人工心瓣热解炭表面微裂纹应力强度因子分析

Analysis of Stress Intensity Factor of Artificial Heart Valves Pyrocarbon Surface Microcracks

人工机械心瓣热解炭涂层表面存在着微小缺陷,大多以半椭圆裂纹的形式存在,在载荷作用下易发生扩展甚至断裂。应力强度因子是判断裂纹是否进入失稳状态的一个重要指标。该文利用三维断裂分析软件,结合有限元分析软件计算了人工心瓣热解炭中心半椭圆裂纹拉伸试样不同位置处的K I,并与基于实验基础的理论值进行对比,同时讨论了初始裂纹大小、位置和形状对K I的影响,结果表明:计算值与理论值最大相对误差不超过3%,验证了该软件计算热解炭K I的有效性,K I随初始裂纹尺寸增大而增大;初始裂纹位于试样中心或边缘对K I几乎没有影响;裂纹长半轴与短半轴比值越接近1,计算结果越稳定。

There are small defects in artificial mechanical heart valves pyrolytic carbon coating , mostly present in semi-elliptical crack form , easy to induce expansion even fracture under load conditions .The stress intensity factors is an important indicator to judge cracks whether the instability state .This paper used the three-dimensional fracture analysis software combine with finite element analysis software to calculate I -mode stress intensity factors （ KI ） of semi-elliptical surface crack of artificial mechanical heart valves pyrolytic carbon center crack tension specimen , and compared with the theoretical values of stress intensity factors based on the experimental basis , and discussed the influence of the initial crack size , position and shape .The results show that：maximum relative error less than 3.0%, verify the effectiveness of the software to calculate KI , KI value increases with the initial crack size;the initial cracks located at the middle or edge almost no effect on the KI;elliptical crack semimajor and semiminor axis ratio is more close to 1 , the results more stable .