A thermal-based approach for determining electroplastic characteristics

Abstract

Recent development of electrically assisted manufacturing processes proved the advantages of using the electric current, mainly related with the decrease in the mechanical forming load, and improvement in the formability when electrically assisted forming of metals. The reduction of forming load was formulated previously assuming that a part of the electrical energy input is dissipated into heat, thus producing thermal softening of the material, while the remaining component directly aids the plastic deformation. The fraction of electrical energy applied, which assists the deformation process compared to the total amount of electrical energy, is given by the electroplastic effect coefficient.The objective of the current research is to investigate the complex effect of the electricity applied during deformation, and to establish a methodology for quantifying the electroplastic effect coefficient. Temperature behavior is observed for varying levels of deformation and previous cold work. Results are used to refine the understanding of the electroplastic effect coefficient, and a new relationship, in the form of a power law, is derived. This model is validated under independent experiments in Grade 2 (commercially pure) and Grade 5 (Ti-6Al-4V) titanium.

Decoupling Thermal and Electrical Effect in an Electrically Assisted Uniaxial Tensile Test Using Finite Element Analysis

“…[13,25,29] The thermal effect in the experimental data on electroplasticity has to be decoupled to derive the mechanical response due to electrical current under isothermal condition. In the present work, the decoupling of electrical and thermal effect is achieved using finite element simulation, which is more accurate than conventional numerical methods used in earlier works.…”

Macroscale Modeling of the Electroplastic Effect

“…A thermal model, accounting for material properties specifically for titanium alloys various levels of plastic deformation, was verified using experimental EAF tests [4]. The conclusions from this section are as follows:…”

“…Figures 4.8 and 4.9 show the true stress-strain profiles of a conventional compression test (at room temperature) and an EAF test for Ti-G2 and Ti-G5, respectively. A die speed of 12.7 mm/min was used and a constant current of 300 A was applied during the EAF test [4]. Both figures show that the flow stress was reduced significantly due to EAF.…”

“…The model tends to slightly underestimate the temperatures in Fig. 4.9 Flow stress reduction due to EAF (Ti-G5) [4]. The flow stress was reduced to EAF, and the specimen was able to be completely formed to the desired length without failure, unlike with the conventionally formed test the middle of the test, but is accurate at the beginning and end of the test.…”

A review of electrically-assisted manufacturing

“…Ross et al 39 suggested isolatable effects due to electricity such as Joule heating, kinetic energy (pushing dislocations), and retained stress-strain energy, while reporting that a higher resistivity of material induced a greater electroplastic effect. Salandro et al 40,41 assumed that the electric current during deformation produced only heating and deformation energy. He suggested a quantified electroplastic effect coefficient to separate the effects of the electric current into thermal and athermal effects.…”