BOUNDARY-ELEMENT CRACK CLOSURE CALCULATION OF 3-DIMENSIONAL STRESS INTENSITY FACTORS

A general method for boundary element-crack closure integral calculati on of three-dimensional stress intensity factors is presented. An equa tion for the strain energy release rate in terms of products of nodal values of tractions and displacements is obtained. Embedded and surfac e cracks of modes I, II, and III are analyzed using the proposed metho d. The multidomain boundary element technique is introduced so that th e crack surface geometry is correctly modeled and the unsymmetrical bo undary conditions for mode's II and III crack analysis are handled con veniently. Conventional quadrilateral elements are sufficient for this method and the selection of the size of the crack front elements is i ndependent of the crack mode and geometry. For all of the examples dem onstrated in this paper, 54 boundary elements are used, and the most s uitable ratio of the width of the crack front elements to the crack de pth is 1/10 and the calculation error is kept within +/- 1.5 percent. Compared to existing analytical and finite element solutions the bound ary element-crack closure integral method is very efficient and accura te and it can be easily applied to general three-dimensional crack pro blems.