Evaluation of lubricants for electrically-assisted forming

Abstract

The automobile and aerospace sectors are increasingly turning their attention to the opportunities created by the use of lightweight alloys with large strength-to-weight ratios, such as aluminium, magnesium, stainless steel, and titanium alloys. However, when using conventional forming processes, these light materials create processing challenges: low formability and high yield strength. Electrically assisted forming (EAF) is a method that can overcome these limitations. Specifically, EAF is a novel forming process where electricity is applied to the metallic workpiece during deformation. Previous investigations have shown that EAF creates a reduction in flow stress, an increase in formability, an ability to reduce/eliminate springback, and an improved precision. This study investigates the influence of electricity on lubricant performance and identifies lubricant candidates for EAF. When electricity is applied, besides the changes due to surface expansion at the interface that occur in conventional processes, the lubricant is exposed to high localized temperatures and current fields. Electrically assisted ring compression tests are conducted and the performance characteristics of three lubricants are evaluated. By combining the experiments and finite element simulation results, friction coefficients can be estimated, and the effect of electric current flow on friction characteristics quantified.