CYCLIC FATIGUE OF NITINOL

Nitinol's superelasticity, biocompatibilty and magnetic resonance compatibility has led to its increasing popularity for the manufacture of endovascular stents. Despite its growing importance in the biomedical industry, especially under conditions involving pulsatile loading, the cyclic fatigue resistance of Nitinol is not well understood. This paper provides a summary of existing data on the fatigue-crack propagation properties of the superelastic alloy and presents preliminary results on crack-growth behavior in samples cut from Nitinol tube used as the starting material for the manufacture of endovascular stents. In addition, a new test sample for measuring the total fatigue life properties is described involving the uniaxial loading of slotted-tubular samples, again machined from Nitinol tube.