摘要
为提高核电设备缺陷评定的准确性,需要考虑裂尖拘束对材料断裂韧性的影响。如何找出一个统一的参数以表征复合拘束,是目前断裂力学研究的主要问题之一。本文采用有限元模拟的方法,分析了εp等值线所围面积作为统一拘束参数的可行性。结果表明:εp等值线所围面积APEEQ与不同面内、面外拘束条件下材料的断裂韧性都有很好的关联性,因而它可能用来统一地表征复合拘束。用标准试样作参考,基于APEEQ定义了一个新的统一的拘束参数Ap。材料的标称化断裂韧性JIC/Jref与Ap呈直线关系,并与所选择的εp等值线无关。JIC/Jref-Ap直线关系对于材料是唯一的,不同材料的JIC/Jref-Ap直线斜率不同,斜率大的材料对拘束更敏感。该直线可能用于评价实际结构中不同拘束条件下裂纹缺陷的安全性。
Background： Constraint can significantly alter the material＇s fracture toughness. Purpose： In order to increase accuracy of the structural integrity assessment. It needs to consider the effect of constraint on the fracture toughness of nuclear power materials and structures. A unified measure which can reflect both in-plane and out-of-plane constraint is needed. Methods： In this paper, the finite element numerical simulation method was used, a unified measure and characterization parameter of in-plane and out-of-plane constraint based on crack-tip equivalent plastic strain have been investigated. Results： The results show that the area surrounded by ep isoline has a good relevance with the material＇s fracture toughness on different constraint conditions, so it may be a suitable parameter. Based on the area ApEEO, a unified constraint characterization parameter Ap is defined. It was found that there exists a sole linear relation between the normalized fracture toughness Jlc/Jref and √Ap- regardless of the in-plane, out-of-plane constraint and the selection of the cp isolines. The sole .JIC/Jref-√Ap line exists for a certain material. For different materials, the slope of JIC/Jref-√Ap reference line is different. The material whose slope is larger has a higher JIc/Jref and is more sensitive to constraint at the same magnitude of normalized unified parameter. Conclusions： The unified JIC/Jref-√Ap reference line may be used to assess the safety of a cracked component with any constraint levels regardless of in-plane or out-of-plane constraint or both.
出处
《核技术》
CAS
CSCD
北大核心
2013年第4期222-228,共7页
Nuclear Techniques
关键词
面内拘束
面外拘束
裂尖等效塑性应变
GTN损伤模型
断裂韧性
In-plane constraint
Out-of-plane constraint
Crack-tip equivalent plastic strain
GTN damage model
Fracture toughness
