Research On Fatigue Life Analysis Method Of Vibration System Under Non-Gaussian Random Excitation

Fatigue failure of mechanical equipment components has long been considered as one of the main factors which cause accidents,so it is important to predict fatigue life about components.At present,the common fatigue-life prediction method is that fatigue life is calculated by rain-flow counting,S-N curve and Miner linear damage rule based on the assume that stochastic loads are Gaussian type.However,these components are usually subjected to non-Gaussian stresses in a real environment.It would be difficult to accurately simulate random stresses by the equivalent Gaussian method,which would cause large errors for fatigue life estimation.In view of this,it is necessary to deeply study non-Gaussian simulation methods which would provide a reliable analysis process for components fatigue life prediction.This paper focuses on a series of studies around non-Gaussian random vibration simulation and vehicle fatigue life analysis:1.Based on mean,variance,skewness,kurtosis,and power spectral density,a numerical simulation method for generating a non-Gaussian random vibration process is proposed by considering non-Gaussian property of actual random vibration.The method is used to simulates non-Gaussian random vibration on the basis of polynomial chaos expansion,Karhunen-Loeve expansion and quasi-Monte Carlo sampling.In order to verify the feasibility of the algorithm,the real results of the non-Gaussian road signal are compared with the simulation results.The results show that with the number of sampling points increase,the error between the measured data and the simulated data becomes smaller and smaller,which indicates the accuracy of this method.2.A two-degree-of-freedom vibration system model of quarter-vehicle is established,the system response process under non-Gaussian excitation is studied,and the impact of input excitation characteristics on the system response is analyzed.The simulated non-Gaussian signal is used as the input of the system,and the response process in the linear and nonlinear cases is studied by the analytical method and the simulation method.The resusts show that the response of the non-Gaussian excitation is also non-Gaussian,which provides an ideal basis for the fatigue life analysis of the vibration system under non-Gaussian stress conditions.3.The fatigue life PDF of the vibration system under Gaussian and non-Gaussian stress conditions is analyzed by fatigue-related theory and saddle point approximation method.The results show that the cumulative fatigue damage of vehicle parts under Gaussian and non-Gaussian assumptions is relatively large.Then,the effect of the deflection,kurtosis of the road surface excitation,the damping,stiffness and other parameters on suspension spring fatigue life in the vehicle system is studied.Then,a reasonable parameter selection scheme is given.In summary,this paper proposes a numerical simulation method for generating non-Gaussian processes based on known information,i.e.,mean,variance,skewness,kurtosis,and power spectral density functions when considering the non-Gaussian nature of random vibrations in real environments.Taking the automobile suspension spring as an object,the response process and the fatigue life of components are studied.The results show that the fatigue life obtained by this method is more in line with the actual engineering,which provides a new calculation method and basis for the fatigue life accurate analysis of the vibration system.