Stain Amplitude Volume Fraction Method for Evaluation of Nitinol Fatigue Durability

Thursday, May 15, 2014: 1:20 PM
Merrill Hall (Asilomar Conference Grounds)
Mr. Craig Bonsignore , Nitinol Devices & Components, Fremont, CA
Mr. Payman Saffari , Nitinol Devices & Components, Fremont, CA
Payam Saffari , University of British Columbia, Vancouver, BC, Canada
Finite element analysis simulation is commonly used to evaluate fatigue durability of Nitinol medical implants. Currently available methodologies for interpreting simulation results are limited in several ways. The most common methodology used today is to obtain point cloud data of the device under expected in-vivo cyclic loading conditions using one of the available fatigue constitutive models. This is then followed by studying the point cloud data in conjunction with a constant life diagram obtained for that device. The study presented here, considers the most basic implementation of the strain amplitude volume fraction (SAVF) method. The methodology is discussed in detail, along with sample analysis results, followed by recommendations for statistically analyzing SAVF results in conjunction with data documenting the volume fraction, size, and distribution of material impurities. The techniques and raw data that are used as part of this study will be released under an open source license, available to the industry for further development.