He Zhubin, Ruan Xianggang, Liang Jiangkai, Ning Jian, Lin Yanli, Chen Kelin
State Key Laboratory of High-Performance Precision Manufacturing, School of Mechanical Engineering, Dalian University of Technology, Dalian 116024, China.
Materials (Basel). 2024 Apr 13;17(8):1796. doi: 10.3390/ma17081796.
Large-dimension complex integral thin-shell components are widely used in advanced transportation equipment. However, with the dimensional limitations of raw blanks and the manufacturing process, there are inhomogeneous geometric and mechanical properties at welded joints after welding, which have a significant effect on the subsequent forming process. Therefore, in this paper, the microstructure of welded joints with a sharp property change was accurately characterized by the proposed isothermal treatment method using the BR1500HS welded tube as an example. In addition, an accurate constitutive model of welded tubes was established to predict the deformation behavior. Firstly, the heat-treated specimens were subjected to uniaxial tensile tests and the stress-strain curves under different heat treatment conditions were obtained. Then, the continuous change in flow stress in the direction of the base metal zone, the heat-affected zone and the weld zone was described by the relationship between the microhardness, flow stress and center angle of the welded tube. Using such a method, a continuous constitutive model of welded tubes has been established. Finally, the constitutive model was compiled into finite-element software as a user material subroutine (VUHARD). The reliability of the established constitutive model was verified by simulating the free hydro-bulging process of welded tubes. The results indicated that the continuous constitutive model can well describe the deformation response during the free hydro-bulging process, and accurately predicted the equivalent strain distribution and thickness thinning rate. This study provides guidance in accurately predicting the plastic deformation behavior of welded tubes and its application in practice in hydroforming industries.
大尺寸复杂整体薄壁构件在先进交通装备中有着广泛应用。然而，受原材料毛坯尺寸及制造工艺限制，焊接后接头处存在几何和力学性能不均匀的情况，对后续成形过程有显著影响。因此，本文以BR1500HS焊管为例，采用所提出的等温处理方法精确表征了性能急剧变化的焊接接头微观组织。此外，建立了精确的焊管理化本构模型以预测其变形行为。首先，对热处理后的试样进行单轴拉伸试验，得到不同热处理条件下的应力-应变曲线。然后，通过焊管的显微硬度、流变应力与圆心角的关系，描述了母材区、热影响区和焊缝区流变应力的连续变化情况。采用该方法建立了焊管连续本构模型。最后，将本构模型作为用户材料子程序（VUHARD）编译到有限元软件中。通过模拟焊管自由液压胀形过程，验证了所建立本构模型的可靠性。结果表明，连续本构模型能够很好地描述自由液压胀形过程中的变形响应，准确预测等效应变分布和壁厚减薄率。本研究为精确预测焊管塑性变形行为及其在液压成形工业中的实际应用提供了指导。
