Effects of Graphite Additive Ratio and Temperature on Rheological Properties of Magnetorheological Grease

To investigate the effect of graphite additive specific gravity on the rheological properties of magnetorheological grease (MRG), graphite magnetorheological grease (GMRG) with 70% mass fraction of carbonyl iron powder and 0%, 2%, 5%, 8%, and 10% mass fractions of graphite powders were prepared using grease as the matrix. An Anton Paar rheometer was used to measure the rheological characteristics of five materials in oscillatory and steady-state shear modes. The results reveal that the incorporation of graphite powder into MRG yields superior yield stresses. In addition, the graphite additive could enhance the viscoelastic characteristics of the MRG and had little effect on the linear viscoelastic interval of the material. Frequency scanning experiments of temperature changes indicate that GMRG is a temperature-hardened material, and that the temperature stability of GMRG viscosity at different frequencies is better, but GMRG exhibits more elasticity than viscosity. However, it is significant to highlight that the presence of graphite reduces the relative magnetorheological action of the MRG.