Sheared edge cracking phenomenon is a key problem limiting the application of high-strength steels. Therefore, it is very necessary to explore the cracking causes to promote the solution of this problem. In this paper, the damage in the sheared edge of DP780 steel is investigated by microstructure characterization, micro/macro mechanical property evaluation, and numerical simulation. Microvoids, microcracks, and work hardening behavior are identified as damage factors affecting the sheared edge cracking. Two types of microvoids are found based on the position of microvoids. Microvoids formed at phase interfaces have the characteristics of small size (≤ 5 μm) and large number (276–340), while microvoids generated from inclusions hold large size (> 5 μm) and small number (6–18). The damage degree of microvoids is evaluated by number, size, and distribution. The result shows the damage of microvoids becomes more serious with the increasing shearing clearance. During shearing, microvoids are split to form microcracks. These microcracks become the cracking source in the subsequent process. Therefore, microcracks are the most crucial to the formability. Reducing microcracks is an effective method to avoid sheared edge cracking. Furthermore, the shearing process is simulated in ABAQUS. A VUSDFLD subroutine is developed for implementing the constitutive model of DP780 steel. The simulated results match the experiment results very well, which indicates the damage of DP780 steel during shearing can be predicted by simulations. The research of this paper is beneficial to understand the cause of sheared edge cracking and design an optimal shearing process.

剪切边裂纹现象是限制高强钢应用的关键问题。因此，探索开裂原因以促进该问题的解决是非常必要的。本文通过显微组织表征、微观/宏观力学性能评估和数值模拟研究了DP780钢剪切边缘的损伤。微孔洞、微裂纹和加工硬化行为被确定为影响剪切边缘开裂的损伤因素。根据微孔的位置可以发现两种类型的微孔。相界面形成的微孔具有尺寸小（≤ 5 μm）和数量多（276-340）的特点，而夹杂物产生的微孔具有尺寸大（> 5 μm）和数量少（6-18）的特点。微孔洞的破坏程度通过数量、大小、和分布。结果表明，随着剪切间隙的增加，微孔洞的破坏变得更加严重。在剪切过程中，微孔被分裂形成微裂纹。这些微裂纹成为后续工艺中的裂纹源。因此，微裂纹对成形性至关重要。减少微裂纹是避免剪切边裂纹的有效方法。此外，剪切过程在 ABAQUS 中进行了模拟。开发了一个 VUSDFLD 子程序来实现 DP780 钢的本构模型。模拟结果与实验结果非常吻合，表明DP780钢在剪切过程中的损伤可以通过模拟进行预测。本文的研究有利于了解剪切边裂纹产生的原因，设计最佳剪切工艺。结果表明，随着剪切间隙的增加，微孔洞的破坏变得更加严重。在剪切过程中，微孔被分裂形成微裂纹。这些微裂纹成为后续工艺中的裂纹源。因此，微裂纹对成形性至关重要。减少微裂纹是避免剪切边裂纹的有效方法。此外，剪切过程在 ABAQUS 中进行了模拟。开发了一个 VUSDFLD 子程序来实现 DP780 钢的本构模型。模拟结果与实验结果非常吻合，表明DP780钢在剪切过程中的损伤可以通过模拟进行预测。本文的研究有利于了解剪切边裂纹产生的原因，设计最佳剪切工艺。结果表明，随着剪切间隙的增加，微孔洞的破坏变得更加严重。在剪切过程中，微孔被分裂形成微裂纹。这些微裂纹成为后续工艺中的裂纹源。因此，微裂纹对成形性至关重要。减少微裂纹是避免剪切边裂纹的有效方法。此外，剪切过程在 ABAQUS 中进行了模拟。开发了一个 VUSDFLD 子程序来实现 DP780 钢的本构模型。模拟结果与实验结果非常吻合，表明DP780钢在剪切过程中的损伤可以通过模拟进行预测。本文的研究有利于了解剪切边裂纹产生的原因，设计最佳剪切工艺。