Establishment of damage estimation rule for brittle fracture after cyclic plastic prestrain in steel
Establishment of damage estimation rule for brittle fracture after cyclic plastic prestrain in steel
复制标题
钢循环塑性预应变后脆性断裂损伤估计规则的建立
DOI：
10.1051/matecconf/201930017005
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发表时间：
2019
影响因子：
--
通讯作者：
Shunsuke Takagi
中科院分区：
文献类型：
--
作者：
Hiroaki Kosuge;Tomoya Kawabata;Taira Okita;Hideaki Murayama;Shunsuke Takagi
钢中脆性断裂的微观过程是由于晶界脆性层中出现的微裂纹在位错堆积增加的驱动下扩展而发生的。因此，相当于位错增加的加载塑性变形直接与脆性断裂风险的增加有关。由于这些机制，预应变意味着接近材料的极限，这可能导致断裂韧性的劣化。为了对钢结构进行寿命评估，总结各种循环预应变的影响是非常重要的，本文研究了拉伸和压缩预应变时材料韧性的变化。采用一般的三点弯曲试验来评价断裂。综合分析，使用传统的机制为基础的应变梯度塑性（CMSGP）理论，其中位错密度是用来确定材料的损伤量，以及采用传统的宏观材料损伤考虑规则进行。电子背散射衍射图（EBSD）的观察支持的模拟和实验结果的一致性。此外，临界应力的计算，并在预应变条件下的临界应力的变化进行了研究。临界应力的变化机制可以用屈服点的增加和位错密度来表示。
The microprocess of brittle fracture in steel is suggested to occur because microcracks appearing in the brittle layer at the grain boundary propagate driven by increased piled-up dislocation. Thus, loading plastic deformation, equivalent to the increase in dislocation, is directly connected to the increase in brittle fracture risk. Because of these mechanisms, prestraining means approaching the limits of the material, which could lead to deterioration of fracture toughness. For a lifetime evaluation of steel structure, it is important to generalize the effect of various cyclic prestrains.In this paper, material toughness changes when tensile and compression prestrain occur were investigated. A general three-point bending test was employed to evaluate fracture. Synthetic analysis using Conventional Mechanism-based Strain Gradient Plasticity (CMSGP) theory, in which dislocation density is used to determine the amount of material damage, was carried out as well as employing conventional macroscopic material damage consideration rules. The consistency of the simulation and the experimental results were supported by the Electron Back Scattered Diffraction Pattern (EBSD) observation. Additionally, critical stress was calculated, and the change in critical stress for prestrain conditions was investigated. Then, the mechanism of critical stress changes could be expressed by the yield point increase and dislocation density.