Abstract The leak-before-break (LBB) concept has been widely used to design the piping system in nuclear power plant, which is based on the fracture resistance (J-R) curves of cracked nuclear pipes. However, accurate fracture resistance evaluation of nuclear pipe is always a tough task. Full-scale nuclear pipe tests are costly and difficulty, and the specimens listed in test standards (e.g. ASTM E1820) are usually too conservative. Thus, compact pipe (CP) specimen has been developed to evaluate the J-R curves of nuclear pipes with high accuracy but much lower cost than full-scale pipe tests. But, the practical application of CP specimen still asks for more theoretical and experimental research. In this study, the assembly of CP specimen was modified to improve the assembly convenience and ensure a more uniform loading condition. Instead of load-line displacement (LLD), crack mouth opening displacement (CMOD) based J-formulation was proposed to determine the J-R curves of modified CP specimens considering more reliable evaluation of CMOD. In addition, the differences of constraint effect among CT specimen, CP specimens and full-scale pipes are distinguished using equivalent plastic strain (ep) isoline regions, which agrees quite well with the results of fracture resistance tests.

中文翻译：

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CP试件对核管抗裂性能评价的进一步研究

摘要 基于裂纹核管的断裂阻力（JR）曲线，断裂前泄漏（LBB）概念已广泛用于核电站管道系统的设计。然而，准确评估核管的抗断裂性始终是一项艰巨的任务。全尺寸核管试验成本高、难度大，试验标准（如ASTM E1820）中列出的试样通常过于保守。因此，开发了紧凑型管道 (CP) 试样，以高精度评估核管道的 JR 曲线，但成本远低于全尺寸管道测试。但是，CP试样的实际应用还需要更多的理论和实验研究。在本研究中，对 CP 试样的组装进行了修改，以提高组装的便利性并确保更均匀的加载条件。考虑到更可靠的 CMOD 评估，提出了基于裂纹嘴张开位移 (CMOD) 的 J 公式而不是载荷线位移 (LLD)，以确定改进的 CP 试样的 JR 曲线。此外，利用等效塑性应变（ep）等值线区域区分了CT试件、CP试件和全尺寸管道之间约束效果的差异，这与抗断裂试验的结果非常吻合。