【作者】 韩方方；

【导师】 关鹏；

【作者基本信息】 沈阳工业大学 ， 机械设计及理论， 2009， 硕士

【摘要】 板材冲压成形是一种先进、优质、高产、低消耗、低成本的加工工艺方法,在汽车,飞机,仪器仪表等工业领域有着广泛的应用。但由于板材成形是一个同时包括几何非线性、材料非线性和边界条件等问题的复杂的弹塑性大变形的力学过程,由此成形过程中必然伴随着多种缺陷如:板材破裂、起皱、回弹等。回弹是板材成形常见的缺陷,并且一直没有较好的解决,为提高冲压件的产品质量,缩短新产品的开发周期,必须对回弹加以控制。由此本文提出了一种带有回弹补偿的模具型面设计的理论解析法,并数值模拟验证此方法具有良好的计算精度。针对板材非圆弧弯曲回弹补偿模具型面的求解问题,本文提出了定弧长结构离散法,将非圆弧弯曲板材离散为若干微板元,并在经典圆弧弯曲回弹理论基础上推导出板材圆弧弯曲回弹前曲率求解公式,结合此公式及每段微板元上节点已知信息构造三次多项式插值,在MATLAB中迭代计算出零件回弹前形状曲线,法向偏置此曲线即可得到回弹补偿模具形状曲线。为了检验此理论解析法是否满足工程需要,本文在第五章中利用ANSYS/LS-DYNA以第三章中设计的回弹补偿模具进行板材动态冲压、回弹数值模拟,获得零件模拟后形状曲线,在UG中与零件实际形状曲线进行比较,分析了两曲线间最大法向误差。经过分析验证得出结论:此方法可根据非圆弧零件实际性状,直接而准确的求得回弹补偿模具型面,因此不仅极大消除了回弹缺陷而且大大减少了设计及实际中反复试模、修模工作量,并降低了冲压件的制造成本、缩短了新产品的开发周期。最后,针对于板材冲压成形的破裂、起皱等其它缺陷,本文在Dynaform中结合某汽车覆盖件的冲压仿真阐述了成形模拟的过程,并深入探讨了如何根据模拟结果预测成形缺陷并进行工艺修正以消除此缺陷。更多还原

【Abstract】 The sheet metal stamping forming is an advanced, highquality, efficient, low consumption and low cost manufacture technology, and is widely applied in automobile, aircraft, electronic instrument and other industries. But because sheet metal forming is a complicated elastic and plastic mechanical process with large deformation, which includes non-liner problem of geometry, material models and boundary conditions, so there are lots of defects in the forming process, for instance: sheet metal’s rupture, wrinkle and springback, etc.Spingback is one of the common defects in sheet metal forming, and have not been solved yet. In order to improve quality of forming parts and reduce production cycle, springback must be controled. A theoretical-analytical method of die’s surface designing compensating springback is proposed in this paper.The dispersing method by constant arc length to solve die’s surface compensating springback of varied curvature bending for sheet metal is proposed, after that the sheet metal is dispersed as lots of infinitesimal cells. Based on classical theory about springback of arc curvature bending, the formula of bending curvature before springback in elastic-plastic arc bending is derived. Cubic polynomial interpolation is established, combining this formula with nodes’ information of every infinitesimal cell, and then part’s shape before springback is described by iterative calculation in MATLAB, finally the punch and die’s figure compensating springback are gained by offsetting this curve.In order to test if this theoretical-analytical method can meet engineering need, dynamic stamping forming numerical simulation with the die compensating springback designed in Chapter 3 by ANSYS/LS-DYNA is carried in Chapter 4, and then after implicit analysis of springback, part’s shape curve is finally gained. Compare with part’s true shape in UG, the maximal normal diviation of this two curves is analyzed.By a train of analysis and demonstration, a conclusion can be reached: die’s surface compensating springback can be directly gained by this method based on part’s ture shape of varied curvature bending, and this method is directly and exactly to solve die’s surface with springback compensation. It can not only eliminate springback largely, but also reduce the work to trial and repair die, cut cost and shorten the development cycle of new products.At last, in order to reduce crack, wrinkle and other defects, stamping forming simulation of an automobile covering panel is carried based on Dynaform to expound the processes of simulation and discuss how to forecast defects and do modification to eliminate these defects.更多还原