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1、南京航空航天大学硕士学位论文板料成形中回弹补偿的曲面映射算法研究姓名：王平申请学位级别：硕士专业：机械工程（制造业信息化技术）指导教师：陈文亮20080101南京航空航天大学硕士学位论文I摘 要板料成形作为一种塑性加工方法广泛应用于汽车航空航天电器造船仪表等工业领域起皱破裂和回弹是板料成形中的三种主要缺陷其中回弹是最难控制的回弹问题的存在对零件的尺寸精度和生产效率造成极大的影响因此对回弹控制进行深入研究有重要意义回弹补偿的方法是根据回弹量的大小和分布对模具的形状进行修正使得工件在回弹后的形状满足几何精度的要求在工程实际中回弹量的大小分布是不易测量的采用传统的模具补偿法确保工件的几何精度是很困难
2、的因此如何利用数值模拟预测出回弹量从而减少零件的几何误差成为板料成形领域中的研究热点之一如何将模具补偿后所获得最终模具的 CAE 几何模型转化成模具 CAD 几何模型以便于 CAM 加工从而建立基于回弹补偿的 CAD/CAE/CAM 一体化系统也是非常关键的一步本文针对板料成形中回弹补偿的曲面映射技术进行了深入的研究研究内容包括? 系统的介绍了与曲面映射相关的曲面造型基础知识为实现曲面映射功能奠定良好的基础? 设计了一套数据结构建立了原始网格节点原始曲面原始曲面边界目标网格以及新曲面之间的关系对原始曲面类型进行了分类建立了曲面映射的顺序采用最小二乘的方法在目标网格上把原始曲面对应新曲面一一生成
3、实现了原始曲面到目标网格的映射功能? 针对新曲面之间连续性较差的情况给出了曲面 G0, G1拼接算法实现曲面之间的光滑连接以满足工程应用的需要在上述技术研究的基础上将基于网格的曲面映射算法与映射后曲面的拼接技术应用于作者参与开发的 CAE 软件模块中该模块功能使用方便可以显著缩短模具设计制造周期提高模具质量降低模具开发成本关键词关键词板材成形回弹补偿曲面映射曲面拼接曲面逼近板料成形中回弹补偿的曲面映射算法研究IIABSTRACTSheet metal forming, as an important method for manufacture of plasticworking, is wi
4、dely used in automobile, aircraft, electronic instrument,shipbuilding, apparatus and other industries. In sheet metal forming,wrinkling, cracking and spring-back are the main problems, amongst whichspring-back is the most difficult one to be controlled. The phenomenon ofspring-back greatly affects p
5、recision of parts and manufacture efficiency, so itis necessary to do further research to control the spring-back.The spring-back die compensation method is that modify the dies shapeaccording to the value and distribution of its spring-back, and then make itsshape after spring-back match the requir
6、ement of geometric precision. It isdifficult to measure magnitude and distribution of spring -back value inengineering practice, and it is difficult to ensure parts geometric precision byusing traditional die compensation method. Consequently, it is one of the hotpoints in sheet metal forming field
7、that how to use numerical simulation topredict spring-back value and then reduce parts geometric error. It is veryimportant that how we can transform the ultimate dies CAE geometricalmodel after die compensation into CAD geometrical model to be convenientfor CAM processing then build CAD/CAE/CAM int
8、egrative system which isbased on spring-back compensation. Therefore, research of surface mappingbase on compensation of spring-back in sheet metal is very necessary and vital.The thesis mainly deals with:? Systematically introduces the fundamental mathematic theory andapproach closely related with
9、the surface modeling , which buildingup the bases for the surface mapping and conjunction;? Build the relation among nodes of original elements, original surfaces,boundaries of original surfaces, the target elements and new surfaces.Sort the original surfaces and establish the sequence of surfacemap
10、ping. Using the lease square method builds new surfaces whichoriginal surfaces corresponding on target elements one by one.Realize the function that mapping the original surfaces on the target南京航空航天大学硕士学位论文IIIelements;? Aiming at condition that the concatenation between the new surfacesare not very
11、well, we give the arithmetic about surface G0, G1 joining,in order to satisfying the requester in industry application;Upon the study of above technology, the thesis applies surface mappingand surface conjunction of Auto Panel Die-face algorithm into Die-faceEngineering module of CAE software which
12、the author participated indevelopment. The module has a convenient function and high implementingefficiency, which shortens mold design and manufacturing period, reducescost and improves quality of mold product significantly.Key words: sheet metal forming, compensation of spring-back surfacemapping,
13、 surface conjunction, surface approach板料成形中回弹补偿的曲面映射算法研究VI图表清单图 1.1 板料成形 CAE 分析的一般过程 .2图 2.1 k 次 B 样条基递推计算公式 .12图 2.2 B 样条曲线的逼近拟合 .15图 3.1 模面补偿流程图 .18图 3.2 工件 1 通过有限元计算的回弹补偿 .19图 3.3 工件 1 通过有限元计算的回弹补偿局部放大图 .19图 3.4 迭代逼近流程.27图 3.5 公共角点类型.31图 3.6 退化成三条边界曲面.31图 3.7 可重构的四边界裁剪曲面 .32图 3.8 零件打散后各个边界的类型加粗表示非等参的裁剪边.33图 3.9 曲面映射的顺序 .34图 3.10 程序界面及说明.35图 3.11 工件 1 的映射结果包含原始曲面和新曲面.35图 3.12 工件 1 的映射结果的新曲面.36图 3.13 工件 1 新曲面与目标网格背离值检测图.36图 3.14 工件 2 的原始网格原始曲面和目标网格.37图 3.15 工件 2 的原始网格原始曲面和目标网格局部放大图.
