Research On Mechanism And Evolution Law Of Reliability Factors In Space Bearing

As the most basic component of the space mechanism, the space bearing is the key components constituting the other components. The reliability of space bearing is the basic guarantee for the space mechanism in aspects such as the normal operation, the realization of intended function and the service life estimation. The space mechanism chronically works in space environment such as high and low temperature, alternative temperature, high vacuum, microgravity and strong radiation, which have an obviously negative impact on its performance and service life. Its failure mode mainly includes the common failure mode in ground environment and the unique failure mode caused by the space environment factors. Considering the complexity of space environment and the difficulties in simulation, the mechanism of the reliability influence factors of space bearing and its evolution law were mainly studied from the theoretical point of view in this paper. The failure mode and failure mechanism of space bearing were revealed. And on this basis, methods and measures were proposed to eliminate or mitigate the failure caused by the environmental factors. Focused on the space bearing in the precision bearing system, the evolution law of the influence factors was revealed in this paper, and the main research contents are as follows:Aiming at the thermal characteristics of space bearing, the friction torque and friction heat of solid lubricated space bearing were analyzed based on the quasi statics, heat transfer and friction theory of rolling ball bearing, and the heat transfer network model of space bearing in space environment was constructed. Three methods including finite element simulation, theoretical calculation and experimental research were used to study the effects of rotational speed, axial load and alternating temperature on the thermal characteristics of space bearings.Aiming at the abrasion of the solid lubricant film Mo S2, the abrasion model and service life model of space bearing abrasion were established, and the influence of speed and load on the abrasion depth of the lubricant film was studied based on the bearing kinematics, dynamics and Archard abrasion theory. On the basis of statics, the relationship between radial position deviation and radial load was established, and the influence of radial position deviation on the abrasion of different angular positions of internal and external ring channel of space bearing was explored allowing for the radial position deviation in the assembly deviation.Aiming at the evolution law of space bearing clearance, the evolution law of the bearing clearance related to the internal and external ring fit, the bearing temperature rise, the axial preload and the abrasion were analyzed respectively. On the basis of elastic mechanics, the deformation of the internal and external ring channel caused by interference was analyzed and the influence law of the surplus amount on the bearing clearance was obtained. According to the relationship between load and deformation, the change law of the bearing clearance with the working load was revealed. New structural parameters of the bearing were determined by converting the amount of abrasion into space bearing radius variation. The bearing clearance was determined after analyzing the change of the rolling ball deformation.Aiming at the evolution law of the preload of the space bearing, the evolution laws of the bearing preload related to the assembly condition, abrasion, alternating temperature and working load were analyzed respectively. In order to apply the preload to the space bearing accurately to ensure the reliable operation of the precision bearing system, The influence law of different amount of interference on the relationship between the initial preload and the tightening torque was analyzed on the basis of considering the friction characteristics of the internal and external rings, and the correctness of theoretical analysis was verified by experimental study. According to the amount of channel abrasion, the variation of the structure parameters of the space bearing was calculated. According to the deformation coordination relationship, the variation of the ball deformation of space bearing in the precision shaft system was analyzed, and the evolution law of the preload changing with the abrasion quantity was obtained. On the basis of thermodynamics, the variations of the component size and the preload of the components in the precision bearing system caused by alternating temperature were calculated. And the change law of the preload that change with the alternating temperature was revealed. The rolling bearing statics was used to calculate of the amount of the ball deformation under the working load. The relationship between the preload and the working load was determined by analyzing the amount of deformation.Aiming at the failure mode of space bearing, the forming factors and the failure mechanism were analyzed by researching the evolution trend of space bearing fault. Considering the characteristics of space bearing and the particularity of space environment, the abrasion of lubrication film Mo S2 will lead to the failure of the space bearing lubrication and the preload. Under the action of alternating temperature, the possible situations with which the space bearing may be faced were predicted such as the preload failure, the accuracy failure, the "stuck" failure, the self-locking phenomenon, the lubrication failure and the interference fitting failure. An experimental platform was established and the friction test software was developed to verify the influence of the alternating temperature on the preload.Based on the service life of the space bearing, a new method for the optimization of the preload of the solid lubrication space bearing was presented. Aiming at the variation of preload caused by the alternating temperature, the method of selecting appropriate spacer sleeve material to reduce or eliminate the thermal preload of space bearing was proposed. A design method of the operational reliability region was proposed in order to adapt to the alternating temperature environment. The operational reliability region can be used to determine the initial assembly interference and the preload that meet the reliable operating conditions.The work summary was carried out at the end of the paper, and the future research direction and the problem worth exploring were also forecasted.