Density, surface tension, viscosity of impacting liquid particle were assumed to be temperature dependent. Fluid flow boundary conditions were no slip and no-penetration at solid surface.
The particle conditions at impact (temperature and velocities for a given diameter) were calculated thanks to the Jets&poudres model [1] with usual zirconia particles plasma spray conditions.
References
[1] http://Jets.poudres.free.frSince the nineties many works have been devoted to splat formation modeling taking into account the molten droplet impact on to a flat surface, its flattening and solidification occurring during flattening. They were mainly developed by the team of Professor J. Mostaghimi in department of mechanical engineering of the University of Toronto (Canada) and resulted in commercial code Simulent Drop ® The model of Toronto allows calculating particle flattening splashing as well the real contact between splat and smooth substrate. The aim of this work is to test if 2D simplified model allows determining the real contact splat substrate and compare the results with experiments and the results of 3-D model.
This simplified modeling is based on the Navier-Stokes equations, with added term to account for surface tension, including a constant contact angle to describe the transport of mass and momentum. The fluid flow was assumed to be Newtonian, lamina rand incompressible. The normal stress was asserted as the only stress applying to free surface. The equations were discretized by finite elements techniques in 2-D Eulerian structured grid.
The free surface deformation was tracked by level function Φ Density, surface tension, viscosity of impacting liquid particle were assumed to be temperature dependent. Fluid flow boundary conditions were no slip and no-penetration at solid surface. The particle conditions at impact (temperature and velocities for a given diameter) were calculated thanks to the Jets&poudres model [1] with usual zirconia particles plasma spray conditions. References [1] http://Jets.poudres.free.frSince the nineties many works have been devoted to splat formation modeling taking into account the molten droplet impact on to a flat surface, its flattening and solidification occurring during flattening. They were mainly developed by the team of Professor J. Mostaghimi in department of mechanical engineering of the University of Toronto (Canada) and resulted in commercial code Simulent Drop ® The model of Toronto allows calculating particle flattening splashing as well the real contact between splat and smooth substrate. The aim of this work is to test if 2D simplified model allows determining the real contact splat substrate and compare the results with experiments and the results of 3-D model. This simplified modeling is based on the Navier-Stokes equations, with added term to account for surface tension, including a constant contact angle to describe the transport of mass and momentum. The fluid flow was assumed to be Newtonian, lamina rand incompressible. The normal stress was asserted as the only stress applying to free surface. The equations were discretized by finite elements techniques in 2-D Eulerian structured grid. The free surface deformation was tracked by level function Density, surface tension, viscosity of impacting liquid particle were assumed to be temperature dependent. Fluid flow boundary conditions were no slip and no-penetration at solid surface. The particle conditions at impact (temperature and velocities for a given diameter) were calculated thanks to the Jets&poudres model [1] with usual zirconia particles plasma spray conditions. References [1] http://Jets.poudres.free.fr
“Parametric Study of Machining Effect on Residual Stress and Surface Roughness of Nickel Base Super Alloy UDIMET – 720”
The Application of Bayesian Neural Network Modeling for the Prediction of Tensile and Fracture Toughness Properties in Alpha/Beta Titanium Alloys The development of computational tools that permit microstructurally-based predictions for tensile and fracture toughness properties of commercially important titanium alloys is a valuable step towards the accelerated maturation of materials. This talk will discuss the development of Neural Network Models based on Bayesian statistics to predict the yield strength, ultimate tensile strength and toughness of Ti-6Al-4V at room temperature. The development of such rules-based models requires the population of extensive databases which contain both compositional and microstructural information. These databases have been used to train and test Neural Network models to predict the tensile and toughness properties. In addition, these models have been successfully used to identify the influence of individual microstructural features on the mechanical properties, consequently guiding the efforts towards development of more robust phenomenological models. The influence of the individual microstructural features on tensile and toughness will be discussed.
Utilization of Modeling Tools for Extrusion Process Optimization Computer modeling programs have been used to optimize the extrusion processes. First, an induction heating modeling program has been developed to predict the temperature profile of billets during induction heating and soaking processes. With the help of this program, induction heating equipment is capable of achieving desired temperature profile and reducing variation between pieces with different diameters. Finite element modeling software (DEFORM) is used to study the metal flow during extrusion to achieve balanced flow at the outlet. It is also used to evaluate different die designs with considerable savings of time and expense because the amount of trial-and-error testing is reduced.
Use of 3-D Simulation to Control Melt Pool Size and its Temperature in Complex Deposits with Laser Additive Manufacturing <>Control of melt pool size and its temperature is important to attaining consistent solidification conditions in laser additive manufacturing. The laser power and speed that will result in such consistency is unknown a priori because the temperature field evolves continuously during the deposition and the geometry of the deposit can vary from one location to another. This paper describes a hands-off automated simulation of laser additive manufacturing. It is developed to solve for the laser power and velocity conditions that control melt pool size and its temperature to user-specified values under complex deposit conditions. The solution outputs the evolving temperature and stress fields as the deposit progresses. It also computes the thermal gradient and velocity of the solidification front for the purpose of correlation with resulting microstructure. Sample solutions will be presented.
Finite Element Weld Modeling for Aerospace Applications Welding and cladding have been considered to use in aerospace industry, especially friction stir welding (FSW), laser beam welding (LBW), laser weldbonding (LWB), and laser additive manufacturing (LAM). Finite element weld modeling has been playing an important role in developing these processes, such as selecting welding parameters for new geometries and materials, optimizing welding sequences for distortion mitigations, and so on. This paper attempts to review the recent weld modeling applications for aerospace industry, particularly LBW and LWB, in Edison Welding Institute (EWI).
Modeling and Experimental Analysis of Micron Surface Dents and Mechanical Behavior During Laser Shock Peening Ti-6Al-4V Laser Shock Peening (LSP) is a mechanical process where pressure waves caused by expanding plasma plastically deform the surface of a material. Typically, LSP is applied to metals as a form of surface treatment. As a result, the mechanical properties on the surface are enhanced to improve the performance of fatigue, wear, and foreign object damage (FOD). Titanium Ti- A 3D finite element model has been developed to simulate micro scale laser shock peening of Ti- Keywords: laser shock peening, surface dent, titanium, dynamic mechanical behavior, finite element analysis
Property Analysis of a High Performance Cu-Ni-Sn Spinodal Alloy Spinodally hardened Copper-Nickel-Tin alloys have been under development for over 40 years. With considerable development effort, the ToughMet® class of Copper-Nickel-Tin alloys have become materials of commerce. One wrought temper, ToughMet® 3 AT110 (UNS C72900), has become the material of choice in high performance wear-critical applications. In preparation for AMS and MMPDS design allowables listing, substantial testing data was generated, including basic tensile and compression mechanical properties, pin bearing performance and shear strength over a wide rod and tube diameter size range.
Modelling of Processing and Materials Phenomena in Nickel-Based Superalloys At the
Computational Materials Science Techniques to Identify Ni-base Superalloys for IGT Applications The successful use of single-crystal alloys in IGT applications is contingent upon overcoming processing problems such as defect formation, and maintaining microstructural stability once in service. The present work uses a design approach aimed toward the development of a set of alloys for industrial gas turbine application. In the hopes of better understanding elemental variation effects on the aforementioned material properties, a baseline alloy composition named the baseline ‘Model’ alloy (based on CMSX-4 and PWA 1483) was used as the foundation from which two iterations of ‘elemental variation effect’ evaluations were conducted (‘Phase I’ and ‘Phase II’). The thermodynamic equilibrium module in the JMatPro Program was utilize to evaluated ‘Phase I’ and ‘Phase II’ theoretical property trends and determine chemistry modifications to the baseline ‘Model’ alloy. Five variant alloy compositions were tailored using JMatPro modeling techniques and were laboratory tested for validation purposes. To address the effects of additions previously shown to influence hot corrosion and material stability, final compositions incorporated characteristic variations of Al/Ti ratio (with Ta variation), Cr (with Al and Ta variations), and Re content for comparison. This study evaluates the computational capabilities of the JMatPro thermodynamic equilibrium module to predict material properties related to defect formation and microstructural stability. Through computational techniques this work also contributes to a better understanding of elemental variation effects on microstructural stability, phase transformation temperatures, and material segregation behavior to facilitate the development of better alloys for future single crystal IGT use.
Phase-field Simulation of Microstructure Formation During Solidification and Homogenisation Processing of Single Crystal Superalloys
Precipitation Simulation of Nickel-Base Superalloys The understanding and control of the precipitation of secondary phases during heat treatments is critical for the properties of age-hardening superalloys. A modeling tool has been developed at CompuTherm to simulate the complicated precipitations and microstructure evolutions during arbitrary thermal histories.
Numerical Modelling of the d-Phase Precipitation Kinetics in the Superalloy Allvac 718PlusTM Aerospace gas turbine discs operate in an environment of relatively high stresses caused by centrifugal forces and elevated temperatures. These severe conditions require materials with excellent high temperature properties. Recently, the new alloy Allvac 718PlusTM was developed to further increase the service temperature by at least 55°C while retaining a comparable processability to alloy 718. The properties of gas turbine disks are sensitive to the microstructure, e.g. grain size and precipitations, which depend on the processing history. The interest in microstructure modelling has gained considerable momentum over the past two decades. However, most of the published models are of Avrami type, which have no predictive capabilities with regard to second-phase precipitation. In order to obtain an adequate final microstructure and hence optimized mechanical properties it is necessary to predict the precipitation history as a function of temperature. The results of the simulations are fed into a physical-based microstructure model. In this paper, we present experimental results on the δ-phase precipitation kinetics in Allvac 718PlusTM. Based on this data, computer simulations were performed using the precipitation kinetics module of the software package MatCalc. Experimental data and simulation results, i.e. time-temperature–precipitation (TTP) diagrams, were compared in order to calibrate the precipitate-matrix interfacial energy. Annealing experiments were performed and the fraction of δ-phase precipitates was determined by means of quantitative optical microscopy. Additionally, differential scanning calorimetry (DSC) investigations were carried out to determine the solution temperature of the δ-phase. The results of the calculations obtained using a temperature-dependent interfacial energy were in good agreement with the experiments.
Modelling of Crack-Tip Deformation and Crack Growth in a Nickel-Based Superalloy at High Temperature Modelling of crack tip deformation and crack growth in a nickel-based superalloy at elevated temperature has been carried out for a compact tension (CT) specimen using the finite element method. A unified viscoplastic model with non-linear kinematic and isotropic hardening rules has been adopted to describe the material constitutive behaviour. The material model was implemented in the finite element software ABAQUS via a user-defined material subroutine (UMAT). Finite element analyses for stationary cracks showed distinctive strain ratchetting behaviour near the crack tip at selected load ratios, leading to progressive accumulation of tensile strain normal to the crack growth plane. Results also showed that low frequencies and superimposed hold periods at peak loads significantly enhanced strain accumulation at crack tip. Finite element simulation of crack growth was carried out under a constant ΔK-controlled loading condition. Similar to stationary crack analysis, crack tip deformation for a growing crack also shows the distinctive feature of strain accumulation. Lower frequency and longer dwell period enhance strain ratchetting and strain accumulation. This is consistent with the observed dependency of crack growth rate on frequency and dwell period from the experimental results, i.e., faster crack growth rate at lower frequency and longer dwell period. A crack growth criterion based on strain-accumulation is proposed where a crack is assumed to grow when the accumulated strain ahead of the crack tip reaches a critical value over a characteristic distance. The criterion has been utilised in the prediction of crack growth rates in a CT specimen at selected loading ranges, frequencies and dwell periods, and the predictions were compared with the experimental results. During crack growth simulation, crack closure behaviour was also examined using the standard compliance offset method for both plane strain and plane stress cases, and confirmed the lack of crack closure for plane strain condition.
Role of Microstructure and Environment on Dwell Fatigue Crack Growth in a Nickel-Based p/m Superalloy The influence of microstructure and environment on interganular crack growth in a P/M nickel base superalloy subjected to loading cycles with hold time has been examined. Research studies have shown that the sizes and spatial distributions of the γ’ precipitates have a measurable influence on the yield strength of Nickel based superalloys. This is due to the fact that these small precipitates make the lattice planes highly resistant to slip band formation at high temperature. The role of the strengthening phases of the microstructure on crack tip damage resistance is not well understood. Furthermore, dwell loading in air environment is known to promote crack tip damage acceleration due to the diffusion of air species, particularly oxygen. The role of microstructure on crack growth rate has been examined through variations in temperature, duration and cooling rates of the heat treatment stages; solutioning, stabilization and aging. Influence of long term exposure at 650°C, a typical service temperature, has also been examined. The changes in the size and volume fraction of the secondary γ’ as well as the formation and development of carbides associated with the modified microstructures were determined through SEM observations. A series of crack growth experiments with different hold times ranging from 100 seconds up to 2 hours has been carried out at 650oC and 700 oC in both air and vacuum environment. The microstructure of the test specimens included the as received conditions as well as microstructures which have seen modified heat treatment cycles. Results of these tests were compared and used to identify the roles pertaining to microstructure variations and environment on dwell crack growth damage mechanisms.
A Coupled Creep-Plasticity Model for Relaxation of Shot-Peened Residual Stresses in a Nickel-Base Superalloy Shot peening is a commonly used surface treatment process that imparts compressive residual stresses into the surface of metal components. Compressive residual stresses retard initiation and growth of fatigue cracks. During the component loading history, the shot-peened residual stresses may change during cyclic loading, or during elevated temperature static loading, such as thermal exposure and creep. In these instances, taking full credit for compressive residual stresses would result in a nonconservative life prediction. As a result, designers are reluctant to incorporate any compressive residual stresses into fatigue life predictions of turbine engine components, subject to elevated temperatures and inelastic loading conditions. This research describes a methodical approach for characterizing and modeling residual stress relaxation under elevated temperature loading, near and above the monotonic yield strength of IN100. The model incorporates the dominant creep deformation mechanism, coupling between the creep and plasticity models, and effects of prior plastic strain. The initial room temperature residual stress and plastic strain profiles provide the initial conditions for relaxation predictions using the coupled creep-plasticity model. Model predictions correlate well with experimental results on shot-peened dogbone specimens subject to cyclic and creep loading conditions at elevated temperature. The predictions accurately capture both the shape and magnitude of the retained residual stress profile.
Modeling of Transport Phenomena and Numerical Simulation of Lack of Fusion during Laser Deposition Direct laser deposition is a solid freeform fabrication process that has the capability of direct fabrication of metal parts. The part is fabricated in a layer-by-layer manner in a shape that is dictated by the CAD solid model. A primary objective of laser deposition is to achieve porosity free deposited layers with good metallurgical bonding and minimal dilution. Of the common defects in laser deposition, lack-of-fusion (LOF) is the most damaging since it may act as a crack under certain loading conditions. This work presents prediction of LOF using a comprehensive heat transfer/fluid dynamics coupled model. This model is used to simulate the coupled, interactive transport phenomena between laser, powder, and the substrate during the laser deposition process. The simulation involves laser material interaction, free surface evolution, droplet formation, transfer and impingement onto the substrate, and melt-pool dynamics. Transient temperature and velocity distributions of the falling particles and melt pool as well as melt pool geometry are calculated in a single model, using the continuum formulation and the volume of fluid technique. Experimental validation of model predictions is also presented.
Evolution of Approaches to HIP Modeling The general task of HIP modeling is in designing the initial shape of the HIP tooling providing the final “net” or “near net shape” part after HIP consolidation of powder. It is well known that there are no precise mechanical models of material behavior for stress and temperature conditions far beyond the yield level typical for HIP. Therefore in most of the cases the initial adequacy of the constitutive equations does not enable to provide the necessary precision of modeling. The real process of adequate mathematical modeling for this complex technological process comprises one or two iterations when after the first modeling and its experimental verification , the necessary corrections are installed into the model. The core of modeling is the description of the mutual deformation of the compressible (powder) and non-compressible (HIP tooling) materials. The paper presents the evolution of the models providing adequate description of the HIP deformation for parts of different geometrical complexity and physical non-uniformity mainly used for the aerospace applications.
Finite Element Modeling of Drilling Processes with Solid and Indexable Tooling in Metals and Stack-ups Aerospace manufacturing relies heavily on drilling processes. Aerospace drilling operations focus on holes for rivets loaded in shear in aluminum, titanium and composite stack-ups. Optimal chip flow and tool life are often in competition with burr formation, general hole quality and cycle time. Physics-based modeling of drilling processes can provide insight and information not readily available or easily obtained from experiments, and in a much faster time frame. A three-dimensional finite element-based model of drilling is presented which includes fully adaptive unstructured meshing, tight thermo-mechanically coupling, deformable tool-chip-workpiece contact, interfacial heat transfer across the tool-chip boundary, and constitutive models appropriate for process conditions and finite deformation analyses. Explicit modeling of entrance, steady-state and exit modeling of aluminum and titanium materials, as well as metal stack-ups is performed. Drilling through stack-up layers is also shown. The modeling includes both solid twist and indexable drills. Metal cutting tests are performed and comparison with predicted data is provided.
Finite Element Simulation of Factors Influencing Surface Integrity in Metal Cutting Processes Disturbance of part surface integrity by a metal cutting process can substantially decrease the fatigue life of a component, and introduce other difficulties in subsequent metal removal operations. Fatigue behavior is influenced by residual stress distribution near the surface, and by surface microstructure changes, commonly known as “white layer” formation. Finite element simulation of the metal cutting process offers an opportunity to gain a better understanding of the role of cutting parameters on surface integrity. Cutting speed, rake angle, tool edge preparation, tool wear, and coolant all play key roles in residual stress and surface microstructure changes. With simulation, limits can be established which optimize cutting performance and avoid abusive regimes of cutting parameters or tool wear. While there are still opportunities for improved understanding of residual stress, this is an area which has received substantial attention in the literature. Several elastic-plastic finite element codes offer residual stress calculations, so there have been numerous papers published regarding residual stress simulation and measurement. The capability to incorporate microstructure evolution into a finite element simulation of metal cutting is unique. Software featuring microstructure integrated process simulation is demonstrated. Microstructure models interact with deformation, stress, and thermal models to provide prediction of grain size and phase transformations. Case studies demonstrating model capabilities will be presented.
Finite Element Modeling of Part Distortion Machining of large monolithic structures is becoming a standard in today’s aerospace world. Driven by cost, as well as performance, it is becoming necessary to machine these parts better, faster, lighter and cheaper than ever before. When machining these large monolithic structures, deformation becomes a large problem. The typical solution to this problem is machine with lower than optimum material removal rates and do additional fixture rotations which adds unnecessary time and cost to the manufacturing process. A Finite Element Model has been developed specifically to predict and control these distortions. The model takes into consideration the machining induced residual stresses as well as the bulk stresses in the material from the manufacturer. It is the combination of these two residual stress components coupled with the geometry of the part and type of material that allows us to accurately predict, manage and control the shape and magnitude of deformation in large thin walled structures. The model can be used to determine the ideal cutting conditions for the process as well as determine the best location within the stock plate to machine the part from. Multiple machining tests have been done in order to validate the accuracy of the model. Being able to predict distortion will change how parts are machined. Distortion prediction can be deeply integrated into the manufacturing process as far back as initial part design.
Revolutionizing Aircraft Assembly – Overview of the Eclipse 500
Application of Materials Technology in the Design of Future Turbine Engines
Composite Propeller Blades: Design, Manufacture and Development Dowty Propellers have established themselves as world leaders in composite aircraft propeller design and manufacturer. From early developments made on hovercraft more than thirty years ago, the composite technology and the company have developed over the years into a world leading position. Currently Dowty propeller systems can be found on a variety of both civil and military aircraft (turbo-props in the region of 4000-12,000 SHP) and hovercraft typically used as military landing craft. Some of the key benefits of turbo-props over the more mainstream turbo-fans will be discussed, including; reduced fuel consumption, reduced exhaust emissions and lower operational costs. Furthermore, for military purposes in particular, the thrust available allows take off and landing on a much shorter runway/airstrip than a turbo-fan aircraft would be able to achieve. The key design considerations for composite propeller blades will be explored. These include high strength to weight ratio, high fatigue resistance and damage tolerance. A composite blade also offers the significant advantage of being largely repairable where a metal blade may have to be replaced. As a primary structure of the aircraft, no fatigue or other structural failure is permissible. Composite blades are subject to stringent certification to evaluate the structural integrity, the detail of which will be outlined. Dowty Propellers are responsible for this certification and testing of the propeller, much of which is done in-house. The composite blade manufacture involves a number of different materials and techniques. The processes explored include dry-fibre preforming of carbon and glass fibre, polyurethane foam injection, over-braiding and resin transfer moulding (RTM). New areas for growth will be outlined, including un-ducted fans, as well as a discussion on potential new markets. Furthermore, developments in materials and processing will be explored with a view to future automated composite propeller manufacture.
Low-Temperature Superplastic Flow of Ultrafine Ti-6Al-4V The superplastic-flow behavior at low temperatures (650 – 800°C) and a range of strain rates (10-4 to 10-2 s-1) of Ti-6Al-4V with an ultrafine two-phase (alpha/beta) microstructure has been established. Program materials comprised billet product manufactured by warm isothermal (‘abc’) forging, tested in compression, and sheet fabricated by warm rolling, tested in tension. Extensive metallography on undeformed and deformed samples water quenched from the various test temperatures was conducted using backscattered-electron imaging in an SEM to characterize microstructure stability. Despite the low deformation temperatures, both lots of material showed similar (measurable) dynamic coarsening, whose kinetics mirrored the flow-hardening observed during compression and tension tests. The plastic-flow phenomenology was interpreted in the context of the classical Bird-Mukherjee-Dorn relation. Over the entire test-temperature range, the stress and grain-size exponents of the strain rate were ~1.4-2 and ~2, respectively, for strain rates of 10-4 and 10-3 s-1. The constitutive analysis suggested that multiple (dislocation glide-climb and diffusional) mechanisms control deformation, thus complicating the interpretation of the apparent activation energy derived from the plastic-flow data. + Currently Consultant with UES at the Air Force Research Laboratory, AFRL/MLLM, Wright-Patterson Air Force Base, OH 45433.
The Effects of Super Plastic Forming on the Mechanical Properties and Hydrogen Content of Titanium Ti 6AL-4V Super plastic forming (SPF) experiments on Ti-6AL-4V are being carried out at elevated temperatures ranging from 1600 oF to 1700 oF under different process parameters. The key process input parameters of the experiments under investigation are starting material thickness, forming time and pressure. The effects of these parameters on grain size, hydrogen content, alpha case, ultimate tensile strength, yield strength and elongation are the focus of this study.
Superplastic Response of Continuously-Cast AZ31B Magnesium Sheet Alloys Magnesium sheet is typically produced for commercial applications with the traditional DC-ingot casting method. As a result of the hexagonal close-packed crystallographic structure in magnesium, multiple rolling passes and annealing steps are required to reduce the thickness of the ingots. Thus, high fabrication costs characterize the creation of magnesium sheet suitable for common forming operations. Recently, continuous casting (CC) technology, where molten metal is solidified directly into sheet form, has been applied to magnesium alloys; this method has shown the potential to significantly reduce the cost of fabricating magnesium sheet alloys. In order to understand the viability of the CC process, a study was conducted to investigate the superplastic potential of alloys produced by this method. This study focused on AZ31B Mg that was continuously-cast on twin-roll casters from three different suppliers. These three materials were compared with a production DC-cast AZ31B alloy in terms of microstructure, elevated-temperature tensile properties, and superplastic forming response. The data from this study found that microstructural features such as grain size and segregation can significantly affect the forming response. Additionally, the CC alloys can have equivalent or superior SPF response compared to DC-cast alloys, as demonstrated in both elevated temperature tensile tests and superplastic forming trials using a rectangular pan die.
Finite Element Modeling, Simulation, Tools and Capabilities at Superform Over the past thirty years Superform has been a pioneer in the SPF arena, having developed a keen understanding of the process and a range of unique forming techniques to meet varying market needs. Superform’s high profile list of customers includes Boeing, Airbus, Aston Martin, Ford and Rolls Royce. One of the more recent additions to Superform’s technical know-how is Finite Element Modeling and Simulation. Finite Element Modeling is a powerful numerical technique which when applied to SPF provides a host of benefits including accurate prediction of strain levels in a part, presence of wrinkles and predicting pressure cycles optimized for time and part thickness. This talk will outline a brief history of Finite Element Modeling applied to SPF and then go into some of the modeling tools and techniques that Superform has applied and continues to do so to successfully make complicated parts. The advantages of employing modeling in the design stages are then presented with real world examples.
Finite Element Analysis of SPF and QPF of AA5083 Sheets In this work, finite element analysis of superplastic forming (SPF) and quick-plastic forming (QPF) of AA5083 is presented. A microstructure-based constitutive model capable of describing the deformation of the material at different strain rates is used in the simulation. Different forming scenarios (e.g. constant pressure, constant strain rate and variable strain rate) are discussed.
Transformation Superplastic Forming of Cast Titanium Alloys One approach to expand the application of titanium alloys is to reduce their processing cost by near-net-shape castings. In near-net shape cast parts, an additional forming step is however sometimes still needed to achieve the final shape with the required tolerances and wall thickness. Superplastic forming is an attractive option, due to the low stresses needed for deformation and to the relatively low tooling costs. However, in the as-cast state, titanium and most titanium alloys have a grain structure too coarse to allow deformation by grain-boundary sliding through microstructural superplasticity. Thus, for most titanium alloys - and in particular for the commercially-dominant Ti-6Al-4V alloy - complicated and costly thermo-mechanical treatments are needed to produce the fine grains with equiaxed shape necessary for microstructural superplasticity by grain-boundary sliding, resulting in high tensile strains (>100%) and low strain-rate sensitivity. An alternative approach to achieve high tensile strains uses transformation superplasticity which has no grain-size requirement as it relies on the biasing by an applied external stress of internal stresses produced by cyclical phase transformation. This presentation explores the application of transformation superplastic forming to superplastic form coarse-grain cast titanium. This work was supported by the National Science Foundation.
SPF: Simply Designing and Forming Complex Parts Successfully Much of the early mystique associated with superplastic forming(SPF) has been replaced by sound economic judgement and by sophisticated computer based part and tool design and process simulation techniques. This presentation examines the best approach to part design aimed at achieving functional performance and optimized forming conditions utilizing FE analysis and techno-economic evaluation. Modern downstream post-forming trimming methods and assembly techniques are also reviewed.
Innovative Titanium Sheet Metal Engine Aft Fairing Heat Shields for Boeing Commercial Airplanes In the past, engine aft fairing heat shields have typically been titanium castings. With the 737 Next Generation, these components were converted to titanium 6Al-4V sheet metal details fabricated in either a “U” shape using hot sizing or a “V” shape using Superplastic Forming (SPF). This conversion saved approximately 20% in both cost and weight. When the 787 was being designed, the engineers were looking to develop a sheet metal version of their heat shields hoping to achieve similar savings. However, the 787 design was considerably different from the 737 due to “plume suppressors” which no longer allowed the details to be simple “U” or “V” shaped. Also, the operating environment was more severe with the sonic db level being higher and the temperature being hotter. The 787 design contains SPF details as well as the first Boeing Commercial Airplane application of Superplastic Forming and Diffusion Bonding (SPF/DB). The SPF/DB stop-off technology being used contains several innovative process developments that are covered by patent applications. Some of the heat shield components are fabricated using the world’s first applications of fine grain 6Al-4V titanium, also covered by patent applications, that was developed to SPF at 1450 °F instead of 1650 °F which is used for standard grain material. Due to the temperature requirements, 6Al-2Sn-4Zr-2Mo titanium had to be used for the lower skin and the internal components that touch the skin. The 787 heat shield assemblies are estimated to save approximately 15% in both cost and weight. The 747-8 program has designed heat shields that are very similar to the 787 except the sonic environment does not require the side skins be as stiff so SPF/DB components are not being used. The 777 is investigating converting to the 787 design that would include SPF/DB hardware.
Some New Developments of Superplastic Forming in the Framework of the euro-spf Group SuperPlastic Forming (SPF) is used in several industrial sectors in
Superplasticity in Continuous Cast AA5083 Al Prepared Via Friction Stir Processing In this work, the effect of friction stir processing on the superplastic properties of continuous cast AA5083 Al sheets have been investigated, optimizing the Mn content. Three continuous cast AA5083 alloys with different Mn (0.5, 0.75 and 1.0wt.%) concentrations were friction stir processed using several parameters and pins. Ultra-fined microstructures with averages grain sizes of 0.8-2.5μm were obtained. Tensile test revealed that the maximum tensile elongation of 810% was achieved at 530 ºC and 3 x 10-2 s-1 in the alloy with the lowest Mn content. The stability of the microstructure at elevated temperature was the most important issue to overcome.
A Historical Perspective of Developing the Superplastic Forming Process for Aerospace Applications at the Boeing Company Superplastic Forming (SPF) was developed concurrently in several different divisions in what has now been consolidated into the Boeing Company. The evolution from pure scientific research through to the current state-of-the-art in automation and mass production are explored. The North American Rockwell organization, along with their subsidiary, the Rockwell Science Center, performed pioneering work in the development of SPF of titanium and later made historical innovations in Diffusion Bonding (DB), which they combined together to create the Superplastic Forming and Diffusion Bonding process (SPF/DB). This organization was granted close to 100 The McDonnell Douglas organization found alternative ways to combine welding technologies with SPF and DB in order to fabricate complex sandwich structure using less press time than was required for the Rockwell methods. The 2-sheet SPF/DB and 4-sheet SPF/DB integrally stiffened panels were used extensively on the F-15E aircraft and several other aero-structures. The major developments for these manufacturing processes occurred during the 1970’s through 1990’s. The Boeing Puget Sound organization developed a primitive SPF process during the late 1960’s and early 1970’s, but then abandoned the process for nearly 20 years. In 1988, a new R&D initiative was undertaken geared towards mass production of both aluminum and titanium parts. A manufacturing center for SPF and SPF/DB was subsequently setup for both military and commercial applications. Many medium to large sized assemblies that had been previously been fabricated in multiple pieces were converted to monolithic structures for cost and weight savings.
Indirect Verses Direct Heating of Sheet Materials: Superplastic Forming and Diffusion Bonding Using Lasers Abstract Many from within manufacturing industry consider Superplastic Forming (SPF) to be ‘high tech’ but it is often criticised as too complicated, expensive, slow and, in general, an unstable process. Perhaps, the fundamental cause of this negative perception of SPF, and also of diffusion bonding (DB), is the fact that the current process of SPF/DB relies on indirect sources of heating to produce the conditions necessary for the material to be formed. In the main, heat is usually derived from the electrically heated platens of hydraulic presses, to a lesser extent from within furnaces, and sometimes from heaters imbedded in ceramic moulds. Recent evaluations of these isothermal methods suggest they are slow, thermally inefficient and even inappropriate for the process. In contrast, direct heating of only the material to be formed by modern, electrically efficient, lasers could transform SPF/DB into the first choice of designers in aerospace, automotive, marine, medical, architecture and leisure industries. Furthermore, ‘variable temperature’ direct heating which, in theory, is possible with a laser beam(s) may provide a means to control material thickness distribution, a goal of enormous importance as fuel efficient, lightweight structures for transportation systems are universally sought. This paper compares, and contrasts, the two systems and suggests how a change to laser heating might be achieved.
Combined Mechanical Deep Drawing and Pneumatic Bulge Forming of Superplastic Materials The superplastic forming technique (SPF) is a unique sheet metal forming process that stretches the limits of formability in lightweight alloys beyond conventional, promising greater potentials for applications in the transportation industry. The technique, primarily practiced by pneumatic bulge forming, offers great advantages over conventional forming operations. The ability to shape hard-to-form alloys into highly intricate shapes remains one of the most attractive. Yet, this is generally achieved at low forming rates, causing a major limitation in SPF’s industrial use on a larger scale. In order to overcome this drawback, superplastic forming can be merged or hybridized with several other manufacturing processes, for enhanced forming efficiency and improved productivity merits.
Progressive Distortion Behaviour of Large SPF Tool Under Thermo-Mechanical Fatigue and Fatigue-Creep Interactions SPF tool distortion due to the thermal cycling and cyclic creep can lead to the forming of faulty SPF parts. In addition, thermo-mechanical fatigue and creep can cause cracking, which eventually lead to un-repairable damage to the tool. The aim of the present research work is to develop a generic methodology for predicting the distortion behaviour of large aerospace SPF tools, made from 40% nickel, 20% chromium alloys. Initially FE modelling of the SPF process is performed under realistic forming conditions to understand distortion behaviour of a large representative SPF tool. Progressive distortion of the tool due to creep relaxation during forming cycle (dwell period) is predicted. Thermo-mechanical fatigue-creep interaction tests and high temperature creep tests are designed and carried out based on FE predicted results. FE predictions and experimental results are compared and analysed. Factors affecting tool distortion such as heating and cooling cycles, heating and cooling rates and the batch size are studied to optimize the SPF process.
Necking Instabilities in the Superplastic Deformation of Coarse Grained AA5182 Aluminium Alloys Two coarse-grained Al alloys AA5182 with as-received grain sizes 19 and 34 μm have been evaluated with respect to their superplastic properties. They exhibited moderate elongation to failure reaching maxima, in excess of 300%, at temperatures between 425 and 450oC and at strain rates 10-2 s-1. Extreme grain refinement by recovery, reconstruction and recrystallization produced microstructures consisting of grains as small as 2 μm at the tip region, suggesting that the precipitates are quite effective in pinning the subgrain boundaries, which in turn are readily converted into low and high angle grain boundaries. This grain refinement, however, occurred also randomly in other locations in the specimens, wherever large strain was localized, resulting in multiple necking in specimens exhibiting maximum elongations prior to failure.This behavior renders coarse grained AA5182 Al-alloys quite unstable, as superplastic materials and, despite their low fabrication cost, their precipitate size needs to be regulated further, so that their superplastic elongation to retain the uniformity that is required in practical applications in the automotive and aerospace industry.
On the Activation Energy for Super Plastic Flow By applying the quantum mechanics and relativistic mathematical model of Muñoz-Andrade the activation energy for super plastic flow in spatially extended polycrystalline systems is obtained. Over this framework, in the present study the activation energy for super plastic flow in spatially extended polycrystalline systems dependence on strain rate and phase velocity de Broglie are obtained, in addition, the nature determination of the wavelength of the cellular dislocations l^ wave associated with super plastic flow. It is concluded that the super plastic flow associated with cooperative grain boundary sliding and self accommodation process is assisted in nature behavior by cellular dislocation dynamics. Furthermore, the most important results of this work are analyzed in the environment of the cosmic micromechanics connection during super plastic flow in spatially extended polycrystalline systems.
Material Models for Simulation of Superplastic Mg Alloy Sheet Forming Magnesium (Mg) alloys are currently the focus of a worldwide effort aimed at increasing their use in automotive components because of their low densities and high strength-to-weight ratios. Because forming at elevated temperatures, e.g. 400 to 500 °C, provides excellent ductility in several wrought Mg alloys, hot forming is of great interest for producing these components. Unfortunately, the availability of accurate material models for plasticity in wrought Mg alloys at elevated temperatures is severely limited. The present study investigates a material constitutive model for high-temperature plasticity in a fine-grained Mg AZ31 sheet material, developed using data from uniaxial tension, and evaluates the accuracy and applicability of this constitutive model to finite-element-method simulations of forming under biaxial tension conditions. Bulge forming experiments, which produce a nearly balanced-biaxial stress state, were conducted at 450 °C using four constant gas pressures. Simulation results are compared with experimental results. It is discovered that wrought Mg AZ31 behaves differently than wrought Al alloys previously investigated, e.g. fine-grained AA5083 sheet. Recommendations on the use of experimental data for constitutive model construction and on applying constitutive models to forming simulations are made.
Basic Studies for Materials State Awareness In integrated vehicle health monitoring and materials damage assessment it is not clearly known how sensitive the damage detection capability will be to changes in material characteristics which may be due, for example, to heat exposure. Additional effects on the damage detection capability can also arise due to other external factors; however, they will not be examined here. This study investigates the influence of heat treatment on damage detection capability through a comparison of wave propagation and vibration characteristics of thermally soaked specimens with those of baseline measurements. A set of Titanium and Aluminum specimens was utilized in these experiments. For each specimen, ultrasonic velocity, and dynamic vibration characteristics were measured before and after each thermal exposure.
Precious-Metal Sensors for HM in Harsh Environments Nickel-based sensor utility is limited when exposed to high temperatures for long periods, due to oxidation effects which affect durability and repeatability. This work addresses these shortcomings using precious metal-based devices, including thermocouples and strain gages, which potentially offer higher longevity and more consistent response over sensor lifetime. Devices are deposited by Mesoplasma Direct Write, a high-precision derivative of thermal spray, capable of embedding multilayer thick-film devices onto surfaces and within coatings. In-situ temperature and strain measurement capability in engines and other harsh environments supports HM by reducing uncertainty, and consequently extending service intervals and increasing asset availability.
Development of a Residual Stress Depth Profile Measurement Instrument 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. Many research 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 component alloys. At the present, there is interest in extending engine life by taking credit for residual stresses that extend fatigue life; however, this requires accurate, nondestructive measurement of the residual stresses. In recent years, 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 eddy current frequency can be used to calculate residual stress as a function of depth in the material. In November 2005 the U.S.A.F. awarded a competitively-bid contract to the - electrical conductivity measurements accurate to within 0.1 percent relative to the nominal alloy conductivity - measurement times of less than 5 minutes - EC frequencies from 100 kHz to 50 MHz - instrument design anticipates eventual usage in a depot environment as part of an automated inspection system
X-ray nanoCT: 3D Analysis of Aerospace Materials with Submicrometer Resolution During the last decade, Computed Tomography (CT) has progressed to higher resolution and faster reconstruction of the 3D-volume. Most recently it even allows a three-dimensional look into the inside of materials with submicron resolution. By means of nanofocus® tube technology, nanoCT®-systems are pushing forward into application fields that were exclusive to expensive synchrotron techniques. High-resolution X-ray CT allows the 3D visualization and failure analysis of the internal microstructure of aerospace materials like light metal alloys, CFKs and other composites – even where 2D X-ray microscopy would give only the integral information of the overlaying internal features.
Laser-Ultrasonic and Laser-Tapping Techniques for Probing Aerospace Composite Structures
Detection of Defects in Aerospace Low Pressure Compressor Blades Using Ultrasonic Techniques Complex geometry components made from titanium material such as aerospace gas turbine Fan engines is often classified as “safety critical” component, and subject to very high stresses and vibration. It required the highest structural integrity. NDT techniques such as Ultrasonic and eddy current have been developed to inspect these components. This paper presents an ultrasonic testing inspection for the fan blades components, modeling using CIVA and Continuum Ultrasonic Modeler has been performed in order to predict the ultrasound propagation and defects responses for different type of scans. A comparison between the experimental and modelling results was shown good accuracy of the modeling in predicting the ultrasonic inspection performance.
Detection of Defects in Aerospace Low Pressure Compressor Blades using Eddy Current Arrays Aerospace gas turbine Turbo Fan engines operate under harsh environmental conditions involving high temperatures, friction, eroding and corroding elements. Low Pressure Compressor blades (Fan Blades) are also subject to very high stresses and vibration, especially during aircraft take-off and landing, which can lead to crack initiation and subsequent propagation. Unless existing cracks are identified before reaching critical dimensions, turbine blades will fail causing a chain of events that could eventually render the host turbine engine inoperable. This paper discusses the development of novel eddy current arrays customised for the inspection of turbine blades using a commercially available eddy current acquisition unit.
Early Fatigue Detection in Aerospace Alloys with MWM-Array Eddy Current Sensors This presentation discusses the results of MWM-Array monitoring during fatigue tests of aluminum 7075-T651 and Ti-6Al-4V coupons. The goal is detection of early-stage cracks in aluminum and titanium alloys. Results are presented for two different coupon geometries. The aluminum coupons are flat plates with electro-polished and as-machined holes. The titanium coupons have exposed, curved surfaces that are shot peened. MWM‑Arrays are used in both scanning and surface-mounted configurations. Acetate replicas provide the actual crack lengths at multiple intervals throughout the fatigue tests of the titanium coupons.
In-Process Quality Assurance for Welding: Applications to Aerospace Manufacturing In-Process Quality Assurance is an emerging field of enquiry in manufacturing technology that started in the 1980s and has seen recent growth in several areas of welding for aerospace applications. This talk reviews the underlying technology for In-Process Quality Assurance as well as recent applications to aerospace and other critical parts manufacture. The historical evolution of the concept will also be traced as it has been applied to the aerospace industry in particular. The basis for In-Process Quality Assurance is the direct interrogation of process physics and dynamics as opposed to exclusive reliance on machine tool monitoring or post-process inspection. In-Process Quality Assurance is complimentary to these other technologies and provides valuable process information not available through other means. Applications to real-time closed loop control will also be discussed. In this modality of operation, In-Process Quality Assurance is used to largely preclude the occurrence of defects altogether. Specific application areas to be discussed include: gas metal arc weld (GMAW) repair of titanium IBRs, rotary friction welding, linear friction welding of titanium, and other welding applications to non-aerospace industries. Case studies will be shown that specifically address how the technology is applied, how it may be integrated into an overall quality system, and what quality questions it can address as well as limitations to applicability.
Analytical model of the interaction of Lamb waves with fastener sites Critical issues remain to be addressed concerning the reliability of in-situ ultrasonic sensors in the structural health monitoring (SHM) domain, where ultrasonic guided waves have been proposed for the frequent monitoring of aircraft joints for fatigue cracks around fastener sites. In particular, the interface conditions between the fastener shaft and hole are found to vary with time, and often independently of the damage state of the joint. Changes in the magnitude of scattered ultrasonic signals from fastener sites can result from dynamic structural loading, thermal cycling, aging of sealant present in some structures, and scheduled maintenance actions. Under certain conditions, the scattered signals from a fastener location can be difficult to distinguish from fatigue crack signals. Prior work from ultrasonic measurements of fastener sites in aging aircraft has highlighted the variation in fastener-hole fit conditions and the challenge of separating crack signals around the fastener site from re-radiated signals from the fastener hole. To better understand the scattering of ultrasonic guided waves from fastener sites in aircraft structures, analytical models are presented and used for studying the interaction of ultrasonic waves with a cylindrical hole and an elastic insert which are coupled by a stiffness interface. Parametric studies are presented which investigate the effect of variations in the fastener contact conditions on the reflection of incident Lamb waves and the generation of secondary waves around the fastener hole.
Magnetostrictive Sensor for Health Monitoring in Aircraft Structures The DoD aircraft fleets consisting of the C-5, C-17, B-52, A-10, F-16, F-15, and others are aging and in many cases either exceeding their intended life or rapidly approaching their intended life with no new aircraft purchases on the horizon. One way to keep the aircraft flying is to use structural health monitoring (SHM) technologies. SwRI has developed the magnetostrictive sensor (MsS) technology that has been successfully used to monitor piping, but has applications to plate geometries such as aircraft structure. The MsS probe has a low profile (approximately 0.005 inch thick) and is bonded to the surface of the structure. The MsS probe generates a guided wave that travels long distances from the probe into the plate or aircraft structure to provide a means of long range inspection and condition monitoring. SwRI has conducted a wide range of laboratory tests to demonstrate the feasibility of MsS to detect defects under fasteners, quality of bond of patches, and defect growth under patches. Recently, SwRI utilized the MsS technology on a C-141 test panel. The MsS was bonded to various surfaces and then the surfaces were subjected to 20,000 ksi loads to study potential issues associated with sensor debonding and slight changes that might occur in the fastener holes. Notches were introduced into several fastener holes and used the MsS to monitor changes in the defects. The purpose of this paper is to describe the MsS technology and the results of the various laboratory experiments showing the potential for MsS aircraft structural health monitoring. The DoD aircraft fleets consisting of the C-5, C-17, B-52, A-10, F-16, F-15, and others are aging and in many cases either exceeding their intended life or rapidly approaching their intended life with no new aircraft purchases on the horizon. One way to keep the aircraft flying is to use structural health monitoring (SHM) technologies. SwRI has developed the magnetostrictive sensor (MsS) technology that has been successfully used to monitor piping, but has applications to plate geometries such as aircraft structure. The MsS probe has a low profile (approximately 0.005 inch thick) and is bonded to the surface of the structure. The MsS probe generates a guided wave that travels long distances from the probe into the plate or aircraft structure to provide a means of long range inspection and condition monitoring. SwRI has conducted a wide range of laboratory tests to demonstrate the feasibility of MsS to detect defects under fasteners, quality of bond of patches, and defect growth under patches. Recently, SwRI utilized the MsS technology on a C-141 test panel. The MsS was bonded to various surfaces and then the surfaces were subjected to 20,000 ksi loads to study potential issues associated with sensor debonding and slight changes that might occur in the fastener holes. Notches were introduced into several fastener holes and used the MsS to monitor changes in the defects. The purpose of this paper is to describe the MsS technology and the results of the various laboratory experiments showing the potential for MsS aircraft structural health monitoring.
Validation of Nondestructive Testing Sensors Used in Structural Health Monitoring There is considerable interest in aerospace and other industries in the use of sensors for structural health monitoring (SHM) that are derived from or are the same as sensors used for conventional nondestructive testing (NDT) applications. Texas Research Institute Austin (TRI/Austin) Inc. and Analytical Processes/Engineered Solutions (AP/ES) Inc. have collaborated to develop a process for the selection and validation of NDT and other sensors applied to SHM in aerospace structures. AP/ES has developed and demonstrated a quantitative process for determining optimum sensor selection and application. This process carefully considers costs of implementation and support in operation of SHM, in comparison to existing procedures. Once a cost-effective SHM system has been designed for an application, validation of the SHM system is required just as validation of new NDT procedures is required. In this work, we discuss the SHM design process, and describe in detail the validation studies being performed by TRI/Austin and AP/ES on sensors for corrosion damage and fatigue damage in aerospace structures. These studies are being performed to demonstrate both the SHM system reliability, as well as the damage detection reliability. Coupon tests using materials, loads, and environments typical of the target application are the key elements of the validation. Results will be presented from these coupon tests. These efforts are supported by SBIR funding from the Air Force Research Laboratories Materials and Manufacturing Directorate.
Sensing, Life Prediction and Probabilistic Analysis Technologies for Turbine Engine Prognosis The development and implementation of prognosis technology for integrated system health management (ISHM) has the potential to significantly enhance the reliability and readiness of high-value assets, while concurrently decreasing sustainment costs. The systems approach includes the acquisition and fusion of on-line sensor information, combined with physics-based models for damage accumulation, and higher order reasoning for decision making. This presentation will summarize and demonstrate the benefits of several recently developed ISHM-enabling technologies. First, enhancements to the DARWIN® probabilistic fracture mechanics code that are relevant to military engine application will be summarized, and example applications will be given. These enhancements will be employed to assess the benefits of tracking actual engine usage and monitoring material damage (i.e. fatigue cracking) in assessing remaining fatigue life and forecasting probability of component failure. Specifically, an advanced fracture mechanics model, which explicitly treats crack nucleation, small crack propagation, and large crack propagation, will be described. This model will be used to demonstrate the benefits of usage tracking to the component level by assess the conservatism in employing Total Accumulated Cycles (TACs) versus actual usage data to predict fatigue life. A probabilistic method for mission identification will also be described and assessed using actual usage data from flight data recorders at USAF bases. The utility of this method for forecasting the impact of projected changes in mission mixing on future fatigue damage accumulation and probability of failure will also be discussed. The development of a statistical model for sensor uncertainty, based on laboratory data on a thin film magnetostrictive sensor for crack detection, will also be described. This sensor model will then be combined with probabilistic simulation to assess the potential benefits of embedded sensors for on-line detection and monitoring of defects, as compared to the more traditional mid-life depot inspection.
Structural Prognosis During an EA-6B Outer Wing Panel Fatigue Test* The Northrop Grumman/DARPA Structural Integrity Prognsosis System (SIPS) was applied to a full-scale fatigue test of a retired EA-6B outer wing panel. The test was conducted by NAVAIR at Patuxent River, MD. The panel had been retired from active service with a Fatigue Life Expended index of 185. Laboratory fatigue testing of the entire panel was performed to evaluate several sensor systems, SIPS fatigue models, and the SIPS reasoning and prediction system. Phased array ultrasonics was used as a non-destructive inspection system to evaluate the starting state, and pitch-catch ultrasonics, eddy current (MWM®-Array) and the electrochemical fatigue sensors were used to monitor fasteners on rib 1 during the test. A FASTRAN-based modeling system was used to predict the evolution of cracking. The SIPS reasoning system combined the model and sensor outputs to provide a probabilistic crack size prediction that was updated daily. After the test, the panel was disassembled and actual crack sizes in the bores of the fastener holes were measured using scanning electron microscopy and compared to the sensor readings. The entire system performed admirably, and much useful data was obtained. *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
Non-Destructive Evaluations and the Advance Life Prediction System The Advanced Life Prediction System (ALPS) is a formidable new tool to incorporate into the Non-Destructive Evaluations (NDE) methodology. Testing in the aerospace industry is expensive and time consuming. The
Scaled Turbine Engine Testing for Cost-effective Health Prognosis Full scale gas turbine engine testing is expensive and time consuming. An efficient alternative is the use of low cost subscale engine testing that can simulate the conditions of a full-scale engine and its failure mechanisms. VEXTEC has developed scaled turbine engine tests as a platform to gather probabilistic data on multiple material failure mechanisms such as thermal mechanical fatigue, biaxial crack growth, creep and foreign object damage. These tests are efficient in terms of cost and schedule and provide insight into full scale engine behavior. Complex multi-axial stress fields and thermal environment typically observed in gas turbine engines are naturally reproduced in the scaled engine testing. Subscale engine testing is validated by comparing the test data with full scale engine testing results. This paper discusses the capabilities of the scaled engine and its benefits compared to full scale engine testing.
Predicting Fatigue Crack Progression in Ti-6Al-4V Under Mini-Sweep Loading In the aerospace industry, rotating engine components are subject to resonant vibratory loads under various operating conditions. These vibratory loads are typically experienced for only brief periods as the rotational speed of the engine traverses critical modes. These relatively brief bursts of resonant vibration, referred to as “mini-sweeps,” can contribute to the initiation of fatigue cracks, or the propagation of existing fatigue damage. This study investigates the propagation of long and small fatigue cracks in Ti-6Al-4V under mini-sweep loading conditions. Bursts of variable amplitude loading were applied to cylindrical, dog-bone specimens and a compact-tension (C(T)) specimen under a frequency of 20 Hz at room temperature. The loading profile is consistent with a typical mini-sweep experienced in rotating hardware during service. Long crack growth rates under the mini-sweep loading profile were monitored in the C(T) specimen using direct current potential drop (DCPD) and optical observation. The growth of small fatigue cracks, initiated from artificial notches, was monitored using a standard replication technique. The fatigue crack growth behavior under these loading conditions will be presented and the implications for improved lifing methods of critical rotating components will be discussed.
Sustainment of Compressor Components Through Low Plasticity Burnishing (LPB) Use of compressive residual stresses in turbine engine compressor parts is proving to be very useful for sustainment of parts prone to different damage conditions. The leading and trailing edge of blades and vanes are subject to fatigue cracking and foreign object damage (FOD). Both the blade dovetail and the rotor disk post contact surfaces are vulnerable to fretting damage, which leads to microcracking and mode I fatigue cracks. Low plasticity burnishing (LPB) has been shown to introduce controlled magnitude and distribution of compressive residual stresses to completely mitigate either FOD on the edges of vanes and blades or fretting-induced microcracks at the edge of bedding on the contact faces of the dovetails and rotor disk posts. Residual stress field design, specialized LPB tooling, quality assurance (QA) of the process exceeding six-sigma, and the ease of application of LPB as a simple machining process on the shop floor will be described. Benefits due to current applications of LPB to the US Navy and other naval groups internationally in improved damage tolerance and reduced total ownership costs of turbine engines will be highlighted.
Probabilistic 3-D Crack Growth Analysis for Gas Turbine Engine Components Traditional full scale engine tests are prohibitively expensive in terms of time and cost. In addition they provide limited insight into the probabilistic nature of fatigue crack growth in the components. VEXTEC Corporation has developed innovative 3-D probabilistic crack growth models in conjunction with scaled turbine testing to accurately capture crack growth behavior in turbine engine rotors. The models combine the automatic re-meshing in commercial available finite element tools with probabilistic crack growth techniques. The stochastic model has the capability to assess crack growth in multi-axial stress fields with random material properties along the crack front and accounts for crack kinking and branching. These models are evaluated based on test data gathered from scaled engine testing with the ultimate goal of predicting fatigue crack growth behavior in a full scale engine.
The Effect of Hydrogen on the Fracture Toughness of Ti-5Mo-5V-5Al-3Cr Ti-5Mo-5V-5Al-3Cr (Ti-5-5-5-3) is an emerging near-β Ti alloy of significant commercial interest as a viable replacement for Ti-6Al-4V, Ti-10Al-2V-3Fe and some high strength steels in a variety of aerospace applications. Ti-5-5-5-3 offers significantly improved thick section hardenability in a product capable of being extruded, rolled, forged, and/or cast. In addition, Ti-5-5-5-3 can be heat treated in several ways to achieve high strength, high fracture toughness, high fatigue resistance, or a good combination of all of those properties. Recently, evidence has emerged that hydrogen content strongly influences the fracture toughness, a critical aerospace design parameter, at all levels below typical specification limits for titanium alloys. Positive identification of hydrogen as a prominent factor in fracture toughness control could have an impact in alloy specification limits, heat-treatment requirements, additional processing, and new alloy grades, all of which could lead to significant cost and/or value added for low hydrogen content material. A wide variety of characterization tools, including light microscopy, SEM fractography, and TEM, were employed to explore the effects of hydrogen on the microstructure of Ti-5-5-5-3 and the resulting fracture toughness. Hydrogen has been verified to have a strong effect, especially at low levels, on the fracture toughness of Ti-5-5-5-3. The reduced fracture toughness appears to be largely associated with an increase in the amount and nature of boundary type fracture modes. The exact mechanism for how hydrogen modifies boundary fracture behavior is still under investigation; however changes in α phase morphology have been observed as well, and may provide a key to further understanding.
Mechanical Properties of Heat Treated Ti-5Al-5V-5Mo-3Cr: an Attempt to Define Critical Properties of Various Microstructural Features The properties and microstructure of Ti-5Al-5V-5Mo-3Cr were characterized under various stress states after the following heat treatments: 1) beta anneal and air cool; 2) solution heat treatment in the alpha-beta range; 3) solution heat treatment and ageing in the alpha-beta range. For each condition, the damage mechanisms and final fracture modes were evaluated and rationalized on the basis of microstructural features. The true fracture stresses for the various conditions are compared. Beta annealed material exhibits intense localized slip deformation leading to early crack formation and fracture. This mechanism is explained in relation to the presence of fine metastable phase precipitates resulting from the air cool step. Grain size dependence of the yield stress is described in terms of the Hall-Petch relationship.
Heat treatment, microstructure, and properties of TIMETAL 555 TIMETAL 555 (Ti-5Al-5Mo-5V-3Cr-0.6Fe) is a titanium alloy that can achieve property combinations potentially useful for structural applications. The alloy is currently under evaluation for several major airframe programs. A wide variety of strength, ductility and fracture toughness values can be achieved depending on thermomechanical processing and heat treatment. This presentation provides recent results regarding the interactions between heat treatment, microstructures and properties.
Evolution of Nanoscale Microstructures in Complex Beta Titanium Alloys The solid-state decomposition of the beta phase of titanium alloys is a rather complex phenomenon involving multiple competing instabilities which includes phase separation in the beta phase and precipitation of the omega and alpha phases. Interestingly, despite their widespread application, the microstructural evolution and resultant mechanical properties of these alloys are rather poorly understood. Furthermore, recent developments in advanced characterization techniques such as high-resolution scanning transmission electron microscopy and 3D atom probe tomography allow for unprecedented insights into the true atomic scale structure and chemistry changes associated with the instabilities in the beta phase of these complex alloys. Such detailed studies are being carried out on different beta titanium alloys including the Ti-5Al-5Mo-5V-3Cr-0.5Fe (TIMETAL-5553 or Ti-5553) alloy, used in aerospace applications, and the Ti-35Nb-7Zr-5Ta alloy, used in orthopedic implant applications. The results of these studies will form the basis of this presentation.
Preliminary Characterization of Processing-Microstructure-Property Relationships for Blended-Elemental, Powder-based, Canless Extrusions Using the results of a workability study program in combination with prior extrusion experience at RTI, the feasibility of canless extrusion in ambient environment of hydride/dehydride blended elemental, Ti-6AL-4V ADMA-Processed powder, previously direct-consolidated by cold isostatic pressing (CIP), followed by vacuum sintering has been successfully demonstrated. The workability tests of powder-based elevated temperature compression specimens showed that powder-based consolidated billets of similar baseline composition as for wrought ingot-based Ti-6AL-4V billets will require lower extrusion pressures at same extrusion temperatures and strain rates. Laboratory analysis showed that the canless powder-based billet extrusion processing step conducted in air added no more than 200 ppm oxygen to the as-vacuum-sintered billet oxygen content. Preliminary tensile properties of the blended-elemental ADMA powder-based extrusions of a Ti-6AL-4V composition processed both in the beta or alpha-beta ranges of extrusion temperatures showed at least equivalent tensile properties as compared to identically processed wrought, ingot-based and extruded Ti-6AL-4V billet materials. In the blended elemental powder-based extrusions both nitrogen and carbon contents were within specification limits for Ti-6AL-4V alloy, while any excessive residual hydrogen was successfully vacuum degassed after extrusion to within specification limits. Further optimization for fracture toughness, stress-corrosion resistance and fatigue properties will build on these encouraging results, while monitoring and controlling powder-based product interstitial content, namely oxygen uptake during pre-extrusion powder-consolidation processing steps.
Processing and properties of TIMETAL 54M, a new alpha-beta alloy with improved machinability TIMETAL 54M (Ti-5Al-4V-0.6Mo-0.4Fe) is an alpha-beta titanium alloy that was developed to improve upon the overall production costs of Ti-6Al-4V while providing similar properties. TIMET has produced significant quantities of 54M via Electron-Beam Single-Melting (EBSM). The alloy is being evaluated for both aerospace and non-aerospace applications. Prior studies have shown that 54M provides improved drill machinability using conventional carbide tools, indicating that 54M may enable improved cutting tool life and/or accommodate increased cutting speeds. In a recent trial, a beta-extruded 54M shape was machined alongside a production Ti-6Al-4V airframe component; this experience reinforced the machinability benefit of 54M. Mechanical properties of the machined component are comparable to typical properties for similarly processed Ti-6Al-4V.
Fatigue Performance of 0.030" thick Machined Ti-6Al-4V Machining of titanium to less than 0.080” thickness is required to take full advantage of titanium's specific properties and make it competitive with other materials. These pocketed machined parts are often composed of thin rib-stiffeners coupled to a thin floor or web. As the machined thickness is decreased, machining has the potential to alter both static and fatigue properties as a result of surface deformation and residual stress. In this paper, Ti-6Al-4V plate was machined to various thicknesses (0.020” to 0.120”) to determine the change in static and dynamic properties. The most notable change in static properties with thickness is a loss of tensile ductility (~25% decrease) at gages thinner than 0.080”. A loss in ultimate tensile strength was observed at a gage thickness less than 0.040”. Fatigue performance was investigated using three different testing configurations on materials that had a nominal thickness of either 0.030” or 0.080”. A rib-stiffener machining practice was used to produce the axial fatigue specimens. The fatigue strength at 10^6 cycles of the 0.030” thick gage was approximately 7% lower than the 0.080” thick gage specimens and the thinner gage specimens had lower cyclic life at the higher stress ranges, which corroborates the lower ductility observed in static tests. Bending fatigue studies using Krouse-type specimens are being conducted to better assess the effects of machining on the surface. These tests are being conducted using a servohydraulic test frame in load control. Sub-component testing on a 0.030” nominal thickness pocketed web and rib specimen with 0.120” fillet radius was also conducted to quantify the performance improvement resulting from hand blending the machined surface. Finite element analysis was used to determine the surface stress as a function of applied load; and, modeling and test results will be presented at the conference.
Canless extrusion process development for blended-elemental powder-based titanium 6Al-4V alloy The feasibility of canless extrusion in ambient environment of hydride/dehydride blended elemental Ti-6AL-4V ADMA-processed powder previously direct-consolidated by cold isostatic pressing (CIP), followed by vacuum sintering has been successfully demonstrated. In these extrusion process trials at Plymouth Engineered Shapes the extrusion processing sequence and parameters used were essentially similar to those used for billets prepared from wrought ingot-based Ti-6AL-4V material. Boeing Laboratory analysis showed that the canless powder-based billet extrusion processing step conducted in air added no more than 200 ppm oxygen to the as-vacuum-sintered billet oxygen content. Preliminary tensile properties of the blended-elemental ADMA powder-based extrusions of a Ti-6AL-4V composition processed both in the beta or alpha-beta ranges of extrusion temperatures showed equivalent or superior tensile properties as compared to identically processed wrought, ingot-based and extruded Ti-6AL-4V billet materials. In the blended elemental powder-based extrusions both nitrogen and carbon contents were within specification limits for Ti-6AL-4V alloy, while any excessive residual hydrogen was successfully vacuum degassed after extrusion to within specification limits. Further optimization for fracture toughness, stress-corrosion resistance and fatigue properties will build on these encouraging results, while monitoring and controlling the only remaining powder-based interstitial element, namely oxygen uptake during pre-extrusion powder-consolidation processing steps.
Effect of Water-jet Cutting on Fatigue Performance of Ti-6Al-4V Sheet Water-jet cutting is an attractive process for the machining of titanium components, but little is known regarding how this cutting operation affects performance. In this paper, Ti-6Al-4V sheet was water-jet cut and the cyclic life determined by load control fatigue testing. Titanium sheet with nominal thickness 0.0415 inches was obtained in the annealed condition as MIL-T-9046J (AB-1). Fatigue specimens were water-jet cut from the Ti-6Al-4V sheet at a pressure of 40,000 psi, using a 80 mesh garnet abrasive of less than 180 ?m diameter, fed at a rate of 0.62 pounds per minute with linear cutting speeds of 5 and15 inches per minute. Specimens cut at the faster speed were randomly selected and the edges were polished using 600 and 800 grit metallographic papers. Fatigue tests were performed in load control with R(Smin/Smax) = 0.1 and using a sinusoidal waveform. All fatigue cracks initiated at the specimen edge and propagated across the gage section. Polishing the water jet surface improved the overall fatigue life and increased the fatigue strength at 10^6 by up to 40%. A modest 8% increase in the fatigue strength at 10^6 cycles was observed for the lower cutting speed. Post mortem analysis revealed that fatigue crack nucleation occurred at surface scars produced during water jet cutting.
Titanium Alloy Development Needs for Commercial Airframes There is continual pressure on the aircraft industry to reduce both manufacturing and operating costs. The former occurs in the form of pressure to reduce component and material costs; the latter in the form of reduced maintenance costs and aircraft weight. Weight and cost are thus interrelated, and sometimes at odds, in the design process. Titanium is historically utilized in airframes to solve specific problems related to high temperatures, specific strength or corrosion. For graphite-reinforced composites, the natural compatibility of titanium relative to aluminum or steel alloys has lead to an increase in the fraction of titanium alloys on the airframe, but with concordant increases in build costs. This has lead to an evolution in the needs of the airframe industry with respect to titanium alloy properties and utilization. This paper will provide an overview of typical applications of titanium alloys and what the design drivers are for these applications. The purpose of this paper is to relate these needs to the titanium industry so that better alloy development solutions can be conceived and offered.
Low Cost Near Net Shape Forgings from Ti-6-4 Considering the high material and machining cost of titanium alloys the development of a near net shape forging technology for titanium alloys is very attractive since it allows reducing the cost both on input weight and on machining.
When Investment Casting is Good Value The term casting often suggests products with properties generally inferior to wrought products. This is not true with titanium cast parts.
Mechanical Properties of Cast Ti-6Al-4V Lattice Block Structures Lattice block structures (LBS) - also called lattice-truss structures, truss-core sandwiches, and cellular lattices - are three-dimensional-periodic reticulated materials that derive their outstanding mechanical performance from a high-symmetry arrangement of internal trusses connected at nodes. They are innovations that provide tremendous opportunities for weight and cost reduction in future aerospace systems, both commercial and military. In this presentation, the structural and mechanical characterization of individual Ti-6Al-4V struts and complete Ti-6Al-4V LBS panels produced by investment casting are reported. Testing in compression, bending, and impact show that high strength, ductility and energy absorption are achieved for both individual struts and full panels, despite the difficulties of casting such fine struts from a highly reactive liquid titanium alloy. The experimental compressive stress-strain behavior of the LBS panels will be compared to finite-element modeling predictions. This work was supported by NASA-Glenn Research Center.
Development of Advanced Titanium Welding Processes for Improved Material Utilization in Aerospace Manufacturing The use of Titanium by the aerospace industry has recently been driven to unprecedented levels, which has resulted in price escalations and temporary supply shortages. Most titanium parts are machined out of plate, blocks, forgings or extrusions, which all result in wasted scrap material and unnecessarily high fabrication costs. In order to reduce the buy-to-fly ratio of titanium parts, more efficient manufacturing techniques must be implemented. Laser Welding of titanium 6Al-4V has been developed for producing near net shape structural components. Process parameters have been identified for producing very repeatable, high quality welds on a variety of material thicknesses and joint configurations. Extensive metallurgical examinations and preliminary mechanical property evaluations have been performed to qualify this process for fabricating structural parts. It has been found that the mechanical properties of automated Laser Welded titanium joints are very close to being the same as the parent metal and that equivalent performance can be achieved with a minimal weight increase to the overall part. Furthermore, the statistical variance in the mechanical test data is very low which is extremely important for efficiently designing any performance critical part as a welded structure. In addition to Laser Welding, Friction Stir Welding of titanium 6Al-4V is being developed for a variety of thicknesses and joint configurations. Friction Stir Welding is a solid state welding process capable of retaining the microstructural integrity of the parent material. This makes Friction Stir Welding very attractive for welding fatigue critical and damage tolerant primary air frame structure. Preliminary mechanical test data has shown that the fatigue properties of Friction Stir Welded titanium butt joints are comparable to parent material. The primary difficulty in the development of heavy gage titanium Friction Stir Welding was to identify the tooling designs and process parameters for producing defect free joints. Finally, by combining one of these advanced welding techniques with Hot Forming, near net shape parts can be produced with aerospace quality dimensional tolerances at a dramatically improved material utilization level. The main considerations for developing Hot Forming of welded titanium structures include tooling designs and processing techniques.
Development of the Hot Stretch Forming Process Technology Hot Stretch Forming of Near Net Shape Titanium Profiles The development of Hot Stretch Forming was motivated by the need to design and manufacture Titanium airframe structures for new aircraft with carbon fiber fuselage skins. Many of these structures are contoured to fit against the inside radius of the fuselage curvature. By combining traditional stretch forming technology with hot metal forming techniques, the new technology of Hot Stretch Forming (HSF) was developed by the Cyril Bath Company. This new forming technology allows design engineers to develop a variety of Titanium structure profiles that will be curved to a specific and precise radius prior to final machining. This new technology is cost effective, repeatable, and available to be used for immediate production in volumes to meet aircraft build rates, now and in the future. The Hot Stretch Forming process saves both material and machining time; both serious cost issues for today’s aircraft build budgets. In addition, the process allows for consistent quality, assuring the sustainable attainment of delivery and build schedules. A general description of the HSF process will be presented, including stretch press designs, control and heating systems, metallurgical issues, tooling issues, and material handling issues. The benefits of this process in controlling and minimizing residual stress allowing consistent machining will be discussed.
Use the HSS Cutters for Titanium Alloys Machining! The paper is focused on milling of Titanium alloy Ti6Al4V using HSS cutters. This kind of material is obviously machined by carbide tools. But, it is possible to use also HSS tools and low cutting velocity. Under this condition performance of the HSS tools can be higher than the performance of the carbide tools. Performance of any machining operation is limited by chattering. When milling, stability diagram can be calculated to find stable depth of cut (DOC) and stable ranges of spindle speed. DOC level depends on dynamic stiffness of the tool – spindle mechanical system. Titanium milling needs a stiff tool-spindle structure powered by a strong motor. Stable DOC at low cutting speeds is significantly higher comparing to stable DOC available within high speed range. The paper shows stable diagrams as well as couple of curves referring the tool life under this condition. The results for tool materials obtained by the technology of Powder Metallurgy are promising.
Machining Titanium Alloy With Pulsed Injecting Coolant Technique To Improve a Eco-Friendly Enviornment in Industries Machining plays a predominant role in making of components in many critical applications such as aerospace, transportation industries, and biomedical engineering. Environmental concerns call for the reduced use of cutting fluids in machining practices. New cutting techniques are to be investigated to achieve this objective. In the present work a specially formulated cutting fluid was applied as a high velocity, thin pulsed jet at the immediate cutting zones at an extremely low discharge with high speed using a fluid application system developed for this purpose during turning of titanium alloy. Aerospace material machining in complement with a plentiful supply of cutting fluid is the normal practice on the shop floor, which is supposed to exploit the cooling, lubrication and chip removal action of cutting fluids. However recent concepts and awareness of sustainable manufacture are often on a collision course with the use of cutting fluids. Large quantity use of cutting fluids pose problems of procurement, storage, disposal and maintenance. In other words, apart from the cost, flood application is not environment or people friendly. This factor assumes considerable significance in the recent climate of strict work safety and environmental protection. According to the Occupational Safety and Health Administration (OSHA) regulations, the permissible exposure Level for mist within the plant (PEL) is 5 mg/m3 and is likely to be reduced to 0.5 mg/m3. This paper aimed at studying the performance of CBN tool inserts in the machining of Titanium alloy. Machining of titanium alloy is investigated in conventional dry turning and wet turning with minimal fluid application methods by varying parameters such as speed and feed, maintaining constant depth of cut. The cutting performance in turning of titanium alloy with pulsed jet coolant system is evaluated by using the performance investigators such as tool flank wear, surface roughness, and cutting force.
Improved Titanium Machining: Modeling and Analysis of 5-Axis Tool Paths via Physics-Based Methods The manufacturing of monolithic aerospace structures entails development of complicated 5-axis tool paths containing thousands of lines of code and dozens of tool changes for milling and drilling operations. In-cut machining cycle times of 50 -100 hours time are common. Meaningful reduction of cycle time while maintaining part quality is predicated upon the ability to model the physics of the machining operations. A methodology to predict forces and temperatures used for analyzing large, complicated 5-axis tool paths for aerospace structure machining is presented. The ability to accurately model lengths scales from the chip load (~100 microns), part thickness (~2 mm), cutter depths of cut (~10 mm) and over part dimensions (~10 m) is provided. Forces and
Progress in Deposited Titanium: Drafting MAI The field of deposited metals continues to grow at a rapid pace. While the technologies face their share of technical challenges, arguably the greatest challenge for these technologies is acceptance. This presentation will give an overview of the technical challenges and progress, acceptance challenges and approaches, and how the past work (e.g.: Metals Affordability Inititive) are being leveraged to qualify new technologies.
CNC Code Generation for Electron Beam Free Form Fabrication Generating CNC (Computer Numerical Control) code for a layer additive process is fundamentally different from a subtractive process. In a subtractive process, tool paths and tool changes are computed to remove material from a billet leaving behind the specified shape. In a layer additive process tool paths and tool changes need to fulfill the opposite goal of building a part in empty space. In the case of Electron Beam Free Form Fabrication (EBF3) another degree of freedom exists, which is changing the tool ‘on-the-fly'. The electron beam parameters can change while the deposition moves along the tool path. The need for changing EBF3 parameters along the tool path arise from three requirements. First, EBF3 parameters may need to change to ensure a uniform deposit as the positioning systems accelerate and decelerate along their axes of motion. Second, parameters may need to change to correct geometry errors from previous deposits such as slight variations in planned versus actual build layer heights (variations will occur without a closed loop control system). Third, parameters may need to change to facilitate a functional gradient in either geometry or material properties. This presentation will summarize effort that has been made in two functional areas: tool path generation and parameter variation along the tool path.
Electron Beam Freeform Fabrication Alliance to Reduce Buy-to-Fly Ratios for Titanium Components NASA Langley is attempting to catalyze a national capability to build metallic industrial components without the huge waste of current large scale milling process. Electron Beam Freeform Fabrication (EBF3) is an additive metal process using an electron beam, wire feed, and computer controls to build near net shaped components, either by addition of details onto a simplified preform or by fabricating the entire component. The EBF3 process can be used to reduce high buy-to-fly ratios (12:1 to 20:1 are not uncommon for some components) down to less than 5:1, offering significant savings in resources such as raw materials, energy consumed, fewer chemicals (cutting fluids), and lead time as compared with current practices of machining large volumes of chips out of a solid billet. Researchers at NASA Langley have led research and development of the EBF3 process since 2002. NASA’s goals in developing this technology include process controls for unattended operation and repeatability, certification of EBF3 processed materials for space hardware applications, demonstration of space-qualified hardware to support long duration human exploration missions, and development of tailored structures with integrated multifunctionality for aerostructural applications. Industrial applications of the EBF3 process include the production of replacement components for aging aircraft as well as reducing cost, lead time, and environmental responsibility for production of new aircraft components more efficiently than hogging out components from oversized billets of metal. An innovative alliance between NASA and industry has recently been formed to accelerate the certification and standards process and stimulate the growth of a competitive supply chain for providing commercial EBF3 services within the next 4 to 5 years. This talk will discuss the alliance technical goals and progress towards those goals as they relate to inserting the EBF3 process into the industrial sector.
The Approach to Solving the EBFFF Aluminum Loss Issue by Operating at Higher Chamber Pressures EBFFF uses an electron beam as an energy source to melt weld wire to build titanium components in a layer by layer fashion. The typical operating environment is done at very low pressures (~1 x 10-4 torr or lower), unlike almost any other welding or additive manufacturing process, which operate under an inert gas. EBFFF has been touted as having deposition rates as high as 40 pounds per hour due to the large available power and high efficiency of the electron beam system. This presentation will focus on the DOE that Spirit AeroSystems completed at Sciaky Inc. The approach of this DOE was to show that operating pressure, the temperature, size/geometry of the melt pool and time at temperature are the major causes of the aluminum loss. Of the above factors, we could only directly measure the operating pressure. Therefore efforts were initiated to gain fundamental understanding of factors that we believed could be affecting melt pool geometry and the time above liquidous temperature. A look at the vapor pressure curves of aluminum, titanium, vanadium, and Ti 6Al-4V will be considered, as well as the coupling of temperature and pressure which places the molten metal above the vapor pressure of this alloy causing aluminum burn-off. To gain a better understanding of the impact of power and energy on melt pool geometry, different power settings were applied to alpha-beta forged base plates for different time spans. The test was performed to form both spots and lines, with and without the addition of wire. The information obtained will be used to develop controls to eliminate or reduce the aluminum burn-off and to validate finite element models.
Microstructural and Microanalytical Study of the Effect of Processing Parameters on the Al Loss and Deposition Efficiency of EBF3 Ti-6Al-4V Alloys Electron beam freeform fabrication (EBF3) represents a significant paradigm shift in the manufacture of metallic aerospace structures from integrally-stiffened structures designed for assembly to novel unitized structures designed for multi-functional performance optimization. EBF3 feeds metal wire into a molten pool formed and maintained by an electron beam in a high vacuum environment (10-5 torr). The challenges of molten pool processing of Ti-6Al-4V in a high vacuum are due to the differences in the vapor pressures of the alloy constituents at the melting point of titanium which result in selective vaporization of aluminum, and make control of the chemical composition and mechanical properties difficult. A three-factor, three-level Taguchi design of experiments (DOE) study was conducted to rank the importance of processing parameters, identify any nonlinear parameter couplings, and define the optimal metal deposition parameters to maintain the Aerospace Material Specification (AMS) compositional requirements for aluminum content in Ti6Al-4V. A broad range of values for each process parameter (beam power, translation speed, wire feed rate) was selected for the study, to produce deposits with chemistries spanning the entire AMS Ti6A-4V composition range for aluminum. Bulk compositions of 27 single-bead deposits were determined by the Direct Current Plasma technique (DCP). By applying DOE response surface methodology (RSM) on the bulk chemistry data, three-dimensional response surface and contour plots enable the prediction of aluminum content, as a function of critical EBF Compositional analysis conducted on a subset of the test matrix (three-factor, two-level) confirmed that EBF3 of Ti6Al-4V in a high vacuum had a negligible effect on the vanadium and H2 content in the single-bead deposits.
Characterization of Electron Beam Free Form Fabrication Systems Using Enhanced Beam Diagnostics Introduction
Microstructure and Mechanical Properties of Ti-6Al-4V Components Fabricated by Shaped Metal Deposition Shaped Metal Deposition (SMD) is an innovative time-compression technology, which creates near-net shaped components in a variety of materials by weld deposition. Especially for Ti alloys, which are difficult to shape by traditional methods such as forging, machining and casting and for which the loss of material during the shaping process is also very dear, SMD promises great advantages. Ti alloys are very sensitive on the thermal history and this method introduces for each welding step another temperature gradient leading to a particular microstructure. The microstructure Ti-6Al-4V components will be correlated with the SMD process. Furthermore, the mechanical properties of the material, elastic modulus, ultimate tensile stress, and plastic deformation will be presented.
Determining Melt Pool Temperature in Ti-6-4 Electron Beam Freeform Fabrication Deposition The electron beam freeform fabrication (EBF3) process uses an electron beam and wire to fabricate metallic structures directly from computer aided design data in a layer-additive process. The EBF3 process is capable of bulk metal deposition at deposition rates in excess of 150 in3/hr or finer detail at lower deposition rates, depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures. In contrast to the conventional approach of machining large volumes of chips to produce a monolithic metallic structure, selective addition of metal onto simpler blanks of material promises significant reduction in lead time, material expenditure and machining costs. However, before the process can be industrially applied and certified for use in flight hardware, the properties of the deposited material and the interfaces between the base and the deposit must be thoroughly characterized. This paper will present tensile, fatigue and fracture data for thin-walled Ti-6-4 EBF3 deposits and compare the data to typical wrought material properties.
Plasma Transferred Arc Rapid Additive Manufacturing The use of a plasma transferred arc welding torch as the high energy source for additive manufacturing results in several advantages vs. alternate high energy beams. These advantages will be discussed and examples of demonstrated capabilities presented. For example, MER has produced billets of Ti-6Al-4V for Spirit AeroSystems for their testing to evaluate the PTA process for manufacturing of aircraft components. In addition to the low cost fabrication of metallic structures, this technology has also been utilized to form very hard surface layers of a cermet composition which are functionally graded to the substrate. These layers have excellent wear and corrosion resistance. Graded composites have also been produced for structural applications. In both the structural and coating applications, the gradation results in an exceptionally strong bond. For the case of titanium alloys, a new very low cost approach will be discussed which utilizes a cold rolled “quasi” wire formed from Ti sponge and prealloyed Al-V powder. High strength titanium foam has also been produced to near net shape and with in-situ skins for structures.
Ti-6Al-4V Alloy Welding using a High Power Continuous Wave Nd:YAG Laser Ti-6Al-4V is the most widely used titanium alloy and falls in the α + β category. Due to its high strength and light weight, along with good tensile and creep properties up to about 300ºC, it is widely used for turbine disks, blades, and airframe structural components. Conventionally, TIG and plasma arc welding techniques are used to weld titanium alloys. CO2 laser welding of Ti-6Al-4V alloy has also been reported. However, little has been published about the weldability of Ti-6Al-4V alloy using high power solid-state Nd:YAG laser. This work reports on the laser weldability of Ti-6Al-4V alloy with four thicknesses ranging from 0.8 to 3 mm using a 4 kW Nd:YAG laser welding system. The effects of main processing parameters including laser power, welding speed and defocusing distance on surface morphologies, welding defects, microstructure, microindentation hardness and tensile properties are investigated. The optimized process windows are determined indicating that Nd:YAG laser welding is an attractive method for Ti-6Al-4V alloy. However, the welding quality of the thinnest sheets is very sensitive to laser processing parameters and the right combination of laser power and welding speed is highly required. Very little porosity was observed in the welded joints of the thin sheets while more microporosity was observed in the thicker titanium alloy sheets. No detectable cracks are observed in all thicknesses used in the present study. The microstructure of the fusion zone revealed a needle-like martensite α’ structure formed from β phase due to the high cooling rate associated with laser beam process, leading to the increase of fusion zone hardness compared with the base metal. The microstructure of the heat-affected zone is a mixture of martenstic α’ and primary α. The effects of selected processing parameters on tensile properties are also discussed in detail.
High Power Continuous Wave Nd:YAG Laser Welding of Inconel 718 Alloy Inconel 718 alloy is a precipitation-hardened nickel-iron base superalloy widely used in gas turbines, rocket motors, spacecraft, nuclear reactors, pumps and tooling due to its good corrosion resistance, high strength, and stable microstructure at elevated temperature. It has excellent weldability but suffers from liquation cracking in the heat-affected zone. However, very little has been reported on high power Nd:YAG laser welding of IN718 alloy. In this study, the weldability of IN718 alloy in two thicknesses (0.76 and 3.18 mm) was investigated using a 4 kW Nd:YAG laser system. The effects of laser power, welding speed, defocusing distance, heat treatment prior to welding and post-weld heat treatment conditions on butt joint quality are characterized from surface morphologies, joint shapes, welding defects, microstructure, hardness and tensile properties. It is found that (sound) welds without macrocracks and with minor (macro) porosity can be obtained, indicating that solid-state Nd:YAG laser welding is a suitable method for IN718 alloy. Optimum process window for welding of IN718 was constituted and sound weld joints with joint efficiencies of 90-100% were obtained. Tensile failure occurred predominantly in the fusion zone. There is a significant increase in hardness in the fusion zone probably due to the presence of the interdendritic Nb-rich Laves and the NbC precipitates inside the dendrites. The HAZ hardness was found to lie between the fusion zone hardness and that of the base material. Higher hardness values measured in the HAZ are probably due to the re-precipitation of the principal strengthening phases (γ’ and γ’’) during post weld cooling. The fusion zone is composed of fine and elongated dendrites. The heat affected zone has similar microstructure to that of the base metal but slight grain growth is observed.
Laser Welding of Advanced High Strength Steel DP980 and Joint Property Restoration by Heat Treatment Dual phase steel DP980, one of the advanced high strength steels, has attracted great attention from automobile industry since it has high strength, high-energy absorption in the crash testing, and good formability. Feasibility study of laser welding of DP980 at butt-joint configuration has demonstrated that the welded joint of this material are characterized by the high strength but with the low toughness and the low formability. Higher welding speed can increase the joint strength since it reduces the size of heat-affected zone, but it cannot effectively improve the toughness of the welded joint. To restore the original material properties at the welded joint, various post-welding heat treatment processes have been tested, including: (1) step quench with heating performed in a furnace followed by quenching in various media, (2) local heat treatment done by direct diode laser beam, and (3) heat treatment using defocused fiber laser beam. The investigations have shown that: (1) step quench can soften the welded joint which results in a decreased joint strength and an extremely high elongation, (2) direct diode laser beam, characterized with a uniform heat input, can soften the weld and the heat affected zone vertically through the thickness of the specimen, so that the strength of the welded joint decreases slightly, but with significantly modified toughness, and (3) a defocused fiber laser beam can re-melt the welded joint such that the joint strength is still high, but with little toughness improvement. Selection of the post-welding heat treatment process strongly depends on the anticipated manufacturing processes following the welding operation. A further investigation has shown that the volume fraction and the distribution of martensite in the weld/heat affected zone play a critical role in the joint strength, and the final tempering of martensite in the weld zone contributes to the improvement of the toughness.
Laser Beam Welding of Titanium – A Comparison of CO2 and Fiber Laser for Potential Aerospace Applications The Laser welding process is increasingly being considered for joining titanium alloy airplane structures and also for manufacture, repair and overhaul of titanium aeroengine components. Recent advancement in gas and solid state laser technology has resulted in the availability of higher beam quality Lasers which can produce narrow welds with low heat input and high weld speeds. This paper describes a study of Laser welding of the Titanium alloys Ti6-4 and Ti5553 using two types of high power Laser - a CO2 Slab Laser and an Ytterbium-Fiber Laser. The differences between both Lasers and their effect on weld quality and performance will be explained. The weld results are evaluated referring to AWS weld quality standards, which particular reference to porosity appearance and weld profile. In addition, micro hardness measurements and tensile test data will be shown.
Gas Metal Arc Weld (GMAW) Repair of Titanium Alloys for Turbine Engine Applications Integrally Bladed Rotors – IBRs – are an important part of current and future military aeroengines. The use of IBR allows lower weight rotors with decreased drag and improved compressor efficiency. Repair of these parts however is currently problematic. The repair process selected must have the following attributes in order to be successful: i) it must not compromise the remaining life of the IBR; ii) it must be amenable to flexible operations that could be located globally; and iii) it must be cost-effective vs. the price of replacement. Arc welding technologies are very cost-effective and are amenable to automated robotic operations, but there are significant process control and weld quality challenges that are barriers to entry for such technologies.
Flaws in Aluminium Alloy Friction Stir Welds Process variables affect joint quality. Successful, reproducible welds may be produced by operating within process “windows”. However, problems arise when welding conditions deviate from the operating window. A need exists to understand the types of flaws that may be generated and their causes. Welds were made in 6mm thick 2014A, in which processing parameters were varied outside of the operating window. They were assessed using radiography, ultrasonic inspection and light microscopy. The types of flaw produced could be categorised either as voids or joint line remnants. The former were produced in two ways: forging pressure exerted on the workpiece was reduced and welding speed was increased, reducing the working of the metal and the heat input. A joint line remnant was introduced by using a tool that was too short for the plate thickness. This left a region of the original interface that had not been adequately disrupted by tool rotation. A root flaw could be very small and may not be detected by NDE. A joint line remnant could also consist of a line of oxide particles from the original interface extending through the weld. This was achieved by anodising the surfaces, prior to welding. It was found that voids may be formed when insufficient forging pressure is applied to the weld or the welding speed is too high. A joint gap of up to 2mm could be tolerated. Joint line remnants occurred when pre-weld cleaning was inadequate but machining, prior to welding, is effective in restricting their occurrence. Joint line remnants, as root flaws, are introduced when either insufficient pin depth or tool plunge depth is selected, or when there is poor tool-to-joint alignment. Appropriate selection of such parameters may eliminate these flaws. However, for critical applications, machining of the weld root may be advisable.
Joint Quality Evaluation and System Verification of Friction Stir Welds For more than a decade, high quality seams have been joined using Friction Stir Welding (FSW) in the aerospace and aircraft industries. The seams have, so far, been joined using large customized machines devoted to single task operations. Although providing a high quality output the lack of flexibility of such machine, mainly caused by the limited dextrous workspace, has limited the process from being used to a greater extent. By introducing a more flexible solution based on an industrial robot, modified to fulfil the requirements of the process to a certain extend, opportunities to join complex shaped objects with FSW is provided. In this paper we investigate the use of an industrial robot to apply FSW, the quality of the joints applied and the limitations of such system.
Degradation Studies of Friction Stir Welds Recently some commercial aircraft have been fabricated with more than 60% of the rivets replaced with FSW joins. The replacement locations have included the cabin, aft fuselage, wings and engine mounts. Benefits include a reduction in painting preparation time, a lighter airframe and smoother structure. In addition, fatigue resistance and durability are comparable with single-row riveted joints. Nevertheless, the degradation in FSW joins is known to be asymmetrical in nature, with the advancing and retreating side of the same weld behaving differently from the electrochemical and corrosion standpoint. During this work, the behavior of aluminum alloys with and without FSW joins has been investigated in an aggressive chloride containing aqueous environment. Joins were assessed for degradation properties using traditional electrochemical methods, EIS, SVET, microscopy and in-situ corrosion fatigue monitoring.
Assessment of Friction Stir Weld Integrity for Process Control This paper reports on the development of innovative inspection methods for the detection of typical defects in friction stir welds (FSW). The defects related to changes in material conditions or welding parameters are lack of penetration, worm holes and kissing bonds (vertical) in butt joints, and hooking, worm holes and kissing bonds (horizontal) in lap and T joints. Kissing bonds originate from the remnants of trapped oxide layers and are known as the most challenging problem for inspection of FSW joints. Ultrasonic immersion or laser-ultrasonics combined with the synthetic aperture focusing technique (SAFT) is investigated. Laser-ultrasonics uses lasers for the generation and detection of ultrasound and is therefore non-contact, ultimately for weld assessment during welding. Another promising method is pulsed eddy current (PEC) technique, which induces electrical currents in conductive parts, while measuring the direction and magnitude of the resulting magnetic fields as an indication of material condition. Various FSW lap and butt joints for aerospace applications are examined, including dissimilar metal welds. Very good performances are achieved with the two methods for lack of penetration in butt joints, the limit of detectability coinciding with the conditions of reduced mechanical properties. Also, discontinuities such as wormholes, hooking and voids in lap joints are clearly detected using SAFT. The detection of kissing bonds seems to be possible in lap joints using high frequency laser-ultrasonics.
Friction Stir Weld Restart Plus Reweld Repair Allowables A friction stir weld (FSW) repair method has been developed and successfully implemented on Al 2195 plate material for the Space Shuttle External Fuel Tank (ET). The method includes restarting the friction stir weld in the termination hole of the original weld followed by two reweld passes. Room temperature and cryogenic temperature mechanical properties exceeded minimum FSW design strength and compared well with the development data. Simulated service test results also compared closely to historical data and were in family with legacy FSW data for normal FSW, confirming no change to the critical flaw size for the repaired welds or inspection requirements. Testing of FSW/VPPA fusion intersection weld specimens exhibited acceptable strength and exceeded the minimum design strength. Porosity, when present at the intersection was on the toe of the fusion weld, the “worst case” being 0.700 inch long. These “worst case” porosity conditions were tested “as is” and demonstrated that porosity did not negatively affect the strength of the intersections. Larger, 15-inch “wide panels” were tested to demonstrate strength and evaluate residual stress using photo stress analysis. All results exceeded design minimums, and photo stress analysis showed no stress gradients due to the presence of a restart and multiple rewelds in the wide panels.
FSW of Ti Alloys - An Update on Recent Developments This presentation will describe recent developments at TWI on the joining of Ti alloys using the novel Stationary Shoulder Friction Stir Welding (SSFSW) method. In SSFSW, heat is generated by a rotating tool probe, which is separate from a non-rotating tool shoulder component. The tool shoulder component provides containment to the weld area, but adds no heat to the top surface of the joint. The SSFSW approach is designed to provide uniform heat input throughout the thickness of the welded material, allowing very stable, high quality, solid-phase joints to be made in Ti alloys. SSFSW has been shown to be a valuable new development of the FSW process, which is particularly suitable for a range of high temperature, low thermal conductivity, materials. This presentation will review the recent development of the SSFSW technique, and its application to Ti alloys. Examples will be shown of the specialist systems that have been produced to carry out this process, and possible applications will be illustrated via a range of demonstration weld samples. The development and exploitation of SSFSW offers the potential for a reliable solid-phase welding method for Ti components. Possible applications of this technique include: joining of Ti components, additive manufacture of Ti prototypes and/or machining pre-forms, selective local reprocessing of Ti parts, and repair of damaged areas in Ti structures. In summary this presentation will provide an overview of recent development work on the FSW of Ti alloys, including examples of demonstration parts produced using the new SSFSW approach.
Nylon-11 based Sealants for Friction Stir Welded Lap Joints Corrosion prevention of friction stir welded joints is an enabling technology for aerospace structures. In this paper, a lap joint sealant based upon the polyamide nylon -11 will be discussed. Nylon-11 is a thermoplastic that can be applied to the faying surfaces of a lap joint and friction stir welded without masking the weld tool path. The nylon-11 melts during welding and bonds the faying surfaces together forming a seal. T-joint assemblies were produced with 2024-T8 top-skins welded to cast A357-T6 stringers in both bare and anodized conditions, with and with out sealants. Joints with the nylon-11 sealant had higher stiffness resulting from adhesive bonding of the lap joint. Bond strength was greatest for the bare aluminum and decreased as the thickness of the anodized layer increased. Limited fatigue testing was performed on nylon-11 sealed friction stir welded T-joints. These assemblies were made using standard sulfuric acid anodized aluminum components and as such the nylon-11 bond was prone to failure. However, these sealed joints had 1 % failure lives comparable to the bare aluminum welds and markedly better fatigue lives than the anodized aluminum welds without sealants. The improved fatigue performance of the sealed joints is attributed to the increase in joint stiffness created by bonding the faying surfaces with the thermoplastic sealant. This bonded configuration also shields the notches created by the junction of the faying surfaces and the weld nugget. In situ corrosion-fatigue tests were also conducted by immersing the bare and anodized specimens in a neutral 3.5% salt solution during fatigue loading. The in situ testing produced a 75% reduction in cyclic life. Addition of a sealant produced only a marginal improvement in life.
Friction Stir Spot Welding of Aluminum Alloys – Process Parameters Optimization Using GONNS Friction stir spot welding (FSSW) is a derivative process of friction stir welding (FSW) in which a solid-state joint is made between adjacent materials at overlap configuration. Feasibility studies of the FSSW process have been performed for more than a decade for materials applied in the aerospace industries. However, for a mass production environment, the selection of optimum process parameters is rather less discussed. In this study, a method based on genetically optimized neural network system (GONNS) is introduced for selecting the optimized FSSW parameters. In this method for a known FSSW setup, type of material, and plate thickness, an artificial neural network (ANN) is designed with the process parameters as inputs and the weld tensile strength, maximum plunging load, and the process duration as outputs. Experiments are performed in order to train the selected ANN. Afterwards, an optimization algorithm is introduced based on the genetic algorithm heuristic search bundled with the trained ANN that aids the algorithm in predicting the value of the target functions. The target functions of the optimization problem are considered as normalized and weighted equations of the weld tensile strength, maximum plunging load, and the process duration. Eventually, the minimization of the target function yields the optimum FSSW parameters which are verified by additional experiments. Results affirm that the analytically obtained optimum of the FSSW parameters is valid, and using the optimum parameters, the higher weld strength, lower plunging load, and shorter process duration are obtained.
Progress at Alcan Aerospace on the friction stir welding of Al-Li 2050 Alcan Aerospace have been very active in the recent past in developing low density Al-Li 3rd generation of alloys, in a collaborative effort with airframers. AA2050 is one such alloy which has received commercial interest for its behaviour in the medium gauge range, where it outperforms reference alloys like 2024 or 2027, with significantly higher static, F&DT and corrosion performance, in addition to lower density and higher modulus. For higher gauges, AA2050 also offers an interesting low density alternative to 7050.
Development of a Novel Friction Stir Welding/Forging Process A novel friction stir welding (FSW) technique has been developed that is a combined welding and forging process. This technique is an additive manufacturing process that can be used for manufacture of fabricated shapes or structural assemblies, and can dramatically reduce buy-to-fly ratios. The welding process is used to join flat (or curved) shapes into tee or I-beam configurations and the forging process is used to form an integral fillet at the intersection of these individual components. A development and testing program was undertaken to develop a viable welding / forging process. The results of this development and testing program will be discussed. Using the process various prototype shapes and assemblies have been fabricated. These and other potential applications will be discussed.
Application of Material and Process Modeling - 1
S. K. Koduri1, V. Dixit1, P. C. Collins2, H. L. Fraser3, (1)The Ohio State University, Columbus, OH, (2)Quad City Manufacturing Lab, Rock Island, IL, (3)Center for Accelerated Maturation of Materials, Columbus, OH
D. Li1, E. Crist2, N. Minakawa2, O. Yu2, (1)RTI International Metals, Inc., Niles, OH, (2)RMI Titanium Company, Niles, OH
A. B. Chaudhary, M. Keller, Applied Optimization, Inc., Dayton, OH
Y. P. Yang1, I. Harris1, G. Ritter1, B. Bishop2, (1)Edison Welding Institute, Columbus, OH, (2)Edison Welding Institute, columbus, OH
Laser welding was used in assembling a thin-panel structure for aerospace applications. The structure consists of a thin plate with many L-shape stiffeners. LBW was used to join the stiffeners to the thin plate. Welding-induced buckling distortion was a major concern. To control the buckling distortion, a three-roller system was designed with the help of finite element weld modeling. Finite element model was used to optimize the relative distances between the laser and the rollers. This improved LBW process has been successfully used to weld the structure by eliminating buckling distortion and producing low weld residual stresses.
Laser weldbonding is a process combining use of a welding method and adhesive bonding in the same joining process. It has been demonstrated to weld an aluminum aerospace structure. Weldbonding offers the potential of greater structural rigidity at lower weight, lower metal gauge, and lower cost over traditional riveting. Finite element modeling was performed to compare the stress characteristics in a laser weldbonded structure and a riveted structure. The analysis results show more preferred stress distributions in the laser weldbonded structure than the riveted structure. Experimental results also show the weldbonded structure has higher load carrying capability.
In addition, this paper also briefly introduces the modeling of FSW in joining titanium structures, and LAM in repairing engine blades.
M. P. Sealy1, Y. Guo1, S. Chen2, (1)The University of Alabama, Tuscaloosa, AL, (2)University of Texas at Austin, Austin, TX
W. R. Cribb1, F. C. Grensing2, (1)Brush Wellman Inc., Cleveland, OH, (2)Brush Wellman Inc., Elmore, OH
Property performance will be described in detail and an initial overview of basic work hardening and fracture characteristics will be presented, including key inputs to modeling and design.Application of Material and Process Modeling - 2
R. C. Reed1, J. C. Gebelin1, N. Warnken1, P. Brown2, (1)University of Birmingham, Birmingham, United Kingdom, (2)Rolls-Royce plc, Derby, United Kingdom
S. A. Tapia, G. E. Fuchs, University of Florida, Gainesville, FL
N. Warnken, R. C. Reed, University of Birmingham, Birmingham, United Kingdom
F. Zhang1, K. -. S. Wu1, W. -. S. Cao1, S. -. L. Chen1, Y. A. Chang2, D. U. Furrer3, (1)CompuTherm, LLC, Madison, WI, (2)University of Wisconsin, Madison, WI, (3)Roll-Royce Corporation, Indianapolis, IN
The modeling tool, which is part of the Pandat™ software, integrates both thermodynamic calculation and kinetic simulation. Thermodynamic calculation provides driving force of precipitation while thermodynamic and mobility databases are also needed for providing model parameters. The package is designed for generalized applications while in this presentation the investigation is focused on nickel alloys 718 and U720. In this presentation, we will present the general features of this modeling tool and some calculation results for the two nickel alloys. The output results include the amount and size change of each precipitate phase with time, particle size distribution, TTT curves and so on. One unique feature of this modeling tool that offers tremendous help for alloy design is a global optimization module for search of the best or worst scenario given alloy chemistry range and heat treatment conditions. This feature will be discussed in this presentation as well.
M. Stockinger1, C. Stotter2, C. Sommitsch2, E. Kozeschnik3, (1)Böhler Schmiedetechnik GmbH & Co KG, Kapfenberg, Austria, (2)Christian Doppler Laboratory of Materials Modelling and Simulation, University of Leoben, Leoben, Austria, (3)Christian Doppler Laboratory for Early Stages of Precipitation, Graz University of Technology, Graz, Austria
L. Zhao, J. Tong, University of Portsmouth, Portsmouth, United Kingdom
S. Kirchhoff, K. Maciejewski, H. Ghonem, University of Rhode Island, Kingston, RIMaterial and Process Modeling Support for Problem Solving and Optimization
D. J. Buchanan1, R. John2, R. A. Brockman1, (1)University of Dayton Research Institute, Dayton, OH, (2)US Air Force Research Laboratory, Wright-Patterson AFB, OH
J. W. Newkirk1, H. N. Chou2, Z. Fan1, F. Liou1, K. Slattery2, M. E. Kinsella3, (1)Missouri University of Science & Technology, Rolla, MO, (2)Boeing Phantom Works, St. Louis, MO, (3)AFRL/RXLMP, Wright-Patterson AFB, OH
V. Samarov, V. Goloveshkin, D. Seliverstov, LNT PM Inc., Garden Grove, CA
T. Marusich1, S. Usui1, D. A. Stephenson1, L. N. Zamorano1, A. J. Shih2, (1)Third Wave Systems, Minneapolis, MN, (2)University of Michigan, Ann Arbor, MI
C. E. Fischer, Scientific Forming Technologies Corporation, Columbus, OH
T. Marusich, S. Lankalapalli, L. Zamorano, J. Backus, S. Heyroth, K. Marusich, Third Wave Systems, Minneapolis, MNPlenary Program
Plenary Session
B. K. Christner, Eclipse Aviation Corporation, Albuquerque, NM
M. Gritton, Rolls-Royce Corporation, Indianapolis, IN
T. Wybrow, Dowty Propellers, Gloucester, United KingdomSuperplasticity and Superplastic Forming
Superplasticity Theory, Modeling and New Materials
G. A. Sargent1, D. Li2, S. L. Semiatin3, (1)University of Dayton, Dayton, OH, (2)RTI International Metals, Inc., Niles, OH, (3)Air Force Research Laboratory, Wright-Patterson AFB, OH
M. Al Bawaneh, J. Brewer, R. Hedrick, Ducommun AeroStructures Incorporated, Parsons, KS
J. M. Boileau, P. A. Friedman, D. Q. Houston, S. G. Luckey, Ford Motor Company, Dearborn, MI
H. Raman1, S. Riley2, (1)Superform USA, Riverside, CA, (2)Superform Aluminium, Worcester, United Kingdom
F. Jarrar1, F. K. Abu-Farha2, L. Hector3, M. K. Khraisheh4, P. Krajewski3, (1)University of Jordan, Amman, Jordan, (2)University of Kentucky, Lexington, KY, (3)General Motors R&D Center, Warren, MI, (4)Masdar Institute of Science and Technology, Abu Dhabi, United Arab Emirates
E. Y. Chen1, Q. Li2, D. R. Bice1, D. C. Dunand3, (1)Transition45 Technologies, Inc., Orange, CA, (2)University of Nevada, Reno, Reno, NV, (3)Northwestern University, Evanston, ILIndustrial Manufacturing Using Superplastic Forming
A. J. Barnes1, R. Stracey2, (1)Superform USA, Riverside, CA, (2)Superform Aluminium, Worcester, United Kingdom
L. D. Hefti, The Boeing Company, Seattle, WA
J. J. Blandin1, W. Beck2, R. Curtis3, G. Bernhart4, (1)Institut National Polytechnique de Grenoble, Saint Martin d Heres, France, (2)FormTech GmbH, Weyhe, Germany, (3)Kings College London, London, United Kingdom, (4)Ecole de Mines d'Albi Carmaux, Albi, France
M. A. Garcia-Bernal1, R. S. Mishra2, R. Verma3, D. Hernandez-Silva1, (1)Instituto Politécnico Nacional-ESIQIE, D.F., Mexico, (2)University of Missouri – Rolla, Rolla, MO, (3)General Motors, Warren, MI
D. G. Sanders, L. D. Hefti, The Boeing Company, Seattle, WASuperplastic Forming Special Topics
A. F. Jocelyn, University of the West of England, Bristol, Bristol, United Kingdom
F. K. Abu-Farha1, M. A. Nazzal2, M. K. Khraisheh3, (1)University of Kentucky, Lexington, KY, (2)German Jordanian University, Amman, Jordan, (3)Masdar Institute of Science and Technology, Abu Dhabi, United Arab Emirates
This work presents one of such hybrid concepts, in which the pneumatic bulge forming practice of superplastic forming is combined with the conventional mechanical deep drawing operation. Sheets are partially formed by a fast deep drawing step, followed by a finishing pneumatic bulge forming step that takes care of the intricate details of the shapes to be formed. Forming according to this concept is first FE-simulated, before being carried out at elevated temperatures, using AZ31 magnesium alloy sheets. Both the FE and experimental results demonstrate how forming time can be considerably reduced, while sustaining the formability merits associated with the superplastic forming process
A. A. Deshpande, S. B. Leen, T. H. Hyde, University of Nottingham, Nottingham, United Kingdom
A. V. Kazantzis1, Z. Chen1, J. T. M. De Hosson2, (1)University of Groningen and the Netherlands Institute for Metals Reseach, Groningen, Netherlands, (2)The University of Groningen, Netherlands Institute for Metals Reseach, Groningen, Netherlands
J. D. Muñoz-Andrade, UNIVERSIDAD AUTONOMA METROPOLITANA UNIDAD AZCAPOTZALCO, Mexico, Mexico
E. Taleff, University of Texas, Austin, TXSymposium on Materials / Structural State Awareness and Prognosis
Materials/Structural State Awareness I
E. A. Medina1, K. V. Jata2, S. A. Martin3, (1)Radiance Technologies, Inc., Dayton, OH, (2)Air Force Research Laboratory, Wright-Patterson AFB, OH, (3)NDE Computational Consultants, Dublin, OH
C. Gouldstone, J. Brogan, J. Gutleber, R. Gambino, R. Greenlaw, B. Keyes, MesoScribe Technologies, Inc., Stony Brook, NY
D. S. Erdahl1, D. A. Stubbs2, W. C. Hoppe2, J. R. Sebastian2, J. D. Hoeffel2, R. B. Olding2, (1)University of Dayton, Dayton, OH, (2)University of Dayton Research Institute, Dayton, OH
K. Brockdorf, phoenix|x-ray Systems + Services Inc., St. Petersburg, FL
The new nanotom is a compact laboratory system that allows the analysis of samples up to 120 mm in diameter and weighing up to 1 kg with exceptional voxel-resolution down to <500 nm (<0.5 microns). It is the first 180 kV nanofocus computed tomography system tailored specifically to the highest-resolution applications in fields like material science, micro electronics, geology and biology. Therefore it is particularly suitable for nanoCT®-examinations e.g. of synthetic and composite materials, metals and metal foams, ceramics etc.
The CT volume data set can be displayed in various ways; it can be sectioned and sliced in all directions, rotated and viewed from any desired angle. Highly applicable to a variety of fields, nanoCT can be a viable substitute for destructive mechanical slicing and cutting. Any internal difference in material, density or porosity within a sample can be visualized and data such as distances can be measured. Some of the many applications of nanoCT® include the analysis of fiber textures, air inclusions or cracks in composite materials with voxel resolutions of less than one micrometer.
The presentation will outline the hard- and software requirements for high resolution CT. It will showcase several quality control applications involving different aerospace materials that were inspected with nanoCT®.
A. Blouin, C. Néron, D. Levesque, B. Campagne, J. P. Monchalin, National Research Council Canada, Boucherville, QC, Canada
E. M. Rasselkorde1, P. Wallace2, (1)TWI Validation Centre (Wales), Port Talbot, United Kingdom, (2)TWI Ltd, Margam, Port Talbot, United Kingdom
E. M. Rasselkorde1, M. Papaelias2, (1)TWI Validation Centre (Wales), Port Talbot, United Kingdom, (2)The University of Birmingham, Birmingham, United KingdomMaterials/Structural State Awareness II
N. J. Goldfine1, V. Zilberstein2, D. Grundy1, J. Cammett1, (1)Jentek Sensors, Inc., Waltham, MA, (2)JENTEK Sensors, Inc., Waltham, MA
The MWM-Array, in both scanning and surface-mounted modes, offers a convenient and effective way to monitor such coupon tests to study early-stage fatigue behavior. One observation from these tests, that is generally well known, was that at early stages, multiple small cracks (<0.005 in. long at the surface) formed and then coalesced into larger cracks. This is true for both shot-peened Ti-6Al-4V and polished or as-machined aluminum 7075. This behavior is observed, for example, in actual engine components, where multiple shallow cracks initiate and grow in regions with fretting damage. For aluminum 7075, multiple small cracks generally initiate at inclusions before coalescing into longer cracks. Although, a single large crack eventually dominates the NDT signature, this appears to occur when the crack is relatively long; for example, when a dominant crack in titanium alloy components is greater than 0.015 in. (length at the surface). This is a concern for both prognostics (life prediction) and for qualification of Nondestructive Testing (NDT) methods.
V. R. Dave, D. A. Hartman, M. J. Cola, Beyond6 Sigma, Santa Fe, NM
K. V. Jata1, S. S. Chellapilla2, J. C. Aldrin3, (1)Air Force Research Laboratory, Wright-Patterson AFB, OH, (2)Radiance Technologies, Inc., Huntsville, AL, (3)Computational Tools, Gurnee, IL
G. M. Light, C. Thwing, A. R. Puchot, Southwest Research Institute, San Antonio, TX
D. S. Forsyth1, T. B. Mills2, J. I. Gonzalez1, C. L. Brooks2, (1)TRI/Austin, Austin, TX, (2)AP/ES Inc., Saint Louis, MOPrognosis
S. J. Hudak Jr.1, R. C. McClung1, M. P. Enright1, H. Millwater2, (1)Southwest Research Institute, San Antonio, TX, (2)University of Texas at San Antonio, San Antonio, TX
J. M. Papazian1, E. L. Anagnostou1, S. Engel1, D. Fridline1, J. Madsen1, J. Payne1, J. Nardiello1, R. Silberstein1, P. C. Hoffman2, A. Roerden3, G. Werczynski3, (1)Northrop Grumman, Bethpage, NY, (2)NAVAIR, Patuxent River, MD, (3)Navair, Patuxent River, MD
E. L. Suarez, Pratt & Whitney, East Hartford, CT
R. Holmes1, E. Pope2, J. Hamler2, T. Brooks2, R. Tryon2, (1)VEXTEC, Brentwood, TN, (2)VEXTEC Corporation, Brentwood, TN
M. J. Caton1, R. John2, (1)Air Force Research Laboratory, Wright-Patterson AFB, OH, (2)US Air Force Research Laboratory, Wright-Patterson AFB, OH
N. Jayaraman1, D. J. Hornbach1, P. S. Prevey1, J. Sides2, R. Ravindranath2, R. Chan2, (1)Lambda Technologies, Cincinnati, OH, (2)NAVAIR, Patuxent River, MD
R. Holmes1, R. V. Pulikollu1, V. Ogarevic2, R. Tryon2, (1)VEXTEC, Brentwood, TN, (2)VEXTEC Corporation, Brentwood, TNTitanium Alloy Technology
Titanum Processing/Metallurgical Characterization I
J. D. Cotton1, D. J. Bryan2, T. Bayha2, M. Leder3, I. Levin3, (1)The Boeing Company, Seattle, WA, (2)ATI Allvac, Monroe, NC, (3)VSMPO-AVISMA, Verkhnaya Salda, Russia
R. Panza-Giosa1, D. Embury2, Z. Wang3, X. Wang2, (1)Goodrich Landing Gear, Oakville, ON, Canada, (2)McMaster University, Hamilton, ON, Canada, (3)University of Toronto, Toronto, ON, Canada
J. Fanning, TIMET-R&D, Henderson, NV
S. Nag1, A. Genc2, S. Rajagopalan2, R. Banerjee1, P. C. Collins3, H. L. Fraser4, (1)University of North Texas, Denton, TX, (2)The Ohio State University, Columbus, OH, (3)Quad City Manufacturing Lab, Rock Island, IL, (4)Center for Accelerated Maturation of Materials, Columbus, OH
S. M. El-Soudani1, O. Yu2, F. Sun3, A. Keskar4, V. S. Moxson5, V. Duz5, (1)The Boeing Company, Huntington Beach, CA, (2)RMI Titanium Company, Niles, OH, (3)RTI International Metals Inc., Niles, OH, (4)RTI International Metals, Inc.,, Houston, TX, (5)ADMA Products, Twinsburg, OHTitanium Processing/Metallurgical Characterization II
S. Nyakana1, M. Harper2, J. Fanning2, (1)TIMET, Henderson, NV, (2)TIMET-R&D, Henderson, NV
K. Doering1, D. C. Van Aken1, R. L. Hanks2, K. A. Young2, R. J. Lederich2, (1)Missouri University of Science and Technology, Rolla, MO, (2)Advanced Manufacturing R&D, Boeing – Phantom Works, St. Louis, MO
S. M. El-Soudani1, M. Campbell2, J. Phillips2, V. S. Moxson3, V. Duz3, (1)The Boeing Company, Huntington Beach, CA, (2)Plymouth Engineered Shapes, Hopkinsville, KY, (3)ADMA Products, Twinsburg, OH
D. C. Van Aken, K. Doering, B. Kudlacek, G. Galecki, Missouri University of Science and Technology, Rolla, MO
R. R. Boyer, J. D. Cotton, K. T. Slattery, G. R. Weber, The Boeing Company, Seattle, WATitanium processing - reduced buy:fly
T. A. Witulski1, G. T. Terlinde1, M. Knuewer2, (1)Otto Fuchs KG, Meinerzhagen, Germany, (2)Airbus Deutschland, Bremen, Germany
R. Gerke-Cantow, Titan-Aluminium-Feinguss GmbH, Bestwig, Germany
The main reason is the β to α+ β phase transformation at a temperature of about 1000 °C, which changes the cast structure completely, leading to an α+ β lamellar structure, which is also typical of β processed wrought alloy.
To reduce the material costs recycling of solid scrap and turnings as well as cold-hearth melting processes for the production of ingots are established in the industry. With this the titanium consumption of foundries related to their casting weight produced (buy-to-fly) can be reduced to values well below 2 (depending on the parts to be produced).
The increasing demand for titanium products in the past led to a substantial increase in the price for the metal. Consequently, old and new designs are considered for a casting solution as the leading near-net-shape technology available. This in turn indicates that for geometrically complex parts with a high amount of human labour in production, casting is a cost effective alternative to milled products due to reduced material and lower machining costs.
Also the reduction of the well known casting factor is once again a topic on customers’ agendas. The investigations performed in TITAL show that the investment casting process is also in terms of process variability (coefficient of variation) on a level playing field with its wrought products competition.
In addition, the advantages of investment castings are the realization of complex structures, run through of load path, reduction of part numbers, minimized assembly, less milling, less drawing expenditure…
E. Y. Chen1, Q. Li2, D. R. Bice1, D. C. Dunand3, (1)Transition45 Technologies, Inc., Orange, CA, (2)University of Nevada, Reno, Reno, NV, (3)Northwestern University, Evanston, IL
P. Edwards1, G. Coleman2, D. G. Sanders1, G. L. Ramsey1, J. Bernath3, T. Trapp4, (1)The Boeing Company, Seattle, WA, (2)Boeing Commercial Aircraft Group, Seattle, WA, (3)EWI, Columbus, OH, (4)Edison Welding Institute, Columbus, OH
M. W. Moffat, Cyril Bath Co., Monroe, NCTitanium machining
P. Bach, Czech Technical University in Prague, Prague 2, Czech Republic
S. Ramesh1, L. Karunamoorthy2, K. Palanikumar1, K. Elangovan1, (1)SATHYABAMA UNIVERSITY, Chennai, India, (2)ANNA UNIVERSITY, Chennai, India
T. Marusich, D. A. Stephenson, S. Usui, L. N. Zamorano, Third Wave Systems, Minneapolis, MN
This presentation will also demonstrate the application of new and existing modeling technology to cost effectively reduce the first 3 of 4 barriers identified above. This will be accomplished by: use of validated process modeling technology specifically developed for modeling metal cutting, use of process modeling techniques to significantly reduce the need (and cost) for testing while increasing the efficiency and successful implementation of new concepts, and use of validated material modeling technology already developed specifically for machining applications.
B. Slaughter1, K. T. Slattery2, R. Martin1, D. Heck3, A. M. Helvey3, R. R. Boyer2, (1)Boeing Phantom Works, St. Louis, MO, (2)The Boeing Company, Seattle, WA, (3)The Boeing Company, St. Louis, MO
W. J. Seufzer, K. M. Taminger, NASA Langley Research Center, Hampton, VATitanium processing - Direct Titanium Manufacturing
K. M. B. Taminger, NASA Langley Research Center, Hampton, VA
B. Woods, R. Nasserrafi, H. Ehlers, Spirit AeroSystems, Inc., Wichita, KS
S. N. Sankaran1, K. M. Taminger2, R. A. Hafley2, C. L. Lach2, (1)Lockheed Martin, Hampton, VA, (2)NASA Langley Research Center, Hampton, VA
K. W. Lachenberg1, S. D. Stecker1, R. C. Salo1, J. W. Elmer2, (1)Sciaky, Inc., Chicago, IL, (2)Lawrence Livermore National Laboratory, Livermore, CA
The development of diagnostic tools for characterizing electron beams has been growing in prominence. The Enhanced Modified Faraday Cup (EMFC) also known as EB-Profiler, developed at Lawrence Livermore National Laboratory (LLNL) and licensed by Sciaky to build, provides measurements of the general size and shape of the beam and the power density distribution across its width. This tool has been utilized in a number of applications, including the characterization of machine performance and repeatability for electron beam welding (EBW) equipment, the transfer of parameters between welders at remote locations, and as a process control tool. The EB-Profiler is proving to be a useful tool in monitoring & diagnosing EBFFF performance.
Results/Discussion
Previous work with the EB-Profiler has been limited to high voltage (150 kV) machines with fixed guns. In this work, the use of the EB-Profiler tool has been expanded to include enhanced low voltage (60 kV) EBW/EBFFF machines with moveable gun configurations designed and manufactured by Sciaky, Inc. Tests have been performed at Sciaky on machines with different configurations and process conditions. Variations in the characteristics of the beams produced by the different generation machines and the differences in sharp focus beams at various work distances will be discussed. The utility of the diagnostic tool in providing a better understanding of the operation of the equipment to improve, monitor and control the EBFFF process will be presented. The outputs from the EB-Profiler include peak power density and through computer tomographic reconstruction, a 3D model of the energy distribution. Differences in output can be a result of many factors including differences in vacuum levels and other operating conditions. Once a process has been qualified, diagnostic tools of this type will insure that the process is properly maintained in production.
B. Baufeld1, O. Van der Biest1, R. Gault2, (1)Katholieke Universiteit Leuven, Leuven, Belgium, (2)University of Sheffield, Rotherham, United Kingdom
R. A. Hafley1, K. M. B. Taminger1, E. K. Hoffman1, S. N. Sankaran2, K. Butcher2, (1)NASA Langley Research Center, Hampton, VA, (2)Lockheed Martin, Hampton, VA
R. S. Storm, V. Shapovalov, J. C. Withers, R. O. Loutfy, MER Corporation, Tucson, AZWelding and Joining
Welding & Joining #1
X. Cao1, M. Jahazi1, J. Cuddy2, A. Birur2, (1)NRC Institute for Aerospace, Montreal, QC, Canada, (2)Standard Aero Ltd, Winnipeg, MB, Canada
X. Cao1, B. Rivaux2, M. Jahazi1, J. Cuddy3, A. Birur3, (1)NRC Institute for Aerospace, Montreal, QC, Canada, (2)Ecole des Mines de Paris, Sophia-Antipolis, France, (3)Standard Aero Ltd, Winnipeg, MB, Canada
D. Lin1, M. S. Yang1, M. F. Kong1, P. D. R. Kovacevic1, R. Ruokolainen2, D. X. (. Gayden2, (1)Southern Methodist University, Dallas, TX, (2)General Motors Corporation, Warren, MI
S. Mueller1, C. Bratt1, J. Cuddy2, M. K. Shanker2, (1)Fraunhofer USA, Plymouth, MI, (2)Standard Aero Ltd, Winnipeg, MB, Canada
D. A. Hartman, M. J. Cola, V. R. Dave, Beyond6 Sigma, Santa Fe, NM
In this work we show a path to develop and validate a prototype process for Titanium Gas Metal Arc Welding (GMAW) for IBR weld repair. Titanium GMAW is challenging on account of the tendency for the cathode spot to wander, thereby creating an arc instability that impacts the weld bead geometry as well as weld quality. Additionally, there are challenges in the synchronization of pulses in the power supply to assure good bead geometry as well as uniform material transfer. To overcome these challenges and to meet the stringent quality requirements for IBRs, a novel monitoring and control methodology known as In – Process quality Assurance – IPQA – is implemented to sense and control vital aspects of the welding process not possible with current approaches. Practical examples are shown and the progress towards a viable GMAW repair process is reviewed, including metallurgical and weld quality aspects, weld parameters and weld process stability, and the end-goal of integration of the technology into commercially available power supplies.Friction Stir Welding Process Evaluation
M. F. Gittos1, A. J. Leonard2, (1)TWI, Cambridge, United Kingdom, (2)BP Exploration Company Ltd, Middlesex, United Kingdom
M. J. Soron, J. Norström, ESAB AB Welding Equipment, Laxå, Sweden
D. Larson, D. B. Mitton, Z. Huq, M. Cavalli, University of North Dakota, Grand Forks, ND
D. Levesque1, L. Dubourg2, C. Mandache3, P. Gougeon1, X. Cao4, M. Jahazi4, (1)National Research Council Canada, Boucherville, QC, Canada, (2)National Research Council Canada, Ottawa, ON, Canada, (3)Institute for Aerospace Research, National Research Council of Canada, Ottawa, ON, Canada, (4)NRC Institute for Aerospace, Montreal, QC, Canada
A. Clifton, Lockheed Martin Space Systems Company, New Orleans, LAFriction Stir Welding Processing
M. Nunn, M. J. Russell, R. Freeman, I. M. Norris, TWI Ltd, Cambridge, United Kingdom
D. C. Van Aken1, R. J. Lederich2, (1)Missouri University of Science and Technology, Rolla, MO, (2)Advanced Manufacturing R&D, Boeing – Phantom Works, St. Louis, MO
H. Atharifar, D. Lin, R. Kovacevic, Southern Methodist University, Dallas, TX
P. Lequeu1, J. C. Ehrstrom2, I. Bordesoules3, C. Hantrais2, (1)Alcan Rhenalu, Issoire, France, (2)Alcan, Voreppe, France, (3)Alcan CRV, Voreppe, France
One of the challenges to the extensive use of Al-Li alloys by airframers has traditionally been the extra cost per kilo saved offered by such alloys. This is the reason why work has been performed to decrease their buy-to-fly ratio, among other cost reduction activities. One way of improving this buy-to-fly ratio consists in replacing integrally machined items by assembled parts, each being adjusted to the local thickness needs. When developing such concepts, one has to consider using as much as practical a low cost assembly technique, like what is offered by friction stir welding instead of standard riveting.
C. B. Smith1, R. Anderson2, (1)Friction Stir Link, Waukesha, WI, (2)Keystone Synergistic, Palm Beach Gardens, FL