Abstract The present work addresses the micromechanical modeling and the simulation of crack initiation and propagation in ductile materials failing by void nucleation, growth and coalescence. A cohesive-volumetric approach is used and the overall material behavior is characterized both by a hardening bulk constitutive law and a softening surface traction-separation law embedded between each mesh of a finite element discretization. The traction-separation law sums up accross a surface all the ductile damage processes occurring in a narrow strain localization band, while the bulk behavior concerns the other elasto-plastic effects. The proposed cohesive zone model is based on a micromechanical approach where the Gurson-Tvergaard-Needleman ductile damage model is adapted to the reduced kinematics of a surface while ensuring the complete effect of the strain rate or stress triaxiality both on the local plasticity and on the void growth. The corresponding cohesive model is implemented in the XPER computer code using the Non-Smooth Contact Dynamics method where cohesive models are introduced as mixed boundary conditions between each volumetric finite element. The present approach is applied to the simulation of crack growth in a standard ferritic steel. Results are compared with available experimental data. The efficiency of the proposed cohesive-GTN model is underlined since the shape of the cohesive law and its mechanical parameters arise directly from the micromechanical approach without any ad hoc fitting parameter.

中文翻译：

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用于延性断裂模拟的内聚 GTN 模型

摘要 目前的工作解决了因空隙成核、生长和聚结而失效的延性材料中裂纹萌生和扩展的微观力学建模和模拟。使用内聚体积方法，整体材料行为的特征在于硬化体本构定律和嵌入在有限元离散化的每个网格之间的软化表面牵引分离定律。牵引分离定律总结了整个表面发生在狭窄应变局部化带中的所有延性损伤过程，而整体行为涉及其他弹塑性效应。建议的内聚区模型基于微机械方法，其中 Gurson-Tvergaard-Needleman 延性损伤模型适用于减少的表面运动学，同时确保应变率或应力三轴性对局部塑性和塑性的完全影响虚无增长。使用非光滑接触动力学方法在 XPER 计算机代码中实现相应的内聚模型，其中引入内聚模型作为每个体积有限元之间的混合边界条件。本方法应用于模拟标准铁素体钢中的裂纹扩展。结果与可用的实验数据进行了比较。