Influence mechanism of alternating temperature on friction torque of aerospace bearings

With the further development of the Beidou navigation satellite network, high precision, high reliability and high security issues of shaft assembly in interstellar link antenna drive unit have been paid more and more attention by the researchers. As the absolutely necessary key components in spacecraft mechanism, the reliability of space bearing is one of the main difficulties in the world's space technology. Due to the harshness, extremeness and uncertainty of the space environment, the alternating temperature first seriously affects the size and stability of the space bearing friction torque. Secondly, the operation reliability is affected in space bearing while temperature changes. Then, the life, accuracy and reliability of the spacecraft mechanism are affected by the space environment. Space bearing is the sensitive and key problem related to the reliability of spacecraft mechanisms. The reliability of space bearing is the basic guarantee of the normal operation of spacecraft mechanisms, the realization of the intended function and the design life. The friction torque of the bearing reflects the operation of the precision shaft system and will affect the function and accuracy of the shaft system. The improper friction torque of the space bearing will cause the spacecraft mechanism to failure, so the dynamic performance of the friction torque is an important factor to restrict the life and reliability of spacecraft mechanism. Aiming at the space ambient temperature alternating between -60 and 80℃ influencing the friction torque issue of space bearing, the mathematical model of friction torque of solid lubricating bearing is established by using contact mechanics and kinematics theory. Then, the friction torque of inner and outer rings is analyzed. Based on the elastic mechanics, thermotics and deformation coordination, the influence law of alternating temperature on the interference and preload force of space bearing is analyzed. On the basis of changing law of the interference and preload force, the influence mechanism of alternating temperature on the friction torque of space bearing is studied by combining the friction torque model. The relationships between the interference and friction torque, the preload force and friction torque, the alternating temperature and the friction torque are investigated by theory and experiment. Meanwhile, the experiment is carried out to verify the theoretical analysis. The results show that the alternating temperature is negatively correlated with the inner ring interference, and the alternating temperature is positively related to the outer ring interference. The increased amount of the friction torque of the inner ring, caused by the increase of the interference, is larger than that of the outer ring. The preload force of space bearing increases with the alternating temperature. Comparing with the preload force at room temperature, the change range of preload force is -40-40 N, while the alternating temperature increases from -60 to 80℃. The increase of preload force or ambient temperature leads to the increase of the friction torque. The friction torque increases with the increase of the alternating temperature, and decreases with the decrease of the alternating temperature. The friction torque cannot reach the maximum and minimum of the initial time. By analyzing the influence law of the alternating temperature on the friction torque of space bearing, the method to reduce or eliminate the influence of the alternating temperature on the friction torque is explored, which provides a theoretical basis for slowing the change of the friction torque. © 2018, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.