Purpose This paper aims to investigate the influence of high-temperature thermal action on grease performance from the angle of film-forming performance. Design/methodology/approach A static thermal aging method was used to prepare high-temperature thermal grease samples after high-temperature thermal action. On the basis of optical interference technology, the film-forming characteristics of fresh grease samples and the grease samples after high-temperature thermal action under variable speed and fixed speed conditions were explored. Findings The decrease in the structural entanglement performance of the grease after short-term high-temperature thermal action makes its film-forming performance better. The mechanism is that the lubricating grease soap fiber entanglement is reduced. Although the continuous high-temperature thermal action can make the grease film-forming performance better, its mechanism is that the soap fiber structure caused by high-temperature thermal action is damaged and is easy to be cut off under the action of shear. Originality/value The effect of structural system change on its film formation performance was discussed in combination with the change in grease structure characteristics, and the mechanism of action was revealed.

As a lubricant, the viscosity of the magnetic fluid changes with the external magnetic field, which improves the bearing capacity of the oil film and hence the lubrication effect, and has a promising application in bearings. Based on the Roelands viscosity theory, the Shliomis model is used to derive the viscous temperature, viscous pressure, and magnetic viscosity characteristics of magnetic fluids under the influence of an applied magnetic field, and further proposes a structural model of magnetic fluid lubricated bearings to investigate the pressure, temperature and magnetic intensity distribution of magnetic fluids under different eccentricity conditions. The results show that the viscosity of the magnetic fluid decreases exponentially with increasing temperature, rises linearly with increasing pressure, and increases and stabilizes with increasing magnetic induction strength. Because the minimum film thickness point is the dividing point between the convergent wedge and the dispersed wedge, the pressure distribution of the lubricant film separates high pressure from low pressure at the minimum film thickness, and the differential pressure increases with the increase in eccentricity. The temperature distribution of the high-temperature zone is mainly distributed in the middle of the film, and the minimum film thickness zone and the maximum temperature increases with the increase in eccentricity. The magnetic intensity distribution of the strong magnetic field is mainly concentrated in the minimum film thickness zone, and the magnetic induction intensity increases with the increase in eccentricity. The results of this study have certain research significance for solving the problem of the poor lubrication effect of bearing lubricant due to high temperature.

A structural model of a bearing is proposed based on a general standard bearing structure and magneto-fluidic lubrication, and the magnetic field of the bearing lubrication gap is analyzed under the action of an applied magnetic source. Results show that the magnetic field can form a magnetic circuit in the bearing structure, and a significant magnetic flux density is formed in the contact area of the rolling element of the bearing. The magnetic induction intensity in the contact area of the rolling element of the thrust bearing can provide magnetic fluid lubrication, and the magnetic induction intensity in the contact area of the rolling element of the point contact bearing is greater than that of the linear bearing. The magnetic inductance of the rolling elements in the rolling element contact area of a double row point contact bearing is greater than that of a single ring. The double permanent magnet ring structure has a more advantageous magnetic field effect than a single ring, and the magnetic inductance in the rolling element contact area of both rows of a double row point contact bearing is relatively the same.

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