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 been carried out to the defects in welded joint structures. There are many welded joints in marine structures. It has possibilities that fatigue defects are initiated in the welded joint structures under severe conditions. It is important to critically examine the mechanical behaviors for the welded joint structures based on the concept of fatigue strength evaluation. SIFs are one of the important parameters to estimate the mechanical properties for the cracked bodies. Finite element analyses (FEA) are often used to calculate the SIFs. There are some difficulties to make a three dimensional FEA model to the complex shaped structures. In this study, quadratic tetrahedral finite element analyses with large scale computation and virtual crack closure-integral method (VCCM) are adopted to evaluate the SIFs for the cracks in welded joint structure. The use of tetrahedral finite elements enables us to make FEA models from 3D-CAD model directly because we are able to use automatic mesh generation software. In this paper, mathematical formulation and numerical implementation for the VCCM analysis using quadratic tetrahedral finite elements are described. Calculation of SIFs for the VCCM analysis is carried out to the three dimensional linear elastic crack problems. And, estimation and evaluation for the SIFs of the cracks in the welded joints are presented.