Abstract In this work the effect of stress triaxiality on cleavage fracture stress was investigated by means of micromechanical modelling. A unit-cell model was used to determine macroscopic conditions for brittle fracture, in accordance with the slip-induced cleavage fracture model, because of included particle fracture and consequent crack initiation in the matrix. This approach allowed to correlate the critical fracture stress to the particle strength and the ability of the matrix to undergo plastic deformations. Numerical simulations results indicate that the critical fracture stress is strongly dependent on the stress triaxiality, which justify the variability observed in experiments on different specimen geometry. Additionally, the unit-cell modelling allowed to establish a simple relationship between the expected cleavage fracture stress and stress triaxiality, also considering temperature and strain rate. Finally, the use of the plastic constrain factor (defined as the ratio of the critical fracture stress and the yield stress) allows to obtain a master curve that can be used to predict the expected critical fracture stress at different stress triaxiality, temperature and strain rate in different steel grades and alloys.

中文翻译：

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应力三轴性对解理断裂应力的影响

摘要 在这项工作中，通过微观力学建模研究了应力三轴性对解理断裂应力的影响。根据滑移诱导解理断裂模型，使用晶胞模型来确定脆性断裂的宏观条件，因为基体中包含颗粒断裂和随之而来的裂纹萌生。这种方法允许将临界断裂应力与颗粒强度和基体进行塑性变形的能力相关联。数值模拟结果表明，临界断裂应力强烈依赖于应力三轴性，这证明了在不同试样几何形状的实验中观察到的可变性。此外，晶胞建模允许在预期解理断裂应力和应力三轴度之间建立简单的关系，同时考虑温度和应变率。最后，使用塑性约束因子（定义为临界断裂应力与屈服应力的比值）可以获得主曲线，该曲线可用于预测不同应力三轴度、温度和应变率下的预期临界断裂应力在不同的钢种和合金。