【作者】 易国锋；

【导师】 柳玉起；

【作者基本信息】 华中科技大学 ， 材料加工工程， 2013， 博士

【摘要】 随着我国汽车产业的高速发展,覆盖件冲压成形仿真技术已经普遍应用,以解决产品早期设计缺陷问题,提高模具设计质量。但现有成形仿真技术还存在一定的局限性,不能满足模具优化设计和现场试模的要求,因此研究汽车覆盖件冲压成形精细化仿真和优化技术是具有重要生产意义的课题。论文结合国家数控重大专项项目基金(项目名称“高强钢板冷冲压成形技术研究”,项目编号：2010ZX04014-072)支持,在分析影响汽车覆盖件成形仿真精度各种因素、优化技术应用现状的基础上,对汽车覆盖件成形精细化仿真和优化技术进行了研究,研究内容主要包括以下几个方面：为研究高强度板流过拉深筋时阻力、举升力变化规律,结合高强度板冲压成形特点,同时考虑对称和非对称形状的拉深筋,设计了试验方案。试验结果表明：在对称的拉深筋中高强度板和普通钢板阻力变化规律基本一致；在非对称的拉深筋中者表现有不一致性；非对称形状拉深筋的相关参数和高强度板成形后卷曲变形量或回弹量变化有关系。在综合分析这种关系基础上,提出了一种通过非对称形状拉深筋控制高强度板成形质量的新方法。采用该方法可以有效减小高强度板成形后的卷曲变形量、回弹量,降低现场调试工作量和缩短调试时间。建立了基于知识的增量法优化拉深筋的方法。对汽车覆盖件进行分类,采用提取关键特征技术,制定了拉深筋优化知识库的创建方案。以成形极限图(FLD)为目标函数,综合考虑过度减薄、破裂、起皱、成形不足因素对冲压件可成形性的影响,以分模线以内区域为主要优化对象,有效解决了传统优化方法初始值不合理及优化时间过长的问题。采用弹性力学分析的方法研究了覆盖件冲压成形过程中压边圈的变形模式。在此基础上,提出了一种考虑覆盖件模具压边圈管理面的模拟方法,同时结合该模拟方法提出了管理面优化设计方法。通过理论推导与仿真技术相结合,建立了管理面高度差计算模型,以及内、外压边力设定准则。该方法对于指导覆盖件冲压工艺设计,减少后期模具研配工作量具有重要意义。论文应用数值模拟技术同时结合试验数据,在对比分析模拟结果的基础上,研究了等效拉深筋和实体拉深筋在各种成形条件下对模拟精度的影响。结果表明,拉深筋的处理方式对压边力、起皱、破裂和厚度减薄率分布的准确性存在很大的影响。论文结论对提高覆盖件成形精细化仿真的精度有指导意义。更多还原

【Abstract】 With the rapid development of the China automobile industry, the technology of numerical simulation for sheet metal forming of auto panel has been widely used to predict product forming defects in early design stage and improve the quality of the process and structure of die design. The simulation technology is still under development to meet the requirements of the higher simulation accuracy at the design and field test stages. Therefore, it is very important to research the subject about the refinement of simulation and optimization techniques of auto panel.The study is supported by the fund of the National numerical control major projects (project name "high-strength steel cool stamping technology research", project No:,2010ZX04014-072). Firstly, both the factors that affect the forming simulation accuracy of auto panel and the optimization technology are analyzed. Then the refinement simulation techniques are studied, which includes the following aspects:In order to study the law of the drawbead resistance and lifting force variation with the high-strength steel und the die structures, the test program is developed. In the program, the drawbeads with the symmetrical and asymmetrical shapes are considered. The results show that:The variation laws are same in the symmetrical and asymmetrical shapes drawbead with common steel. But the laws are different with the high strength steel. The geometric parameters with asymmetrical shape drawbead will affect the deformation and springback to some extent.Basis on the experiments and simulation analysis, a control method for high-strength steel forming quality with asymmetrical shape drawbead is developed, which can reduce the curl amount of deformation and springback of high-strength steel with less workload and shorten debug time.The drawbead optimization method with knowledge using the incremental finite element method is developed. Firstly, the key features of auto cover is classified to build the drawbead optimization knowledge base. Then optimization method is developed using the Forming Limit Diagram (FLD) as the objective function. In the method, the factors for forming formability, such as, severe thinning, rupture, wrinkling, unsufficient forming within the region of open line are considered, with can solve the problem of the initial value and the long time optimization effectively.The Influencing factor for forming formability of the blank holder deformation is analyzed with the elasticity finite element method. A process optimization and simulation technology is developed to control the gap (Referred as the management face) between the blank holder and the forming sheet. Both the calculation model of height difference within the management face and the setting rules of inner-outer blank holder force are developed using the theoretical derivation and simulation technology.Basis of the simulation results and experimental data, the process parameters for forming formability, such as, the equivalent and real shape drawbead, the blank holder deformation and the gap between blank holder and forming sheet are studied. The conclusions with test and simulation to improve the refine simulation accuracy of auto panel is Significance.更多还原