The Research Of Reliability Modeling About Mechanical System Based On Physics Of Failure

The mechanical parts and mechanical system have several failure modes, due to thelack of their failure data and the correlations among different failure modes and differentparts, the traditional reliability model based on failure data which is suitable for forelectronic equipment is not feasible. Therefore, the reliability modeling theory and methodabout mechanical parts and mechanical system based on Physics-of-Failure is proposed.Firstly, as to the two main failure modes (bending fatigue failure and contact fatigue failure)of mechanical part (gear) and the corresponding failure mechanisms, physical models ofstress and strength are set up against two main failure modes of a gear respectively. Then,the corresponding performance functions to the two failure modes are obtained according tostress-strength interference theory regarding randomness of variables in physical models ofstress and strength. Furthermore, joint distribution of the two performance functions isdeduced by Total Probability Theorem considering the correlation of random variables. So,reliability of a gear with correlated failure modes can be computed based on the jointdistribution. What’s more, an example is given and in this example the reliability modelbased on joint distribution and the traditional reliability model without considering thecorrelation of failure modes, are respectively adopted to calculate reliability of a gear. Thecalculation results are compared with that by Monte Carlo simulation. Similarly, tworeliability models of the planetary gear mechanism which doesn’t consider failure ofbearing and consider failure of bearing are setted up based on Physics-of-Failurerespectively. Both the example analysis and Monte Carlo simulation are also conducted.Finally, all results show that both the analysis of reliability modeling of the mechanicalparts (gear) and mechanical system (planetary gear mechanism), there are larger error whenthe reliability models don’t consider the correlations among different failure modes anddifferent parts, and the reliability models proposed in this paper that consider thecorrelations based on Physics-of-Failure are more accurate.