Recent developments in joint modeling for crash simulations

Because of computational efficiency detailed joint models are not applicable in crash simulations of whole cars with thousands of joints. Therefore simplified models are used to describe the overall deformation and fracture behavior of joints with minor numerical cost. These simplified modeling techniques for point-shaped, line-shaped and plane joints are available in different crash codes. The main problems in the application of these models are the lack of suitable failure models and verified procedures for the determination of model parameters. In this paper a load dependent damage initiation and damage evolution model for a point-connector model are described and compared with experimental results. Additionally a method for parameter determination is presented. The damage model describes the failure of the joint itself. For the modeling of crack initiation in the surroundings of a joint and subsequent crack propagation in the component as it occurs in the heat affected zone of spot welds in press hardened steels, two different modeling techniques are developed and presented. The first method uses the surrounding shell elements with an adapted damage model for the heat affected zone. The second method uses a multi model coupling technique to combine a detailed model of a spot weld including the heat affected zone with the simplified modeling technique for crash simulation