ABSTRACT
The weight functions G A J and g i j k can with advantage be se parated into two terms. A direct term appropriate for a single force in the absence of any boundaries and an image term analytically canceling the traction across the crack faces. The direct term which introduces a Cauchy singu larity in the integrals is advantageously dealt with by using the boundary element method, where these terms are integrated analytically over straight line segments. These line segments are connected in order to model the specimen boundary as well as the transformation zone boundary. The image term can be integrated numerically along the boun daries with good accuracy as this involves no singularities except at the intersection between the transformation zone boundary and the crack line, where a weak singularity imposes a vertical tangent for the transformation zone boundary (Stump and Budiansky 1989).
