Constitutive Model for Fatigue Strain Limit Prediction

Finite element analysis (FEA) simulation is commonly used to evaluate fatigue durability of nitinol medical implants. Different constitutive fatigue prediction models have been developed and are currently used by the Medical Device industry to determine the strain limit of Nitinol material. In this study, a superelastic Nitinol diamond surrogate geometry is modeled using FEA under strain-controlled cyclic loading conditions and the resulting fatigue stress/strain domain is obtained. These results are then used in context with different constitutive fatigue prediction models to predict the fatigue strain limit of Nitinol material. This study also compares the predicted fatigue strain limit obtained from these constitutive models and further investigates the sensitivity of these results to different modes of cyclic loading.