Morphology of Fatigue Fracture Surface for TiNi Shape Memory Alloy Stent

Abstract

The fatigue life of a high-dilatation stent fabricated from TiNi shape memory alloy tube with a high reduction of area was investigated in the radial and uniaxial compression mode. In this study, fatigue properties of the stent were discussed focusing on morphology of the fatigue fracture surface. In addition, the local strain during compressive deformation was examined by observation of the stent subjected to the compression. The main points obtained in the study are as follows (1) Fatigue fracture occurs at base of a strut of the stent specimen. (2) Fracture surface appears at an angle to the strut axis. This means torsional deformation occurs at base of the strut of the stent specimen. (3) The fatigue crack initiation point appears on the outside of the strut part because of the maximum positive bending strain.