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, Yinglin; Wang, X.M.; Frotscher, M.; Eggeler, Gunther; Yue, Zengji

doi:10.1002/mawe.200700207

Cited by 7 publications

(9 citation statements)

References 14 publications

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“…In brief, when a defect position is within the range of 0.28 mm displacement along stent arm, the stent's maximum stress is at the defect. If a defect position is outside the range of 0.28 mm displacement, its maximum stress is near knots as like a stent [13]. So it can be concluded that a defect at some given region can result in a higher stress concentration near the defect, and at other given area a defect has a small impact on the stent.…”

Section: Stent With Bulge Defectmentioning

confidence: 95%

“…So our results represented the maximum loading conditions will be presented. The detailed information can be referred to references [13].…”

Section: Fea Modelsmentioning

confidence: 99%

“…4 was analyzed. The model mesh and the refinement at the notches/fillets can be referred to references [13].…”

Section: Fea Modelsmentioning

confidence: 99%

“…16 shows the results obtained from studies of the comparison. From the stress distribution of stent without defect [13], stresses of the designated-position nodes along stent arm are obtained (curve A). Curves B and C are the maximum Von Mises stress of each inclusion defect and each stent with defect, respectively.…”

Section: Stent With Bulge Defectmentioning

confidence: 99%

“…In our previous work [13], the stress distributions of stents without defect mainly had been studied. In order to investigate further Nitinol stents, in this paper the primary emphasis is on the analysis of the stent with a defect (void or face bulge) under the loading/unloading.…”

Section: Introductionmentioning

confidence: 99%

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

Zhi

Wang

Gao

et al. 2008

Materialwissenschaft Werkst

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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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Section: Stent With Bulge Defectmentioning

confidence: 95%

“…So our results represented the maximum loading conditions will be presented. The detailed information can be referred to references [13].…”

Section: Fea Modelsmentioning

confidence: 99%

“…4 was analyzed. The model mesh and the refinement at the notches/fillets can be referred to references [13].…”

Section: Fea Modelsmentioning

confidence: 99%

Section: Stent With Bulge Defectmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Zhi

Wang

Gao

et al. 2008

Materialwissenschaft Werkst

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Elementary Deformation and Damage Mechanisms During Fatigue of Pseudoelastic NiTi Microstents

Frotscher

Simon

et al. 2011

Adv Eng Mater

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The blood circulatory system in the human body is associated with a pulsating blood flow which results in cyclic widening of the vessels in the rhythm of the heart beat. For a medical stent, which is supposed to stabilize vessels, this results in cyclic mechanical loading, which can lead to fatigue phenomena, such as fracture of strut elements of the stent. It is important to understand the elementary deformation and damage processes which govern the fatigue of microstents. [1] We have previously shown that fatigue life is affected by surface-related defects such as intermetallic surface particles, laser burrs, and electropolishing artifacts. [2] The purpose of the present work is to document that mechanical cycling of microstents also affects the microstructure. The mechanical experiments performed in the present study are not designed to simulate in vivo conditions of microstents. Instead, the purpose of this study is to contribute to a better understanding of the role of microstructure during mechanical cycling of microstents. Materials and Methods Microstents and Phase Transition TemperaturesPseudoelastic NiTi microstents with a length of 20 mm and an expanded outer diameter of 3 mm were obtained from Abbott Vascular Instruments Deutschland GmbH (Rangendingen, Germany). The stents had a Ni content of 50.8 at.%. Stent struts, the elementary building units of the stents, have rectangular cross-sections of 90 Â 112 mm 2 . The phase transformation behavior of the as-received microstent can be characterized by differential scanning calorimetry (DSC) using a DSC 2920 from TA Instruments. DSC experiments were performed according to ASTM-2004-03 in the temperature range of AE 150 8C at a cooling/heating rate of 10 K Á min À1 , with 3 min hold times at the highest and lowest temperatures. [3] In the as-received condition, the stents showed a two-step martensitic transformation upon cooling from B2 to R phase and from R phase to B19 0 . Upon heating, a two-step reverse transformation back to austenite is observed, as shown in Figure 1. An A f temperature of 21 8C suggests that the material is fully austenitic at room temperature. After 30 million fatigue cycles, the phase transformation temperatures increased slightly and the peaks are broader and less pronounced. Similar observations were made by Grossmann et al. [4] with spring actuators, where it was found that dislocations accumulate in the microstructure duringIn the present study, we investigate the fatigue behavior of Nickel Titanium (NiTi) microstents at 22 8C (room temperature) and 37 8C up to 30 Â 10 6 load cycles. We briefly describe our test procedure, which applies displacement-controlled pull-pull fatigue cycling between displacements corresponding to apparent strains of 5 and 7.5%. The response of the microstents to mechanical loading indicates cyclic softening during 30 Â 10 4 cycles. Subsequently, the maximum load remains constant throughout the remainder of the test. We use transmission electron microscopy (TEM) to clarify the microstructural reasons...

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Analysis of the compression process and dimensional optimization of self‐expanding stent of a nickel titanium alloy

Wang¹,

Zhou

Liu

et al. 2012

Materialwissenschaft Werkst

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The vascular stents are important devices introduced into the vessel to protect the lumen from unfriendly stenosis so that the blood can flow naturally. During its implantation to the vessel, the stent should be compressed to a delivery system with very small dimension to accomplish the minimal invasive operation. At this stage, the stent will withstand very large stresses which will cause large damages in the structure. In this paper, the compression process of the stent was analyzed by finite element analysis method with software ABAQUS. The stress, strain and martensite volume fraction distributions were investigated at the end compression. Results show that the stent fillets are the dangerous areas for the potential failure. Subsequently, the dimensional optimization was performed to decrease the maximum concentration stress. After the optimization, the maximum stress can be decreased by 14.2%, which means the stent's work life can be increased.

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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

Cited by 7 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

Elementary Deformation and Damage Mechanisms During Fatigue of Pseudoelastic NiTi Microstents

Analysis of the compression process and dimensional optimization of self‐expanding stent of a nickel titanium alloy

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