Experimental Study on the Rheological Properties of MF Lubricant Based on the Herschel-Bulkley Model.

As an effective method to improve the load capacity of the oil-film bearing, a kind of nano-scale magnetic fluid (MF) by taking silicon oil as carrier fluid was prepared using the chemical coprecipitation method. The microstructure and magnetism of the magnetic particles (MPs) were analyzed based on SEM, VSM, and TGA. It is shown that the MPs are spherical particles with an average diameter of 20 nm, and the MPs behave superparamagnetism. A natural sedimentation control group was developed to investigate the sedimentation stability of the MF. The results indicated that the prepared MF presents good sedimentation stability. The viscosity of MF was measured from temperature and magnetic field by a single factor experiment, and the data was regressed according to the Herschel-Bulkley (H-B) model. According to the regression results, the effects of temperature and magnetic field intensity on the properties of MF were investigated. It is found that the yield stress τ0, viscosity coefficient K, and the shear thinning effect n of the MF were increased by 38–54%, 7–11%, and 6–9%, respectively, as the current increased from 0 to 2.0 A. The increase in temperature (from 20 to 80 ℃) reduces the yield stress and viscosity coefficient of MF by 3–6.85% and 1.13–1.36% and aggravates the shear thinning effect by 1.03–1.06%. Furthermore, the regression analysis of the H-B model parameters vs. temperature was carried out, and the equation of viscosity, η = f(T, γ), was obtained, which can be directly used to predict the lubrication state of MF. [ABSTRACT FROM AUTHOR]