Studies with Rheological Behavior of Composite Lithium-Based Magnetorheological Grease

Abstract

Magnetorheological (MR) grease has advantages of the anti-settlement behavior and excellent sealing property compared with conventional MR materials. However, the rheological behaviors of MR effect and shear yield stress are too small to limit the further applications with MR grease. This paper proposes a composite lithium-based MR grease with boric acid-hydroxyl stearic acid to improve the rheological behaviors. Eight different samples of composite lithium-based MR grease with different ratios of mass between lithium stearate and lithium borate are prepared by the saponification method. The rheological behaviors are tested and discussed with qualitative and quantitative analysis. The experimental results show that the off-state viscosity reduces with the decrement of the ratio of mass under low shear rate which changes from 68.7 Pa·s to 16.5 Pa·s. Lithium stearate content has more effects with off-state viscosity. Based on the Herschel-Bingham model, the shear stress of composite lithium-based MR grease can be improved dramatically by adjusting the ratio of mass which is increased by 170% under the magnetic flux density of 0.2 T. Compared with single lithium-based MR grease, the maximum yield shear stress is increased by 166.7% at off-state and the maximum MR effect is also increased by 19.1%. The MR effect can reach 23,600% with a specific mass ratio of the composite MR grease. The experimental results validate that the feasibility of the performance improvement by the composite lithium-based MR grease.

Structural Design and Controllability of Magnetorheological Grease Buffers under Impact Loading

“…For conditions where the nature of the shock load was defined, the MREA could be used to provide a cushioning damping force so that the carrier could stop smoothly at the end of the stroke after fully utilizing the available stroke [ 17 ]. In order to ensure that the impact load is adequately absorbed during the buffering phase, a reasonable control of the MREA damping force is necessary [ 18 , 19 , 20 , 21 , 22 ].…”

“…In addition, the settling that does not show complete solid–liquid separation (i.e., light settling) also leads to uneven distribution of magnetic particles inside the MRF, which affects the accurate control of the buffer damping force during buffer control. The MRG material can easily solve the problems of settling and turbulent flow, and is more suitable for application in impact conditions [ 26 , 27 , 28 , 29 ].…”

Research on the Rheological Characteristics of Wind Power Grease Based on Rheological Parameters

“…Mohd Nasir et al [13] investigated the improvement in the rheological properties of magnetorheological greases by introducing graphite as an additive in 2021 and compared their properties with those of reference samples. In the same year, a boric acidhydroxystearic acid composite lithium-based magnetorheological grease was proposed by Yan et al [14] to improve the rheological properties of conventional magnetorheological greases. The experimental results verified the feasibility of the lithium-based composite magnetorheological grease to improve performance.…”