Failure behaviour of crash-relevant welded aluminium joints

To improve the design and the assessment of MIG-welded aluminium joints under crash loading conditions, experimental tests and numerical investigations on the deformation and failure behaviour have been performed. For the experimental investigations, specimens have been cut out of the base materials AW6060 (AlMgSi) and AW7003 (AlZn6Mg0.8Zr) and their welds. For the age-hardened aluminium alloys, the weld shows a lower yield strength than the base material. Thus, failure takes place in the weld and in the region of the fusion line. The residual stresses obtained by a weld simulation were taken into account as initial conditions for a subsequent crash simulation. As a result, the influence of the welding residual stresses on the failure under crash loading is negligible. For the computational simulation of tensile and shear failure, a failure curve consisting of a combination of the Gurson model and the strain criterion of Johnson-Cook was qualified as a suitable failure model. A simplified approach based on a constant lower bound failure strain also results in a good approximation to describe the failure of the weld metal.