# Study of the Effect of Continuous Thermal Effects on the Shear Stability of Magnetheological Grease
## 3 Results and Discussion
### Rheological Properties in Oscillatory Shear Mode
At a fixed 20 \({}^{\circ}\)C, the degree of entanglement of 00#MRG showed a steady increase with the increase in the magnetic field strength, because the lower viscosity of number 0 Lithium grease showed signs of shear thinning under continuous shear [28], the soap fiber structure is insufficient to inhibit the movement of magnetic particles under the excitation of the magnetic field, which leads to the formation of a columnar magnetic chain, and the composite structure composed of the magnetic chain and the soap fibers effectively enhances its own strength. The platform modulus of 1#MRG at a lower magnetic field was larger than that of 00#MRG, which is due to the fact that when the magnetic field strength is weaker, the magnetic particles aggregate to form a smaller scale of magnetic chains, and the soap fiber structure with the higher degree of entanglement of number 1 lithium grease creates a great resistance to the movement of magnetic particles, and the magnetorheological grease composite strength is dominated by the continuous phase. With the increase in the magnetic field strength, the overall platform modulus of 1#MRG tended to remain unchanged, indicating that the magnetic chain has a limited influence on the composite strength of 1#MRG. Considering that the magnetorheological grease is subject  
Figure 8: Frequency sweep curves of MRG: (**a**) 00#MRG, (**b**) 0#MRG, (**c**) 1#MRG. to multiple influences such as temperature, magnetic field and continuous shear under actual working conditions, the evolution law of its rheological properties is analyzed in conjunction with the influence of temperature change on the platform modulus under a fixed magnetic field. Figure 10 shows the variation curves of the platform modulus of each sample at different temperatures. At a fixed magnetic field of 55 mT, the platform modulus of 00#MRG showed a large increase with increasing temperature, indicating that the soap fiber structure in the magnetorheological grease appears to be untangled and broken and reorganized with increasing temperature [29], and the continuum phase cannot provide enough external force to bind the movement of magnetic particles. As a result, the large-scale magnetic chains formed under the action of magnetic fields can effectively enhance the composite structures. Under a low temperature field, the change in the platform modulus of 00#MRG was low, and when the experimental temperature reached 80 \({}^{\circ}\)C, 00#MRG showed a significant increase, indicating that the soap fiber structure was greatly damaged at 80 \({}^{\circ}\)C, a large number of magnetic particles could be released, and the magnetorheological grease composite strength was dominated by the discrete phase. Sample 1#MRG had a platform modulus change curve that flattens out over the entire experimental temperature range. It is shown that when considering the effect of a single temperature, the successive resistance to temperature change is also increased for higher consistency relative to temperature change. It can be seen that the degree of soap fiber entanglement in the continuous phase is directly related to the external resistance during the movement of the magnetic chain, which has a more obvious effect on both the magnetic and rheological properties of magnetorheological grease. When the thermomagnetic coupling conditions are considered comprehensively, 00#MRG, which has a lower platform modulus, showed a large increase in apparent viscosity, a decrease in the thixotropic ring area, and a deterioration in shear stability after being subjected to external excitation by high temperature or a strong magnetic field. Sample 1#MRG, which has a higher platform modulus, did not show any obvious drastic change under external excitation during the entire experimental period and exhibited better shear stability. Figure 9: Variation curves of platform modulus of each sample under different magnetic fields: (a) 00#MRG, (b) 0#MRG, (c) 1#MRG.