Fatigue Strain Verification for Cardiovascular Implantable Nitinol Devices

Strain-based criteria is most often used for characterizing the fatigue reliability of Nitinol cardiovascular devices. Fatigue testing of Nitinol specimens has also relied on finite element analysis (FEA) to compute cyclic strain amplitudes and mean strains. Recently, the digital image correlation (DIC) technique has been shown to have high resolution to experimentally determine the local material strains of Nitinol fatigue specimens. In this study, the authors explored the feasibility of alignment between DIC strain measurement, and the strain calculated by the continuum mechanics approach used in the FEA technique. The agreements and discrepancies are discussed with their implications on fatigue reliability assessment of Nitinol cardiovascular devices.