Electrically assisted pulse forming using closed-loop force control

Abstract

The direct application of an electric current to a metallic workpiece during a manufacturing process, more commonly known as electrically-assisted manufacturing (EAM), produces many beneficial effects. During forming, significant flow stress reductions can be achieved. While there is much literature characterizing the effects of an electric current on the mechanical properties of materials during deformation, few feasible control systems for use in industrial processing have been developed. One such method is developed and tested herein using tensile testing in which electric current is triggered once a user-defined stress level is reached. The current then remains on until the stress reaches a desired minimum level. This cycle repeats until fracture occurs. The influence of several process parameters is discussed and an empirical formulation for determining the pulse frequency and the required energy per pulse is developed. This control method was found to be successful for forming metals while not exceeding a desired stress level. Furthermore, its application towards industrial use is also discussed.