Effect of process variables on the tube drawing process and product integrity

Quality is a very important feature in the manufacturing of products, such as tubes. Non-homogenous deformation, common to most metal forming operations, leaves the product in a state of residual stress. These residual stresses may be detrimental or beneficial to the strength and reliability of the product. In order to evaluate the residual stresses in the product, a complete stress analysis of the workpiece throughout the duration of the tube drawing process is needed. In this study, ABAQUS, an elastic-plastic nonlinear finite element code, is used to investigate the drawing load and the residual stress distributions in the drawing of Oxygen-Free High Conductivity (OFHC) copper tubes. This study focuses on the effect of the die and plug angles on the performance of the drawing operation. The simulations are run at four die angles for each area reduction, and three plug angles for each die angle. The simulations are carried out for two area reductions: 10.9 percent and 37.1 percent. Thermal effects, due to friction and plastic work, are also investigated. The results of this study demonstrate that the finite element method is an effective tool for predicting the residual stress distribution and optimum process parameters. The results also show that the magnitude and distribution of the residual stresses are greatly influenced by the die and plug angles. It is concluded that a certain combination of die and plug angles can minimize the drawing load, and optimize the effect of the residual stresses. For slow drawing speeds, the thermal effects are determined to be minimal.