Temperature effects and a prediction method of field-dependent yield stress in graphite magnetorheological grease

Abstract

Graphite additives have become increasingly prevalent in magnetorheological (MR) materials, as they can substantially improve the shear yield stress of such materials. However, the effect of graphite additive proportion and temperature on graphite magnetorheological grease (GMRG) has not yet been fully reported, which limits the engineering application of GMRG. This work prepared magnetorheological greases with five different graphite ratios and investigated how their steady-state shear properties responded to temperature. The shear yield stress and relative MR effect of GMRG at different magnetic field strengths were measured and calculated. The results verified that the yield stress of GMRG increased with the increase of graphite additive ratio, but the relative MR effect decreased significantly. Besides, the steady-state shear mode was employed to evaluate the rheological properties of GMRG under varying magnetic field strengths and temperatures. The yield stress was analyzed through fitting experiments conducted under different magnetic field strengths and temperatures. The results showed that the addition of graphite powder increased the shear yield stress of the GMRG. But the enhancement effect was weakened by increasing temperature. In addition, a support vector machine (SVM)-based prediction method was proposed to predict the performance of GMRG with different ratios under complex operating conditions. The SVM-based estimation results showed good agreement with actual experimental values. This method provides a new approach for proportioning, characterization, and performance prediction of other materials.