APPLICATIONS OF PHENOMENOLOGICAL FAILURE MODELS IN AUTOMOTIVE CRASH SIMULATIONS

In the automotive industry, an ongoing trend towards mixed material concepts in the body in white has been established. Components made of high- and ultra-high strength sheet steels, extruded and casted aluminium alloys, non-reinforced as well as reinforced thermoplastics, curable plastics like sheet moulding compound (SMC) are an integral part of innovative design concepts, see Grünn et al.1. Therefore, crash simulations have to be able to describe the vastly different behaviour of these materials across the whole range of deformations − from elastic deformations up to more or less large deformations at failure. In addition, the mechanical behaviour of an increasing number of design materials is strongly influenced by the production process. Incorporating these effects in an industrially applicable manner to material models for crash simulations as well as modelling the behaviour of joints (spotwelds, linewelds, rivets, adhesive joints, etc.) is of primary importance for crash simulations. 2 PHENOMENOLOGICAL FAILURE MODELLING The basis for a successful failure modelling is a correct simulation of macroscopic stresses and strains in a crash simulation. The main features of the material models used for metals and short-fibre reinforced or non-reinforced plastics are: • isotropic/orthotropic linear-elastic behaviour up to the onset of yielding • a stress state dependent criterion for the onset of yield (yield locus), see figure 1. • a strain rate dependent hardening rule • criteria for the onset of failure depending on the loading condition (stress triaxiality η and a parameter θ characterizing the shear loading, see table 1) and the material specific dependencies affecting the failure process (strain rate, orthotropy, porosity, fibre orientation, etc.). Three different mechanisms leading to failure are taken into consideration: o Plastic Instability leading to the formation of a neck in thin sheet metals loaded in the membrane plane. The onset of necking is immediately