# Study of the Effect of Continuous Thermal Effects on the Shear Stability of Magnetheological Grease
## 1 Introduction  
Magnetroheological fluid (MRF) is a kind of intelligent material that can achieve millisecond-level, solid-liquid reversible changes by adjusting the magnetic field strength, and full lubrication in the working area can be achieved by controlling the magnetic field, overcoming the problem of insufficient adhesion with the cavity wall when the conventional grease encounters a temperature rise. It has great prospects in magnetorheological apparatus applications, such as vibration dampers, clutches, and transmission mechanisms [1]. However, the magnetorheological grease (MRG) device has a settling problem during service, which restricts the application and development of related magnetorheological devices. Magnetorheological grease uses grease as a continuous phase matrix, and grease is a structured colloidal dispersion system with a unique soap fiber structure that can greatly improve the settlement problem of magnetic particles [2, 3]. Additionally, magnetorheological devices are subject to temperature increases due to internal friction during frequent shearing, and changes in the operating temperature have a great impact on the rheological properties of magnetorheological grease. At present, the domestic and international research on magnetorheological grease mainly focuses on the study of its rheological properties by focusing on its components,additives and preparation methods. [PERSON] et al. [4] found by employing steady-state shear test experiments on the content of carbonyl iron powder in magnetorheological grease that, within a certain range, the higher the content of hydroxy iron powder in magnetorheological grease, the wider the adjustable range of shear viscosity and shear stress in the steady-state shear mode. [PERSON] et al. [5] found that temperature had a significant effect on the field-induced yield stress of magnetorheological grease based on the temperature-sensitive properties of the grease components in magnetorheological grease by analyzing the rheological properties of magnetorheological grease with different temperatures and magnetic fields. [PERSON] et al. [6] investigated the rheological properties of soft carbonyl iron particles by adding additives to magnetorheological grease and found that the shear viscosity versus shear rate profile of magnetorheological grease was greatly reduced with the addition of 5 wt% kerosene at the same magnetic field strength. [PERSON] et al. [7] found that by adjusting the thickener content in magnetorheological grease, the magnetorheological effect could be effectively improved and its magnetic properties could be enhanced through experiments on the magnetorheological properties of magnetorheological grease. [PERSON] et al. [8] analyzed the magnetic particle size in magnetorheological grease by building a body-centered columnar model and found that the magnetorheological grease shear yield stress increased faster with increasing particle size when the particle size was within a certain range. [PERSON] et al. [9; 10; 11] investigated the magnetic field-dependent rheological properties of magnetorheological grease in continuous shear and oscillatory shear modes by means of platelike carbonyl iron particles and found that platelike particles have higher apparent viscosity relative to spherical particles due to the larger surface contact area of the particles, which resulted in a strong magnetic moment interaction between the particles. Magnetorheological grease consisting of platelike magnetic particles had a lower energy storage modulus relative to spherical particles. [PERSON] et al. [12] found through experiments on the magnetic particle content of magnetorheological grease that the yield stress of magnetorheological grease was highly correlated with the particle content, and the magnetic field greatly weakened the shear rate correlation at the maximum yield stress of magnetorheological grease as the content of magnetic particles increased.