Non-proportional multiaxial fatigue of super-elastic NiTi shape memory alloy micro-tubes: Damage evolution law and life-prediction model

Abstract

Based on the experimental observation to the non-proportional multiaxial fatigue tests of super-elastic NiTi SMA micro-tubes and the uniaxial damage-based fatigue failure model established by Song et al. (2015) [52], an appropriate damage variable for the multiaxial fatigue failure is introduced, and the corresponding evolution law of the multiaxial damage is also proposed to describe the damage accumulation observed in the multiaxial fatigue tests of the NiTi SMA micro-tubes with different non-proportional loading paths. From the evolution law of damage, an adequate life-prediction model is then developed for the multiaxial fatigue of super-elastic NiTi SMA micro-tubes. The simulated evolution curves of the multiaxial damage and the predicted fatigue lives are in good agreement with the experimental results of super-elastic NiTi SMA micro-tubes.