Reliability modeling of gear system considering strength degradation

The traditional reliability models of gear system were usually developed without considering strength degradation of gear tooth. Although some analysis methods considered strength degradation, but they ignored the uncertainty of strength degradation that is due to the random load. In order to consider the statistically dependent failure between the gears and the uncertainty of gear strength in the strength degradation process, the reliability models of gear system are developed based on the theory of stress - strength interference. The failure relationships between teeth are expressed by the minimum order statistics. The uncertainty of the strength degradation is expressed by the distribution of material parameter. Using the Monte Carlo simulation, the proposed model is validated. Taking a planetary gear system for a case study, the system reliabilities with strength degradation are analyzed. The results show that the strength degradation has a little influence on the gear system reliability at the early stage and it has a great influence on the gear system reliability at the middle and late stages.