Abstract

Low carbon steel is widely used in industry due to its excellent elastoplastic behavior with the mechanism of damage accumulation during severe plastic deformation processes which lead to increase strength resistance. In this study, the strain locus of the failure is predicted based on the stress triaxiality and Lode angle-dependent damage model by considering damage evolution during the process. Therefore, by performing various tests for several stress states and modeling the load paths related to damage accumulations, the coefficients of the modified Mohr–Coulomb damage model and Johnson–Cook are determined. According to results achieved among the test with good accuracy, the predictor locus of the failure strain is illustrated. Then, using the determined coefficients, the steel damage evolution is investigated during the process of Equal Channel Angular Extrusion (ECAE). It is shown that the damage accumulation during the ECAE process in a die with respectively internal and external angles of 90 and 30 degrees grows from the region closer to the internal angle as reaches a maximum value in central regions. Also, the amount of damage in vicinity of the outer angle is extremely reduced. According to experiments, the steel does resist fracture events after the ECAE process.

Graphic Abstract

中文翻译：

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等通道角挤压过程中低碳钢现象损伤演化的混合建模

摘要

低碳钢由于其优异的弹塑性行为以及在严重塑性变形过程中的损伤积累机制而被广泛应用于工业中，从而增加了强度阻力。在本研究中，考虑过程中的损伤演化，基于应力三轴性和 Lode 角相关损伤模型来预测失效的应变轨迹。因此，通过对几种应力状态进行各种测试并对与损伤累积相关的载荷路径进行建模，可以确定修正的 Mohr-Coulomb 损伤模型和 Johnson-Cook 的系数。根据在测试中获得的结果，精度良好，说明了失效应变的预测轨迹。然后，使用确定的系数，在等通道角挤压 (ECAE) 过程中研究了钢损伤演变。结果表明，在内角和外角分别为 90 度和 30 度的模具中，ECAE 过程中的损伤累积从靠近内角的区域开始增长，在中心区域达到最大值。此外，外角附近的损坏量也大大减少。根据实验，该钢在 ECAE 工艺后确实能抵抗断裂事件。

图形摘要