自增强厚壁圆筒轴向内表面裂纹的应力强度因子

STRESS-INTENSITY FACTORS FOR AXIAL SURFACE CRACKS INSIDE AN AUTO-REINFORCED THICKWALLED CYLINDER

本文研究用有限元通用程序计算具有残余应力的自增强厚壁圆筒内半椭圆形表面裂纹的应力强度因子的方法。所考虑的应力强度因子被分为相应于工作内压及残余应力两部分，分别用三维有限元通用程序算得的裂纹前沿单元节点的垂直位移直接计算，对后者又运用了＂叠加原理＂。结果表明，残余应力的存在能有效地降低内裂纹的应力强度因子值，自增强度高者这一作用亦显著，残余应力引起的应力强度因子对裂织数目不敏感。

This paper presents calculations of the mode I stress intensity factors (KI) for an auto-reinforced thick walled cylinder with one or two internal axial semi-elliptical surface cracks under two degrees of auto-reinforcement. The stress intensity factor is decomposed into two parts: KIP and KIR. KIP is produced by the internal work pressure and KIR is produced by the residual stress. KIP and KIR are calculated by 3-D finite element method from nodal point displacements at the crack surface. Besides, the superposition principle is applied in the determination of KIR. The general purpose finite element program SAP5,to which a few modification have been made, is used for the analyses. The results show that the existence of residual stresses can reduce the stress intensity factor KI of internal crack efficiently. The higher the reinforced degree, the more obvious is this effect.