铝型材柔性三维拉弯成形工艺研究

发布时间：2018-04-05 05:15

本文选题：多点成形　切入点：铝型材　出处：《大连理工大学》2015年博士论文

【摘要】：铝型材三维弯曲成形零件能够提供轻量化的车身结构,良好的空气动力学性能,以及更加安全舒适的乘坐空间等,越来越受到人们的关注。然而,由于型材三维弯曲成形的复杂性和成形件形状难于控制,铝型材的三维弯曲成形加工工艺制约了其快速发展。为了实现复杂截面型材的快速、精确、以及柔性的三维弯曲成形技术,同时为了满足我国高铁列车车头制造过程中对三维弯曲结构件的紧迫需求,本文提出了一种新型的柔性三维拉弯成形工艺。新工艺采用离散化多点模具柔性成形方法,开发了多组联动离散化的单元体模块及多自由度的三维拉弯机械臂,并研制了成形装备。基于变形叠加理论,将铝型材三维变形分解为水平和垂直两个平面内的变形分量,分步实现了铝型材复杂三维空间构型的成形工艺。通过解析计算、数值仿真与实验相结合的方法,对柔性三维拉弯成形工艺、装备、单元体调形技术及成形件的形状控制进行了研究,分述如下。采用自动化的调形方法,设计开发了配套的单元体串行水平调形与并行垂直调形机构。建立了调形控制系统的框架,设计了水平方向(DSP2812搭配步进电机)与垂直方向(STC89C52搭配直流电机)的调形控制单元,采用主从通信的方式编写了控制程序。自动化的调形方式较传统的人工调形方式提高效率60%以上。采用液压动力单元替换垂直方向上的直流电机调形控制单元,开发了一种水平拉弯与垂直压弯相结合的三维弯曲成形新方法,实现了型材更为复杂的W形状三维拉弯成形。另外,文中还建立了描述三维弯曲成形件形状的数学模型,确定了成形过程中控制成形件形状相关工艺参数的计算方法,包括单元体的调形参数和夹钳的运动轨迹。建立了一套三维拉弯成形零件回弹的评价方法,开发了配套的检测工具。将原有的二维拉弯成形力学解析模型扩展至三维,对成形后零件轴向上的主应力状态进行了讨论和分析,推导了计算三维弯曲回弹的解析计算公式。将实验、解析计算、仿真的结果进行了对比,三者的回弹结果基本吻合,证明解析计算模型与仿真模型均取得了较为满意的回弹预测结果,实验结果表明三维拉弯成形过程中,垂直方向的弯曲会减小水平方向上的回弹变形,且垂直方向上变形的幅度越大,水平方向上回弹减少的越多。最后,本文对回弹补偿的方法进行了研究,提出了一种多点模具包络面修正直接补偿的方法。通过有限元仿真的方法对高铁列车车头骨架成形件的模面进行了优化,成形件轮廓度误差由1.01%降至0.06%。优化后的模面实际实验测得的轮廓度误差为0.05%,实现了柔性三维拉弯成形零件的精确成形。目前,该工艺及装备已实现产业化的生产。
[Abstract]:Three-dimensional bending forming parts of aluminum profile can provide lightweight body structure, good aerodynamic performance, and more and more safe and comfortable ride space, etc., which has attracted more and more attention.However, because of the complexity of profile 3D bending forming and the difficulty of controlling the shape of forming parts, the rapid development of aluminum profile is restricted by the 3D bending forming process.In order to realize the rapid, accurate and flexible three-dimensional bending forming technology of the complex section profile, and to meet the urgent need of the three-dimensional bending structure in the manufacturing process of the high speed train front in China,In this paper, a new flexible three-dimensional bending process is proposed.In the new process, the discrete multi-point die flexible forming method is used to develop the unit body module of multi-group linkage discretization and the three-dimensional bending machine arm with multiple degrees of freedom, and the forming equipment is developed.Based on the theory of deformation superposition, the three-dimensional deformation of aluminum profile is decomposed into two deformation components in horizontal and vertical plane, and the forming process of complex three-dimensional spatial configuration of aluminum profile is realized step by step.By means of analytical calculation, numerical simulation and experiment, the flexible three-dimensional bending process, equipment, unit body shape adjusting technology and shape control of forming parts are studied, which are described as follows.The serial horizontal and parallel vertical tweaking mechanism of the unit body is designed and developed by the automatic adjusting method.In this paper, the frame of the profile control system is set up, and the adjusting control unit of horizontal direction DSP2812 with stepping motor and vertical direction STC89C52) is designed. The control program is compiled by master-slave communication.The efficiency of automatic tweaking is more than 60% higher than that of traditional manual tweaking.A new 3D bending forming method combining horizontal tension bending and vertical bending is developed by replacing DC motor profile control unit in vertical direction with hydraulic power unit.In addition, a mathematical model is established to describe the shape of three dimensional bending parts, and the calculation method for controlling the shape related process parameters of the forming part is determined, including the adjusting parameters of the element body and the motion track of the clamp.A set of springback evaluation method for three-dimensional bending forming parts is established, and a set of testing tools are developed.The original analytical model of two-dimensional tensile bending forming is extended to three dimensions. The principal stress state of the formed parts is discussed and analyzed. The analytical formula for calculating the three dimensional bending springback is derived.The results of experiment, analytical calculation and simulation are compared. The springback results of the three models are basically consistent. It is proved that both the analytical model and the simulation model have achieved satisfactory springback prediction results, and the experimental results show that in the process of three-dimensional bending, the results show that,The bending in the vertical direction will reduce the springback deformation in the horizontal direction, and the larger the amplitude of the deformation in the vertical direction, the more the springback will be reduced in the horizontal direction.Finally, the method of springback compensation is studied in this paper, and a direct compensation method for multi-point die envelope correction is proposed.By means of finite element simulation, the die surface of the forming part of the head frame of the high-speed train is optimized, and the contour error of the formed part is reduced from 1.01% to 0.06%.The contour error measured by the optimized die surface is 0. 05. The precise forming of the flexible three dimensional bending parts is realized.At present, the process and equipment has been industrialized production.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG306

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