applicable to LP and LPB treatments. Although the approach is general and applicable to a range of structural configurations and surface treatments, example results are provided for LP applied to the leading edge of turbine engine airfoils to suppress crack growth due to Foreign Object Damage (FOD).
Finite Element Modeling of the Dynamical Contact between a Compressor Blade and an Abradable Thermally Sprayed Coating
J. L. Seichepine1, F. Peyraut1, H. I. Faraoun1, C. Coddet2, (1)University of Technology of Belfort-Montbeliard, Belfort Cedex, France, (2)University of Technology Belfort-Montbeliard, Belfort Cedex, France
Abradable seals are located on the statical parts of gas turbines, in front of blades, allowing them to cut a track, but this has to be achieved with minimum wear, in order to control the over-tip leakage. These coatings are usually validated by rig tests, where samples are rubbed by the contact of a dummy blade with given running speed and incursion rate, simulating actual working conditions in an aircraft engine. The aim of this work was to develop a finite element model of abradable coating rig tests, allowing extensive studies on the influence of coating properties and test conditions on their performances. The FE code ANSYS was used to simulate a single contact between a blade and a part of the abradable coating. Target and contact elements were used to model the contact between both parts. The coupling of thermal and mechanical analyses is allowed by these elements, where the heat generation due to frictional dissipated energy is computed. For the coating, an elastic linear orthotropic law of behaviour was set up, with the parameters issued from previous works on abradable materials modelling. The motions of the two parts during the tests were simulated by dynamical displacements. An initial incursion of the blade into the coating was taken into account by an initial distortion of the mesh, resulting from a preliminary static calculation. Relevant algorithms and pertinent parameters were chosen for the contact analysis, the non-linear analysis and the dynamical analysis. The results obtained for reference coatings were dynamical fields of stresses and temperatures, for several sets of inlet parameters. Comparisons between the maximum computed values in each studied case and the corresponding blade wear measurements showed some consistency. Furthermore, these results contribute to explain why different test rigs work sometimes differently.
Engineered Residual Compressive Stress – Deterministic Approach via Laser Peening
L. Hackel1, C. B. Dane2, F. Harris2, J. Rankin1, C. Truong2, (1)Metal Improvement Co., LLC, Livermore, CA, (2)Metal Improvement Company, Livermore, CA
Laser peening is a qualified process, highly deterministic in its application, that is in reliable production use extending the fatigue life and stress corrosion cracking resistance for aerospace and automotive alloys. Deterministically applied stress enables engineers to systematically call for residual stress to the intensity and depth desired so as to achieve design goals. The process employs a unique solid state laser system with 1GW peak power, real time adjustment of power density and relatively high repetition rate. Each laser pulse is directed on to the metal surface creating a highly controlled pressure wave that is capable of imparting residual compress stress. Through control of laser power density, pulse duration and percent coverage, the depth and intensity of the compressive stress is precisely controlled on a point by point basis. Residual stress as deep as 10 mm in specific materials can be generated with several repetitive layers of peening. Shallow peening with less intense surface stress is achieved using lower laser fluence, smaller spot size or pulse duration and minimal layers of coverage. Each of these parameters is precisely controlled with each laser pulse and recorded for quality assurance in processing. Over 15,000 wide chord fan blades and blade hubs have been laser peened for operation in commercial jet engines. Fixed systems are used to treat meter scale components and transportable systems handle field operations directly on large structures. The technology has been FAA/JAA certified and ISO 9001 approved. A broad range of materials are in production or development, including but not limited to Ti 6-4 (alpha and beta and BSTOA), 300M and 9310 steels, Al 7050, and Al 2024, Al 5059 and MP35N and C22 corrosion resistant alloys. The Authors will describe the system and present materials performance data contrasting as-machined and shot peened to laser peened results.
Turbo-Abrasive Machining for Edge and Surface Finishing
M. Massarsky1, D. Davidson2, (1)Turbo-Finish Corporation, Barre, MA, (2)Deburring/Surface Finishing Specialist, Spokane, WA
Turbo-Abrasive Machining [TAM] is a mechanical deburring and finishing method originally developed primarily to automate edge finishing procedures on complex rotationally oriented and symmetrical aerospace engine components. Since its inception this method of utilizing fluidized free abrasive materials has facilitated significant reductions in the amount of manual intervention required to deburr large components by these manufacturers. Additionally, the process has also proved to be useful in edge and surface finishing a wide variety of other non-rotational components by incorporating these components into fixturing systems. The advantages of this method go beyond the simple removal or attenuation of burrs. The method is also capable of producing surface conditions on these critical edge and surface areas that contribute to increased service life and functionality of parts that are severely stressed in service. Among these are: (1) the creation of isotropic surface conditions. (2) the replacement of positively skewed surface profiles with negative or neutral skews and (3) the development of beneficial compressive stress and development of a stress equilibrium among part features
Laser Peening for Improved Fretting Fatigue Life
D. Sokol1, A. Clauer1, D. Lahrman1, D. See2, L. Bernadel3, (1)LSP Technologies Incorporated, Dublin, OH, (2)USAF Air Force Research Lab, Wright Patterson AFB, OH, (3)Navair, Patuxent River, MD
Laser peening has been a commercial surface enhancement process for over six years, and the number of applications has been gradually expanding. A new use for laser peening involves increasing the fretting fatigue resistance of Ti-6Al-4V and other titanium alloys. Fretting fatigue is a problem associated with many mechanical systems where there is metal-to-metal contact under vibrating load conditions. This is a particular concern in some aircraft engine components such as the contact surfaces between the dovetail attachments of the engine airfoils or blades and the disk slots in which they are seated in the rotating disks. Laser peening has the potential to enhance the resistance of these components to failure by fretting fatigue.
Fretting fatigue tests were performed at
Small spot laser peening enables the processing of the inside of small, generally inaccessible areas such as the insides of holes and dovetail disk slots. A review of the of the process equipment and fatigue results will be presented.
Inertia Weld Repair of Damaged Holes using StressWave Cold Working
M. Landy1, E. T. Easterbrook1, J. E. Pillers2, B. Zlicaric3, (1)StressWave Incorporated, Kent, WA, (2)The Boeing Company, Seattle, WA, (3)Boeing Integrated Defense Systems, Seattle, WA
A structural repair method for reworking damaged titanium structure using inertial welding has been developed. Damage is removed from the structure by drilling slightly tapered holes or series of holes within the repair area. Tapered titanium plugs are then inertially welded into the holes using a automated machine tool that accurately controls rotational speed, applied force and displacement. By controlling the welding parameters using continuous feedback the plug is perfectly bonded to the hole wall with minimum change to the base mechanical property and grain structure. The residual stresses resulting from the localized frictional heating and subsequent cooling are mechanically stress relieved using the StressWave cold working process. The StressWave process can also be used to impart beneficial compressive stresses around the plug giving the repaired area better fatigue life than the base material. In many cases disassembly of the structure is not required prior to repair as the heating is very localized. The process parameter of the entire process are well predicted and allow for a high degree of automation. Fatigue cracks at holes and battle damaged structure can be readily repaired.
Numerical Simulation of the HR15Y Hardness Test of Abradable Thermally Sprayed Coatings
F. Peyraut1, J. J. Seichepine2, H. I. Faraoun2, C. Coddet3, M. Hertter4, (1)University of Technology of Belfort-Montbeliard, Belfort Cedex, France, (2)Belfort-Montbéliard University of Technology, Belfort Cedex, France, (3)University of Technology Belfort-Montbeliard, Belfort Cedex, France, (4)MTU Aero Engines GmbH, München, Germany
The aim of our work is twofold. The first objective is to compute abradable material parameters by an optimization process directly connected to a FE analysis. The second objective of this work is to perform an extensive study of the influence of coating thickness on hardness by using a finite element model of the HR15Y hardness test. To identify plastic parameters by indentation test, material properties are fitted in such a way that measured and computed hardness are matched. By using the FE code ANSYS and assuming a bilinear plastic law for the coating, the difference between measured and computed hardness has been minimized. Among various methods offered by ANSYS, the first order optimization method is selected to achieve the optimal solution and excellent agreement between computed and measured hardness has been found. To match up experimental and computational results, two coating thicknesses (1.2 and
Overview of Titanium Applications on Advanced Commercial Transports
G. A. Tomchik, T. G. Dunder, Boeing - 787 Airplane Integration, Seattle, WA
Commercial aircraft designs are transitioning from primarily aluminum construction to primarily composite structures. Titanium's unique compatibility with Carbon Fiber Reinforced Polymer (CFRP) composites has spurred a significantly increased usage of titanium. This increased usage of titanium has created new requirements and opportunities for titanium fabrication technologies, new alloys, and improved processing methods. In many cases components that traditionally were fabricated from aluminum are now made from titanium due to it's superior corrosion resistance, strain rate compatibility and thermal expansion characteristics when coupled with CFRP components.
This presentation discusses, from a design perspective what properties and characteristics are needed from titanium components. It will also compare and contrast the forms of titanium components on primarily composite commercial aircraft designs with titanium structure used on previous commercial and military aircraft.
With the replacement of significant portions of aluminum structure with titanium in commercial transports, new challenges are created due to the higher costs of titanium, more difficult fabrication, and relative immaturity of high-volume production equipment and processes when compared to aluminum. This presentation will explore many opportunities for development of titanium production methods, new requirements for alloys and processing methods, and the need to develop new, improved and more automated fabrication processes.
Overview of Single-Hearth-Melting of Titanium Alloys for Aerospace Applications
R. Boyer1, T. Bayha2, E. M. Crist3, J. Fanning4, D. Tripp5, K. O. Yu6, (1)The Boeing Company, Seattle, WA, (2)ATI Allvac, Monroe, NC, (3)RTI International Metals, Inc., Niles, OH, (4)TIMET-R&D, Henderson, NV, (5)TIMET, Morgantown, PA, (6)RMI Titanium Company, Niles, OH
Production of Ti-6Al-4V and other titanium alloys by single by Electron-Beam Single-Melting (EBSM) or Plasma Arc Melting (PAM) offers the opportunity of cost savings in aerospace and other applications. The cost savings of single hearth melting are related to ingot shape, increased scrap utilization and/or economies of scale. Since the single hearth melting production method is substantially different from the traditional vacuum arc re-melting (VAR) production method, extensive testing and evaluation has been performed on the single melt product to ensure that the properties and quality are equivalent to those of the traditional product. These evaluations have included static mechanical properties, chemical homogeneity, fracture toughness, fatigue crack growth resistance, high cycle fatigue and ballistic properties. Additionally, production experience has demonstrated that single hearth melted titanium alloys can be welded, machined, and fabricated into structural components using similar techniques as those that currently exist for traditional VAR product.
Update of RTI's PAM Single Melt Technology Development
K. O. Yu1, E. M. Crist2, (1)RMI Titanium Company, Niles, OH, (2)RTI International Metals, Inc., Niles, OH
For the last several years, RTI has worked on the development of PAM single melt technology, and some of the results have been reported in previous AeroMat meetings. This presentation will update the status of this development effort. Products to be discussed include plates, sheets, bars, and extruded shapes and tubulars. Alloys include Ti-6Al-4V and Beta C.
Electron-Beam Cold Hearth Melting for Ti-6Al-4V (ELI) Plate Materials
T. F. Soran1, E. J. Haas1, T. Bayha2, (1)ATI Allvac, Richland, WA, (2)ATI Allvac, Monroe, NC
As a part of the Air Force Research Laboratory-sponsored Metals Affordability Initiative (MAI) Consortium program, Ti-6Al-4V ELI alloy plate products were manufactured from single melt, electron beam cold hearth melted (EBCHM) slab ingots. The main objective of the program is to achieve significant cost savings for the EBCHM single melt slab product compared to the standard double VAR round ingot processing route. Reduced production cost results from the use of less costly input raw materials, higher melt rates, fewer melt and hot work process steps, and improved yields compared to the standard double VAR processing route. Melting large quantities of Ti-6Al-4V alloy in an EBCHM furnace presents challenges. High vapor pressure elements such as Al vaporize preferentially from the molten pool in the high vacuum of EB furnaces. The vaporization loss is a function of a number of variables including raw material makeup, raw material feed method, gun performance, melt rate, as well as hearth and casting surface area. Control of Al in the final product involves the use of a number of tools including raw material chemistry control, mathematical modeling, feedback controls and operator experience. Raw material must be chemically homogenous in order to have consistent chemistry in the final product. The MAI program has previously demonstrated that the EBCHM process can produce standard grade Ti-6Al-4V ingots with both chemical homogeneity and resultant mechanical properties that are equivalent to current, double vacuum arc remelted (VAR) ingots. AMS 6945 was published for standard Ti-6Al-4V flat-roll products. ATI Allvac Standard plate processes have been applied for manufacture of beta-annealed Ti-6Al-4V (ELI) plate products up to 3” thick, and both static and dynamic mechanical test data have been generated. A summary of the microstructure and rolled plate test data will be presented.
The Manufacture of Advanced Titanium Alloys by Electron Beam Single Melt (EBSM)
D. Tripp1, J. Fanning2, Y. Kosaka3, S. Nyakana4, M. McCann3, (1)TIMET, Morgantown, PA, (2)TIMET-R&D, Henderson, NV, (3)Timet, Henderson, NV, (4)TIMET, Henderson, NV
Electron Beam Cold Hearth Melting has been successfully used for many years for the manufacture of commercially pure titanium materials. In the last 5 years, TIMET has developed electron single melted [EBSM] Ti-6Al-4V for land based military and aerospace applications. In addition to Ti-6Al-4V and CP, EBSM is appropriate for other alloys. In this paper, we will discuss developments in the production of TIMETAL 21S, TIMETAL 54M and examine the potential for melting other alloys using this technology.
Chemical Homogeneity of Titanium Alloys Produced by EBSM
S. Nyakana1, M. McCann2, (1)TIMET, Henderson, NV, (2)Timet, Henderson, NV
Ti-6Al-4V products made by EBSM were sectioned and systematically analyzed to determine chemical homogeneity. Product results are compared to corresponding dip-sample results obtained during melting.
"Armstrong," Development of a New Titanium Manufacturing Industry for America
S. Borys, International Titanium Powder LLC, Lockport, IL
The Effect of Low-Cost TiCl4 in Titanium Powder Processing
C. A. Lavender1, K. S. Weil2, M. T. Smith1, Y. Hovanski1, (1)Battelle Memorial Institute, Pacific Northwest National Laboratory, Richland, WA, (2)Pacific Northwest National Laboratory, Richland, WA
A recent cost study commissioned by the Department of Energy and prepared by Camanoe Associates concluded that the use of a low-cost titanium ore as the feedstock source in a continuous reduction process could drive down the cost of titanium sponge and powder substantially, to the point that it could be considered for application in standard automotive components. Pacific Northwest National Laboratory (PNNL) is currently leading a program to develop this low-cost titanium processing stream. Working with E.I. DuPont de Nemours and International Titanium Powder (ITP), PNNL has employed low-cost, ilmenite-derived titanium tetrachloride (of the type used titanium dioxide paint pigment production) as the precursor in titanium powder synthesis. The resulting titanium powders, while containing additional impurities are being evaluated for powder metallurgy (P/M) processing. Progress on powder characterization and P/M processing will be reported.
Titanium Alloy Ti-5111 in Naval Applications
E. J. Czyryca, Naval Surface Warfare Center, Carderock Division, West Bethesda, MD
Titanium and its alloys are finding increasing applications on U.S. Navy surface ships and submarines. The physical, mechanical and corrosion properties of titanium favorably impact current U.S. Navy ship design requirements for increased reliability with reduced maintenance, reduced weight, and shock integrity. Based on the excellent erosion-corrosion properties of titanium, commercially pure grades are used extensively for seawater pumps, cooling and piping applications on surface ships and for a number of seawater system components on submarines. For high-strength critical applications, the US Navy is using Ti-5Al-1Sn-1Zr-1V-0.8Mo (Ti-5111) alloy in lieu of Ti-6Al-4V ELI due to its high toughness, weldability, and seawater stress corrosion cracking resistance.
This presentation will describe the advantages of titanium in ship applications and systems where the use of titanium is service proven. The focus will be on the results of studies to characterize the strength, fracture toughness, fatigue, and seawater corrosion/stress corrosion resistance properties of the Ti-5111 alloy, including the results of fracture testing under dynamic conditions. The characterization of Ti-5111 products has included evaluation of plate for ¼ to 2 inches thick, rod, bar, forgings, and castings. One and two inch thick weldments were fabricated by the gas tungsten arc welding process using standard titanium joint preparation and shielding techniques. The results of tensile, fracture toughness, and seawater corrosion/stress corrosion resistance tests demonstrated that Ti 5111 welds possess high strength, good fracture toughness and excellent resistance to seawater corrosion. In addition, the presentation will describe current and candidate applications of this alloy for Navy combatant ships.
Synthesis of Powder Metallurgy Titanium Using Hydrogenated Titanium
O. M. Ivasishin1, D. G. Savvakin1, V. S. Moxson2, V. Duz2, A. N. Petrunko3, F. H. Froes4, C. A. Lavender5, (1)Institute for Metal Physics, National Academy of Sciences Ukraine, Kiev, Ukraine, (2)ADMA Products, Twinsburg, OH, (3)State Titanium Research and Design Institutute, Zaporoshye, Ukraine, (4)University of Idaho, Moscow, ID, (5)Battelle Memorial Institute, Pacific Northwest National Laboratory, Richland, WA
Powder metallurgy (P/M) is an attractive method to reduce the cost of titanium components provided a low cost powder supply can be developed; One low-cost powder under development is titanium hydride. In the present study 98+% dense compacts of Ti-6Al-4V alloy were produced by blending titanium hydride with elemental powders and consolidating with conventional press-and-sinter techniques. The compacts were evaluated for microstructural homogeneity, residual hydrogen, mechanical properties including fatigue and tension tests, and uniformity of density. The advantage of hydrogenated titanium approach in attaining uniform high relative density and sufficient tensile and fatigue properties for P/M titanium components will be discussed.
Static, Fatigue, and Fracture Properties of Laser Additive Manufactured Ti-5-5-5-3
H. N. Chou, B. Slaughter, Boeing Phantom Works, St. Louis, MO
The test was sponsored by Hybrid Material Deposition and Removal project
in Center for Aerospace Manufacturing Technologies program. The program
mission is to serve as a center of excellence for research, development,
evaluation and demonstration of new and optimal methodologies and tools
for rapid and affordable manufacture of aerospace products. The program
was contract funded by Air Force Research Laboratory with cost match
from Boeing. University of Missouri at Rolla provided technical support.
Titanium 5Al-5V-5Mo-3Cr wrought and casting exhibited higher mechanical
properties than 6Al-4V titanium alloy products and offers good potential
for aerospace applications. This presentation summarized the machining
and tests of Laser Additive Manufactured (LAM) Ti 5Al-5V-5Mo-3Cr
specimens excised from three (3) powder deposited test panels. One panel
was as-deposited, one panel was solution treated and aged for high
strength, and one panel was beta annealed slow cooled and aged for high
toughness.
A total of 88 specimens were tested in different test matrix. They
included 52 tensile at room and elevated temperatures, 4 fracture
toughness, 2 compact tension for fatigue crack growth, 12 strain-life
for fatigue crack initiation, and 18 open hole fatigue. All the fatigue
tests were performed at room temperature. The specimens were machined
from the 3 panels in accordance with Boeing drawings. In addition, 6
metallography specimens were di-sected from the panels for evaluation.
The specimens were NDT inspected and met Boeing requirements. The
mechanical tests were performed in accordance with applicable ASTM
specifications and the Boeing test matrix in laboratory environment. The
test results from the LAM Ti 5Al-5V-5Mo-3Cr panels are discussed in the
presentation and were also compared with those generated from LAM 6Al-4V
titanium powder. The predicted results show a good agreement with test
data.
High Strength Ti-15Mo Beta Titanium Alloy
V. R. Jablokov1, L. D. Zardiackas2, M. Roach2, S. Williamson2, H. Freese1, (1)ATI Allvac, Monroe, NC, (2)University of Mississippi Medical Center, Jackson, MS
Low strength solution treated Ti-15Mo beta titanium has been used for several years in the biomedical market primarily due to its excellent biocompatibility with the human body. However, due to the alloys relative low strength in the solution annealed condition, it has found limited use mostly in fracture fixation type applications where fatigue resistance is not an issue.
Much work was invested the past several years by ATI Allvac to develop a higher strength version of Ti-15Mo to expand its use in the biomedical market and to make it suitable in other markets such as aerospace. The main goal of the development program undertaken by ATI Allvac was to create an alloy suitable for use in high load, fatigue critical applications. Using patent pending processing techniques, a uniform, very fine-grained material was successfully developed which has resulted in a material with excellent smooth and notch fatigue resistance. The thermo-mechanical processing methods used to develop the high strength alloy as well as the resulting microstructure, fatigue, SCC, and tensile properties will be presented.
Effect of Heat Treatment on the Microstructure and Mechanical Properties of Titanium Alloys
N. Lynn, C. Brady, S. Parks, S. Malinov, C. Armstrong, Queen's University Belfast, Belfast, United Kingdom
Titanium alloys have been used extensively in the aerospace, structural and power industries due to their attractive combination of physical and mechanical properties. It is widely understood that these properties depend closely upon the microstructure of the alloy. This microstructure is in turn formed during the thermomechanical processing of the alloys. It is therefore desirable to know the effect of different processing routes on the microstructure of the alloy so that the required mechanical properties can be achieved.
In this work the mechanical properties of a typical α alloy, Ti-6Al-4V, and a typical β alloy, β21s, are determined after appropriate heat treatment. The α alloy is heated into the 100% β phase field (1100ºC) and then cooled at six different rates (5-50ºC/min). The β alloy is solution treated at 810ºC and then aged at three different temperatures (480-595ºC) for 8 hours.
The microstructure after heat treatment is studied by optical microscopy for both alloys. Mechanical testing consists of tensile testing (room and elevated temperatures), impact testing and hardness testing.
Ti-6Al-4V forms a fully lamellar microstructure on cooling from the β phase field. Increasing the cooling rate leads to refinement of the lamellar spacing. The faster cooling rates result in a stronger material, as the slip length of the alloy is related to the lamellar width.
The aging of β21s is results in the precipitation of α, which causes strengthening. The amount of precipitation is related to the degree of under-cooling of the alloy. Beta grain size also affects the ductility of the material
Recommendations are given for the optimum processing route for desirable mechanical properties.
Titanium alloys have been used extensively in the aerospace, structural and power industries due to their attractive combination of physical and mechanical properties. It is widely understood that these properties depend closely upon the microstructure of the alloy. This microstructure is in turn formed during the thermomechanical processing of the alloys. It is therefore desirable to know the effect of different processing routes on the microstructure of the alloy so that the required mechanical properties can be achieved.
In this work the mechanical properties of a typical α alloy, Ti-6Al-4V, and a typical β alloy, β21s, are determined after appropriate heat treatment. The α alloy is heated into the 100% β phase field (1100ºC) and then cooled at six different rates (5-50ºC/min). The β alloy is solution treated at 810ºC and then aged at three different temperatures (480-595ºC) for 8 hours.
The microstructure after heat treatment is studied by optical microscopy for both alloys. Mechanical testing consists of tensile testing (room and elevated temperatures), impact testing and hardness testing.
Ti-6Al-4V forms a fully lamellar microstructure on cooling from the β phase field. Increasing the cooling rate leads to refinement of the lamellar spacing. The faster cooling rates result in a stronger material, as the slip length of the alloy is related to the lamellar width.
The aging of β21s is results in the precipitation of α, which causes strengthening. The amount of precipitation is related to the degree of under-cooling of the alloy. Beta grain size also affects the ductility of the material
Recommendations are given for the optimum processing route for desirable mechanical properties.
Effect of heat treatment on the microstructure and mechanical properties of titanium alloys
Titanium alloys have been used extensively in the aerospace, structural and power industries due to their attractive combination of properties. It is widely understood that these properties depend closely upon the microstructure of the alloy. This microstructure is formed during the thermomechanical processing of the alloys . It is therefore desirable to know the effect of different processing routes on the microstructure of the alloy so that the required mechanical properties can be achieved.
In this work the mechanical properties of a typical α alloy, Ti-6Al-4V, and a typical β alloy, β21s, are determined after appropriate heat treatment. The α alloy is heated into the β phase field (1100ºC) and then cooled at varying rates (5-50ºC/min) [Fig. 1]. The β alloy is solution treated at 810ºC and then aged at different temperatures (480-595ºC) for the same length of time [Fig. 2].
The microstructure after heat treatment was studied by optical microscopy. Mechanical testing consisted of tensile testing (room and elevated temperatures), impact testing and hardness testing.
Ti-6Al-4V forms a fully lamellar microstructure on cooling from the β phase field [Fig. 3]. Increasing the cooling rate leads to refinement of the lamellar spacing [Fig. 4]. It is expected that the faster cooling rates will result in a stronger material, as the slip length of the alloy is related to the lamellar width.
The aging of β21s is expected to result in the precipitation of α, which causes strengthening. It is expected that the amount of precipitation will be related to the degree of undercooling of the alloy.
Recommendations will be given for the optimum processing route for required properties.
High Strength Beta Titanium Forgings of Alloy Ti-5Al-5V-5Mo-3Cr (Ti 5553)
M. H. Buescher1, G. Wegmann2, D. G. Terlinde1, (1)Otto Fuchs KG, Meinerzhagen, Germany, (2)Airbus Deutschland GmbH, Bremen, Germany
A major challenge for future aircraft projects will be the implementation of high strength beta titanium forgings for structural applications against the background of weight reduction and overall performance improvement. Metastable beta titanium alloys provide the benefit of very high specific strength levels combined with a high fracture toughness and an excellent high cycle fatigue behaviour. Due to a relatively slow kinetics the alloy Ti 5553 can be solution treated by air cooling and therefore provides a better possibility of controlling internal stresses in contrast to the water quenching of the alloy Ti 10-2-3. Together with a considerable cost saving against Ti 10-2-3 the alloy Ti 5553 becomes an alternative for highly loaded parts like flap tracks and pylon or landing gear applications.
The main objective of this research project is the optimisation of the thermomechanical processing (forging and heat treatment) of the alloy Ti 5553 to achieve the optimum combination of medium strength (Rp0,2 ³ 1000 MPa), fracture toughness and crack propagation resistance. Within the project in a first step the influence of different parameters like deformation degree, deformation temperature, solution treatment temperature and ageing temperature on the properties is investigated on different hand forgings. In a second step the mechanical characteristics of a die forging made of Ti 5553 are evaluated. The results will be presented and discussed.
Recent Developments in Linear Friction Welding of Ti for Aerospace Applications
M. J. Russell1, R. R. Boyer2, (1)TWI Ltd, Cambridge, United Kingdom, (2)The Boeing Company, Seattle, WA
This presentation will describe recent developments in the joining of Ti alloys using Linear Friction Welding (LFW). The talk will focus on the use of LFW to produce machining pre-forms for aerospace components. Currently, such components are usually machined out from solid blocks of Ti alloy, resulting in relatively poor material buy-to-fly ratios. The use of welded pre-forms can significantly reduce production costs for a range of these machined Ti parts.
Build up of machining pre-forms by LFW also provides the opportunity for selection of appropriate Ti alloys in different parts of the structure. This approach allows production of tailored components, resulting in both functional and economic benefits. Examples will be shown of the application of this approach to aerospace components, from simple two-piece LFW fabrications, to complex multiple-part pre-forms produced by sequential addition of material by LFW.
Selected results will be presented from a recent development programme on the LFW of Ti-6Al-4V machining pre-forms, which has been conducted by TWI Ltd. on behalf of The Boeing Company.
In summary this presentation will provide an overview of recent Linear Friction Welding development work aimed at improving product effectiveness and reducing production costs for a wide range of Ti alloy aerospace components.
Producing Parts from Ti-6Al-4V Using Hot Roll Forming and Hot Stretch Forming
C. Swallow1, K. Slattery1, G. A. Tomchik2, T. G. Dunder2, D. G. Sanders3, S. Houston4, R. Pincoski5, (1)Boeing Phantom Works, St. Louis, MO, (2)Boeing - 787 Airplane Integration, Seattle, WA, (3)The Boeing Company, Seattle, WA, (4)Cyril Bath, Monroe, NC, (5)Dunkirk Specialty Steel, Dunkirk, NY
The growing use of composites in transport aircraft has led to the use of titanium in components that were previously aluminum. These components were typically extruded shapes that were formed to the contour of the aircraft at room temperature in the solution annealed and quenched condition. The high room temperature strength of titanium does not lend itself to being formed at room temperatures. Modifications have been made to existing stretch forming machines allowing parts to be heated before and during stretch forming. Challenges include induced residual stresses during cool-down and differences in coefficients of thermal expansion between the tooling and the work piece. Studies were also performed on hot roll forming titanium plate to shape for subsequent hot stretch forming in lieu of extruding due to the higher mechanical properties which can be achieved.
Advanced Machining of Titanium Alloys
K. Young1, G. A. Tomchik2, E. J. Stern1, (1)Boeing Phantom Works, St. Louis, MO, (2)Boeing - 787 Airplane Integration, Seattle, WA
Commercial aircraft designs are transitioning from primarily aluminum construction to composite skins with aluminum and titanium substructure. Aggressive performance and fuel efficiency requirements are requiring more focus on lightweight titanium substructure. In areas of aircraft structure which are lightly loaded, titanium is still desired for corrosion and stiffness characteristics, but the manufacturing minimum gauge can be higher than required for carrying loads. Advanced machining technologies are enabling weight reduction through reduced minimum gauge and small corner radii in deep pocketed, monolithic titanium. Traditional uses of high speed steel cutting tools and single step finishing results in a hard limit of manufacturing minimum gauge. The use of modern indexible and solid micro-grain tungsten carbide is coupled with thin wall machining approaches, plunge milling and end milling to enable lighter, less expensive titanium machinings.
An Overview of Titanium Alloys Modified with Boron
S. Tamirisa1, D. Miracle2, (1)FMW Composite Systems Inc., Bridgeport, WV, (2)Air Force Research Laboratory, Wright-Patterson AFB, OH
Titanium alloys continue to be vital structural materials for various aerospace as well as non-aerospace applications. There is a strong motivation to develop technologies that can reduce the processing costs and increase the performance of conventional titanium alloys to enhance the affordability and expand their usage. Small boron additions to conventional titanium alloys have shown significant promise in this direction. The physical metallurgy of boron-modified titanium alloys (Ti-B) will be briefly described, including compositions, phases, processing, microstructures, and properties. It has been established that trace (~0.1 wt%) boron addition dramatically refines the cast grain size by an order magnitude. The grain refinement could lead to reduction/elimination of processing steps and also provides opportunities to design novel and affordable processing paths. Addition of boron of the order of 1 wt%, on the other hand, significantly (25-30%) increases the strength and stiffness of conventional Ti alloys at room as well as elevated temperatures without causing debit in fracture related properties. Better understanding of the processing-microstructure-property relationships has been found to be the key in the development of Ti-B alloys for aerospace applications where fatigue and damage tolerance are critical factors. Research and development programs that are currently underway at the Air Force Research Laboratory, aimed at exploring and establishing the benefits of boron addition to Ti alloys will be reviewed.
Microstructure and Properties of Ti64-1.55B Alloy
D. Miracle, O. Ivasishin, Air Force Research Laboratory, Wright-Patterson AFB, OH
Titanium alloys modified with boron additions are stronger, stiffer, and more processable than conventional titanium alloys. Among other techniques, conventional ingot metallurgy is considered as a viable way to expand usage of these advanced materials. In this paper, ingot melted Ti–6Al–4V–1.55B (the eutectic composition) was studied in the as-cast and thermomechanically processed conditions. The exact eutectic composition produced the highest possible content of TiB without formation of coarse primary borides that limit ductility. The goal was to develop an understanding of how the microstructure governs the properties of boron-modified titanium alloys. It was shown that solidification microstructure, the most important features of which are uniformity in distribution of TiB crystals, their morphology and directionality, is key to controlling the material’s final characteristics. It was concluded that the as-cast microstructure of boron-modified eutectic titanium alloy should be carefully controlled to provide enhanced performance for anticipated applications.
Affordable Rolling of Titanium Alloys via Boron Addition
K. O. Yu1, S. Tamirisa2, R. Srinivasan3, J. Gunasekera4, D. Miracle5, (1)RMI Titanium Company, Niles, OH, (2)FMW Composite Systems Inc., Bridgeport, WV, (3)Wright State University, Dayton, OH, (4)Ohio University, Athens, OH, (5)Air Force Research Laboratory, Wright-Patterson AFB, OH
Adding boron to titanium can refine the ingot’s as-cast grain structure which can potentially improve the ingot’s hot workability and reduce the processing cost of the final product. In an Ohio State Government (through EMTEC) funded project, efforts are undertaken to evaluate the effects of boron addition on ingot grain structure and hot workability as well as the microstructure and property of sheets rolled from these ingots. Ti-6Al-4V ingots with (0.1% B) and without boron addition were cast by Induction Skull Melting and Plasma Arc Melting processes. Transverse and longitudinal slices were cut from these ingots and rolled to plates and sheets. Evaluations include ingot grain structure, sheet/plate microstructure and mechanical property.
Evaluation of Newly Developed Ti-555 High Strength Titanium Fasteners
L. Zeng1, L. Haylock2, J. Fanning3, S. Sweet4, A. Zenke5, M. March6, (1)Alcoa Fastening Systems, Carson, CA, (2)Alcoa Fastening Systems, Torrance, CA, (3)TIMET-R&D, Henderson, NV, (4)Perryman Co.,, Houston, PA, (5)Alcoa Fastening Systems, Hildesheim, Germany, (6)Alcoa Fastening Systems, Carson operation, Carson, CA
Ti-6Al-4V has been the most commonly used titanium alloy for aerospace fasteners for almost 50 years. However, the need to increase the strength of Ti-6Al-4V fasteners combine with the inherent limitation in through hardenability of Ti-6Al-4V, has created interest in other alloys. In addition, there is also a need to eliminate cadmium plating associated with alloy steel and Cres fasteners, and high strength titanium is viewed as an alternative to these materials. Over the past few years, Alcoa Fastening System (AFS) evaluated the capabilities of many emerging titanium alloys for their potential application as high strength fastener materials. Recently, AFS had successfully developed high-strength titanium fasteners using Timetal 555 (Ti-5Al-5Mo-5V-3Cr-0.5Fe). The Ti555 is a newly developed near b titanium alloy introduced by Timet.
High strength Ti-555 fasteners were manufactured using conventional fastener manufacturing processes. Detailed qualification tests, including non-destructive, mechanical, and metallurgical tests as revealed that the newly developed Ti555 fasteners demonstrated excellent properties, meeting or exceeding the typical specification requirements of 1250MPa (180ksi) cadmium plated alloy steel fasteners. Non-destructive testing, including dimensional verification and identification, met product specifications. Metallurgical testing, including discontinuities, hydrogen contents, and grinding burns, were within specification limits. Mechanical properties evaluation showed a tensile strength of 1309 MPa (190 ksi) with more than 10% elongation. Double shear testing showed a minimum strength of 779 MPa (113 ksi) for uncoated parts and 744 MPa (108 ksi) for coated fasteners. Further microstructural evaluation revealed finely distributed secondary a phase within primary b matrix after aging.
Microstructural evolution in Titanium 5%Al-5%V-5%Mo-3%Cr upon ageing
R. Panza-Giosa, Goodrich Landing Gear, Oakville, ON, Canada
Status of Enhanced Ti-6Al-4V Development
B. Hanusiak1, R. Grabow1, S. Tamirisa2, F. Yolton3, (1)FMW Composite Systems, Inc., Bridgeport, VA, (2)FMW Composite Systems Inc., Bridgeport, WV, (3)Crucible Research Corporation, Pittsburgh, PA
Titanium alloys have been utilized in aero space structures and propulsion systems to enable weight reduction due to attractive specific properties. This benefit was enhanced over the last ten years as a result of the transition-to-production of continuous SiC fiber reinforced titanium matrix composites (TMC) which offers high uni-directional increase the specific strength and stiffness. The TMC material, however, is not readily applicable to multi-axis loaded components due to the low transverse properties.
Recently, significant progress has been made in the development of enhanced titanium alloys which exhibit strength and stiffness improvement while maintaining ductility and formability. In the Ti-6Al-4V alloy, strength improvements of 75% and stiffness improvements of 35% have been demonstrated along with improved fatigue properties. Formability has been demonstrated with; near net shape powder metal (PM) processing, extrusion, forging and plate rolling. Hot rolled sheet exhibits a near isotropic strength behavior in the rolling and cross-rolling direction and the benefit is retained at temperatures up to 1000 F. The process utilizes current titanium fabrication equipment and methods and therefore is essentially cost neutral relative to standard titanium PM processing. This offers an opportunity to achieve exceptional property enhancements at negligible cost increase. This paper describes the status of this development effort in the Ti-6Al-4V base alloy with a focus on transitioning to practical application.
Productionization of Investment Cast Ti-5553 Alloy:
D. S. Lee, S. J. Veeck, Howmet Research Corporation, Whitehall, MI
Howmet has continued efforts to develop investment cast Ti-5553 alloy (Ti-5Al-5V-5Mo-3Cr) which has the potential to replace wrought Ti-6Al-4V in aerospace and airframe structural applications. Prior studies with Ti-5553, a near beta alloy, focused on the development of both static and dynamic mechanical properties. These studies showed Ti-5553 to have superior tensile and fatigue characteristics relative to Ti-6Al-4V and better hardenability than Ti-15-3-3-3. More recent efforts have focused on the productionization of the alloy, including the development of preliminary process specifications, the development of baseline weld parameters, X-ray inspection (POD) efforts and validation of the heat treatment in a production environment. The results of these studies will be discussed, and a specific production application for Ti-5553 alloy castings will be reviewed.
Low-Temperature Coarsening and Plastic Flow of Ti-6Al-4V with an Ultrafine Microstructure
G. A. Sargent1, S. L. Semiatin2, D. Li3, (1)UES, Inc., Dayton, OH, (2)Air Force Research Laboratory, Wright-Patterson AFB, OH, (3)RMI Titanium Company, Niles, OH
Static and dynamic coarsening and the impact of such coarsening on the plastic-flow response of Ti-6Al-4V during hot deformation at low temperatures (775, 815°C) and low-to-moderate strain rates (10-4 – 10-2 s-1) were established using hot compression and hot tension tests. Program materials comprised both billet and sheet material produced via warm severe plastic deformation to obtain an ultrafine microstructure. The influence of particle size, diffusivity, alpha/beta interface energy, and phase equilibria (phase composition/volume fractions) on coarsening was established. The observed static and dynamic coarsening kinetics were both successfully interpreted in terms of models previously validated for the behavior at higher temperatures (900, 955°C). In addition, flow-hardening observations at low temperatures were analyzed in the context of the dynamic-coarsening rates. Detailed characterization studies enabled the determination of the effect of microstructural parameters/microstructure stability on plastic flow at temperatures between 775 and 955°C.
Assessment of Advanced Titanium Alloys for Affordability
J. Meudt1, D. S. Lee2, S. Tamirisa3, V. Venkatesh4, D. U. Furrer5, (1)Ladish Co., Inc., Cudahy, WI, (2)Howmet Research Corporation, Whitehall, MI, (3)FMW Composite Systems Inc., Bridgeport, WV, (4)TIMET-R&D,, Henderson, NV, (5)Roll-Royce Corporation, Indianapolis, IN
The concern with cost in the aerospace industry is increasing and there is a need to reduce these costs creating affordable applications. There are new advanced titanium alloys being developed to reduce costs and improve performance over traditional titanium, steel, and aluminum alloys. These new alloys are being designed to reduce the overall processing costs and to improve performance such as strength, stiffness, or microstructure. Three titanium alloys, Timetal54M, Ti6-4 modified with boron, and Ti5553, are being evaluated and results to date will be presented.
Evaluation of Metal Additive Manufactured Ti-6Al-4V
K. T. Slattery1, D. Heck2, M. Kinsella3, F. Liou4, J. W. Sears5, K. W. Lachenberg6, (1)The Boeing Company, Seattle, WA, (2)The Boeing Company, St. Louis, MO, (3)AFRL/MLLMP, Wright-Patterson AFB, OH, (4)Missouri University of Science & Technology, Rolla, MO, (5)South Dakota School of Mines & Technology, Rapid City, SD, (6)Sciaky Inc., Chicago, IL
There are a number of Metal Additive Manufacturing (MAM) processes that have the potential to produce Ti-6Al-4V parts directly from an electronic model. The processes differ greatly in energy source, feedstock, and scale. In order to design, specify, and build aerospace components, it is necessary to understand the differences in these processes and their effect on the ability of components to meet service requirements.Microstructure, mechanical properties, and soundness of Ti-6Al-4V deposits made using different Metal Additive Manufacturing investigated under the Center for Aerospace Manufacturing Technologies and Metals Affordability Initiative Program are presented.
Fabrication of Titanium Components by Laser Powder Deposition
J. W. Sears, South Dakota School of Mines & Technology, Rapid City, SD
Fabrication of titanium components by Laser Powder Deposition (LPD) offers some unique solutions for high performance aerospace applications. LPD is a CAD/CAM solid freeform fabrication technology that uses metal powder and laser fusion to produce components. This paper describes the mechanical property and metallurgical results obtained from LPD titanium structures as well as the parameters required to produce them. Some examples of titanium fabrications and repairs are provided. LPD’s unique capabilities allow direct fabrication of titanium components with design features that are difficult or expensive to obtain by other technologies.
Friction Stir Welding Lap Joining with Sealant as a Rivet Replacement Technology for Aircraft Structure
T. Li1, G. Ritter2, J. Bernath1, N. Kapustka2, T. Stotler2, R. J. Lederich3, (1)EWI, Columbus, OH, (2)Edison Welding Institute, Columbus, OH, (3)The Boeing Company, St. Louis, MO
The implementation of friction stir welding (FSW) as a rivet replacement technology has drawn a tremendous interest from the aerospace industry in recent years. The traditional riveting process is labor intensive and costly. Moreover, mechanical properties of FSW lap joints are superior to the riveted ones. However, the inherent issue of crevice corrosion in FSW lap joints must be resolved before FSW lap joining can be fully implemented on aircraft structures. A desirable approach to this problem is to apply an adhesive or sealant between two metal sheets prior to FSW to act as a sealant and improve overall lap-joint performance. In this program, FSW lap joining with a sealant was conducted on 0.080-in. (2 mm) thick AA7075-T7 sheet. The sealant was applied in two ways: in the weld path and adjacent to the weld path. FSW lap welding was carried with both a cured and uncured. The presence of sealant at or between the welds has little effect on the resulting joint strengths. No crevice corrosion was observed at the faying surfaces of all FSW lap joints after exposure to salt fog spray for 500 hr. This feasibility study has shown promising results for resolving the inherent crevice corrosion issue for brining FSW lap joints into production.
Friction Stir Welding of Ti-6Al-4V Alloy
T. Li1, T. Trapp1, T. Stotler2, J. Coffey1, (1)EWI, Columbus, OH, (2)Edison Welding Institute, Columbus, OH
Friction stir welding (FSW) was conducted on 0.5-in. thick Ti-6Al-4V plate. Plates with embedded thermocouples were welded to obtain thermal profiles at various locations in stir and heat-affected zone during the FSW process. The results indicate that the highest peak temperature in the stir zone is above beta-transus temperature. However, the peak temperature at the location near backside in the stir zone is below the beta-transus temperature. The resultant weld microstructure was characterized in an attempt to understand the thermal history. Tensile properties of FSW were evaluated and compared to that of pulsed gas metal arc welds in the as-welded and postweld heat treated conditions. Unique process characteristics in FSW Ti alloy will be discussed and compared with FSW steel.
Friction Stir Welding and Hybrid Laser Welding of Ti-64 Structural Components
J. Bernath1, S. Krem2, T. Li1, B. Shinn2, (1)EWI, Columbus, OH, (2)Edison Welding Institute, Columbus, OH
The development of Friction stir welding (FSW) has progressed rapidly since its inception. The process has been applied to a variety of high-temperature alloys, including titanium, with increasing success. In the current study, FSW was used to join Ti-64 structures in the butt, corner, and T-joint configurations combining varying thicknesses of material.
One of the greatest challenges in FSW high-temperature alloys is designing a tool with the proper geometry and material combination to prevent tool deformation and wear. EWI has designed a non-conventional tool referred to as a variable penetration tool (VPT). The VPT geometry was combined with a low cost tungsten-based alloy. The result is robust process for FSW Ti-64 providing a full penetration, defect free weld, with very little tool wear.
The initial process development successes lead to the application of this technology to butt, corner, and T-joint geometries. These joint geometries were joined in lengths exceeding 60-in and in a variety of material thicknesses including .188-, .250-, and .500-in.
Hybrid laser welding (HLW) is a process that combines laser welding and gas metal arc welding (GMAW). This process combines the robustness of the GMAW with the penetration of lasers to create a process that can achieve deep penetration at high travel speeds with reduced fit up requirements. The HLW process was used to join material combinations similar to FSW trials. HLW of Ti-64 structures is discussed and compared to FSW.
This work was completed under Army Contact # DAAD19-03-2-002 to investigate joining of complex structures using these new advanced processes combined with modular tooling for rapid prototyping. The success of this program has demonstrated feasibility of building Ti components in production for aircraft structures using both FSW and HLW.
The development of Friction stir welding (FSW) has progressed rapidly since its inception. The process has been applied to a variety of high-temperature alloys, including titanium, with increasing success. In the current study, FSW was used to join Ti-64 structures in the butt, corner, and T-joint configurations combining varying thicknesses of material.
One of the greatest challenges in FSW high-temperature alloys is designing a tool with the proper geometry and material combination to prevent tool deformation and wear. EWI has designed a non-conventional tool referred to as a variable penetration tool (VPT). The VPT geometry was combined with a low cost tungsten-based alloy. The result is robust process for FSW Ti-64 providing a full penetration, defect free weld, with very little tool wear.
The initial process development successes lead to the application of this technology to butt, corner, and T-joint geometries. These joint geometries were joined in lengths exceeding 60-in and in a variety of material thicknesses including .188-, .250-, and .500-in.
Hybrid laser welding (HLW) is a process that combines laser welding and gas metal arc welding (GMAW). This process combines the robustness of the GMAW with the penetration of lasers to create a process that can achieve deep penetration at high travel speeds with reduced fit up requirements. The HLW process was used to join material combinations similar to FSW trials. HLW of Ti-64 structures is discussed and compared to FSW.
This work was completed under Army Contact # DAAD19-03-2-002 to investigate joining of complex structures using these new advanced processes combined with modular tooling for rapid prototyping. The success of this program has demonstrated feasibility of building Ti components in production for aircraft structures using both FSW and HLW.
Friction Stir Welding of Titanium 6Al-4V
R. E. Jones, Z. S. Loftus, Lockheed Martin Space Systems, New Orleans, LA
The Lockheed Martin Advanced Programs team has investigated the feasibility of friction stir welding (FSW) titanium 6Al-4V at 0.200-inch thickness. Appropriate pin tool material and optimal processing parameters were determined. Both thermal and environmental management systems were tested, and an A-basis design allowable was calculated for weld strength at cryogenic and elevated temperatures.
FSW of titanium 6-4 presents a number of challenges due to its high temperature strength and reactivity with other elements. Pin tool survivability and compatibility is a critical consideration in the weld development process. Thermal management concerns and the need for an inert weld environment must be addressed to promote weld stability and inhibit interstitial contamination. Finally, to mature titanium 6-4 FSW into a viable production process, continually longer welds must be performed and an A-basis allowable strength value must be calculated. A description of the approach taken to meet these challenges is presented.
Advanced Processes and Practices in Gas Metal Arc Welding for Thin Titanium Structures
B. Baughman, C. Conrardy, Edison Welding Institute, Columbus, OH
Small titanium components are commonly welded using the Gas Tungsten Arc Welding (GTAW) process. While GTAW is highly flexible and can yield a high quality weld, it is also slow, requires a high degree of skill for manual welding, and can produce significant distortion due to the high welding heat input. Edison Welding Institute (EWI) has been investigating alternatives to GTAW for welding large thin titanium structures. This paper describes the results of work to evaluate Gas Metal Arc Welding (GMAW) for welding titanium sheet-metal components. Thicknesses studied are 1.5 mm, consisting of fillet and butt joint configurations. Research was conducted on process parameter settings, shielding requirements, weld quality evaluations, and mechanical properties of weld joints.
GMAW has traditionally been applied to “non-critical” applications where productivity is a primary concern and weld quality and properties are of less importance. Modern GMAW power-source control technology offers increased precision to allow the process to be contemplated for quality-critical applications. This work investigated two alternative GMAW processes: pulsed-current GMAW and reciprocating wire feed GMAW. Each type offers distinct advantages for particular thin titanium applications.
A significant challenge for titanium GMAW is maintaining good arc stability, which is necessary for achieving adequate weld bead shape, weld fusion, and avoiding spatter. Welding process parameters and consumables must be carefully selected to produce precise deposits with no spatter. Evaluation of arc stability and metal transfer was done through the use of a high speed data-acquisition system, allowing the synchronized capture of welding process parameters and high-speed video.
Another important consideration for welding large titanium sheet-metal components is inert gas shielding. Several methods of supplying shielding gas coverage for both the weld bead and the back-side of the joint are being evaluated. The goal is to achieve adequate coverage while minimizing set-up and purge time.
Near Net Manufacturing Using Thin Gage Friction Stir Welding
J. Takeshita, Lockheed Martin, New Orleans, LA
Friction stir welding and near net spin forming of friction stir welded aluminum blanks were investigated for large-scale pressure vessel applications. With a specific focus on thin gage 2xxx and 7xxx aluminum alloys, the program concentrated on the following: the criteria used for material selection, a potential manufacturing flow, and the effectiveness and associated risks of near net spin forming. Discussion will include the mechanical properties of the friction stir welds and the parent material from before and after the spin forming process. This effort was performed under a NASA Space Exploration initiative focused on increasing the affordability and performance of pressure vessels larger than 10-ft diameter.
Friction Stir Lap Welding Methods for Manufacturing Efficient Large-Scale Spaceflight Pressure Vessels
Z. S. Loftus, W. R. Martin, R. W. Anderson, R. E. Jones, Lockheed Martin Space Systems, New Orleans, LA
Two promising methods of friction stir lap welding were investigated and demonstrated on large-scale thin-gage hardware in order to address the growing need to save weight and cost on spaceflight pressure vessels. The first method investigated the productivity that could be achieved using conventional tooling to lap weld extruded stiffeners onto skin panels to form a 7-m (23-ft) diameter 3.2-mm (0.125-in) thick Al7075 payload fairing barrel section. The second method followed a more unconventional approach to circumferentially lap weld three 5.5-m (18-ft) diameter 2-mm (0.080-in) thick Al2090 Al-Li barrels together using a retractable pin tool with a SIN-pattern transverse oscillation on the first weld and a straight self-reacting process on the other. The SIN-pattern lap weld in particular was proven to substantially increase strength compared to a straight lap weld, and with a weld length of 32-m (1260-in) it became the longest friction stir weld made to date at the NASA Michoud Assembly Facility. These efforts were undertaken primarily to optimize spaceflight structures, however the aeronautic and automotive industries could benefit as well by using similar techniques.
Recent Developments in Friction Stir Welding of Ti for Aerospace Applications
M. J. Russell, P. L. Threadgill, I. M. Norris, TWI Ltd, Cambridge, United Kingdom
This presentation will describe recent developments in the joining of Ti alloys using Friction Stir Welding (FSW). FSW is now an established production technology for Al components, and work is continuing on the development of FSW for high temperature materials including Ti alloys.
Potential benefits of the application of FSW to Ti alloys include:
Ti alloys represent an extremely challenging application for FSW, due to their high strength, high melting point, and very low thermal conductivity. Recent developments at TWI have led to significantly improved results in the FSW of Ti alloys, particularly in the areas of process control and stability. Sections of sample welds, and the results of preliminary mechanical testing, will be shown.
A number of possible applications for Ti FSW will also be discussed, including the potential for rapid prototyping, and the production of tailored components using sequential FSW operations.
In summary this presentation will provide an overview of recent Friction Stir Welding development work on the joining of Ti alloys, and will highlight future areas of interest in this exciting field.
Comparison of the Effects of Tool Geometry for Friction Stir Welding Thin Sheet Aluminum Alloys for Aerospace Applications
J. Merry1, J. Takeshita2, B. Tweedy1, D. Burford3, (1)National Institute of Aviation Research, Wichita State University, Wichita, KS, (2)Lockheed Martin, New Orleans, LA, (3)National Institute for Aviation Research, Wichita State University, Wichita, KS
In this presentation, the results of a recent study on the effect of pin tool design for friction stir welding thin sheets (0.040”) of aluminum alloys 2024 and 7075 are provided. The objective of this study was to investigate and document the effect of tool shoulder and pin diameter, as well as the presence of pin flutes, on the resultant microstructure and mechanical properties at both room temperature and cryogenic temperature. Specifically, the comparison between three tools will include:
All samples were naturally aged for a period greater than 10 days. Prior research has shown 7075 may require post weld heat treatment. Therefore, an additional pair of room temperature and cryogenic temperature samples was post-weld aged to the 7075-T7 condition prior to mechanical testing.
Chosen Aspects of 18-8 Stainless Steel Brazing by AgCu42Ni2 Filler Alloy
T. Babul1, J. Senkara2, J. Kopec3, A. Nakonieczny1, S. Kowalski1, J. Jakubowski2, (1)Institute of Precision Mechanics, Warsaw, Poland, (2)Warsaw University of Technology, Warsaw, Poland, (3)WSK Rzeszów, Rzeszów, Poland
The paper deals with chosen issues related to application of AgCu42Ni2 alloy in brazing hydraulic, air- and fuel-operated pipes use in the aircraft engines. One of the alloy feature is a significant difference between solidus (771oC) and liquidus (893 oC) temperatures which is rather unusual for fillers. Hence, it has the tendency to split into two phases in the course of the joining process.
Brazing experiments were conducted in 10-6 Tr vacuum environment. Impact of different means of isotropic and anisotropic surface preparation (including sand blasting, polishing, wear cloth application, and nickel plating) on the filler spreading was tested. Surface area covered by the liquid alloy as a function of brazing temperature and time is also presented. Structures of obtained joints were investigated by optical microscopy, scanning electron microscopy, x-ray diffractometry, and micro-hardness measurements. A particular attention was attracted onto interfaces and diffusion layers. The paper presents also the analysis of phenomena that occur during the liquid front movement through the gap between two cylindrical surfaces.
Investigation and Recent Progress of Formation Mechanism of Blowhole in Stainless Steel Weld
A. T. Olabode, Olabode Adewumi Taiwo Steel Construction Company Limited, Lagos, Nigeria
Finite Element Analysis of Residual Stress and Distortion in Laser Welded Stainless Plate
S. Marimuthu, D. K. Bandyopadhyay, S. P. Chaudhuri, D. Misra, P. K. Dey, Jadavpur University, Kolkata, India
In fabrication industries residual stresses and distortion of welded steel continues to be a major problem. Though many works has been done in the past to assess residual stress in conventional welding, very few works has been done for the case of laser welding. This paper investigates the effects of welding speed, laser power, work piece thickness and work piece width on residual stress and distortion of the workpiece using Finite Element Analysis code ABAQUS. Transient 3-D FEA has been carried out following a two-step approach. In the first step a non-linear heat transfer analysis is carried out find the dynamic temperature distribution. Subsequently an elasto-plastic analysis is performed to compute the residual stress and distortion arising out of the transient temperature field. A moving Gaussian heat source is assumed at top surface. Convection and radiation heat losses are considered at all the surfaces. Based on the simulation results, distortion and residual stress of the weldment are predicted. Thus, the experimental analysis, which might be costly, can be avoided. A few pertinent observations obtained from the simulation are given below. With increase in laser power residual stresses and distortion increase. On the other hand, as the speed increases distortion and residual stress decrease. As the thickness of the job increases there is a reduction of residual stress and distortion. Similarly, as the width of the job increases there is a reduction of residual stress and distortion.
An Investigation On Mechanical Properties Of AISI 304 Austenitic Stainless Steel Weldment Using E308,E316 & E347 Electrodes
V. Ananthanarayanan1, M. Nambi2, (1)Hyundai Motor India Limited, Chennai, India, (2)Sri Venkateswara College of Engineering, Chennai, India
Austenitic stainless steels have been widely used because of their excellent high temperature and corrosion resistance properties and good cryogenic properties. The coefficient of thermal expansion for austenitic stainless steel is 50% greater than that of carbon steel and this must be considered to minimize distortion. The low thermal and electrical conductivity of austenitic stainless steel is helpful. Less welding heat is required to make a weld because the heat is not conducted away from a joint as rapidly as in carbon steel.
AISI 304 is most widely used in chemical, petrochemical, nuclear, pulp and paper, pharmaceutical and textile industries and production of artificial fibers and electrical equipments. AISI 304 can be welded by several welding processes including the arc welding, resistance welding, electron and laser beam welding, friction welding and brazing. The present work is AISI 304 austenitic stainless steel was welded with shielded metal arc welding process using the electrodes E347, E308L, E316L with V groove edge preparation and to evaluate the microstructure and mechanical properties of the welded joints and to analyzes mode of fracture the tensile and impact test specimens after testing by obtain the fracto-metallograph using scanning electron microscope.
It has been established that the austenitic stainless steel grade AISI 304 welded with low carbon grade electrodes have comparatively higher ultimate tensile strength, impact energy and delta ferrite content.