Modeling of notch effects due to multi-material joints in automotive body components

Subject of the present paper is the investigation of notch effects due to mechanical joints in press-hardened steel components. It can be observed that joints within a component structure result in a stress concentration. This stress concentration in combination with the load history of the material due to the joining process may result in failure of the component under crash load. A self-piercing riveted (SPR) joint between a 22MnB5 steel sheet with a thickness of 1.2 mm and an EN-AW 6016 aluminum sheet with a thickness of 2.0 mm has been experimentally and numerically investigated. The main investigations are concerned with the press-hardened sheet metal, as this is used in safety-relevant areas of the car body. First, experimental and metallographic investigations of the punched hole in the 22MnB5 have been performed to assess the quality of the punched edge. Then an elastic-plastic material model with additional phenomenological damage model has been calibrated for the 22MnB5. With the calibrated material model, a simulation of the SPR joining process has been performed to determine the load history of the joint. Based on the results of this process simulation, simplified shell models have been created, which consider the preload caused by the joining process. It was shown, that the SPR joining process results in high plastic strain and pre-damage of the sheet metal. By taking this process-related pre-damage into account the accuracy of crash simulations can be significantly increased.