On the experimental evaluation of the fracture toughness of shape memory alloys

Abstract

A methodology for measuring the fracture toughness of shape memory alloys (SMAs) from a single compact tension (CT) nominally isothermal load-load line displacement record is proposed. The methodology uses J-integral as the fracture criterion, relies on the ASTM standards E1820 modified to accommodate the Young’s moduli mismatch between the austenite and martensite phases. Finite element analysis (FEA) is employed to validate the methodology while experimental data from CT specimens are interpreted accordingly. The fracture toughness of martensitic equiatomic NiTi at room temperature is much higher than the phenomenological value reported on the basis of linear elastic fracture mechanics.