Effect of Expansion Ratio on Formability in Tube Drawing with Diameter Expansion

Conventional tube drawing methods have the disadvantage that thickness reduction in one pass is small. This paper proposed a tube drawing method for overcoming this disadvantage, and the method expands the diameter at the same time of drawing. At first, the tube is flared by pushing the plug into the tube end. After that, the plug is drawn by chucking the flared end, and the entire tube is expanded. Tensile circumferential and axial stress reduces the tube thickness effectively during the plug drawing. In this study, the effect of expansion ratio on formability, such as thickness reduction and dimensional accuracy, was investigated by experiments and finite element analyses (FEA) for verifying the effectiveness of the proposed method. As a result, the thickness reduction increased with an increase in the expansion ratio, and the maximum thickness reduction ratio was 0.3 when an aluminum alloy of AA1070 was used. Furthermore, the deformation mechanism was considered by FEA.