Remarks on constitutive and structural modelling of small radii in sheet metal and crashworthiness simulation

Abstract

In recent years, one has seen a tremendous progress in methods for the simulation of production processes, especially in the automotive industry. Besides sheet metal forming, casting of alloys, moulding of polymers and various additive techniques are the key methods in manufacturing. In this list, sheet metal forming is unarguably the most mature virtual discipline to predict part producibility and the local properties. However, when it comes to transferring results from sheet metal forming simulation to further disciplines, like stiffness, NVH or crashworthiness simulation, a number of incompatibilities between the models need to be resolved. This is particularly pronounced when locally varying part properties are relevant. For situations in which the discrepancies in the constitutive models are not too dominating, this has been done successfully in the past by simply transferring thickness, plastic strain and possibly stresses, using shell elements in both disciplines. But since local effects, like extreme thinning, sharp bending or the onset of instability may dominate the fracture process in crashworthiness, especially when modern high strength alloys are regarded, these effects need to be investigated in more detail. In particular, their accurate evaluation may require modelling with 3D solid elements. On the one hand, the incompatibilities of the models become clearly obvious from the spatial discretization, while on the other the demand w.r.t. accuracy in crashworthiness is ever increasing. The present contribution focuses on the ability to capture demanding deformation states with classical and advanced shell formulations, which is seen as a first step in order to close the corresponding gap in the simulation process chain in a more general sense.