Optimization Of The Fatigue Resistance Of Nitinol Stents Through Shot Peening
Abstract “Nitinol” (NiTi) is an intermetallic alloy of approximately equal atomic percentages of nickel and titanium that is widely used in less invasive and self-expanding implantable medical devices such as cardiovascular stents, due to its superelastic, shape memory and biocompatibility properties. Most of its applications in the medical industry involve the application of repeated stresses or strain cycles that drive the need of increasing the fatigue and fracture resistance of this alloy. The Nitinol stent supporting a biological heart valve prosthesis is considered one such example and is the critical structural component in many of the heart valve prostheses. Continuous effort is made to increase the fatigue resistance of these cardiac devices through experimenting with various manufacturing and surface treatment techniques. This study proves that the shot peening (SP) process improves the fatigue resistance of Nitinol stents and also describes the effect of different peening intensities on the treated surfaces, through the application of the Almen test.