On the Thermomechanical Behavior of Ni₆₀Ti₄₀ Coupons via High Performance Full Field Experiments

Emerging applications for shape memory alloys, such as actuation and energy absorption devices, require better understanding of the mechanics and failure behaviors associated with these materials. In this paper we study the inelastic response of a NiTi alloy under combined thermomechanical actuation. In particular, failure due to strains generated by cooling under isobaric and isothermal conditions is investigated. Strain measurements are performed using a new technique known as Direct Strain Imaging, which provides full field strains of both higher accuracy and higher spatial resolution than previously achievable. The experimental data support the conclusion that the type of fracture observed may be attributed to stress redistribution, caused by a phase transformation.