M. Riedler, M. Stockinger, Böhler Schmiedetechnik GmbH & Co KG, Kapfenberg, Austria; M. Stoschka, B. Oberwinkler, W. Tan, H. Leitner, University of Leoben, Leoben, Austria
The tendency of increasing operating temperatures in order to produce more efficient and green engines leads to development of new materials and processes. Furthermore, aerospace structural parts are optimized in respect of light weight in order to increase pay load and efficiency.
With the objective of optimizing forgings with respect to desired mechanical and micro structural properties, design and weight an application tailored forging and heat treatment process can be worked out, when the affecting mechanisms are clarified.
Therefore, in addition to engine and structural parts, special purpose tailored parts are designed for the analysis of fatigue and fracture properties depending on the forging process (hydraulic press, screw press and hammer; influences of process temperature, strain, strain rate), heat treatment process (influences of temperature and time on temperature, cooling medium, cooling rate) and technological influences from machining and surface treatment (surface layer, shot-peening, residual stresses and distortion).
In order to optimize the heat treatment processes defined process parameters have to be analyzed and optimized. For characterization of different types of heat treatment and quenching possibilities available at Böhler (air, pressed air, salt, polymer and water) special field tests with highly instrumented forged parts are performed. Additional quenching tests with specimens are done with special laboratory equipments. This allows the investigation and implementation of a wide variety of possible process matrix parameters in simulation tools like DeformTM (temperature dependent emissivity, convection and heat transfer coefficient).
Based on a deep knowledge of micro structure affecting fatigue and fracture and the possibility of creating and using finite element tools a tailored multidisciplinary forging, heat treatment and part optimization and a useful definition of the demanded specifications (micro structure, mechanical properties, static and cyclic properties) can be worked out together with the aerospace part designers in order to deliver economic and safe parts.
Summary: New materials and processes have to be developed due to the tendency of increasing operating temperatures in order to produce more efficient and green engines. New simulation possibilities have to be worked out for structural parts in order to optimize them in respect of light weight with the aim of increasing pay load and efficiency.
Supported with the future work of linking the forging and heat treatment process simulation with microstructure simulation, residual stress simulation and fatigue simulation the whole simulation chain can be closed, which allows a multidisciplinary optimization.
