板材柔性拉边多点成形工艺及其数值模拟研究

发布时间：2018-12-17 16:36

【摘要】：多点成形是一种新型的板材柔性成形技术,目前已经广泛应用于航空航天、船体外板、汽车覆盖件、建筑外观等制造领域。随着板材加工技术的不断发展,人们对产品的个性化要求也越来越高,因此本文提出柔性拉边多点对压成形技术。它是利用多点模具对金属板材进行对压成形,采用四周拉边的方式,由离散夹钳夹紧板材,并对板材施加垂直板材方向的正压力和平行板材方向的拉边力,保证夹钳与板材始终不发生脱离现象,从而成形出复杂曲面件的一种板材加工方法。与其他冲压技术相比,该技术不仅可以成形出质量更好、形状更加复杂的曲面件,还可以通过调整上、下基本体群的模具型面实现板材的快速成形。本文详细介绍了柔性拉边多点成形工艺的研究背景、基本原理及设备结构。以球形件和马鞍件为例,利用ABAQUS有限元分析软件建立了板材柔性拉边多点对压成形有限元模型,并对不同的工艺参数进行了一系列的数值模拟分析。具体研究内容如下:1.以球形件和马鞍件为例,建立了刚性压边、柔性压边和柔性拉边三种多点对压成形工艺的有限元模型,并对其数值模拟结果进行了详细的对比分析。结果表明:刚性压边多点成形得到的成形件的直壁区出现应力集中现象,容易出现拉裂缺陷;柔性压边多点成形得到的成形件边缘区处的柔性压边圈与工件曲面变化趋势一致,但其应力应变不均匀,边角处容易出现起皱缺陷;柔性拉边多点成形得到的成形件边缘区处的离散夹钳排列方式与板材变形趋势一致,应力应变分布均匀,不易出现拉裂和起皱缺陷,成形效果最好。2.研究了夹钳数量、拉边力、材料参数及摩擦系数对柔性拉边多点成形结果的影响。结果表明:离散夹钳的数量越多,成形件应力应变越均匀,工件的质量越好;在一定范围内,拉边力越大,板材受力时材料流动性越好,成形件变形越均匀;与2024铝板相比,屈服强度较大的08AL钢板容易得到质量较好的成形件;摩擦系数越小,弹性垫和金属板材之间的接触阻力越小,板材变形时内部金属流动性更好,成形效果也更好。3.研究了弹性垫厚度对柔性拉边多点成形结果的影响。结果表明:弹性垫厚度越大,成形后工件的表面接触应力越小,分布越均匀,压痕缺陷逐渐消失,但是其精度会随之下降。
[Abstract]:Multi-point forming is a new type of sheet metal flexible forming technology, which has been widely used in aerospace, hull outer plate, automobile panel, building appearance and other manufacturing fields. With the development of sheet metal processing technology, the individuation requirement of products is becoming more and more high, so this paper puts forward the flexible edge drawing multi-point pressing forming technology. It uses multi-point die to press the sheet metal, uses the way of drawing the edge around, clamps the plate by the discrete clamp, and exerts the positive pressure in the vertical direction of the plate and the pull force in the direction of the parallel plate. It is ensured that the clamping clamp and the sheet metal do not break away from each other at all times, thus forming a kind of sheet metal processing method for complex curved surface parts. Compared with other stamping technologies, this technology can not only produce better quality and more complicated curved surface, but also realize rapid forming of sheet metal by adjusting the top and bottom basic body groups' die surfaces. In this paper, the research background, basic principle and equipment structure of flexible edge drawing multipoint forming process are introduced in detail. Taking spherical parts and saddle parts as examples, the finite element model of multi-point compression forming for flexible edge drawing of sheet metal was established by using ABAQUS finite element analysis software, and a series of numerical simulation analysis for different technological parameters were carried out. The specific research contents are as follows: 1. Taking spherical parts and saddle parts as examples, the finite element models of rigid blank holder, flexible blank holder and flexible edge drawing are established, and the numerical simulation results are compared and analyzed in detail. The results show that the stress concentration in the straight wall of the forming parts obtained by multi-point forming with rigid blank holder is obvious, and the tensile cracks are easy to appear. The change trend of the flexible edge holder is the same as that of the workpiece surface, but the stress and strain are not uniform, and the wrinkle defect is easy to appear at the edge corner. The discrete clamp arrangement at the edge of the forming part obtained by flexible drawing multi-point forming is consistent with the deformation trend of the sheet metal, the stress and strain distribution is uniform, the defects of tensile crack and wrinkle are not easy to appear, and the forming effect is the best. 2. The effects of the number of clamps, drawing force, material parameters and friction coefficient on the multi-point forming results of flexible edge drawing were studied. The results show that the more the number of discrete clamps, the more uniform the stress and strain of the forming parts, the better the quality of the workpiece, the greater the drawing force, the better the material fluidity and the more uniform the deformation of the forming parts. Compared with 2024 aluminum sheet, the 08AL sheet with higher yield strength is easy to obtain the forming parts with better quality. The smaller the friction coefficient, the smaller the contact resistance between the elastic pad and the sheet metal, the better the metal fluidity and the better forming effect when the sheet is deformed. The effect of the thickness of elastic pad on the results of flexible edge drawing multipoint forming was studied. The results show that the greater the thickness of the elastic pad, the smaller the surface contact stress, the more uniform the distribution, and the less the indentation defect is, but the lower the precision is.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG306

【参考文献】