A multiple mechanism weakest link model for intergranular and transgranular brittle fracture is developed on the basis of experimental observations of a thermally aged low alloy steel. The model development is carried out in tandem with micro mechanical analysis of grain boundary cracking using crystal plasticity modeling of polycrystalline aggregates with the purpose to inform the weakest link model. The fracture modeling presented in this paper is carried out by using a non-local porous plastic Gurson model where the void volume fraction evolution is regularized over two separate length scales. The ductile crack growth preceding the final brittle fracture is well predicted using this type of modeling. When applied to the brittle fracture tests, the weakest link model predicts the fracture toughness distribution remarkably well, both in terms of the constraint and the size effect. Included in the study is also the analysis of a reference material.

基于热时效低合金钢的实验观察，建立了晶间和晶间脆性断裂的多机理最弱连接模型。该模型的开发与多晶团聚体的晶体可塑性建模一起使用了晶粒边界开裂的微观力学分析，旨在告知最薄弱的环节模型。本文介绍的断裂模型是通过使用非局部多孔塑料Gurson模型进行的，其中空隙体积分数的演变在两个单独的长度尺度上是规则的。使用这种类型的模型可以很好地预测最终脆性断裂之前的韧性裂纹增长。当用于脆性断裂测试时，最弱链接模型可以很好地预测断裂韧性分布，无论是在约束方面还是在规模效应方面。该研究还包括对参考物质的分析。