Finite Element Simulation of the TRIP-effect in Austenitic Stainless Steel

A requirement for any material to be accepted by the automotive industry is that finite element (FE) simulations can be used to predict its behavior in both forming operations and crash conditions. So far, FE-simulations have been less accurate for austenitic stainless steel than for lower alloyed steels. The reason for this is the temperature sensitivity of the Transformation Induced Plasticity (TRIP) - effect in the low-alloyed austenitic grades of highest relevance for the automotive industry. Typically, temperature effects are not considered when sheet forming is simulated today. Therefore, new material models as well as a different simulation approach must be introduced for austenitic stainless steel compared to the materials used today.

This paper describes the implementation of a new material model into LS-DYNA, which is capable of predicting the TRIP-effect in austenitic stainless steel in different forming operations with different temperature scenarios. As the TRIP-effect is temperature sensitive the forming simulation must take the thermal effects into account, such as the heat conduction in both blank and tools as well as the heat transfer between tools and blank.

The implementation has been verified by comparing simulations with experimental data for tensile tests as well as for a stamping operation.