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.
Highlights
Since the magnetorheological (MR) fluid has been developed, it has attracted much attention as a typically smart and intelligent material due to its perfect controllable rheological properties with an external magnetic field
The experimental results validate that the feasibility of the performance improvement by the composite lithium-based MR grease
The vis and input shear rate is measured with eight MR grease samples which are shown in cosity decreases with increasing of the shear rate [30,31]
Summary
Since the magnetorheological (MR) fluid has been developed, it has attracted much attention as a typically smart and intelligent material due to its perfect controllable rheological properties with an external magnetic field. Under the applied magnetic field, the MR fluid can be transformed from the liquid state to the solid-like state with milliseconds. MR fluid has been utilized in many different engineering fields [1,2,3], with vehicle suspension [4], cable-stayed bridges [5], semi-control [6,7,8], seals [9,10], and machine tool isolations [11]. Because of the huge density difference between the magnetic particles and carrier liquids of MR fluid, the properties of sedimentation with MR fluid is of great significance in further studies and applications. MR grease is one of the typical MR materials which has a thixotropic crosslink structure. MR grease shows a better development compared with MR fluid in the engineering applica-
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