In-plane and out-of-plane constraint characterization of different constraint parameters for semi-elliptical surface cracks in pipes. (August 2020)

• Record Type: Journal Article
• Authors: Wang, Y.H.; Wang, G.Z.; Tu, S.T.; Xuan, F.Z.
• Is Part Of: Engineering fracture mechanics. Volume 235(2020)
• Publication Date: 2020-08
• Subjects: Constraint parameters -- In-plane constraint -- Out-of-plane constraint -- Semi-elliptical surface cracks -- Pipes; Fracture mechanics -- Periodicals; Rupture, Mécanique de la -- Périodiques; Fracture mechanics; Periodicals; 620.112605
• DOI: 10.1016/j.engfracmech.2020.107161
• Languages: English
• ISSNs: 0013-7944

Abstract

Highlights: In- and out-of-plane constraints of surface cracks in pipes are characterized using six parameters. The crack depth and aspect ratio can influence both in- and out-of-plane constraints. The parameters Q and h are equivalent and they can capture both in- and out-of-plane constraints. The parameters Ad and Ap can equivalently characterize both in- and out-of-plane constraints. The advantages and limitations of different constraint parameters are analyzed. Abstract: Six constraint parameters (namely T -stress, Q, h, Tz, Ad and Ap ) have been numerically calculated for semi-elliptical surface cracks in pipes so as to comparatively investigate their capability, applicability and ease of use for characterizing in-plane and out-of-plane constraints. The results show that the parameters T -stress and Tz can separately characterize in-plane and out-of-plane constraints. The crack depth a/t and aspect ratio a/c of semi-elliptical cracks can influence both in-plane and out-of-plane constraints. With decreasing a/c (increasing crack length) and increasing crack depth a/t, both in-plane and out-of-plane constraints increase. The parameters Q and stress triaxiality factor h are equivalent, and they can capture both in-plane and out-of-plane constraints for the cracks in pipes. But they may overestimate constraint for longer cracks with lower a/c . The parameters Ad and Ap based on crack-tip plastic deformation (or strain) can equivalently characterize both in-plane and out-of-plane constraints for the cracks in pipes. The advantages and limitations of different constraint parameters in terms of their engineering applications are analyzed and appropriate parameters are recommended.