一个基于孔洞演化机制的韧性断裂预测模型

在韧性断裂中微观孔洞演化机制的基础上,提出了一个基于孔洞演化机制的非耦合型韧性断裂预测模型.模型充分考虑了两种典型的孔洞演化机制:孔洞的长大机制和孔洞的拉长扭转机制.该模型引入了三个具有不同物理意义的材料参数:材料对不同孔洞演化机制的敏感度、应力状态敏感度系数和材料的损伤阈值,并使用等效塑性应变增量表征其对韧性损伤累积过程的驱动作用.为了使模型可以更好地反映三维应力状态对材料韧性断裂性能的影响,将该模型从主应力空间转换到由应力三轴度、罗德参数和临界断裂应变构成的三维空间,得到了由模型确定的三维韧性断裂曲面,并研究了相关参数对三维韧性断裂曲面及平面应力二维韧性断裂曲线的影响.利用5083-O铝合金、TRIP690钢和Docol 600DL双相钢三个典型的轻质高强板材的韧性断裂数据验证了该模型对不同材料和不同应力状态的适用性和准确性.

A micromechanically motivated uncoupled model for ductile fracture prediction

This paper is a contribution to the ductile fracture prediction by the proposal of a new uncoupled ductile fracture criterion. In the new criterion, two typical void deformation models were carefully considered, with the plastic strain increment regarded as a key impetus of the damage evolution and its accumulation. The new ductile fracture criterion was constructed with three model parameters with different physical meanings. A 3D ductile fracture surface model was obtained by transforming the proposed criterion from stress space to the space of stress triaxiality, Lode parameter, and fracture strain, and a parametric study was carried out to better understand their effects. To validate the performance of the new criterion, it was used to construct the 3D fracture surfaces of 5083-O aluminum alloy, TRIP690, and Docol 600DL (a dual-phase steel). Comparisons of the results with experimental observations indicate that the proposed criterion provides good prediction capability over a large range of stress states for various materials, with good flexibility and considerable accuracy.