FRACTURE PREDICTION IN STRETCH FORMING USING FINITE-ELEMENT SIMULATION COMBINED WITH DUCTILE FRACTURE CRITERION

A criterion for ductile fracture is introduced in the finite element s imulation of sheet metal forming. From the calculated histories of str ess and strain in each element, the fracture initiation site and the c ritical stroke are predicted by means of the ductile fracture criterio n. The calculations are carried out for axisymmetric stretch forming o f various aluminium alloy sheets and their laminates clad by mild stee l sheets. The predictions so obtained are compared with experimental o bservations. The results show that the combination of the finite eleme nt simulation and the ductile fracture criterion enables the predictio n of forming limit in a wide range of sheet metals.