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通过对厚度分别为 ３， ６， ９， １２和 １５ ｍｍ的 ＣＴ试样的断裂韧性实验和微观断口分析，研究了 Ｘ６０高韧性管线钢的断裂韧性和裂纹扩展阻力曲线的厚度与分层裂纹耦合效应．结果表明，分层裂纹与厚度方向的离面应力存在约束互相作用，厚度增加，分层开裂加剧，局部有效厚度并未增加，导致断裂过程中裂纹端部的三维应力约束总是近平面应力的低约束状态，表观断裂韧性不随厚度变化．在有分层裂纹出现时，无法靠增加试样厚度获得材料的平面应变断裂韧性．由于分层与厚度的耦合作用与裂纹扩展方向与厚度方向的相对方位密切相关，应用穿透裂纹的表观断裂韧性数据进行管道结构的安全评定并不完全可靠研究还表明，塑性区修正的有效应力强度因子与弹塑性Ｊ积分参量在失稳扩展前保持良好的等效性。
The fracture toughness and fracture analysis of CT specimens with thickness of 3, 6, 9, 12 and 15 mm respectively were studied to study the fracture toughness and crack growth resistance of X60 high toughness pipeline steel. effect. The results show that there is a constraint interaction between delamination crack and thickness-direction out-of-plane stress, the thickness increases, delamination cracks intensify, and the local effective thickness does not increase, resulting in the three-dimensional stress constraint at the crack tip being always near-plane stress Low constraints, apparent fracture toughness does not vary with thickness. In the presence of delaminated cracks, the plane strain fracture toughness of the material can not be obtained by increasing the thickness of the sample. Because the coupling of delamination and thickness is closely related to the relative orientation of crack propagation direction and thickness direction, the safety evaluation of pipeline structure using apparent fracture toughness data of penetrating crack is not completely reliable. The study also shows that the plastic zone correction is effective The stress intensity factor and elastic-plastic J-integral parameters maintain good equivalence before instability expansion.