| In this paper,the fatigue reliability of mechanical systems was studied systematically through theoretical analysis,Monte Carlo simulation and experimental study.The specific research content is as follows:(1)The difference between logarithmic and exponential degradation processes through the simulation method of Mont Carlo,the influence of degradation parameter v on the statistical moment of measurable residual strength distribution is analyzed.The parameter calculation method of residual strength degradation model considering the life data is given,the accuracy of the original degradation model is improved.Residual strength degradation experiments of 20MnTiB smooth specimens and notched specimens were carried out,the power degradation curve parameters of the 20MnTiB specimens with all information(including failure data)taken into account are obtained.In this paper,the strength degradation process of the series system is discussed.the residual strength model of the series system with equivalent constant amplitude cyclic load is established according to the minimum strength order statistics of the system and the PSN curve of the system.(2)Under the condition of failure correlation,the concepts of "system strength" and"system PSN" curve are proposed,and the system level failure correlation reliability evaluation model is established.For steady random loads,using "system strength" and"system PSN" curves,The concept of equivalent "system residual strength" is proposed and a reliability evaluation method considering system strength degradation is presented.(3)the difference between the algorithms for the reliability evaluation of gear pair and non-variable series mechanical system.The interval estimation method of gear pair reliability is studied.The influence of gear tooth ratio,strength probability distribution parameter and stress probability distribution parameter on the static strength reliability curve of gear pair was studied.(4)Taking each gear tooth in the gear as the research object,the influence of the dispersion of each component in the system on the life of the whole transmission system is considered more fully.Under random loading,the Monte Carlo life simulation model is established.According to the relation between the statistical characteristic value of life and the parameter function of load distribution,the linear regression equation between the parameter of life distribution and the parameter of load distribution is obtained.The life evaluation method of series system based on PSN curve is proposed.The life calculation method(the method based on PSN curve of parts,the extrapolation method of system life,and the method based on assumption of independent failure)of gear transmission system is discussed. |
