摘要
目的优化CS无支架四叶心包二尖瓣设计,有限元分析瓣叶应力。方法按照仿生原则,设计新型无支架四叶二尖瓣,根据瓣膜几何形态及牛心包组织材料特性,建立模拟新型瓣膜启闭的有限元动态模型,应用有限元软件ANSYS,采用八节点曲线薄壳单元并充分考虑大应变和瓣叶闭合过程中的接触。以体外脉动流仪测得瓣膜平均跨瓣压差作为面载荷,应用Newton-Raphson方法求解有限元方程,计算在开启和关闭状态时,各瓣叶的应力分布。结果有限元计算的瓣膜变形和实际变形十分接近。瓣膜关闭时,大部分区域第一主应力为0.22～0.70Mpa,主瓣叶最大应力为1.64Mpa,出现在瓣叶基部与瓣环连接区;侧瓣叶最大应力为1.17Mpa,出现在瓣叶游离缘;大部分区域第二主应力为0.15～0.34Mpa,主瓣叶最大应力为0.54Mpa,出现在瓣叶基部。瓣膜开启时,主、侧瓣叶最大应力为0.58Mpa,出现在瓣叶交界缝合处。新型瓣膜四个瓣叶应力分布较原型瓣均匀。结论采用有限元模型计算瓣膜变形与应力分布方法合理;新型瓣应力分布较均匀,有益于防止瓣叶撕裂和减少钙化,从而延长心包二尖瓣的寿命。
[Objective] To improve the design for CS stentless quadrileaflet pericardial mitral valve(PCSV) and to identify their static stress distribution. [Method] According to the bionical rule, the modified PCSV (MCSV) was fabricated. The MCSV was established as a reasonable dynamic model and effective computational method for imitating opening and closing phase of the mitral valve. A finite element code was developed to solve this computational problem using the 8-node super-parameter nonlinear shells and the Newton-Raphson method. This model incorporated the geometry, tissue thickness, and elastic modulus of the bovine pericardium. the load was the mean transvalvular pressure gradient of the tested valves at open and closed position, and the stress was determined with ANSYS analysis software. [Result] When mitral valve were at closed position, the first major stress in the most areas of MCSV was 0.22 to 0.7 Mpa, the largest first and second major stress was 1.64 Mpa and 0.54 Mpa, both occurred in the base of the leaflets. The largest major stress of. side leaflets. was 1.17Mpa and occurred in the border of the leaflets. When mitral valve was at open position, the largest stress of the main and side leaflets was 0.58Mpa and occurred in the border of the leaflets. The average stress of MCSV displaied more uniform stress distribution than that of the PCSV. [Conclusion] The finite element computational method for identifing stress distribution of MCSV is convincible. The stress distribution on the leaflets of MCSV is relatively even, that may conduce to decrease tear and calcification, and to improve the endurance of the pericardial mitral valve.
出处
《中国医学工程》
2005年第3期280-283,共4页
China Medical Engineering
