Ductile fracture prediction based on J-integral and unified constraint parameters for cracked pipes

Validation and application of a two‐parameter J‐Ad approach for fracture behaviour prediction

“…It has been shown that the two parameters A p and A d can characterize both in-plane and out-of-plane constraints for specimens and cracked components under both brittle and ductile fracture conditions. [24][25][26] Recent theoretical analyses and experimental investigations in the literature 5,27,28 further verify the ability of the crack-tip plastic area to measure both in-plane and out-of-plane constraints.…”

“…The two-parameter approach can be used for fracture analysis of any specimens and structures. 8,20,24,26,39,40 In this work, to validate the J-A d two-parameter approach, extensive experimental fracture toughness data of SEN(B) specimens having various sizes (different inplane and out-of-plane constraints) measured by Neimitz and Galkiewicz 35 were used. The experimental materials are 40H steel with two different heat treatments, namely, material A and material B.…”

“…The J C /J ref -A d correlation lines are linear, which are consistent with those in the previous work. 24,26 The lines in Figure 7A,B can be regarded as the toughness loci for materials A and B, respectively. The correlation line equations for the two materials can be fitted as Equations 2 and 3 below, respectively:…”

“…The intersection of crack driving force line and the material toughness locus indicates crack initiation, and the corresponding fracture toughness or load level at the intersection is the predicted fracture toughness or fracture load. 26 The crack driving force lines (the change lines of the average A d with the average J-integral along thickness) were calculated by FEM for all SEN(B) specimens made of materials A and B, and the fracture toughness of each specimen was predicted. In the fracture prediction and assessment based on CDF approach, the sensitivity of material's fracture toughness to constraint has been included in the material toughness loci (J C /J ref -A d ), and the sensitivity of A d to crack driving force or load levels was reflected in the crack driving force lines (J/J ref -A d ).…”

“…[36][37][38] To incorporate both constraints, the two-parameter J-A p and J-A d approaches have been developed by authors. 25,26,39 It has been shown that the use of the J-A p and J-A d approaches can reduce conservatism degree for shallower and shorter cracks with lower constraints in cracked components. It was suggested that the J-A d approach may be preferentially chosen for the structure fracture assessments due to the easy measurement and determination of the CTOD-based parameter A d .…”