Cracks are one of the main factors influencing the structural integrity of ships, offshore platforms, pressure vessels and other structures. Surface cracks occur frequently at weld toes 1). These cracks take various shapes, for example, cracks in fillet welded joints show long-shallow shapes. For linear elastic fracture mechanics problems, the principle of superposition is effective for cracks in residual stress fields and crack cohesive force models. However in case of simple crack problems, they are usually analyzed by applying remote loads. For example, when analyzing a crack in a residual stress field, the influence of the stress field can be taken into account through applying a traction force on crack faces, where the value of traction force is the negative of the stress field 2).
It is important to examine the accuracy of numerical domain/interaction integration methods for crack face traction force cases. In this study, the principle of superposition is applied for 3D surface cracks in flat plate and T-butt welded models. This study shows the significance of the crack face traction term for obtaining accurate calculated stress intensity factors (SIFs).