Experimental and numerical comparison of void growth models and void coalescence criteria for the prediction of ductile fracture in copper bars

Ductile fracture of round copper bars is investigated within the scope of the local approach methodology Two damage models are analysed: the Rice and Tracey model and the Gurson-Leblond-Perrin model. A comparative study of four coalescence criteria is conducted: a critical value of the damage parameter, the Brown and Embury criterion, the Thomason criterion and a criterion based on the reaching of the maximum von Mises equivalent stress in a Gurson type simulation. Ellipsoidal void growth and void interaction are accounted for. As far as possible, all the parameters of the models are identified from experiments and physical observations. The effect of stress triaxiality is studied using specimens presenting a wide range of notch radii. The effect of strain-hardening is analysed by comparing the behaviour of the material in the cold drawn state and in the annealed state. (C) 1998 Acta Metallurgica Inc.