Finite Element Model to Determine KI

A finite element method utilizing quadrilateral elements to obtain an efficient solution to determining the opening-mode stress intensity factor KI is presented. Two plane stress element types are constructed: (1) "Regular" which does not contain a crack but which may be in the interior or on a boundary; and (2) "singular" or "super element" which contains the crack and is assumed to be on the boundary which is a line of symmetry. Each element utilizes as primary unknowns the displacements and strains at each node. Hermitian interpolation functions are used to describe the displacements in the regular element and Williams' stress function is used to develop the singular element. Good agreement with published results is obtained for single-edge-notch beams in three-point bending and four-point bending for relatively coarse meshes.