Steady State Crack Growth in Shape Memory Alloys

Shape memory alloys experience phase transformation from austenite to martensite around crack tip. When the crack advances, martensitic transformation occurs at the tip and the energy that goes into transformation results in stable crack growth like in the case of plastic deformation. In literature, there are studies on steady-state crack growth in elasto-plastic materials with small scale yielding around crack tip that use stationary movement methods similar to non-local algorithms. In this work, Mode I steady-state crack growth in an edge cracked Nitinol plate is modeled using a non-local stationary movement method. The Zaki-Moumni (ZM) constitutive model is utilized for this purpose. The model is implemented in ABAQUS by means of a user-defined material subroutine (UMAT) to determine transformation zones around the crack tip. Steady-state crack growth is first simulated without considering reverse transformation to calculate the effect of transformation on stress distribution in the wake region, then reverse transformation is taken into account. Stress distribution and transformation regions calculated for both cases are compared to results obtained for the case of a static crack.