Thermorheological properties of magnetorheological grease and its thermomagnetic coupling mechanism

Abstract

A heating phenomenon exists in the service process of magneto-rheological devices. For magnetorheological devices using magnetorheological grease (MRG) as the working medium, changes in the medium’s rheological behaviors caused by temperature increase will generate challenges in the reliable service of the devices. With laboratory-prepared MRG as the research object, MRG rheological property laws under different temperatures and magnetic field intensities are investigated, and the magnetic properties of carbonyl iron (CI) powder under different temperatures are analyzed. The relationship between the evolution of the MRG structural system and changes in rheological properties under the action of thermomagnetic coupling is discussed. The results show that the MRG structural system is composed of base carrier liquid soap fibers and magnetic chains under the action of a magnetic field, and the soap fibers can strengthen the structural intensity of the MRG. A decrease in the entanglement degree of the soap fiber structure caused by temperature increase will obviously weaken the intensity of the entire MRG system and narrow the regulation and control scope of the MRG rheological properties. The structural evolution of soap fibers under thermomagnetic coupling will affect the chain formation of magnetic particles and ultimately their rheological properties. At low temperature and magnetic field intensity, the entanglement degree of soap fibers is relatively high, and the magnetic force on magnetic particles is weak, which cannot completely overcome the binding of soap fibers. The influence of soap fibers is the dominant factor affecting the MRG rheological properties. As temperature and magnetic field intensity increase, the entanglement degree of soap fibers decreases, magnetic particles gradually disperse from the soap fibers under the action of a large magnetic field force, and the magnetic chain structure gradually becomes the dominant factor affecting the MRG rheological properties. Moreover, the weakening degree of the temperature increase effect on the MRG rheological properties decreases, and the rheological law changes gradually.

Rheological Analysis on Hardening of Magnetorheological Grease with Kerosene

“…Currently, materials with drastic changes in viscoelasticity are MR fluids [23], greases [2], [10], [24] and plastomers [25], [26]. The fluid nature of the materials allows CIP to move around freely enough within the matrix, allowing more defined formations of CIP chains.…”

Prediction and analysis of thermal aging behavior of magnetorheological grease

“…Wang et al [8] observed that temperature has an effect on the apparent viscosity, and this effect decreases with the increase of magnetic field strength. Pan et al [9] found that MRG and grease have similar thermal rheological characteristics. The yield stress and consistency coefficient decrease with the increase of temperature.…”

High-velocity micromorphological observation and simulation of magnetorheological gel using programmable magneto-controlled microfluidics system and micro-tube dynamic models

“…Furthermore, during impact, the compressibility of MRG enables the objects to be protected from peak forces, and particles chains formed by magnetic fields can further dissipate the complex impact energies. Inspired by these advantages, certain achievements have been made at the macro-mechanical level, such as the relationship between stress-strain, shear yield stress-magnetic flux densities, and modulus variation, etc [29][30][31][32]. Although these macroscopic characteristics corroborate the influence of microstructural changes on materials properties, regular experiments cannot accurately reveal the instantaneous natures and complexity of such variations.…”