涡轮盘表面裂纹的应力强度因子及其扩展

STRESS INTENSITY FACTORS AND THE PROPAGATION OF SURFACE CRACK IN TURBINE DISK

表面裂纹是飞机和发动机构件常见的故障。本文提出利用三维有限元素法和裂纹表面位移法相结合 ,求解某型发动机涡轮盘冷却孔内表面半椭圆裂纹的应力强度因子 KI 的近似解 ,并对裂纹的疲劳扩展寿命进行预估。为了验证计算方法 ,文中有表面裂纹体典型算例的计算结果对比以及光弹性冻结应力实验分析。实践表明 ,本文提出的方法对于工程构件的三维裂纹问题分析研究十分简便。

A displacement method is provided to determine the stress intensity factors of nodes on crack surface in cracked body.The K I at the points along crack front of surface crack are obtained from the curve of K I versus r by the extrapolation.The K I of semi circular and semi elliptical surface crack in the finite thickness plates subjected to tensile load are calculated by the three dimensional finite element method.The photoelastic experiments with stress frozen method are made to examine the accuracy of the calculated results by the present method.Based on the expression proposed by Elber and Newman for the crack growth rate,the crack growth pattern and the life prediction of semi elliptical crack in a turbine disk of a jet engine are investigated.It is shown that the method presented in this paper is simple and convenient to analyse surface crack problems of engineering components.