Ductile damage analysis for small punch specimens of type 304 stainless steel based on GTN model

Based on small punch (SP) tests on Type 304 stainless steel at room temperature, a finite element (FE) model with Gurson-Tvergaard-Needleman (GTN) constitutive equations was established to analyze the ductile damage in SP specimens. Influences of the friction coefficient between SP specimen and steel ball and element size to the FE results were discussed. The evolution of void volume fraction (VVF) with time along different paths and the relation between VVF and equivalent plastic strain (PEEQ) under constant punching velocity were analyzed further by using the FE model. Good agreements between experimental results and simulation data were proved by load-displacement curves and failure locations. The numerical results show that initial crack occurs at the bottom surface about 0.86 mm away from the centre and damage localization phenomenon is extraordinarily severe in the SP specimen, and PEEQ has great effect on the evolutional rate of VVF.