A VALIDATED PERIPHERAL STENT MODELING TO INVESTIGATE THE RISK OF FATIGUE FRACTURE

Nitinol stents are nowadays widely used for the treatment of occlusions in peripheral arteries. However, the risk of stent fatigue rupture due to cyclic loads related with the patient daily activities [Smouse et al. 2005] is source of concerns for Nitinol devices: in some recent clinical studies it is shown that stent rupture may induce re-occlusion of the artery [Gibbs et al. 2010]. Accordingly, the assessment of the stent fatigue behaviour is of primary importance to assure the effectiveness of stenting procedure. The complexity of the material behavior and of the stent geometries suggests the finite element (FE) analysis as a useful tool to study peripheral stents. However, the prediction accuracy of computational analyses is strictly dependent on the correctness of the material model, as well as on a thorough knowledge of its fatigue behavior. In this study we approached the problem in several steps: i) design of stent-like specimens for material characterization; ii) experimental test for Nitinol fatigue characterization; iii) development of a FE peripheral stent model; iv) fatigue tests on real stents for model validation; v) study of the stent behavior under realistic conditions and evaluation of its risk of fatigue fracture using the experimental fatigue limit previously obtained.