INSIDE BEADING OF A HEXAGONAL TUBE BY ELECTROMAGNETIC FORMING

In this paper local compressive deforming of a hexagonal tube of aluminum (JISA1050) is investigated by an electromagnetic forming. The hexagonal tubes are annealed for 1h. at 400℃， which have 55mm width with 1mm thickness, and 10mm corner edius. The deformed ation of the hexagonal tube, i.e., bead width, is 10, 15, 20mm, respectively. The magnetic flux density in the gap between the field shaper and the external surface of hexagonal tube is measured, and the result is that the magnetic flux density for a given voltage is almost identical along the gap) and decreases with increasing the gap. The profiles and the strain distribution of the hexagonal tube de- formed are affected by the change Of the charging voltage and the dimensions of a bead width. The greater compressive strum in the cireuwtrential direction is develOPed on plane part near corner,while tensile strain on the corner occurs. A metallic block is inserted inside the hexagonal tube so that uniform profile can be obtained. The simulation of the forming is performed by a finite-element method and compared with the experimental results.

Tendency of homogeneous radial deformation during electromagnetic compression of aluminium tube

Electromagnetic forming is one of the high-rate forming methods that can be extensively used to form and join axisymmetric metal sheet and tube. Tendency of homogeneous radial deformation during electromagnetic compression of aluminium tube was investigated through the design optimization method based on sequential coupling numerical simulation and experiments. The results show that the tendency depends on the length ratio of tube to coil (R), which has a critical value (Rc) corresponding to the relatively homogeneous radial deformation along axial direction. The tube length relative to Rc is insensitive to the discharge voltage. When R is greater than Rc, the deformed tube presents horn shape and the shorter coil makes for local deformation. If R is less than Rc, the deformed tube presents drum shape and the longer coil contributes to larger deformation at tube end. Rc increases with coli length and could approach to 1; inversely, it could approach to 0. These results indicate the design optimization method based on the sequential coupling numerical simulation is feasible, which can be used to realize the controllable and precise deformation of metal tube.

管件电磁成形研究

管件电磁成形是依靠磁脉冲力来实现的。影响磁脉冲力的因素很多，但是本文主要研究线圈与工件的轴向相对位置对磁脉冲力分布的影响；进而分析管件受到磁脉冲力变形时，其变形模式（方式）与准静态塑性变形不同；磁脉冲力的形式（峰值、脉宽）、分布与端部约束条件决定管件变形后的形状。在实验中，调节管件与线圈之间的轴向位置，可以完成管件的多种变形形状，验证了理论分析的正确性。

管材内高压成形变形模式研究

基于薄壳理论分析管材胀形变形机理,确定与管坯几何尺寸相关的长、短管坯变形模式的界限划分表达式,并给出相应的成形内压力学模型。为薄壳理论在管材成形工艺研究中的应用,以及实际成形工艺中对成形内压的准确预测提供参考依据。研究表明,当管材胀形区长度小于管坯几何参量所确定的某临界值时,胀形区端部支撑条件对成形内压会产生影响,且随着胀形区长度的缩短影响逐渐剧烈;而当胀形区长度超过临界值时,成形内压不再受胀形区长度增加而发生变化。通过数值模拟与工艺试验对长、短管坯变形模式的准确性进行验证。数值模拟证实由于理论模型的刚端假设使内压计算值比实际偏大。设计与力学模型相匹配的典型零件、模具结构和工艺流程,得到成形过程中内压与变形形状的对应数据,与理论模型进行对比分析,讨论两种模型的区别及误差产生的原因。

双管件电磁约束成形的电磁分布与均匀性变形研究

管件电磁胀形因其在轻质工领域具有成形极限高、回弹小等优点而得到广泛研究。然而传统电磁胀形过程中,存在轴向变形非均匀的问合金加题,制约了这一金属加工技术的发展。为此文中在驱动线圈和成形工件引入一约束管件来改善电磁力的分布特性,构建了基于双管件电磁约束成形方法。仿真结果表明,通过调节约束管的高度和电导率可以使成形工件取得比较高的轴向变形均匀度。此外,电磁力和成形速率的对比分析进一步表明采用基于双管件电磁约束成形方法时轴向均匀变形长度为36.3 mm,该值是传统电磁胀形方法下的2倍。显然,通过合理的引入一约束管件亦可以调节电磁力的分布规律,该研究为改善电磁力分布方式的创新提供了新的研究思路。