FINITE-ELEMENT ANALYSIS OF FORMING LIMIT IN BORE EXPANDING OF ALUMINUM-ALLOY SHEETS

A recently proposed method to predict the forming limit of sheet metal s is applied to the problem of bore expanding. Axisymmetric bore-expan ding processes of various aluminium alloy sheets are simulated by the rigid-plastic finite element method. From the calculated histories of stress and strain, the forming limit, i.e. the fracture initiation, is predicted by means of the ductile fracture criterion. The comparison with the experimental results shows that the fracture initiation site and the critical punch stroke are successfully predicted by the presen t approach.