Three Dimensional Fracture Mechanics Analysis for Welded Joint Structures Using Virtual Crack Closure-integral Method

摘要

In this study, evaluation of stress intensity factors (SIFs) has beenrncarried out to the defects in welded joint structures. There are manyrnwelded joints in marine structures. It has possibilities that fatiguerndefects are initiated in the welded joint structures under severernconditions. It is important to critically examine the mechanicalrnbehaviors for the welded joint structures based on the concept ofrnfatigue strength evaluation. SIFs are one of the important parameters tornestimate the mechanical properties for the cracked bodies. Finiternelement analyses (FEA) are often used to calculate the SIFs. There arernsome difficulties to make a three dimensional FEA model to therncomplex shaped structures. In this study, quadratic tetrahedral finiternelement analyses with large scale computation and virtual crackrnclosure-integral method (VCCM) are adopted to evaluate the SIFs forrnthe cracks in welded joint structure. The use of tetrahedral finiternelements enables us to make FEA models from 3D-CAD modelrndirectly because we are able to use automatic mesh generation software.rnIn this paper, mathematical formulation and numerical implementationrnfor the VCCM analysis using quadratic tetrahedral finite elements arerndescribed. Calculation of SIFs for the VCCM analysis is carried out tornthe three dimensional linear elastic crack problems. And, estimationrnand evaluation for the SIFs of the cracks in the welded joints arernpresented.