压力容器疲劳加载下埋藏裂纹扩展规律的研究

Research on embedded crack propagation law of pressure vessel under fatigue loading

摘要:

针对压力容器埋藏裂纹扩展过程中其几何形状变化难以确定的问题，运用Newman和Raju方法获得裂纹前沿的应力强度因子，并结合Paris公式得到不同裂纹的深度与长度变化的关系式.同时，通过将椭圆形裂纹前沿离散化成为距离相等的多个点，并使用Simpson求积法，获得不同材料压力容器埋藏裂纹在循环载荷作用下埋藏裂纹的几何形状变化关系.结果表明：在拉力作用下，埋藏裂纹的疲劳扩展总是趋向于最优扩展路径的方向扩展.初始裂纹深长比和指数m越大，则收敛于最优扩展路径的速度越快，即形成近似于圆形的趋势更快.

Abstract:

This paper mainly focuses on the problem that is difficult to determine the geometric shape change of embedded crack propagation in pressure vessels. The stress intensity factor of crack front is obtained by using the methods of Newman and Raju, and the relationships between depth and length changes of different cracks are obtained by combining with Paris formula. Meanwhile, by discretizing the elliptical crack tip into multiple points with equal distances and using the Simpson quadrature method, the geometric change relationships of the embedded cracks of pressure vessels with different materials are obtained under cyclic loading. The results show that under the action of tensile force, the fatigue growth of buried cracks tends to expand in the direction of the optimal expansion path. The larger the initial crack aspect ratio and the exponent m gives rise to the faster the speed of convergence to the optimal propagation path, namely, the faster tendency to form an approximate circle.