Characterization of Flow Stress for Commercially Pure Titanium Subjected to Electrically Assisted Deformation

Abstract

Uniaxial tension tests were conducted on thin commercially pure (CP) titanium sheets subjected to electrically assisted deformation using a new experimental setup to decouple thermal–mechanical and possible electroplastic behavior. The observed absence of stress reductions for specimens air-cooled to near room temperature motivated the need to reevaluate the role of temperature on modeling the plastic behavior of metals subjected to electrically assisted deformation, an item that is often overlooked when invoking electroplasticity theory. As a result, two empirical constitutive models, a modified-Hollomon and the Johnson–Cook models of plastic flow stress, were used to predict the magnitude of stress reductions caused by the application of constant dc current and the associated Joule heating temperature increase during electrically assisted tension experiments. Results show that the thermal–mechanical coupled models can effectively predict the mechanical behavior of commercially pure titanium in electrically assisted tension and compression experiments.

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

“…They also found that the threshold energy decreases with Zn addition. Magargee et al, in a recent publication [19] presented an interesting result where commercially pure thin titanium sheets were subjected to electric currents at near isothermal condition by external cooling. The usually observed stress drops were not present and fundamental questions on the role of electric current in such experiments were raised.…”

“…[9,10] The interest in electroplasticity has gained much interest of late [11][12][13][14][15][16] in the potential application of enhancing formability [7] and reducing spring-back [17] in sheet metal components. The application is especially useful in materials such as magnesium, [18] titanium, [19] and certain aluminum alloys, [15] which exhibit poor formability at room temperature. The warm forming which is generally required for such alloys can be replaced by electrically assisted forming.…”

“…To understand the effect of electricity in the mechanical properties and to develop a suitable constitutive model accounting for the electroplastic effect, it is necessary to separate the effect of temperature and electricity in the mechanical properties. [19,20,25] External cooling has been attempted to conduct experiments under isothermal condition to decouple the thermal and electroplastic effect. [19] However, this is not practical for higher current density and for a wide range of materials.…”

“…[19,20,25] External cooling has been attempted to conduct experiments under isothermal condition to decouple the thermal and electroplastic effect. [19] However, this is not practical for higher current density and for a wide range of materials. Instead, numerical methods [25] can be used effectively to isolate the mechanical behavior due to electrical effect.…”

Effect of Electric Current Pulse on Mechanical Properties of Ultra-High Strength Steel 1180cp

“…The temperature profiles in Fig. 2 shows that temperature distributions during the tests were quite uniform along the gage length in comparison with those of titanium [18] tested under a continuous electric current with low electric current density. Pulsing strain of 1.5% Figure 3.…”