Dynamic effect of time-variant wear clearance on mechanical reliability

In order to overcome the drawbacks of constant wear rate and wear factors randomness hypothesis and to accurately predict the dynamic process of mechanical wear reliability, a time-variant wear equation of joint clearance is constructed by using a nonlinear equivalent spring-damp contact force model and discretization of wear process. Then, the joint wear evolution equation is converted into a time-dependent reliability equation by introducing a PHI2 method and defining an up-crossing rate. Therefore, a wear reliability analysis method which combines the mechanical multibody dynamics considering time-variant clearance with PHI2 is put forward. At last, by taking a two-axis positioning mechanism of satellite antennas as an example, dynamic reliability of the mechanism, parameters reliability sensitivity and their influence on reliability are studied. Results show that contact force is the dominant factor of reliability which is 10 times sensitive than other factors before the end of the product's steady wear process stage, while joint clearance will be the new dominant factor of reliability after this stage. What's more, there is a critical value for joint clearance, and appropriate augmentation of joint clearance before this critical value is propitious to the improvement of product's reliability. Compared to the current methods where randomness is emphasized, while the nonlinear process of wear and the consequence of concomitant time-variant clearances to product reliability are neglected, the present method could accurately analyze the dynamic process of wear and wear reliability. ©, 2015, AAAS Press of Chinese Society of Aeronautics and Astronautics. All right