发动机罩外板拉深回弹的数值模拟分析

Numerical simulation about springback drawn engine hood panel

发动机罩外板结构简单,表面平直,曲率半径大,整体高度低。如果对外板拉深成形时的毛坯形状与尺寸、冲压方向与速度、拉延筋布局与结构以及压边力大小、凸凹模间隙、摩擦润滑等工艺因素的选择或控制不当,则容易导致其卸载后的回弹量增大。文章以eta/DYNAFORM软件为计算平台,利用正交实验法,对某轿车发动机罩外板的拉深回弹现象进行了数值分析,并在此基础上确定了控制回弹的拉深工艺参数和模具结构参数。实验结果表明,该外板零件的拉深回弹呈扭曲倾向,即存在一部分区域上翘,而另一部分区域下陷,其中下陷趋势较上翘明显。根据数值模拟分析得到满足外板技术要求的最优拉深工艺参数和模具结构参数组合为:压边力900kN,虚拟冲压速度1000mm/s(相当于实际冲压速度的10倍),拉延筋高度6mm,凸凹模间隙0.8mm。

Engine hood exterior panel of automobile has generally several characteristics such as simple structure, smooth surface, large curvature radius, small drawing depth and so on. When exterior panel is formed by drawing, if the technique factors can not be correctly selected or controlled which include blank shape and size, stamp direction and speed, drawbead layout and struc- ture, magnitude of blank holder force, gap size between die and punch, as well as friction and lubricate, etc. , it will result in springback increase of the panel drawn after unload. In this paper, based on eta/DYNAFORM and orthogonal test, the spring- back of a drawn car engine hood exterior panel was simulated, and drawing technical parameters and die structure parameters which control springback of the panel were confirmed. The simulating datas show that the springback of the panel which was drawn had a warp tendency, viz. some regions rising on the panel, others sinking, and sinking tendency greater than rising. And the optimum parameter combination, which was found in the numerical simulation and accorded with forming technical de- mands, for drawing plan and die structure of the panel is blank holder force 900kN, virtual stamp speed 1000mm/s （relative to 10 times of real stamp speed）, drawbead high 6mm and gap between die and punch 0.8mm.