There is much controversy surrounding using laboratory specimens to predict the fracture behavior of high-grade pipeline steel due to their different constraints. Since there is a lack of unified parameters to quantitatively characterize the constraint effects, a model for the transformation of crack arrest toughness between different specimens and pipes has not been formed. In order to solve this problem, the evolution law of the plastic zone of the crack tip with the crack tip opening degree under different in-plane and out-of-plane constraints is explored using the finite element simulation technology. On this basis, a constraint parameter η which is based on the area A_PEEQ surrounded by the isoline of equivalent plastic strain ε_p at the crack tip is proposed. The feasibility of this parameter to characterize both in-plane and out-of-plane constraints is discussed, and a quantitative correlation model between it and the crack arrest toughness, critical crack tip opening angle (CTOA_C), is established. The results show that the proposed parameter can be used to characterize the overall constraints caused by different specimens with different loading forms and geometries. The normalized arrest toughness, CTOA_C/CTOA_ref, has a linear relationship with η^1/2, and the correlation line is only related to the material. The quantitative correlation model has universal applicability for different specimens and is expected to predict the transformation of crack arrest toughness between laboratory specimens and pipelines.

由于高等级管线钢的约束不同，使用实验室试样来预测其断裂行为存在很多争议。由于缺乏统一的参数来定量表征约束效应，因此还没有形成不同试件和管道之间止裂韧性的转换模型。为解决这一问题，利用有限元仿真技术探索了不同面内和面外约束条件下裂纹尖端塑性区随裂纹尖端张开度的演化规律。在此基础上，约束参数η基于等效塑性应变等值线ε _{p 所}包围的面积A _PEEQ在裂纹尖端提出。讨论了该参数表征平面内和平面外约束的可行性，并建立了该参数与裂纹止裂韧性、临界裂纹尖端张开角 (CTOA _C )之间的定量关联模型。结果表明，所提出的参数可用于表征由具有不同加载形式和几何形状的不同试件引起的总体约束。归一化止回韧性 CTOA _C /CTOA _ref与η ^1/2呈线性关系，而相关线仅与材料有关。定量关联模型对不同试件具有普遍适用性，有望预测实验室试件与管道止裂韧性的转变。