Abstract In this study, the mechanical behavior of two cold rolled commercial dual phase steels (DP) were analyzed on micro and macro scales. First, the anisotropic behavior of these steels were investigated by standard tensile tests in three directions. The results showed that the anisotropy behavior of the fracture strain of DP980 is more pronounced than of DP600. Then, in order to assess the influence on the stress state on the mechanical behavior, four specimens with different stress states were analyzed by ARAMIS approach which is based on digital image correlation (DIC). The ARAMIS results were compared with 3D numerical simulations using the Abaqus/Explicit solver. In this part, the effect of stress state on flow curve and strain distribution in the specimens (i.e. tensile, notched-tensile, shear and bulge specimens) were investigated. To predict the fracture behavior of DP600 and DP980 steels under various loading conditions, the Modified Mohr-Coulomb (MMC) damage model was utilized. A VUMAT subroutine was developed to include a MMC damage model in the 3D models, and good agreement between the numerical and experimental results was observed. Finally, the microstructure failure mechanisms at three different stages (i.e. strain localization, micro-crack initiation and micro-crack coalescence) during uniaxial tensile loading were investigated inside the microstructure of DP600 and DP980 steels using an interrupted in-situ setup. In the results three different damage localizations were observed in both materials, and strain localization in the center of large ferrite phases and at the boundary of ferrite and martensite phases were dominant in DP600 and DP980, respectively. Two different micro-crack initiation mechanisms were observed that were similar in both materials.

中文翻译：

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DP600 和 DP980 钢力学行为和损伤情景的比较研究

摘要 在这项研究中，从微观和宏观尺度分析了两种冷轧商用双相钢 (DP) 的力学行为。首先，通过三个方向的标准拉伸试验研究了这些钢的各向异性行为。结果表明，DP980断裂应变的各向异性行为比DP600更显着。然后，为了评估应力状态对力学行为的影响，采用基于数字图像相关（DIC）的 ARAMIS 方法分析了四个不同应力状态的试样。使用 Abaqus/Explicit 求解器将 ARAMIS 结果与 3D 数值模拟进行比较。在这部分中，研究了应力状态对试样（即拉伸试样、缺口拉伸试样、剪切试样和膨胀试样）的流动曲线和应变分布的影响。为了预测 DP600 和 DP980 钢在各种载荷条件下的断裂行为，使用了修正的莫尔-库仑 (MMC) 损伤模型。开发了一个 VUMAT 子程序以在 3D 模型中包含 MMC 损伤模型，并且观察到数值和实验结果之间的良好一致性。最后，在 DP600 和 DP980 钢的微观结构内部使用间断的原位设置研究了单轴拉伸加载过程中三个不同阶段（即应变局部化、微裂纹萌生和微裂纹合并）的微观结构破坏机制。在结果中，两种材料都观察到三种不同的损伤定位，在 DP600 和 DP980 中，大铁素体相中心以及铁素体和马氏体相边界处的应变局部化分别占主导地位。