不锈钢外板对5A06铝合金板材液压胀形行为的影响

薄壁曲面铝合金零件整体液压成形时,易发生起皱和破裂缺陷,探讨通过施加外层板能抑制缺陷发生的机理。采用5A06铝合金内层板材和1Cr18Ni9Ti不锈钢外层板材,对双层板液压胀形行为进行研究。通过塑性理论分析板材液压胀形屈服半径,讨论经向摩擦力及法向压力对板材应力大小的影响;利用数值模拟给出内层板的应力、应变分布;通过双层板液压胀形试验,对比单层板和双层板条件下,铝合金内层板极限胀形高度、极限应变,分析双层板的变形协调性。结果表明:通过施加不锈钢外层板,减小了5A06铝合金内层板顶部位置面内的双向拉应力,减小了内层板变形区应力、应变梯度,使胀形变形更加均匀,胀形高度提高32%,顶部极限应变提高51.7%,极限应变显著提高。

Effect of Outer Stainless Steel on the Deformation Behavior of Hydro-bulging of 5A06 Aluminum Alloy Sheet

In order to avoid the occurrence of wrinkle and fracture during the integral forming process of the huge curved parts with super thin wall, double-layer sheets forming method is developed. Double-layer sheets hydro-bulging with the inner side sheet of 5A06 aluminum alloy sheet of 2.0 mm thick and outer side sheet of 1Cr18Ni9Ti stainless steel sheet of 1.0 mm thick is investigated. The bulging radius of sheet is analytically calculated when material yields, and the effect of radial friction and normal pressure on the distribution of stress of blank is analytically studied. The distribution of stress and strain of the inner side sheet during the double-layer sheets hydro-bulging is obtained by Finite element analysis (FEA) method. In addition, experiment of double-layer sheets hydro-bulging is conducted to investigate the effect and of outer side sheet on the limited bulging height and limited strain of the inner side sheet, and the deformation compatibility of the inner and outer side sheets is verified. The results shows that, when 1Cr18Ni9Ti stainless steel outer sheet is imposed on the 5A06 aluminum alloy inner side sheet, the biaxial tensile stress of inner sheet decreases at the peak of the semi-sphere, and the stress and strain gradient of the whole deformation region of inner sheet decreases. As a result, the deformation of the semi-sphere is more uniform, and the limited bulging height increases by 32%, and the limited strain at the peak increases by 51.7%.