Phase shifted moiré interferometry is used to measure full-field strain during uniaxial tension and four point bend loading of nitinol test samples. Differences between global and full field measurements reveal the effects of localized transformation behavior. Results for two heat treatments of commercially available superelastic Nitinol are presented for tests conducted under controlled temperature conditions. The results highlight the effect of martensite, austenite and R-phase transformations on the thermomechanical response of superelastic nitinol. Finally, the technique is applied to a nitinol implantable medical component to demonstrate the opportunities for improved material characterization, numerical modeling and design validation.
You can download our paper on strain measurement and phase transformation in Nitinol using moire interferometry that we presented at the 2006 SMST conference: