Crack Propagation Analysis of Steels with Initial Defects by New Peridynamics

Steel structure specimens exhibit high strength and ductility and are often subjected to complex loading conditions and pre-existing cracks in critical engineering applications. In this study, peridynamics (PD) theory—known for its unique advantages in modeling structural damage and failure—is employed to establish specimens with bilateral cracks and double central cracks at varying longitudinal spacings. To address the complexity of elastic–plastic behavior, the D-M model is applied to transform the nonlinear problem into an equivalent linear elastic one. This approach is integrated with PD theory and the crack tip opening displacement (COD) concept of fracture mechanics to derive a novel linear fracture criterion, termed the PD-COD. Furthermore, numerical models based on PD and the PD-COD criterion are developed for central cross double-crack specimens, enabling analysis of crack propagation under loading. The results validate the effectiveness of the PD-COD damage criterion and elucidate the underlying mechanisms of crack propagation in centrally intersecting double-crack configurations. This work contributes to a deeper understanding of the damage evolution in defective steel structures under load and provides theoretical guidance for engineering design.