铝合金覆层板成形极限图

来源期刊:中南大学学报(自然科学版)2017年第5期

论文作者:郎利辉 王耀 孔德帅 张泉达 高铁军

文章页码:1149 - 1155

关键词:铝合金;覆层板;厚度法向应力;成形极限图;椭圆胀形;方板对角拉伸试验

Key words:aluminum alloy; overlapping sheet; thickness normal stress; forming limit diagram (FLD); elliptical bulge; Yoshida bucking test

摘    要:提出一种创新的试验方法研究铝合金覆层板的成形极限图,即采用单拉试验获得成形极限图的左半区域,右半区域采用不同椭圆度的凹模得到不同应力状态下覆层板的成形极限应变,并且在成形极限图中引入方板对角拉伸试验数据,用于预测板材成形过程中起皱缺陷的产生,使成形极限图的预测功能更加完善。同时,进一步研究不同覆板材料和厚度对铝合金目标板材成形极限图的影响。研究结果表明:在覆层板方式下,目标板材成形极限图中的极限临界区向上移动,并向右移动,成形极限增大,并且成形极限图中起皱区域面积减小,抗失稳能力提高。成形过程选择强度系数K较高、加工硬化指数n较大及适当厚度的覆板有助于成形板材成形性能的提高。

Abstract: A novel experimental approach to research the forming limit diagrams (FLDs) of aluminum alloy by overlapping sheet metal was presented, namely, the tension-compression side of the FLD was obtained by the uniaxial tension test. The limit strains of tension-tension side for the aluminum alloy by overlapping sheet metal were obtained by elliptical bulging test with different aspect ratios. In addition, the experimental data of YBT test were introduced into the FLD to predict the wrinkling defect in the sheet forming, in which the predictive features of FLDs were more improved. Meanwhile, the influence of the material performance and thickness of the overlapping sheet on the FLD of the target sheet were further investigated. The results show that, in the overlapping mode, the limit critical zone of FLD of the target sheet moves up and to the right, the forming limit increases and the area of wrinkling region decreases, and the anti-instability of the target sheet is improved correspondingly. Meanwhile, the formability of the target sheet can be improved by choosing higher strength coefficient K, larger work hardening exponent n and proper thickness of the overlapping sheet.

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