Fracture analysis of shape memory alloys in martensite and austenite phase based on the voids behavior

This study has been conducted to investigate the voids behavior in shape memory alloys (SMAs) up to fracture. Two kinds of NiTi samples with different geometries are studied including a smooth thick sheet which includes the phase transformation and a smooth round bar without phase transformation. The SEM images are utilized to observe the voids and their propagation over the fracture surfaces. A constitutive model is developed that is a combination of the Boyd and Lagoudas phase transformation model and the Gurson-Tvergaard-Needleman micro-mechanical model. The model is utilized and implemented using Abaqus/Explicit via the user subroutine VUMAT to evaluate its accuracy in predicting the voids behavior. The comparison between the numerical results and the experiments indicates a good accuracy of the proposed model.