Simulation of Fatigue Tests on a NiTi Superelastic Spring

Behavior of NiTi wire under proportional and non-proportional loading was recently subject of intensive experimental research. Based on analysis of experimental results, a new thermomechanical model for simulation of NiTi under non-proportional loading was proposed. The model is formulated within the framework of generalized standard materials and introduces a novel form of dissipation potential, which combines contributions from transformation and reorientation mechanisms in an unconventional way.

Numerical simulations of response of simple geometric structures can provide valuable information for optimum product design and critical loading modes. In presented case, analysis of stress and martensite distribution on the surface of a NiTi helical spring related to corresponding experiments shed more light on a problem of fatigue failure of a NiTi product with oxide layer in combined loading.