This paper studied the mechanical performance of four bioresorbable PLLA stents, i.e., Absorb, Elixir, Igaki-Tamai and RevaMedical, during crimping and expansion using the finite element method. Abaqus CAE was used to create the geometrical models for the four stents. A tri-folded balloon was created using NX software. For the stents, elastic-plastic behaviour was used, with hardening implemented by considering the increase of yield stress with the plastic strain. The tri-folded balloon was treated as linear elastic. To simulate the crimping of stents, a set of 12 rigid plates were generated around the stents with a radially enforced displacement. During crimping, the stents were compressed from a diameter of 3 mm to 1.2 mm, with the maximum stress developed at both inner and outer sides of the U-bends. During expansion, the stent inner diameter increased to 3 mm at the peak pressure and then recoiled to different final diameters after balloon deflation due to different stent designs. The maximum stress was found again at the U-bends of stents. Diameter change, recoiling effect and radial strength/stiffness were also compared for the four stents to assess the effect of design variation on stent performance. The effect of loading rate on stent deformation was also simulated by considering the time-dependent plastic behaviour of polymeric material.

中文翻译：

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生物可吸收聚合物支架的压接和膨胀的计算研究。

本文利用有限元方法研究了四种生物可吸收性PLLA支架在压接和扩展过程中的机械性能，即Absorb，Elixir，Igaki-Tamai和RevaMedical。Abaqus CAE用于创建四个支架的几何模型。使用NX软件创建了一个三折气球。对于支架，使用了弹塑性行为，并通过考虑屈服应力随塑性应变的增加来实现硬化。将三折球囊视为线性弹性。为了模拟支架的压接，在支架周围产生一组12个刚性板，并在径向上施加位移。在压接过程中，将支架从3毫米的直径压缩到1.2毫米，在U形弯头的内侧和外侧都产生了最大应力。在扩展期间，支架内径在峰值压力下增加到3 mm，然后由于不同的支架设计而在球囊放气后回缩到不同的最终直径。在支架的U形弯曲处再次发现最大应力。还比较了四个支架的直径变化，回弹效果和径向强度/刚度，以评估设计变化对支架性能的影响。还通过考虑聚合物材料随时间变化的塑性行为来模拟加载速率对支架变形的影响。还比较了四个支架的回弹效果和径向强度/刚度，以评估设计变化对支架性能的影响。还通过考虑聚合物材料随时间变化的塑性行为来模拟加载速率对支架变形的影响。还比较了四个支架的回弹效果和径向强度/刚度，以评估设计变化对支架性能的影响。还通过考虑聚合物材料随时间变化的塑性行为来模拟加载速率对支架变形的影响。