Local plastic collapse conditions for a plate weakened by two closely spaced collinear cracks

• We develop a model for residual strength of a plate with two collinear cracks.
• The model is based on the distributed dislocation technique for an edge dislocation.
• The model investigates the plastic collapse of the ligament between collinear cracks.
• An experimental technique is developed to validate the model.

Fracture assessment of structures weakened with multiple site damage (MSD), such as two or more interacting cracks, currently represents a challenging problem. Strength calculations of structural components with MSD are still largely based on two-dimensional solutions for single (or isolated) cracks available in various texts and handbooks or derived from a simplified finite element analysis. Such simplifications could often result in non-conservative predictions. Therefore, there is a strong motivation for the development of more advanced modelling approaches, which could incorporate effects of the interaction between multiple cracks, thickness-induced constraints and other nonlinear phenomena. The primary purpose of this work is to develop and validate a simplified three-dimensional analytical model for the evaluation of the residual strength of two through-the-thickness cracks in a plate of finite thickness subjected to uni-axial loading.