A comprehensive investigation on the damage induced by the shearing process in DP780 steel
A comprehensive investigation on the damage induced by the shearing process in DP780 steel
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DOI：
10.1016/j.jmatprotec.2021.117377
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发表时间：
2021-09-24
影响因子：
6.3
通讯作者：
Dong, H.
中科院分区：
文献类型：
--
作者：
Han, S.;Chang, Y.;Dong, H.
剪切边裂现象是制约高强钢应用的关键问题。因此，探讨开裂原因，促进这一问题的解决是非常有必要的。采用显微组织表征、微观/宏观力学性能评价和数值模拟等方法对DP780钢剪切边缘损伤进行了研究。微孔洞、微裂纹和加工硬化行为是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。在相界面处形成的微孔具有尺寸小（5 μ m）、数量少（6 ~ 18个）的特点。通过微孔的数量、大小和分布来评价微孔的损伤程度。结果表明，随着剪切间隙的增大，微孔洞的破坏程度越来越严重。在剪切过程中，微孔洞被劈开形成微裂纹。这些微裂纹成为后续工艺中的裂纹源。因此，微裂纹是影响成形性能的最关键因素。减小微裂纹是防止剪边开裂的有效方法。在ABAQUS中对剪切过程进行了模拟。开发了实现DP780钢本构模型的VUSDFLD子程序。模拟结果与试验结果吻合较好，说明通过模拟可以预测DP780钢在剪切过程中的损伤。本文的研究有助于了解剪边开裂的原因，设计最优剪边工艺。
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 mu m) 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.