Abstract: Magnetorheological grease (MRG) has wide application prospect in the field of engineering due to the distinguished advantages such as, no settlement, simple sealing and simple preparation. The rheological properties of MRG are the basis for the design of magnetorheological absorber. In this study, lubricating grease based MRG with 30%, 50% and 70% weight fraction of carbonyl iron (CI) were prepared. Rheological properties including shear viscosity and shear stress of MRG with different CI weight fraction were examined from steady shear with and without magnetic fields applied. It is found that the constitutive relation of MRG can be described by Bingham model, and the higher the weight fraction of CI particles is, the wider adjustable range of shear viscosity and shear stress of MRG can reach. The critical strain between linear viscoelastic range and nonlinear viscoelastic range of MRG with 70% CI weight fraction obtained by using the large amplitude oscillatory shear method is 0.02%. In addition, the yield stress is 24.7kPa under the magnetic field of 0.96T; the maximum magneto-induced storage modulus is 1.17MPa; the relative magnetorheological effect reaches as high as 3814%.

Key words: magnetorheological grease (MRG), constitutive relation, large amplitude oscillatory shear, yield stress, magnetorheological effect