Physically-based modelling of the fatigue crack initiation life of stent components under cyclic loading employing the Finite-Element-Method (FEM)

Abstract

Most of the micro-components, such as coronary stents, consist of an oligo-crystalline micro-structure. This means that the detection of the few coarse grains which are columnar and parallel to the longitudinal ingot axis is possible. The deformation behavior of such micro-structures is obviously different from polycrystalline materials, since the anisotropic properties of one grain, in relation to its nearest neighbors should be considered. The goal of this study is the simulation of the crack initiation process under a cyclic loading situation in the oligo-crystalline micro-structure of the stent component made of X2CrNiMo-18-15-3. The crack initiation process is simulated employing the physically-based Tanaka-Mura model implemented in Finite Element Method (FEM). The available experimental result data have also been used as the input parameters to the current modelling approach. In this regard the grain size and the grain orientation are changed, and their effect together with the influence of the surface roughness on the fatigue life of the stent components has been studied.