Experimental and Numerical Investigations on the Development and Stability of Residual Stresses Arising from Hot Forming Processes

Residual stresses are an important issue as they affect both the manufacturing process as well as the performance of the final parts. Taking the whole process chain of hot forming into account, the integrated heat treatment provided by a defined temperature profile during cooling of the parts offers a great potential for the targeted adjustment of the desired residual stress state. The aim of this work is the investigation of technological reproducibility and stability of residual stresses arising from the thermomechanical forming process. For this purpose, a long-term study of residual stresses on hot-formed components is conducted. In order to develop finite element models for hot forming, a comprehensive thermomechanical material characterisation with special focus on phase transformation effects is performed. The numerical model is validated by means of a comparison between residual stress states determined with X-ray diffraction on experimentally processed components and predicted residual stresses from the simulations.