Crack extension in aluminium welds: a numerical approach using the Gurson–Tvergaard–Needleman model

Ductile tearing of laser welded Al sheets is studied both experimentally and numerically. The mechanical behaviour of the various zones is characterised by means of micro-flat-tensile specimens, and the respective microstructure is analysed. Fracture tests are carried out on compact specimens, and three positions of the initial crack are studied, namely in the base metal, in the fusion zone and at the interface between fusion zone and heat affected zone. The numerical simulations are based on the Gurson–Tvergaard–Needleman model for ductile damage. Whereas crack extension is strictly confined to the ligament, if the initial crack is in pure base material or in the fusion zone, it may kink and deviate from the heat affected zone into the softer fusion zone. Good agreement between experimental results and numerical simulations could be achieved in all cases.