Finite element analysis of Charpy tests on extruded aluminium alloys

Nonlinear finite element simulations of Charpy V-notch impact tests are carried out for two 6xxx aluminium alloys having recrystallized and non-recrystallized grain structure and significantly different strength and ductility. These alloys have applications in automotive safety components such as bumper beams and crash boxes. In a crash situation, energy is dissipated in these components by means of bending and plastic folding, while fracture should be avoided to ensure the integrity of the structure. The numerical simulations are carried out using the explicit finite element code LS-DYNA. The material behaviour is described using a thermoelastic-thermoviscoplastic constitutive model and a ductile fracture criterion. Crack propagation is modelled by element erosion. The material parameters are obtained from tensile tests at a wide range of strain rates. The results of these simulations, using 2D plane strain elements and brick elements, are compared with the experimental data. In addition, the influence of mesh size and mesh regularity is studied