薄壁件多向无模渐进成形的弹塑性-屈曲耦合变形行为与控制策略

Under the pressure of intensive global competition, the manufacturers in today’s marketplace face many challenges to produce high-quality thin-walled production in a cost-effective and productive way. As a flexible manufacturing technology of thin-walled parts without the need of dedicated dies, incremental forming has attracted huge attention in recent years due to the vast potentials in rapid and economical production of sheet metal products. However, up to date the technology is mainly applied in a limited domain of sheet forming, mostly belonging to a biaxial stretching deformation, a relatively complete processing chain based on incremental forming has not yet been established. This project puts forward a novel method called Multi-directional Dieless Incremental Forming for the production of thin-walled parts by combining the incremental forming with the fabrication of tubular parts, as well as some specific forming processes such as flanging and hole-flanging, etc. The new technology not only can extend the application scope of incremental forming to a large degree, but also can produce workpiece which is hard to form integrally by any other methods, providing a strong support to the realization of light weight of productions. By taking into account of the particular force and deformation modes during the courses, which are quite different from those of traditional processes, the elastic-plastic and buckling coupled deformation of sheet metal during typical forming processes will be investigated using experiment and numerical simulation after introducing the concept and method of the structural mechanics. Formative mechanism and critical condition of typical defects will be clarified, and the defect control strategies will be developed based on the feature analysis, the automatic control technology, and the modified bar tools, and so on. Then, theoretical and technical basis regarding the application of the new technology can be established.

在竞争日趋激烈的全球化市场环境下，制造领域对高效、低成本的薄板成形技术有着迫切的需求。渐进成形作为一种无需专用模具的板件数字化柔性制造技术，因在快速经济板成形方面极具潜力而在近年来备受关注，但迄今其应用仅限于以“双拉”为主的板料的成形类加工，未能形成相对完整的加工链。本项目将渐进成形与管件成形以及板料的翻边（孔）、卷边等多种成形需求相结合，提出薄壁件多向无模渐进成形的新工艺，不仅能大大拓展渐进成形的应用范围，还能得到传统方法难以整体成形的薄壁件，从而为实现产品结构的轻量化提供重要技术支撑。项目将针对新工艺存在的异于传统成形过程的特殊力与变形模式，结合物理实验与数值模拟并引入结构力学的概念和方法，研究典型成形过程的弹塑性与屈曲等多机制耦合变形的规律，阐明主要缺陷的形成机理与临界条件，综合运用特征分析、自动控制以及改进工具头等手段建立多渠道的变形控制策略，为相关应用奠定理论和技术基础。

随着产品更新换代速度不断加快，制造领域对快速、经济薄板成形的需求日益迫切。渐进成形作为一种无需专用模具的数字化柔性制造技术，由于在单件、小批量板料成形方面极具潜力而受到重视。本项目将渐进成形与管件成形以及板料的翻边（孔）、卷边等多种成形相结合，提出了薄壁件“多向渐进成形（MISF）”的系统方法，大大拓展了以“双拉”为主的传统板料渐进成形的应用范围，同时还能得到传统冲压难以整体成形的薄壁件，从而为实现产品结构的轻量化提供关键技术支撑。在此基础上，结合物理实验与数值模拟并引入结构力学的概念和方法，系统研究了典型薄壁件的多向渐进成形过程，取得了预期目标。课题组共发表SCI/EI检索论文13篇，申请发明专利4项（其中已获权2项）。重要结果包括：（1）提出了基于MISF的管端翻卷、扩（缩）口、管壁压槽以及薄板卷边、翻孔（平面、斜面以及曲面）等成形的系统工艺方法，形成了一个基于渐进成形的相对完整的板料柔性成形加工链。（2）系统研究了薄壁件MISF的变形机理，阐明了成形过程的弹塑性与屈曲多机制耦合变形规律。其中，分析了润滑条件、预制孔直径、水平步距和整形路径等因素对多向无模渐进翻孔成形极限的影响；探讨了不连续变形对无模渐进翻孔变形的影响；利用微观组织分析与铁磁检测法，研究了形变诱发马氏体相变现象对SUS304渐进翻孔成形极限的影响。发现由于渐进斜面翻孔的非轴对称性，各个位置的回弹大小存在差异，翻折角度越大的部位回弹与尺寸偏差也越大；工具头直径d、倾斜角度θ、螺旋轨迹螺距△Z是影响回弹的重要因素。（3）阐明了MISF过程主要成形缺陷的形成机理与临界条件，建立了改进工具头形状、优化加工路径等缺陷控制手段，初步形成了MISF工艺设计的基本规范与准则，对生产实践具有直接的指导作用。