The influence of stress ratio on fatigue lifetime of NiTi shape memory alloy

Abstract The influence of stress ratio on fatigue lifetime of pseudoelastic NiTi alloy are studied. The stress-, strain- and energy-based criteria were used for analysis under on low-cycle fatigue. Increasing the stress ratio from 0 to 0.5 significantly reduces the fatigue life of the NiTi alloy when used to describe the stress range, strain range and dissipation energy density and increases when using the Odqvist’s parameter. A good agreement between experimental and calculated values of predicted lifetime was obtained. The low–cycle fatigue failure criterion of pseudoelastic NiTi alloy - total elastic strain energy density that takes into account the stress ratio was proposed.