Fatigue Life Prediction And Reliability Evaluation Of Typical Escalator Truss Structure

With the rapid growth of population and urbanization in China,the demand for escalators is also increasing.The escalator industry in China is developing rapidly.Escalators provide convenience for people's life and travel.As the main supporting part of escalator,the truss structure of escalator is the key structure of the whole escalator,which bears the random changing passenger load.Therefore,the bearing capacity and reliability of truss structure is the key to ensure the normal operation of escalator.It is necessary to predict the fatigue life and evaluate the reliability of the escalator truss structure,so as to ensure that the escalator does not have fatigue damage within the service life and has high reliability.In this paper,the nominal stress method is used to calculate the fatigue life of the dangerous parts of the escalator truss structure and evaluate its reliability.The main research work includes:(1)A three-dimensional model of escalator is established and simplified in Solid Works.The static analysis of truss structure is carried out by using ANSYS Workbench,and the influence of bolt on displacement and stress of escalator truss is compared by using the sub model method.Modal analysis and buckling stability analysis of truss structure are carried out to check whether resonance and instability will occur.(2)In order to provide basis for fatigue life prediction,the load time history acquisition scheme is designed,and the number of passengers on the escalator is measured on the spot in Qingniandajie subway station of Shenyang,which is transformed into the load time history and processed.The load spectrum of the escalator is obtained by rain flow counting method.(3)The dangerous parts are determined according to the finite element analysis,the eight level fatigue load spectrum of the escalator truss is compiled,the P-S-N curve of the structural material of the escalator truss is modified to get the P-S-N curve of the structural parts,and finally the fatigue life of the dangerous parts of the escalator truss is predicted by Miner linear fatigue damage accumulation theory.(4)According to the results of the finite element analysis and the calculation of the fatigue life of the dangerous parts,based on the stress strength interference model,considering the influence of the strength degradation,the escalator random load is regarded as the Poisson random process,using the theory of sequence statistics,the fatigue reliability model of the CCF series system under the random load is established and the time-varying reliability curve is calculated and plotted.The reliability evaluation results of single part,independent failure and common cause failure are compared and verified by Monte Carlo simulation.