基于变压边力—变冲压速度的铝合金成形研究

发布时间：2018-08-21 20:32

【摘要】：铝合金板料因其质量轻、密度低、耐腐蚀、比强度高等特点,使其在汽车白车身中得到广泛应用。汽车白车身的制造精度影响到装配精度、车辆NVH、驾驶体验以及车辆的寿命。而冲压工艺作为汽车白车身制造的重要工艺之一,其工艺参数的制定将显著影响铝合金成形的性能。本文考虑到铝合金板料具有应变率敏感性的力学特性,提出压边力—冲压速度成形窗口的概念。利用压边力—冲压速度成形窗口对铝合金板料成形中的压边力和冲压速度的合理范围进行限制,从而避免起皱与破裂。此外,在压边力—冲压速度成形窗口中构建最佳回弹控制压边力—冲压速度加载曲线,以此抑制材料的回弹问题。首先,本文从压边力成形窗口的概念出发,引申出压边力—冲压速度成形窗口的概念,并提出压边力—冲压速度成形窗口的基本形式和构建方法。其次,进行必要的材料力学测试实验和摩擦性能测试实验。通过不同应变率下的单向拉伸试验,研究应变率对力学性能的影响,并建立相应的真实应力—应变本构模型。进行刚模胀形实验,分析成形极限曲线和最大拉深深度与冲压速度关系。在不同的正向载荷和滑动速率的作用下进行销盘摩擦实验,观察不同工艺条件下的表面摩擦质量,分析摩擦系数和摩擦表面质量的变化规律。再者,建立盒形件拉深的有限元模型,从而构建压边力—冲压速度成形窗口。通过MATLAB样条函数内插法,将不同冲压速度下的临界起皱压边力成形曲线和临界破裂压边力成形曲线,分别拟合为临界起皱压边力—冲压速度成形曲面和临界破裂压边力—冲压速度成形曲面。并且,将该两种临界条件下的成形曲面合并为压边力—冲压速度成形窗口。最后,从单向拉伸试验的回弹现象出发,分析回弹的一般性规律;并在安全裕度控制下的压边力—冲压速度成形窗口内,设计最佳回弹控制压边力—冲压速度成形曲线,以此抑制铝合金板料的回弹量。
[Abstract]:Aluminum alloy sheet is widely used in automobile body because of its light weight, low density, corrosion resistance and high specific strength. The manufacturing accuracy of the car's white body affects assembly accuracy, vehicle NVH, driving experience, and vehicle life. The stamping process is one of the most important processes in automobile white body manufacturing, and the formulation of its process parameters will significantly affect the forming properties of aluminum alloy. In this paper, considering the mechanical properties of aluminum alloy sheet with strain rate sensitivity, the concept of blank holder force-stamping speed forming window is put forward. In order to avoid wrinkling and cracking, the reasonable range of blank holder force and stamping speed in aluminum alloy sheet forming is limited by using blank holding force and stamping speed forming window. In addition, the best springback control beam-pressing speed loading curve is constructed in the blank holding force-stamping speed forming window to suppress the springback problem of materials. Firstly, from the concept of blank holding force forming window, this paper generalizes the concept of blank holder force stamping speed forming window, and puts forward the basic form and construction method of blank holder force stamping speed forming window. Secondly, the necessary material mechanics test and friction performance test are carried out. The effect of strain rate on mechanical properties was studied by uniaxial tensile test at different strain rates, and the corresponding true stress-strain constitutive model was established. The forming limit curve and the relationship between the maximum drawing depth and the stamping speed were analyzed by the bulging experiment of the rigid die. The friction experiments were carried out under different positive loads and sliding rates to observe the surface friction quality under different technological conditions and to analyze the variation of friction coefficient and friction surface quality. Furthermore, the finite element model of box drawing is established to construct the blank holder-stamping speed forming window. By means of MATLAB spline function interpolation, the critical wrinkle blank holder forming curve and the critical fracture blank holder forming curve at different stamping speeds are obtained. The surface is fitted as critical wrinkling beam-pressing speed forming surface and critical fracture beam-pressing speed forming surface respectively. Furthermore, the forming surface under these two critical conditions is combined into a blank holder-stamping speed forming window. Finally, from the springback phenomenon of uniaxial tensile test, the general law of springback is analyzed, and the optimum springback control beam-blank-pressing velocity forming curve is designed in the blank-holder forming window controlled by safety margin. In this way, the springback of aluminum alloy sheet is restrained.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG389

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