多点冲头主动加载拉形数值模拟研究

发布时间：2018-07-29 18:40

【摘要】：多点拉形是一种新的板料柔性成形技术,能够节省模具制造成本,缩短零件制造周期。但由于多点拉形与传统拉形存在相似的局限性,在成形过程中板料变形并不均匀,容易出现拉裂、滑移线、起皱等缺陷。因此,需要探讨新的加载方法提高板料变形均匀性。随着多点技术的发展,多点模具的基本体冲头能够在承受一定压力的条件下主动调整各自冲头的高度,对板料施加载荷,迫使板料渐进成形。本文基于上述基本体冲头的特点,将其应用到拉形中,研究了多点冲头主动加载路径对板料成形质量的影响。在这种成形方式中多点模具始终与板料处于贴合状态,能够提高板料变形均匀性,避免成形缺陷,获得合格的零件。本文主要内容和结论如下:1.板料受力分析及有限元模型建立对板料的变形条件做了基本假设,采用解析方法对板料的拉形过程进行了力学分析,得出板料在成形过程中应力、应变和厚度减薄的表达公式。同时建立了有限元模型,确定了边界条件。2.多点冲头主动加载拉形与加载路径设计介绍了多点冲头主动加载拉形的特点,分析了它与普通多点拉形的异同点。阐述了多点冲头主动加载拉形的路径设计原则,根据冲头运行时间、速度和板料变形曲率设计了三种加载路径,分别为等时冲头主动加载、等速冲头主动加载和等差曲率冲头主动加载。同时对多点拉形与等差曲率冲头主动加载拉形中板料的受力特点进行了分析,表明等差曲率冲头主动加载能够提高板料变形均匀性。3.多点冲头主动加载拉形的数值模拟分析基于多点冲头主动加载拉形与多点拉形,分别对球面件和鞍面件进行数值模拟分析,研究了不同加载路径对板料成形效果的影响规律。结果表明:与多点拉形相比,多点冲头主动加载拉形中的等时冲头主动加载、等速冲头主动加载和等差曲率冲头主动加载均能减小板料钳口处应力集中,提高成形件有效区域的应力分布、应变分布、厚度分布和延伸率分布的均匀性,对回弹的抑制作用比较明显。4.多点冲头主动加载拉形工艺参数研究通过数值模拟研究了工艺参数对鞍面件成形质量的影响,主要涉及到的工艺参数有板料预拉量、弹性垫厚度、过渡区长度、拉伸速率和基本体参数。研究结果表明,合理的工艺参数组合能够使板料变形更加均匀,提高零件的整体成形质量。
[Abstract]:Multi-point drawing is a new flexible forming technology for sheet metal, which can save the manufacturing cost of die and shorten the manufacturing cycle of parts. However, due to the similar limitation between multi-point drawing and traditional drawing, the sheet metal deformation is not uniform in the forming process, and the defects such as tensile crack, slip line and wrinkle are easy to appear. Therefore, it is necessary to explore a new loading method to improve the uniformity of sheet metal deformation. With the development of multi-point technology, the basic punch of multi-point die can adjust the height of their punches under certain pressure, and apply load to the sheet metal, forcing the sheet metal to form gradually. Based on the characteristics of the basic punch, this paper applies it to the drawing, and studies the influence of the active loading path of the multi-point punch on the forming quality of the sheet metal. In this way, the multi-point die is always fit with the sheet metal, which can improve the uniformity of sheet metal deformation, avoid forming defects, and obtain qualified parts. The main contents and conclusions of this paper are as follows: 1. The stress analysis of sheet metal and the establishment of finite element model have made the basic hypothesis to the deformation condition of the sheet metal. The mechanical analysis of the drawing process of the sheet metal has been carried out by using the analytical method, and the expression formula of stress, strain and thickness thinning of the sheet metal in the forming process has been obtained. At the same time, the finite element model is established, and the boundary condition is determined. Design of active loading and loading path for multi-point punch the characteristics of multi-point punch active loading and drawing are introduced and the similarities and differences between multi-point punch and common multi-point tension are analyzed. This paper expounds the principle of path design for active loading and drawing of multi-point punch. According to the running time, speed and deformation curvature of sheet metal, three loading paths are designed, which are isochronous punch active loading. Active loading of constant speed punch and active loading of isometric curvature punch. At the same time, the mechanical characteristics of sheet metal in active loading of multi-point tension and isodyne curvature punch are analyzed. It is shown that active loading of isometric curvature punch can improve the uniformity of sheet metal deformation. Numerical simulation analysis of multi-point punch active loading and drawing based on multi-point punch active loading and multi-point drawing respectively numerical simulation analysis was carried out on spherical parts and saddle surface parts. The influence of different loading paths on sheet metal forming effect was studied. The results show that the isochronous punch active loading, the constant velocity punch active loading and the isodyne curvature punch active loading can reduce the stress concentration at the clamp of sheet metal compared with the multi-point drawing, the multi-point punch active loading, the isochronous punch active loading and the isokinetic curvature punch active loading can reduce the stress concentration at the clamp of sheet metal. Increasing the uniformity of stress distribution, strain distribution, thickness distribution and elongation distribution in the effective zone of forming parts, the inhibition of springback is obvious. The influence of process parameters on the forming quality of saddle surface was studied by numerical simulation. The main process parameters involved included sheet metal pretension thickness of elastic pad length of transition zone. Tensile rate and basic body parameters. The results show that the reasonable combination of process parameters can make the sheet metal deformation more uniform and improve the integral forming quality of the parts.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG306

【参考文献】