There is much controversy in using laboratory specimens to predict the fracture behavior of large industrial constructions because of their different constraints. Although several parameters have been proposed to characterize the constraint effect, there are still some limitations. To address this issue, a novel unified characterization parameter of constraint based on the critical crack tip opening angle (CTOA_C) is defined. Firstly, the calibrated finite element technologies for simulation of static and dynamic crack are used to determine the equivalent plastic strain (ε_p) distribution around the crack tip and the evolution history of CTOA for specimens with different in‐plane and out‐of‐plane constraints, respectively. Secondly, the feasibility of the equivalent plastic strain at the crack tip when CTOA reaches its critical value to unified measure both in‐plane and out‐of‐plane constraints is investigated. The results indicate that the area A_PEEQ surrounded by the isoline of equivalent plastic strain ε_p can describe both in‐plane and out‐of‐plane constraints and the interaction between them. Finally, a novel constraint characterization parameter η is defined. It is found that there is a linear relationship, which depends only on the material and regardless of the selection of the ε_p isoline, between the normalized fracture toughness CTOA_C/CTOA_ref and η^1/2. The work in this paper is expected to realize the matching of constraints between different laboratory specimens or industrial constructions.

中文翻译：

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基于关键CTOA的平面内和平面外约束的新型统一表征参数

使用实验室标本来预测大型工业建筑的断裂行为存在很多争议，因为它们的约束不同。尽管已经提出了几个参数来表征约束效果，但是仍然存在一些局限性。为了解决这个问题，定义了一种基于临界裂纹尖端张开角（CTOA _C）的约束的统一特征参数。首先，对于静态和动态裂缝的模拟校准有限元技术被用于确定所述等效塑性应变（ε _p）分别具有不同的面内和面外约束的试样的裂纹尖端周围的分布和CTOA的演化历史。其次，研究了当CTOA达到其临界值以统一测量面内和面外约束时，裂纹尖端处等效塑性应变的可行性。结果表明，该区域甲_PEEQ包围由等效塑性应变的等值线ε _p既可以在面内和面外约束以及它们之间的相互作用描述。最后，定义了新的约束特征参数η。发现存在线性关系，该线性关系仅取决于材料并且与ε的选择无关_p等值线，归一化的断裂韧性CTOA之间_Ç / CTOA _REF和η ^1/2。本文的工作有望实现不同实验室标本或工业建筑之间约束的匹配。