Experimental and Numerical Investigation of the Stable Crack Growth Regime under Pseudoelastic Loading in Shape Memory Alloys

A combined experimental and numerical analysis of fracture and crack growth in SMAs is presented. Crack extension is investigated under mode-I, isothermal, monotonic, mechanical loading in near-equiatomic nickel-titanium (NiTi) SMA compact tension (CT) specimens. Stable crack growth is observed and the associated J-R curve is evaluated along with the crack initiation toughness. Finite element analysis (FEA) with an energetics based fracture toughness criterion is also carried out and crack is assumed to extend when crack-tip energy release rate reaches the material specific critical value. Fracture toughening behavior is observed during crack growth and is mainly associated with the energy dissipated by the progressively occurring phase transformation close to the moving crack tip. A comparison between the experimental and numerical results is presented.