Fatigue-crack growth in the superelastic endovascular stent material nitinol

摘要

This paper describes a study of fatigue-crack propagation behavior in the superelastic alloy Nitinol. This work is motivated by biomedical applications, and the current interest to improve the design and performance of medical stents for implantation in the human body. Specifically, the objective of this work is to study the effect of environment on cyclic crack-growth resistance in a approx50Ni-50Ti (at. percent) alloy, and to provide the necessary data for the safe life predication of Nitinol endovascular stents. The material selected for this study has been heat treated such that it is superelastic at human body temperature. Characterization of fatigue-crack growth rates has been performed at 37deg C on disc-shaped compact-tension samples,in environments of air, aerated deionized water, and aerated Hank's solution. Results indicate that, in fact, Nitinol has the lowest fatigue-crack growth resistance of metallic alloys currently used for implant-applications.