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Purpose: The purpose of this paper is to test and analyze the friction torque of double-row angular contact ball bearings under vacuum or ordinary pressure environment, horizontal or upright installation mode, and different rotational speeds, and to provide theoretical bases for the development of aerospace equipment. Design/methodology/approach: The experiments were carried out to investigate the effects of vacuum or ordinary pressure environment, horizontal or upright installation mode and different rotational speeds on bearing friction torque. To explore the relationship between working conditions and bearing friction torque, firstly, based on the generation source of friction torque, the test principle was determined, a test system was developed and the reliability of data was verified. Secondly, the friction torque of bearing was tested, and the values under various working conditions were obtained. Finally, this paper compared and discussed the test results. Findings: The test results show that the friction torque value of vacuum environment horizontal installation condition is the largest at different rotational speeds, and the rotational speed has the most significant influence on the friction torque. Originality/value: The friction torque test system of double-row angular contact ball bearing under vacuum environment was designed and built. The influence rules of vacuum or ordinary pressure environment, horizontal or upright installation mode and different rotational speeds on bearing friction torque were obtained. Peer review: The peer review history for this article is available at: http://dx.doi.org/10.1108/ILT-08-2023-0259 [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to propose a method for finding the maximum rotational speed of an inclined turntable at which the stability of the bearing oil film is maintained. Design/methodology/approach: The finite difference method was used to solve the Reynolds equation. Variation of bearing capacity of a tilted hydrostatic turret over time was determined. The combined effect of tilt and rotational speed of the turret on the oil film stability was also analyzed. Findings: When the turntable is operated at low speeds with only small angle of tilt, stability of the oil film is maintained. At lower rotational speeds, a smaller angle of tilt improves the bearing capacity and ensures stability of the oil film. Whereas, higher rotational speeds can have a considerable influence on the bearing capacity. Originality/value: The results demonstrate that the inclination or tilt of the turntable significantly affects the stability of the oil film. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to obtain the film thickness, friction torque and pumping rate and analyze the effects of roughness and surface micro-dimple texture (circular, square and equilateral triangle) on the performance of the oil seal. Design/methodology/approach: On the basis of elastohydrodynamic lubrication and the pumping mechanism of rotating shaft seal, this paper establishes a numerical model of hybrid lubrication of oil seal in sealing area. The model is coupled with fluid mechanics, rough peak contact mechanics and deformation analysis. Findings: The results show that surface texture significantly improves the lubrication properties of the oil seal. The oil seal with the square texture has the largest oil film thickness, while the equilateral triangle texture has a better effect on the pumping rate. Originality/value: To get closer to the real working environment of the oil seal, based on the surface roughness, this paper studies the effect of the texture shapes applied to the oil seal lip surface on the performance of the oil seal. The critical roughness and rotational speed values with zero pumping rate are obtained, which provides a theoretical basis for the correct selection of oil seals. [ABSTRACT FROM AUTHOR]