Effect of Material on Strain Direction in Tube Expansion Drawing Process

Conventional tube drawing methods have the disadvantages that thickness reduction in one pass is small. This paper proposes a tube drawing method for overcoming this disadvantage and the method expands the diameter while drawing. At first, the tube is flared by pushing the plug into the tube end. Then, the plug is drawn by chucking the flared end, and the entire tube is expanded. Tensile circumferential and axial stress reduce the tube thickness effectively during the plug drawing. In this study, the influence of the material on the forming characteristics, such as thickness reduction and strain state, was investigated by experiments and finite element analysis. The results show that the forming limit is larger when the elongation to initiating the necking and the R-value of the material are large. Materials with large n values and large friction coefficients undergo a deformation close to biaxial stretching to realize high thickness reduction.