【作者】 金涛；

【导师】 李志刚； 柳玉起；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2005， 硕士

【摘要】 汽车覆盖件多是尺寸大,形状复杂的三维曲面,从外观质量到配合精度等要求都很高。覆盖件冲压成形过程是几何,材料和边界条件三重非线性问题,需要用以计算机为基础的数值方法来分析其成形规律。但是,现有的增量法板料成形有限元方法计算时间长,仅适合模拟覆盖件拉延成形过程,然而在覆盖件产品设计、工艺设计和模具设计初期,许多因素都是未知的,增量法板料成形有限元方法无法完成模拟。而有限元逆算法可以很好地解决这个问题,基于形变理论的有限元逆算法只考虑初始构形及最终构形两个形态,因而具有快速,高效的特点。同时它也具有比较高的模拟精度,可作为一个设计早期应用的分析工具。本文详细阐述了逆算法的理论和方法。采用三角形薄膜单元开发了精度较高的有限元逆算法,算法中真实、精确地考虑了摩擦、压边力、拉深筋、背压力、曲压料面等实际工艺条件; 方程组求解引入快速求解算法,比一般的LDLT 解法快几倍,尤其对于大型复杂冲压件问题来说求解效率提高更多。压边力和拉伸筋是覆盖件冲压成形中重要的工艺参数。由于逆算法计算速度快,计算准备数据量少,可以快速地对这些工艺参数进行优化。本文在逆算法的基础上,以变形后工件的厚度分布和厚向应变为目标函数,分别用一维搜索方法和灵敏度分析的方法,建立了冲压过程中的压边力和拉伸筋的优化算法。并通过实例证明逆算法以及基于逆算法的工艺参数优化的有效性。初步探索了逆算法用于工艺参数优化的可行性。本研究得到了国家自然科学基金重点项目(编号50335060)和教育部重点项目(编号03111) 的联合资助。更多还原

【Abstract】 The automobile body panel forming technology plays an important role at the sheet forming industry. From the viewpoint of mechanics, it concerns three kinds of non-linear problems, i.e. geometry, material and boundary friction. Therefore, the prediction and analysis of the forming behaviors have to use numerical simulation methods based on computer. But the incremental Finite Elements Method (FEM) requires considerable computation time, especially at the initial stage of panel die design, since many factors are unknown at this stage which leads to redundant iterations. The finite elements Inverse Approach (IA) can solve this problem well. Only considering the initial and final stage of the parts makes IA method fast and high-effective. So it is a good choice to use this method in the initial stage of the die design. The theories and application of IA method were introduced in this thesis in detail. IA method considerates the parameters such as friction, blank hold forces and drawbead precisely. By using the fast–solving arithmetic, this method is more effective, especially for the large punch parts. The IA method is applied to the optimization of important process parameters such as the blank holding force (BHF) and drawbeads restraining forces (DBRF) where the objective function is defined to minimize the error tolerance of thickness distribution on the workpiece. Numerical simulation shows that this method can analyze the deformation of sheet metal forming part qualitatively rapidly, and can be used for the optimization of the process parameters.更多还原