Institut für Kontinuums- und Werkstoffmechanik

Mechanical Analysis of a Vascular Stent

Background
In medicine, a stent is a metal tube inserted into the blood vessel to prevent or alleviate its blockage. Vascular stents may be fabricated from magnesium alloys which provide optimal properties for use as an absorbable implant material. During the surgery, the stent will be crimped and subsequently expanded, with inelastic (plastic) deformation and possible failure as a consequence. Stent design has therefore to minimize the risk of cracking during expansion.

Objective
With a given simple stent design, finit-element (FE) simulations will be conducted in order to analyse the stress and strain fields during stent crimping and expansion. Emphasis will be placed on the material law of the stent alloy. Textured magnesium alloys commonly exhibit a tension-compression asymmetry (different yielding in tensiion and compression), load reversal require a specific treatment of strain and stress evolution. Constitutive relations will be extended by a damage model which needs to be calibrated by tension tests of rods and compression tests of rings machined for the rods. Fintie-element models of these tests generate the data required to assess the expansion process.