Time-Varying Reliability Analysis And Design For Multiple Failure Mode Of The Filtering Reducer

As the requirements of speed reducers, such as accuracy, reliability, service time and volume, are growing in engineering fields, this thesis focuses on a new reducer, filtering reducer, which is proposed by Professor Wang Jiaxu, etc. and carries out the researches of time varying reliability analysis, reliability design optimization, wear reliability analysis as well as fatigue reliability analysis based on tooth flanks contact strength and tooth root flexural fatigue strength aiming to realize high reliability, long life and light weight of the filtering reducer.As the main failure parts of the filtering reducer are gears, this thesis sets its gears as research object. Firstly, the time varying reliability models under two failure modes of tooth surface contact fatigue and tooth root flexural fatigue are respectively built. Secondly, take these reliability models as reliability constraints of the optimal design and carry out the reliability design optimization of the gears’ related parameters. Because the models of wear reliability and fatigue reliability are complex, the computational efficiency of reliability design optimization will be greatly reduced when take them as constraint conditions of optimal design. Therefore, the analysis of wear reliability and fatigue reliability is completed for the filtering reducer after optimum design to test whether the wear reliability and fatigue reliability can meet the engineering requirements. The specific researches of this thesis are as follows.(1) Analysis the structure and movement principles of the filtering reducer, and Establish the time varying reliability model of the gears under random loads. Besides, the time varying reliability model of common cause failure considering two failure modes both of surface contact fatigue and tooth root flexural fatigue is constructed.(2) Carry out the reliability model analysis of the common cause failure mode based on surface contact fatigue and tooth root flexural fatigue with the target of the volume minimization of the Filter reducer. And the reliability model is set as reliability constraint conditions to optimize the gear parameters of the filtering reducer, thus to guarantee its optimal design parameters being lightweight and reliable.(3) Do the statistical analysis of gear stresses under the random loads based on the rain flow counting method. What’s more, the fatigue life of the filtering reducer’s gears is estimated using Miner linear cumulative damage rule and S-N curve and comprehensively considering the randomness of loads and gear structure parameters to obtain the probability distribution of the gears’ fatigue life.(4) Established the numerical simulation model based on the motion principle of the friction work gear pair to simulate the dynamic wear process of the filtering reducer’s gears. Besides, the change rule between wear rate and time during gear wear failure is studied and the time varying reliability model based on wear degradation is built. Finally, develop the research of the reliability analysis method and verify the feasibility of the Optimized parameters.