柔性压辊拉形方式及其夹钳对板材成形的影响

Influence on sheet forming by flexible rollers stretch-forming and it's clamps

为提高大型板类件拉形精度,介绍了传统整体夹钳拉形机的特点,提出了新型柔性压辊拉形原理.以球形件为例,分别对两种夹钳结构的拉伸成形过程建立有限元模型,并进行数值模拟,对比分析了两种夹钳结构作用下的成形结果.研究表明:柔性压辊拉形方式所得的成形件,其应力、应变分布均匀,成形质量较整体夹钳方式明显提高;而采用传统整体夹钳所成形的部件,其局部应力集中现象相对严重.利用柔性压辊拉形理论,分别对采用平板式结构夹钳和拉延筋式结构夹钳成形球形件的过程建立有限元模型并进行模拟分析,根据板材拉形过程的流动理论,对比分析两种夹持方式下板材的流动状态.研究发现:采用拉延筋式夹钳进行拉伸成形,处于夹钳中的板材流动效果较好;而利用平板式夹钳的成形过程中,板材流动量较小.实验验证结果与模拟结果趋势一致.

In order to improve the dimensional accuracy of large sheet parts after stretch forming,a new flexible rollers stretch-forming process was proposed on the basis of the conventional stretch-forming technology. Finite element models of forming spherical parts were established for both the conventional and the proposed new stretch-forming processes. Numerical simulation results indicated that the stress and strain were distributed more uniformly in the parts formed by flexible rollers stretch-forming process and the overall quality of the part was improved. On the contrary,the stress in the parts formed by the conventional process was relatively more concentrated in various regions. By applying the principles of flexible rollers stretch-forming,finite element models of the spherical parts formed by the plate clamp and draw-bead clamp were also established respectively. The numerical calculation showed that the material of the sheet part clamped by the draw-bead clamp flowed more severely in the forming process,while there were only a little fluxion in the the parts formed by the other approach. The simulation agreed well with the followed experimental results.