Determination of hardening behaviour and contact friction of sheet metal in a multi-layered upsetting test

This paper describes the identification of hardening parameters of DC05 sheet metal and contact friction coefficients using a multi-layered upsetting test (MLUT), the modified two specimen method (MTSM) and a finite element based inverse method. The MLUT is an alternative compression test that is based on the stacking of small circular specimens on top of one another. This test was designed in order to identify frictional and material behavior under severe local forging of sheet metal as encountered during a clinching operation. The MTSM is adopted in order to identify the friction coefficient between the tools and the stacked circular specimens which are cut from the base material by spark erosion. Next, the hardening behavior is identified inversely by combining the results of a MLUT and finite element simulations of the test setup. Finally, the results are compared with standard tensile tests and it is shown that the MLUT is a viable alternative for the identification of the local hardening behavior of sheet metal where standard test specimens cannot be prepared due to size limitations of the specimen.