【作者】 许恒建；

【导师】 柳玉起；

【作者基本信息】 华中科技大学 ， 数字化材料成形， 2012， 博士

【摘要】 在汽车结构件、五金家电、仪器仪表、以及3C产品(计算机、通信和消费电子)等领域,多工位级进模得到广泛的应用。随着制造业的快速发展和行业竞争的日益激烈,产品形状越来越复杂,质量要求越来越高,生产周期越来越短,成本控制越来越严格,再加上新型的高速机床的应用,使级进模零件成形工艺不仅非常复杂,而且成形工序也很多。此外,级进模前后工序之间的关联性非常强,在产品、条料和模具设计的过程中需要考虑的因素也非常多,造成级进模工艺和模具设计难度很大,传统的依靠经验和反复试模的方法已经不能满足行业的需求。有限元数值模拟技术在汽车覆盖件和航空钣金件等大中型模具的冲压成形中已经得到了广泛应用,并且取得了良好的经济效益,但是,数值模拟在精密多工位级进模领域应用不多。因此,需要开发一套面向级进模产品、条料和模具设计全流程的仿真系统。论文结合国家自然科学基金资助项目“复杂汽车结构件多工位级进模条料设计的快速仿真模型与关键算法研究”(项目编号50905067)和华富集团昆山嘉华电子有限公司资助项目“级进模成形仿真系统研究”,对基于实体壳单元的中厚板或厚板成形和回弹模拟算法、复杂级进模零件中间构型生成算法以及CAD/CAE集成技术进行了深入研究,并在此基础上,开发了面向复杂级进模产品、条料和模具设计全流程的CAD/CAE集成系统Stamping Works。为了准确模拟级进模零件厚向挤压成形效果,开发了一种新的全三维实体壳单元模型。在求解实体壳单元节点内力时采用了平面内单点、厚向多点积分方案,既能剔除体积闭锁和剪切闭锁的不良影响,也能准确描述弯曲效应,并对这种平面内不精确积分激活的沙漏模式进行了处理。针对实体壳单元在板料成形中常常出现的厚向闭锁问题,提出了一种改进的平面应力本构模型,使得实体壳单元能同时获得实体单元和壳单元的特性。此外,推导了实体壳单元隐式增量算法列式,针对实体壳单元平面内完全减缩积分可能引起的病态情况,提出了一种基于二阶泰勒展开的稳定化方法。并编写了实体壳单元动力显式和隐式增量计算程序,用于中厚板/厚板的成形和回弹模拟。给出了实体壳单元模拟成形和回弹的若干个算例,并通过模拟结果与实验结果进行对比来验证实体壳单元的有效性和有限元求解程序的稳健性。复杂级进模条料中间构型设计基本以手工造型为主,耗时费力,精度差,是设计过程中的主要难点。针对级进模零件中大部分的成形工序都是弯曲成形的特点,在已知产品最终构型的情况下,提出了一种基于几何旋转和有限元逆算法的中间构型生成算法,用于复杂级进模条料设计。这种算法通过设置相关的求解条件,如旋转轴、固定区、固定约束线、变形区、形状约束线、非变形区、等长线、等长线缩放因子以及旋转角度等,通过曲面网格快速求解零件初步中间构型。将获得的初步中间构型网格作为修边线逆向展开的参考区域,能准确地获得级进模零件中间构型的边界线,完成中间构型的精确设计。在SolidWorks软件上还没有一套完整的板料成形数值模拟解决方案。本文基于所开发的实体壳单元求解器和中间构型生成算法,开发了首个无缝集成于SolidWorks平台的板料成形数值模拟系统Stamping Works,提供面向复杂级进模零件产品、条料及模具设计全过程的专业分析工具。该系统包括面向级进模零件产品设计的整体毛坯展开与可成形性评估系统Blank Estimation Xpert(BEX)、面向条料设计的级进模零件中间构型设计与分步展开系统Multistep Unfold Xpert(MUX)以及面向工艺与模具设计的级进模全工序成形同步仿真系统Forming Analysis Xpert(FAX),并在汽车结构件和3C等多个企业推广应用,解决复杂级进模设计和成形过程中的很多难题。更多还原

【Abstract】 In the fields of automotive structural parts, hardware appliances, instruments, meters and3C products, progressive dies are widely applied. With the rapid development of the manufacturing sector and the increasing competition of industry, the more complex shape features of progressive die stamping parts, the higher quality requirements, the more stringent controls of costs, and the application of new high speed machine tools, lead to the more complex forming technology and the more forming process number. In addition, the relevance of adjacent processes is quite strong, and quite a few factors are needed to be considered in the designs of products, strips and dies, which greately increase the design difficulty of forming technology and dies. The traditional experience and repeated tryout can no longer meet the industry needs. FE simulation technology has been widely used in the large dies such as automobile covering parts and aircraft sheet metals, and achieved good economic benefits. However, numerical simulations are hardly applied in the multi-position progressive die field. Therefore, it is necessary to develop an analysis system for the whole design process of products, strips and dies.The paper is supported by a grant from National Natural Science Foundation of China (No.50575080) and Research and development on smulation technology for progressive die forming from JIAHUA Electronics CO., Ltd. The forming and springback simulation algorithms based on solid-shell element for medium thick or thick sheet metal, the generating algorithm of complex intermediate shapes and CAD/CAE integration technology are deeply studied. On that basis, a CAD/CAE integration system named Stamping Works for the whole design process of products, strips and dies are developed.A3D solid-shell eleent is developed to simulate accurately the normal extrusion process of thick progressive die parts. An in-plane one-point and thickness-direction multiple-point integration approach is developed to solve the internal force, which inhibits transverse shear locking and volume locking and describe accurately bending effects. And the hourglass mode actived by this integration method is eliminated. An improved plane-stress constitutive model is employed to inhibit the thickness locking. In this way, the solid-shell element obtains both solid-like and shell-like behaviours. In addition, the solid-shell implicit incremental formulas are deduced. Aimming at the pathologies activated by in-plane reduced integration scheme, a stabilization method based on taylor expansion is developed. The solid-shell dynamic elplicit and implicit incremental solvers are developed for the medium thick or thick sheet metal forming and springback simulation. Some numerical examples are taken to verify the effectiveness of the solid-shell element and the robustness of the FE solving programs.The progressive die intermediate shape design is main manual modeling, which is inefficient, inaccurate and the main difficulty of design. According to the situation that most of forming processes in progressive die are bending, a generating algorithm of intermediate shapes based on geometry rotation is developed for complex progressive die strip design. This algorithm need to input some corresponding solving conditions such as rotation axis, fixed area, fixed restraint lines, deforming area, shape restraint lines, un-deforming area, constant-length lines and rotation angle. The intermediate shapes of final products are obtained by surface mesh. The obtained intermediate shape mesh is considered the reference area of trimming line inverse unfolding model to obtain the precise boundry line and complete the accurate design of intermediate shape.There is no a complete sheet metal forming simulation solution in SolidWorks. A sheet metal forming simulation system which is firstly seamlessly integrated within SolidWorks is developed based on the solid-shell solvers and the generating algorithm of intermediate shapes. The system provides professional analysis tools for the whole design process of products, strips and dies. StampingWorks includes the blank estimation and formability prediction system-BEX for product design, the intermediate shape design and multistep unfold system-MUX for strip design, and the complete process forming analysis system-FAX for technology and die design. This system is extended and applied in enterprises such as automotive structural parts and3C products and can solve many difficulties in design and forming process of progressive die.更多还原