【作者】 刘志国；

【导师】 胡平；

【作者基本信息】 吉林大学 ， 车身工程， 2011， 博士

【摘要】 中国工业的快速发展和消费者个性消费对汽车制造企业的改型换代提出了新的要求,在新车型开发的过程中,覆盖件冲压模具的开发和制造能力将很大程度上决定开发周期和开发成本。为了实现缩短覆盖件冲压模具开发周期和降低开发成本的目的,在模具设计过程中使用板料成形CAE软件是切实可行的方法之一。通常在冲压模具设计阶段,设计人员将使用CAD软件设计好的仿真模型导入CAE软件,在CAE环境中设定相关仿真参数后进行成形模拟,模拟结果可以显示模具设计方案的优劣,并为模具修改提供参考。冲压模具型面是在零件模型的几何数据基础上,通过模型修复和编辑、补孔、法兰展开、边界光顺和工艺补充等工序完成的,在零件几何模型基础上生成冲压模具的过程成称之为模面设计过程,因此,冲压模具型面设计的关键就是模面设计。为了实现在CAE环境中完成冲压模具模面设计的目的,本文对模面设计的相关功能进行了分析,对部分关键技术进行了深入研究,并结合ACIS开发平台完成了部分关键算法,主要内容如下:冲压件模型在不同CAD造型系统间传输很容易出现非二边流形体错误和因系统最小容差不同导致的曲面间存在裂缝等缺陷,这些缺陷会严重妨碍冲压件仿真前处理的工作,同时存在裂缝的冲压件模型也不能生成符合仿真分析的有限元网格,因此,研究模型转换缺陷修复技术具有非常重要的学术价值。本文针对冲压件模型转换存在的缺陷进行了较深入的研究,着重对非二边流形体和几何修复后的拓扑重构进行了研究,分析了冲压件模型转换缺陷的类型及产生的原因,针对不同的类型提出了相应的修复方法。为了实现模型的参数化编辑目的,结合ACIS提供的InterOp数据输入接口,研究了三维模型的修改和编辑功能,并编写了适用不同编辑目的组件,包括边界重构功能、局部操作功能、混合和抽壳等。针对边界重构操作可能产生的多解问题进行了分析和处理;混合操作生成Coons混合曲面,并针对等半径混合、变半径混合和顶点混合编制了不同的实现程序,还设计了混合操作后的拓扑重构。根据现有的一步逆成形有限元基础理论,以弹塑性成形体积不变和不关心加载过程为假设条件,完全考虑成形板料物理性能的前提下实现曲面的合理展开。曲面展开的算法过程中,充分考虑板料物理性能的一步逆成形展开算法克服了几何展开尺寸不准确的弊端,在比例加载的假设条件,按照金属的弹塑性变性理论对法兰面进行展开,达到冲压模具型面设计的要求。通过对典型冲压件的法兰展开测试以及试模样件的尺寸测量,证明了法兰展开算法的准确性。传统的基于知识系统的工艺补充设计、基于参数化的工艺补充设计等工艺补充设计算法解决了工艺补充面的插值生成,但对工艺补充面本身在零件“尖角”处的连续程度,工艺补充面与零件的过处及工艺补充面与压料面间的过渡连续性一直没有很好的解决。另外,传统算法生成的工艺补充面的连续性仍然是依靠设计人员的经验,通过选择、设定参数的过程来保证的。而且传统的基于截面线的工艺补充面设计过程需要设计人员在冲压件的每条边界上构造多条用于生成插值曲面的截面线,这种在多条截面线间插值生成工艺补充曲面片的方法容易造成曲面片不连续的情况。本文提出了截面线和指定方向的方法生成参数化的压料面的方法,该方法能够生成符合拉延仿真要求的压料面。摒弃了工艺补充曲面片生成过程中采用三段截面线的做法,提出采用两段6控制点的可调B样条曲线作为截面线,以截面线、边界线和截面线的连接线为边界轮廓的插值曲面生成工艺补充曲面片的方法。为了满足工艺补充曲面片的C1连续性要求,采用“滚动球”的混合方法实现了锋利边和尖点的光顺过程。KMAS/Die_Face冲压模型面参数化设计模块基本功能包含:网格生成、法线一致、冲压方向优化、补孔、翻边隐藏、镜面对称、边界光顺、法兰展开、压料面设计、工艺补充设计及拉延筋设计等功能,但如何将这些基本功能进行合理安排、整合,实现准确、快速的完成设计是覆盖件冲压模型面设计模块的核心内容。覆盖件冲压模型面参数化设计基本功能的实现为KMAS/Die_Face实现提供了前提,本文通过研究覆盖件冲压模型面设计的工艺特点,结合各个基本功能的特点、覆盖件产品特征和成型预测结果设计并实现了具有零件模型特征匹配和成型结果预测的型面快速设计模块。设计模块着重就冲压件型面特征和相似性进设计,研究分类算法并建立数据库,建立模型属性特征模板,从而实现快速型面设计模块。更多还原

【Abstract】 Rapid development of china industry and individual demand put into a higher level for reform and regeneration of automobile-manufacturing enterprises, in the process of development of a new car type, the design and manufacture capacity of panel stamping die determines the circle and cost of development to a large degree. In order to reduce the development circle and lower the development cost of panel stamping die, one of the methods is that the CAE software for sheet metal forming be used in the process of die design. At the phase of design of panel stamping die, designer usually import the simulation model to the CAE software and simulates in the environment of CAE after some parameters is inputted, the simulation judges superior or inferior of the die design scheme and provides the preference for modify of die. Stamping die is designed on the base of geometry data of part model through mending holes, flange expansion, boundary smoothing and addenda. The stamping die that is created on the base of the geometry model of the part is defined as die-face design, so the die-face design is the key to design of stamping die.The related theories and key technologies of panel die face digital design are studied thoroughly based on CAE system. This paper has researched on the following several key technical issues. In order to realize the die-face design for stamping die, the related function of die-face design is analyzed and the key algorithm on ACIS platform is finished, the main content is as following:It is easy to make the error that non two edges form when the stamping die is transferred among the system of CAD styling. The defect, such as crack among the surface, appears due to the different of minimal tolerant, these defects hinder the simulation of pre-process of stamping parts, at the same time, the cracking stamping parts do not produce the finite element meshes that meet the simulation analysis. Therefore, the study of fixing technology at the process of the transformation of model has very important academic value of study. The study is made for the transformations defect of tamping model and the type and reason of transformation is analyzed, more important is, the study of manifold and topology re-building. The corresponding fixing method is proposed in view of different types.In order to realize the purpose of model parametric editing, through the InterOp of ACIS platform, the modification and editing of 3D model is studied, and some components for different editing purposes are also compiled, including the following functions: boundary re-building, local editing, blending and shell, etc. In accordance with the problem of possible multi-solutions, when the boundary re-building operation is executed, the analysis and solution are studied in this paper. The blending operation creates Coons surfaces, and according to the equal radius blending, variable radius blending and point blending, the corresponding programs are compiled. The topology of blending operation is also re-built.According to the finite element basis theory of one-step inverse forming and assumption conditions that constant volume of elastic-plastic remains, the premise of the consideration of physical properties, the rational expansion of surface is realized. In the algorithm of surface expansion, one-step inverse forming expansion overcame drawbacks of inaccurate size in the geometry expansion. Under the condition of proportional loading, the flange-face is expanded according to the theory of metal elastic-plastic and the expansion accuracy of surface is improved. Through the testing of flange-face expansion for typical stamping parts and dimension measurement, the accuracy of flange-face expansion algorithm is proved.The traditional algorithms of addenda design, which based on knowledge system and parameter, can realize the interpolation generation of addenda surfaces, but can not solve the following problems well: the continuity degree between addenda surfaces on the sharp corner of parts, the continuity degree between addenda surfaces and parts’surfaces or blank surfaces. Additionally, the continuity of addenda surfaces by traditional algorithms can only be realized by the experience of designer and setting parameters. And the traditional addenda design basing section curves need the designer to build several section curves on every edges of stamping parts for the interpolation generation, and this kind of method of construct interpolation surfaces basing several section curves will cause the continuity fault of addenda surfaces. The method of section curves and defined direction to build parametric blank surfaces are proposed in this paper, and these blank surfaces can fulfill the requirement of simulation of drawing. The method of using three parts of section curves during the construction of addenda surfaces is disused in this paper, and two alterable B-Splines with 6 controlling points are proposed as sections curves in this paper, and the method of construction boundary of interpolation surfaces basing section curves, boundary curves and connecting curves are also proposed in this paper. In order to fulfill the requirement of C1 continuity of addenda surfaces, the blending method with rolling ball is used to realize the smoothing of sharp corners and sharp edges.The parametric design of stamping die face module of KMAS/Die_Face includes the following basic functions: meshing, normal consistence, stamping direction optimizing, holes filling, flange hiding, symmetry operation, boundary smoothing, flange expansion, blank surface design, addenda surfaces design and draw bead design. But how to rational arrange and integration the above basic functions, and realizes fast and precise die face design is the kernel content of stamping die face design module. The basic functions of parametric design of stamping die face provide the premise of KMAS/Die_Face. Through the study of technology characteristics of stamping die face design, and the integration of corresponding basic functions, and the product characteristics of stamping parts, and the simulation results of forming, the fast design module of stamping die face is designed and realized, which includes the matching of parts model features and the prediction of forming results. This design module focus on the design according to the geometry characteristics and similarity of stamping parts, and the research of classify-algorithm, and construction of databank, and the construction of model characteristics templates, thus the fast design module of die face is realized.更多还原