Ductile fracture prediction in aluminium alloy 5A06 sheet forming based on GTN damage model

The Gurson-Tvergaard-Needleman model (GTN model) was employed to predict the ductile fracture behaviour in the forming of aluminium alloy 5A06 sheet. The in-situ tensile test with scanning electron microscope (SEM) was conducted to determine the original void volume fraction, the critical void volume fraction, and the failure void volume fraction in GTN model. The other parameters in GTN model were determined by an inverse approach. Eleven types of uniaxial tension tests including shear specimen, dog-bone specimen, notched specimens with different root radius, and V-notched specimens, were carried out to investigate the influence of stress triaxiality on predictability for fracture. The results show that the GTN fracture criterion can give a good prediction under high stress triaxiality. The ductile fracture behaviour in hydro-bulging aluminium alloy semi-ellipsoidal shell was researched by experiments and simulation based on the GTN model. Four kinds of semi-ellipsoidal shell with aspect ratio 1, 1.5, 2.0, and 2.5 were studied. The predicted results show good agreements with the experimentally determined bursting position, bursting pressure, and the maximum dome height.