大波段Z形镍钛自膨胀支架的植入压缩和脉动服役行为的有限元分析

Finite analysis of the compression in deployment and pulsating service behavior of the big band and Z-shaped self-expanding stent

超弹性镍钛合金支架在植入前的大幅度压缩和脉动受载过程对支架的安全性有重要影响。大幅度压缩会使支架局部产生较大的应变,当此应变超出了材料的应变极限时会使材料发生永久性变形。支架植入体内后,血管的脉动会使支架受到周期的压缩载荷,并形成疲劳循环。针对大波段Z形支架,运用有限元法分析了支架V形连接弧半径和支撑筋长度对支架压缩过程和脉动循环过程受力的影响。结果表明,支架在植入压缩和脉动服役时,V形连接弧内侧受压缩,外侧受拉伸;增加支架支撑体长度和连接弧半径均使支架的压缩应变减小并使其耐疲劳性增加。另外在评价支架安全性时,不仅要分析支架的长期耐疲劳性,也要考虑其在植入前大幅度压缩时的受力情况。

The significant compression before implantation and pulsating load process of the super-elastic nitinol stent have important impacts on its security application.Significant compression can result in substantial strain in local area of the stent,and when the strain exceeds the strain limit of the material,the permanent deformation will occur.While in service,the stent will receive a periodic pulsating compressive load,and undergo fatigue cycles.Regarding the big band Z-stent,in this paper,we make use of the finite element method to analyze the influence of V-type connector radius and the length of the support strut of stent on its compression and pulsation cycle.The results showed that during the implantation and pulsating process,V-type connector is compressed inside and stretched outside;increasing the length of the support strut and the arc radius will reduce the compressive strain and increase fatigue resistance.Moreover,to evaluate the safety of the stent,it needs to analyze not only the long-term fatigue resistance,but also the significant compression deformation before implantation.