Influence of thickness on distribution of stress intensity factors

Abstract

This thesis offers an extensive investigation of the influence of specimen thickness on the distribution of the mode-I stress intensity factor (SIF) along the fracture front of the compact tension specimen. The analysis is carried out in a fully 3D context and the characteristic of the SIF-distribution and width of the layer in the vicinity of surface breaking points where the stress intensity factor exhibits rapid variation and the layer where the SIF is nearly constant are thoroughly examined for various thicknesses of testing specimens. In the modeling, a well-known numerical technique, called a weakly-singular symmetric Galerkin boundary element method (SGBEM), is employed. The most attractive features of this technique include that the mesh generation cost is comparatively cheap since only 2D discretization on the outer boundary of the specimen and on the fracture surface is required and the calculated stress intensity factor along the fracture front is highly accurate with use of relatively coarse mesh. The latter feature results from applications of high order, special crack-tip elements in the local region surrounding the fracture front along with the use of a direct formula to extract the SIF. Extensive results are reported and discussed for specimens made from both isotropic and transversely isotropic materials.