K. E. Perry, P. Labossiere, ECHOBIO, LLC., Bainbridge Island, WA
Phase shifted moiré interferometry is used to measure full-field strain under precise loading conditions for superelastic and shape memory nitinol component test samples. Uniaxial tension and four point bend loading is accomplished with a single sample geometry fabricated with commercially available tubing, similar to what is used for medical implants. Material property changes as a function of cyclic loading for a range of loading intensities are presented for two process methods. Our results are used to demonstrate typical thermomechanical processing effects including the presence of R-phase and thermally recoverable strain on the evolution of performance properties of medical components. Compact tension samples with sharp fatigue pre-cracks will also be discussed to provide further insight into the initiation and growth of critical flaws from process and design related stress concentration conditions. Experimental data from the full-field, in situ interferometric measurement technique provides a self-consistent method for calibrating finite element analysis results and validating implantable medical device components.
Summary: Phase shifted moiré interferometry is used to measure full-field strain under precise loading conditions for superelastic and shape memory nitinol component test samples. Uniaxial tension and four point bend loading is accomplished with a single sample geometry fabricated with commercially available tubing, similar to what is used for medical implants. Material property changes as a function of cyclic loading for a range of loading intensities are presented for two process methods. Our results are used to demonstrate typical thermomechanical processing effects including the presence of R-phase and thermally recoverable strain on the evolution of performance properties of medical components. Compact tension samples with sharp fatigue pre-cracks will also be discussed to provide further insight into the initiation and growth of critical flaws from process and design related stress concentration conditions. Experimental data from the full-field, in situ interferometric measurement technique provides a self-consistent method for calibrating finite element analysis results and validating implantable medical device components.
