Functionality of a Novel Percutaneous Aortic Valve Stent – A Fracture Mechanics Study

To design against mechanical failure, most implants such as valve stents are assessed on the basis of survival on a long term. However, accurate investigation of the stress/ strain distributions in such valve stents, which govern their deformation and fracture behavior, is essential for their prolonged, and safe use. Nitinol, a shape-memory alloy, can “remember” a previous shape and can recover strains as high as 10% by deformation (super-elasticity) or temperature change. As such, deformation mechanisms of Nitinol are more complex than the conventional modes of plastic deformation in traditional alloys. Consequently, the mechanical behavior of Nitinol under multi-axial conditions remains poorly understood. With this background, an S-N type fatigue analysis was done on three stents with Von Mises stress component having the infinite life at 1.e+008. The results of this study may aid biomedical scientist to zero in on the material that could be used to analyse and fabricate percutaneous valve stents.