Numerical Investigation of the Mechanical Performance of NiTi stent for application in Thoracic Aortic Aneurysm (TAA)

Abstract

Nowadays, Superelastic NiTi stent is used in Thoracic Aortic Aneurysm (TAA) because of its effects on minimizing such problems as low twistability, unsuitable dynamic behavior, and the shortage of radial mechanical strength. In our simulations, NiTi superelasticity is modeled based on Auricchio theory and Tanaka, Liang and Rogers theory. Auricchio Model show more consistency with the experimental data than Tanaka and Liang and Rogers Models. In the present study, a Finite Element Analysis (FEA) was used to evaluate the impacts of the applied strain on the superelastic behavior of the new geometry designed for Z-shaped TAA NiTi wire stent, for which axial strain (crushing) and radial strain (crimping) force are applied. The results showed that NiTi stent with 50% crimping and 90% crushing displayed the highest mechanical performance owing to suitable Chronic Outward Force(COF), appropriate Radial Resistive Force(RRF), complete mechanical hysteresis loop pertaining to superelastic behavior, and the lower stress and higher strain on the internal curvature of the NiTi stent. Finally, this FEM model can provide a convenient way for evaluating the biomechanical properties of TAA stents given the influences of strain applied.