X. Zhou, Z. You, University of Oxford, Oxford, United Kingdom
Nitinol has become an ideal material for minimal invasive surgery because of its superelastic and shape memory properties as well as its biocompatibility. Most conventional stents have a cylindrical and thus axisymmetric shape. A large amount of work has been carried out using finite element method to analyse the mechanical properties of cylindrically shaped stents. Stents assuming a helical shape are a relatively new design, but have proved successful with commercially available devices including the aSpire covered stent (Vascular Architects) and the Horizon stent (Endocare). However, knowledge of mechanical properties of helical stents is far from comprehensive, with few publications providing experimental or numerical data. This paper uses the finite element method to provide a comprehensive investigation of the mechanical properties of helical stents manufactured from Nitinol. Analyses are conducted to examine the deformation modes associated with helical stents and the strain-stress distribution is studied under different loads and boundary conditions. ABAQUS is used as the analysis platform. Its user material routine UMAT/Nitinol, which is based on the theory of generalized plasticity, can be easily used to model Nitinol numerically.
Summary: A detailed investigation is conducted using the finite element method to examine the mechanical properties of helical stents manufactured from Nitinol. Deformation modes are examined and the strain-stress distributions are studied under various loads and boundary conditions.
