A Direct Method For Predicting The High-Cycle Fatigue Regime In SMAs: Application To Nitinol Stents
1 Département Génie Mécanique et Matériaux, Ecole des Ponts Paris, F-77455 Marne la Vallée, France
2 Univ Paris-Est, Laboratoire Navier (UMR 8205), CNRS, Ecole des Ponts ParisTech, IFSTTAR, F-77455 Marne la Vallée, France
In fatigue design of metals, it is common practice to distinguish between high-cycle fatigue (occurring after 10000–100000 cycles) and low-cycle fatigue. For elastic-plastic materials, there is an established correlation between fatigue and energy dissipation. In particular, high-cycle fatigue occurs when the energy dissipation remains bounded in time. Although the physical mechanisms in SMAs differ from plasticity, the hysteresis observed in the stress-strain response shows that some energy dissipation occurs, and it can be reasonably assumed that situations where the energy dissipation remains bounded is the most favorable for fatigue design. We present a direct method for determining if the energy dissipation in a SMA structure is bounded or not. That method relies only on elastic calculations, thus bypassing incremental nonlinear analysis. Moreover, only a partial knowledge of the loading (namely the extreme values) is needed. Some results related to Nitinol stents are presented.
© Owned by the authors, published by EDP Sciences, 2015
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