不同释放程度下下肢动脉支架的疲劳强度及寿命预测

目的 探究释放程度和支架结构对支架疲劳寿命的影响。方法 利用有限元法分析3款镍钛合金下肢动脉支架（Complete SE、E–luminexx–B和Pulsar–35）在脉动载荷作用下的力学性能，基于疲劳应变理论评估支架的疲劳强度，使用Fe–safe和Abaqus软件预测支架在不同释放程度（80%、85%、90%）下的疲劳寿命及安全性。应用Origin软件对支架应力与疲劳寿命进行拟合。结果 支架在释放尺度为80%～90%下的疲劳强度均满足10年疲劳寿命的要求。3种支架释放程度为90%时，疲劳强度大，寿命长；释放程度为80%时，疲劳强度、寿命及安全系数小。相同释放程度下，偏置型波峰结构支架变形后的交变应变及弹性应力值最大，支架寿命及安全系数最小；对称型波峰结构支架CE的寿命及安全系数小于EB。通过LangevinMod函数拟合PR支架疲劳寿命，拟合优度R2>0.99。结论 随着释放程度的增大，3款支架疲劳强度、寿命及安全系数呈增大趋势。在相同释放程度下，支撑单元对称型波峰结构支架疲劳强度、寿命及安全系数比偏置型波峰结构支架大，减小对称型波峰结构支架的连接体宽度有利于提高支架寿命。

Fatigue Strength and Life Prediction of Lower Extremity Arterial Stents under Different Release Degrees

The work aims to explore the effects of release degree and structure on fatigue life of stents. The mechanical properties of three Nitinol lower extremity arterial stents (Complete SE, E-luminexx-B and Pulsar-35) under pulsating load were analyzed by the finite element method. The fatigue strength of stents was evaluated based on the fatigue strain theory. Fe-safe and Abaqus software were used to predict the fatigue life and safety of stents under different release degrees (80%, 85% and 90%). Origin software was used to fit the stress and fatigue life of the stents. The fatigue strength of the stents at the release degree of 80%-90% met the fatigue life requirement of 10 years. When the release degree of the three stents was 90%, the fatigue strength was high and the service life was long; while the release degree was 80%, the fatigue strength, life and safety coefficient were small. Under the same release degree, the alternating strain and elastic stress of the skewed wave crest structure were the largest, and the life and safety coefficient of the stents were the smallest. The life and safety coefficient of the symmetrical crest structure stent CE were less than those of EB. The fatigue life of PR stent was fitted by LangevinMod function, and the goodness of fit R2 was >0.99. With the increase of the release degree, the fatigue strength, life and safety coefficient of the three stents increase. Under the same release degree, the fatigue strength, life and safety coefficient of the symmetric wave crest structure of the stent element are larger than those of the offset wave crest structure. Reducing the width of the connecting body of the symmetric wave crest structure is beneficial to improve the life of the stents.