Combined effect of prestrain history and strength mismatch on crack tip constraints in welded specimen

Plastic predeformation (prestrain) in pipe reeling process not only influences the steel yield and flow properties but also reduces fracture toughness. In this work, a combined effect of prestrain history and weld strength mismatch on the crack tip constraint was investigated. Three prestrain histories and three mismatch levels were considered. A four-parameter approach (crack tip opening displacement [CTOD], Q, P, and M) was employed to characterize the crack tip constraint levels. The study addressed an evaluation procedure for the fracture resistance in mismatched welded joints under different prestrain levels using CTOD values. Furthermore, it illustrates the interaction including prestrain histories and strength mismatch effect. The findings indicated that the constraints of prestrain history and overmatch degree are positive for the same crack tip opening displacement level. The crack tip stress field was more significantly influenced by the strength mismatch than the prestrain history in examined cases.