Fatigue Reliability Optimization Design And Reliability Growth Technology Of Primary Steel Springs For Fast Metro Vehicles

Under the background of the gradual extension of the urban subway network,with the improvement of the subway operation speed,the fatigue fracture of the primary steel spring is more frequent.Although the subway operation company has certain preventive measures for the spring breaking accident: the spring group adopts the combination of internal and external springs and rubber pads at both ends,although it will not immediately cause serious accidents such as vehicle derailment,However,the phenomenon of frequency interruption is a potential threat to passenger safety and subway operation efficiency.The poor operation environment of rail transit puts forward higher requirements for subway vehicle parts.The traditional spring design mostly adopts the safety factor method,which ignores the randomness of the spring’s own factors.Therefore,it is necessary to build a fatigue reliability model based on probability theory to ensure the reliability of the spring structure.Whether from the perspective of operation safety or based on social and economic benefits,we should carry out the fatigue reliability and optimization design of primary steel spring,and put forward effective fatigue life reliability growth technology.Aiming at the fatigue failure of primary steel spring,firstly,the finite element model of spring is established to verify the accuracy of the model from the perspectives of stiffness and stress;Secondly,taking an urban subway vehicle as the carrier,the dynamics model of fast subway vehicle is established by using Simpack dynamics software,and the measured track wave wear data of 14 km is used as the external excitation source to simulate the vibration displacement time history of the primary steel spring under the condition of measured track polygon wheel;Finally,Fesafe software is used to predict the fatigue life of the primary steel spring combined with the finite element analysis results and S-N curve.For the problems of scattered fatigue life and many geometric parameters of primary steel spring structure,the parametric model is established by using APDL language,the Ansys-Fesafe-Isight joint simulation platform is built,and the uncertain spring fatigue reliability analysis and optimization design framework is constructed.With DOE experimental design and surrogate model technology,Kriging model,RBF radial basis function model and RSM response surface model are established respectively to simulate the relationship between fatigue life response of primary steel spring and structural parameter variables;Through the accuracy comparison between the proxy models,the fatigue reliability proxy model of primary steel spring is finally established;Then the Monte Carlo sampling of the model is carried out to obtain the fatigue life reliability of the primary steel spring.Based on the principle of sensitivity analysis,the sensitivity of the fatigue life of the primary steel spring to structural variables is obtained,and the relationship between fatigue life and structural parameters is analyzed.In order to further improve the fatigue life of primary steel spring,its structural parameters need to be optimized.Based on the fatigue reliability model of primary steel spring,the longest fatigue life is taken as the objective function,and SA annealing algorithm is used as the optimization method to carry out the deterministic optimization and reliability optimization design of primary steel spring in the environment of multidisciplinary design integration software Isight;Then the Monte Carlo sampling method is used to obtain the fatigue life distribution of the primary steel spring under the two optimization methods.Compared with the two optimization methods,the reliability optimization improves the average fatigue life of the primary steel spring and significantly improves its fatigue reliability.