Stress Intensity Evaluation for Surface Cracks by Means of Boundary Element Method and Influence Function Method and the Surface Crack Extension Analysis

To evaluate the LBB (leak before break) of a pressure vessel and piping, it is important to analyze the surface crack extension behavior under fatigue conditions. It is also necessary to analyze the stress intensity factors for a surface crack in a structual component. In this study. three-dimensional boundary element elastostatic analysis is carried out for various surface crack problems. The present BEM uses Mindlin's solution as well as Kelvin's solution as a fundamental solution. Thus we can obtain accurate solutions for a surface crack just before or after penetration. The obtained solutions for various shapes of surface cracks are stored as the data base, in terms of the influence function method. We develop the surface crack extension analysis system using the stress intensity factor data base and also the fatigue crack growth law. Our system seems to be useful especially for the analysis of the surface crack just before or after the penetration, and also under residual stresses.