Field–Frequency-Dependent Non-linear Rheological Behavior of Magnetorheological Grease Under Large Amplitude Oscillatory Shear

Huixing Wang,Shaoqi Li,Tianxiao Chang,Guang Zhang,Jiong Wang,Yancheng Li

doi:10.3389/fmats.2021.642049

Abstract

This article investigates the influence of frequency on the field-dependent non-linear rheology of magnetorheological (MR) grease under large amplitude oscillatory shear (LAOS). First, the LAOS tests with different driving frequencies were conducted on MR grease at four magnetic fields, and the storage and loss moduli under the frequency of 0.1, 0.5, 1, and 5 Hz were compared to obtain an overall understanding of the frequency-dependent viscoelastic behavior of MR grease. Based on this, the three-dimensional (3D) Lissajous curves and decomposed stress curves under two typical frequencies were depicted to provide the non-linear elastic and viscous behavior. Finally, the elastic and viscous measures containing higher harmonics from Fourier transform (FT)-Chebyshev analysis were used to quantitatively interpret the influence of the frequency on the non-linear rheology of MR grease, namely, strain stiffening (softening) and shear thickening (thinning), under LAOS with different magnetic fields. It was found that, under the application of the magnetic field, the onset of the non-linear behavior of MR grease was frequency-dependent. However, when the shear strain amplitude increased in the post-yield region, the non-linear rheology of MRG-70 was not affected by the oscillatory frequency.

Highlights

Magnetorheological (MR) grease is a kind of magneto-induced smart material that is normally prepared by dispersing magnetic particles in grease matrix
Compared with commonly used approaches, namely elastic Lissajous curves, storage/loss modulus, and Fourier transform (FT) analysis, we found that the FT-Chebyshev analysis could provide more insight on non-linear viscoelastic (NLVE) behavior of MR materials under large amplitude oscillatory shear (LAOS)
We studied the field-dependent non-linear rheology of MRG-70 under LAOS at different driving frequencies

Summary

Introduction

Magnetorheological (MR) grease is a kind of magneto-induced smart material that is normally prepared by dispersing magnetic particles in grease matrix. With the utilization of viscoelastic continuous phases, i.e., grease matrix, MR grease can effectively avoid the sedimentation problem of magnetic particles, which often occurred in conventional MR fluid. Field-Frequency-Dependent Non-linear Rheology Magnetorheological Grease fluid, the MR grease device can maintain good settlement stability for a long period of time. Considering the lubricating properties of the grease matrix, it can reduce the wear and tear of the moving parts of the devices and increase life, which eventually will reduce the maintenance cost in the long run. It is necessary to conduct investigations on the rheological properties of MR grease under steady shear and oscillatory shear, which can provide insight and understanding for the design and application of MR grease devices

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Results

Conclusion