Finite element simulation of the influence of TiC inclusions on the fatigue behavior of NiTi shape-memory alloys

The vascular stents are important medical devices introduced into a vessel to protect the lumen from unfriendly stenosis. However, Nitinol stent is easy to fail in practice. The present paper focuses on the influence of defects on its mechanical behavior by finite element analysis. The essential stent cell is used with two different type of defects, which includes the face bulge defect resulted from laser burrs or TiC inclusion arises and C-contained particle voids. Auricchio's super-elastic consititutive equations are used in the finite element simulations. It is found that the stress distribution is not only related to the defect type but also to the defect position. With the increasing distance from the TiC defect to the knot's notch, the influence of defects on stress distribution of stents becomes small. For void defects, those near both the inner fillet and the outer fillet have grand influence on the stent's global stress distribution. In particular, the higher stress concentrations are undergone near knot's defects. For all models, the maximum Martensite Volume Fraction is near knots. The finite element analysis shows that cracks/fractures can easily appear near knots. A stent with a TiC inclusion or void defect is likely to fail. All obtained conclusions can be useful to design against stent premature mechanical failure.

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“…In the FE calculation, the TiC inclusion is assumed to be linear elastic with an elastic modulus of E=440GPa and a Poisson's ratio t = 0.19 [15].…”

Section: Materials Parametersmentioning

confidence: 99%

Mechanical property analysis of Nitinol defective stent under uniaxial loading/unloading

Zhi

Wang

Gao

et al. 2008

Materialwissenschaft Werkst

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“…In the FE calculation, the TiC inclusion is assumed to be linear elastic with an elastic modulus of E=440GPa and a Poisson's ratio t=0.19 [14].…”

Section: Fe Modelmentioning

confidence: 99%

The FEM simulation of mechanical properties characterization of the stent under the quasi‐static loading/unloading. FEM‐ Simulation zur Charakterisierung der mechanischen Eigenschaften von Stents unter quasistatischer Beanspruchung

Zhi

Wang

Frotscher

et al. 2007

Materialwissenschaft Werkst

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In this paper, the detailed stress distributions of NiTi stents have been studied. The primary object of this study is to set up a cell model to reveal the cause of crack initiation for stents. Auricchio's super-elastic model is used to analyze the essential stent cell. Two different kinds of models are analyzed. One model is the stent without defect and the other model is a stent with defects caused by laser burrs or TiC inclusions. The structural stress distribution is not only related to a specimen without defect but also to the material of a bulge defect. The maximum stresses of the stent without defect are near the knots, while the one with defects possesses the maximum stress near the surrounding of the bulge defect. It was found that cracks/fractures can easily appear within a distance of 1/3 of the knot to knot spacing. In particular, a stent with TiC inclusion defects is likely to fail near the bulge face defect. Our simulations agree with experimental results.

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Study of the Influence of Inclusions on the Behavior of NiTi Shape-Memory Alloys in Thermal Cycling by Means of Finite Element Method

Urbano

2011

Metall Mater Trans A

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Finite element simulation of the influence of TiC inclusions on the fatigue behavior of NiTi shape-memory alloys

Cited by 6 publications

References 14 publications

Mechanical property analysis of Nitinol defective stent under uniaxial loading/unloading

Mechanical property analysis of Nitinol defective stent under uniaxial loading/unloading

The FEM simulation of mechanical properties characterization of the stent under the quasi‐static loading/unloading. FEM‐ Simulation zur Charakterisierung der mechanischen Eigenschaften von Stents unter quasistatischer Beanspruchung

Study of the Influence of Inclusions on the Behavior of NiTi Shape-Memory Alloys in Thermal Cycling by Means of Finite Element Method

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