伺服控制下非等厚板料体积成形机理及流动控制研究

Under the current situation that high-performance manufacturing has become the significant developing strategy of manufacturing industry in China, sheet bulk forming technology with advantage of structure and high performance has been increasingly used to manufacture the 3D functional part in net shape. However, sheet bulk forming technology using the sheet of equal thickness cannot meet the forming capacity needs of some complex parts with three-dimensional characteristics, which brings new requirement and challenge to the press and equipment. For this purpose, servo-control technology as well as sheet of unequal thickness is brought into sheet bulk forming process in this project to realize the production of some complex parts with three-dimensional characteristics.On one hand, through establishing thickness domain function to characterize sheet of unequal thickness and introducing a variety of constaint into the thickness domain for Topology Optimization, in order to obtain optimal topological layout for manufacturing, through which the beneficial local metal accumulation is realized. On the other hand, the speed changing, pressure conservation and rebounding modes are brought into the servo-control forming, and the inherent mechanism of the macroscopic mechanical properties of the sheet of unequal thickness under complex stress conditions caused by the internal mechanism of the different movement patterns is analyzed. Through the relevant physical experiments and numerical simulation, the flow of metal forming defects will be well controlled and improved, and finally, a series of process methodology related to sheet bulk forming process under servo control condition will be established.

在高性能化制造已成为我国制造业重要发展战略的今天，具有结构和性能优势的板料体积成形技术已越来越多用于含三维立体特征零件的近净成形。然而，以等厚度板料为坯料的板料体积成形已无法满足一些复杂立体特征零件的成形能力需求，这对成形装备和技术提出了新的挑战。本项目旨在通过采用非等厚板为坯料进行板料体积成形的研究，实现复杂立体特征零件的制造。一方面，建立表征非等厚板的厚度域函数，将多种约束引入非等厚板的厚度域拓扑优化，从而获得面向制造的非等厚板最优拓扑布局，实现有益的局部聚料；另一方面，引入伺服控制技术中的变速、保压、回弹模式，分析非等厚板在复杂应力条件下不同运动模式造成材料宏观力学性能变化的内在机理。在此基础上，通过相关物理实验与数值模拟，对成形缺陷和金属流动加以控制和改善，最终建立一整套伺服控制下以非等厚板为坯料的板料体积成形工艺方法。

板料体积成形工艺可以在板料上制造高性能功能件，为汽车零部件设计提供了新的设计思路，有利于汽车轻量化的实现，促进汽车节能减排。板料体积成形工艺区别于常规板料成形的典型特征是控制板料厚度的变化—减薄和增厚。板料体积成形工艺相比传统工艺，也出现了很多新的技术问题。“伺服控制下非等厚板料体积成形机理及流动控制研究”项目以离合器毂、双联齿轮和侧壁增厚件三类典型变厚功能件为例，深入系统地研究了板料体积成形过程中的金属流动影响因素和流动规律。.离合器毂体件成形时主要存在杯底圆角变薄拉裂和齿形填充不满缺陷，针对前述问题，本项目提出了一种伺服控制下拉深-挤压复合成形工艺，可以一步完成离合器毂的成形。研究了伺服压力机的速度、振荡和间歇模式对杯底减薄的影响，发现间歇模式下杯底圆角的减薄程度最小。针对齿形填充的问题，提出了两步挤压工艺，采用合理分配挤压比的方法，可以使齿形第二步成形时处于压应力状态，提高齿形填充率。.板料体积成形工艺的材料是轧制板坯，金属流动存在各向异性。为了更准确地预测板料体积成形过程中的金属流动，本项目提出了一种方形压缩试验方法，可以得到压缩态大应变下的各向异性模型参数。.为了研究减薄类零件板料体积成形工艺过程中的金属流动规律，选取了双联齿轮这一典型零件，研究了外齿成形过程中的各向异性影响因素，并利用得到的各向异性模型准确地预测了金属的流动差异。采用背压控制金属流动方式抑制了内齿剪切时出现的裂纹。研究了几种冲裁下料方式对后续板料体积成形金属流动的影响，并得到了最优的下料方案。.为了研究增厚类零件板料体积成形工艺过程中的金属流动规律，以侧壁增厚件为例，研究了侧壁镦粗过程的金属变形规律。针对增厚比大引起的失稳折叠和载荷过大的问题，提出了可控变形区的浮动镦锻工艺，可以有效解决侧壁镦厚折叠问题，并且可以拓展到任意区域局部变形以及侧壁齿形等功能特征的成形。