冠状动脉植入支架的动态特征分析

采用有限元分析方法，研究了镁合金冠状动脉支架在植入过程中由膨胀产生的弹塑性大变形行为，得到了支架内等效应力随膨胀加载位移的变化规律. 考虑了支架回弹后残余变形、残余应力以及血管约束对其动态特征的影响，计算了支架前5阶的固有频率、相应的振动模态以及在简谐激励下的位移响应. 分析结果指出，植入支架经过膨胀和回弹变形后，前5阶固有频率均会显著降低，并且残余应力对支架固有频率和振动模态影响较小. 考虑血管约束时，支架的前4阶固有频率有所改变，但是不影响振动模态特征. 并且指出支架较之扭转和呼吸变形更易产生弯曲变形. 这些结果可为支架强度和刚度的优化设计提供参考. 

Analysis on Dynamic Characteristics of Implanted Coronary Artery Stents

The elastic-plastic deformation behaviors of magnesium alloy coronary stent were studied by finite element method, and the variation of equivalent stress in the stent with the displacement of expansion loading was obtained. The influences of residual deformation and residual stress of the stent after springback on its dynamic characteristics were analyzed. Modal analysis and harmonic response analysis were employed to calculate the first five natural frequencies of the stent, corresponding vibration modes and displacement response under harmonic excitation. The results show that the first five natural frequencies of the implanted stent are significantly reduced due to the large structural deformation after expansion and springback, while the residual stress has little influence on the natural frequencies and vibration modes of the stent. When vascular constraints were considered, the first four order natural frequencies of stents changed, but the vibration modes were not. The stent is more prone to bending deformation than torsion and breathing deformation. These analysis results can provide reference for the optimal design in strength and stiffness of stents.