Abstract
This paper investigates the quasi-static rheological properties of lithium-based magnetorheological (MR) grease under large deformation. Three types of lithium-based MR grease comprising different mass ratios of carbonyl iron (CI) particles and lithium-based grease were prepared. The dependence of the magneto-induced stress–strain curves for MR grease on CI particles content, shear rate, and shear deformation under quasi-static monotonic shear conditions were tested and discussed. The results demonstrate that the shear rate dependence of the maximum yield stress is significantly weakened by the magnetic field, and this weakening is further enhanced as the CI particles content of MR grease increases. In addition, to evaluate and characterize the behavior of the cyclic shear–stress curves of MR grease under quasi-static condition, cyclic shear tests under different controlled conditions, i.e., CI particles content, shear rate, shear strain amplitude, and magnetic field strength, were conduct and analyzed. The magneto-induced shear stress of MR grease with higher CI particles content shows a sharp decrease during the transition from loading to unloading. Moreover, the experiment results also show that the damping characteristics of MR grease are highly correlated with CI particles content, shear strain, and magnetic field strength.
Highlights
Magnetorheological (MR) grease is a new type of magneto-induced smart material composed of soft magnetic particles and grease matrix, which exhibits a transition state between traditionalMR fluid [1,2,3] and MR elastomer [4,5,6] in the absence of a magnetic field.Compared with the severe problems of sedimentation and leakage faced by liquid MR fluid [2,7,8], the MR grease has advantages of high stability and low leakage [9]
After the shear strain increased to 20%, the shear rate has a significant impact on shear stress, i.e., shear stress of MRG-70 increased from 0.075 kPa to 0.15 kPa, as high as impact on shear stress, i.e., shear stress of MRG-70 increased from 0.075 kPa to 0.15 kPa, as high as
E.g., 391 kA/m, shear stress, especially at high shear strain, was unaffected by temperature, which is similar to the temperature-dependent properties of grease almost unaffected by temperature, which is similar to the temperature-dependent properties of under the shear mode of steady and oscillatory
Summary
Magnetorheological (MR) grease is a new type of magneto-induced smart material composed of soft magnetic particles and grease matrix, which exhibits a transition state between traditional. The rheological properties demonstrated by MR grease under quasi-static shear test have been rarely investigated. The field-induced properties of MR materials under quasi-static shear will determine the performance of MR damper used in bridges and buildings. The rheological properties of MR grease with different weight percentages of carbonyl iron (CI) particles under quasi-static shear mode and large shear deformation were investigated. The filed-induced stress of MR grease under the quasi-static monotonic shear condition with different shear rate and CI particles content were tested and discussed. The dependence of the stress–strain curves and damping performance for MR grease on shear rate, magnetic field strength, CI particles content under quasi-static cyclic shear condition were calculated and analyzed
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