Study On Service Performance Of Key Suspension Components Of Railway Vehicles

With the gradual improvement of high-speed railway network of China,EMUs are faced with a variety of complex geographical environments,line states and climatic conditions,which not only affect the boundary conditions of EMUs’ operation,but also change the nonlinear parameters of the suspension system,posing challenges to the dynamic stability of EMUs in long-term service.The vehicle operation performance is mainly affected by the track state,environmental state and vehicle state,and its dynamic behavior shows significant differences under different service conditions.In view of the complex service conditions of high-speed EMUs,in order to ensure the safe and comfortable operation of the vehicle in actual service,the vehicle must have good adaptability to line conditions,environmental temperature and performance degradation.From the viewpoint of vehicle dynamics,the dynamic performance of railway vehicles is determined by the vehicle structural parameters,suspension parameters and wheel/rail contact relationship of vehicles.Under different service conditions,the vehicle structural parameters are usually constant,while the suspension parameters and wheel/rail contact status will change significantly with the change of service conditions such as operating environment and running mileage.Therefore,in order to improve the adaptability of vehicles to complex service conditions,it is necessary to study the dynamic performance evolution of vehicle suspension components under different service conditions and its impact on vehicle dynamic behavior.Based on such background,this thesis focus on the service performance of key suspension components and carries out detailed experimental and simulation researches,the main work and conclusions are as follows:(1)Aiming at the dynamic performance of key suspension components under different service conditions,the dynamic performance tests of the hydraulic damper,rubber component,air spring and coil spring under different vibration inputs and different ambient temperatures are carried out.The evolution of the performance parameters of the above suspension components with vibration frequency,vibration amplitude and ambient temperature is analyzed.The results show that the dynamic stiffness and damping of the hydraulic damper,rubber component and air spring have strong frequency variation,amplitude variation and temperature variation characteristics under different service conditions.Especially,when the temperature is lower than-20℃,the damper will show empty stroke phenomenon within a certain amplitude range,and the rubber component also has a more significant frequency variation characteristics at low temperature because it is lower than the glass transition temperature of the rubber material;In addition,the dynamic performance parameters of the coil spring show obvious frequency variation characteristics near its resonance frequency.(2)The service load spectrum characteristics of suspension components with significant performance degradation are analyzed.Based on the load spectrum decomposition of Fourier transform and the principle of equal energy loss,the equivalence of service mileage and loading times is realized.Then,a fast test method for performance degradation of suspension components is proposed.Further,the performance degradation tests of damper and rubber j oint under different service mileage and loading times are carried out,which shows that the damper and rubber joint have obvious degradation phenomenon under service conditions,and the evolution rules of the performance with service mileage and loading times are obtained,thus the performance degradation trajectory model of key suspension components is established.(3)In order to accurately describe the dynamic performance of suspension components under different service conditions,nonlinear mechanical models of service performance of key suspension components are established respectively.For the hydraulic damper,a method based on the combination of physical parameter model and BP neural network model is proposed.The physical parameter model is used to consider the structural characteristics such as the orifice and damping valve,and the BP neural network model is used to consider the individual characteristics such as the oil leakage and internal friction of the damper,and then an accurate hybrid neural network model of the damper is established.For the rubber joint,a hybrid neural network model combining the nonlinear model of the rubber joint with the generalized regression neural network is established.The nonlinear model is composed of elastic element,friction element and viscous element,and the temperature factor is added to elastic element and viscous element to characterize the change of elastic modulus and damping factor with temperature;The generalized regression neural network model is introduced to make up for the defects of large dispersion and inaccuracy in high frequency domain which are not considered in the nonlinear model.For the air spring model,according to the structural parameters and connection mode of the air spring,the physical parameter model considering the orifice,the pipe,the bellow,the auxiliary reservoir and the supplementary space is established.On the basis of the physical parameter model,the generalized regression neural network based on the test data is added to further improve the simulation accuracy of the air spring.To integrating the dynamic characteristics of the coil spring into the simulation,three equivalent dynamic models of the coil spring are established by treating the coil spring as multi-mass spring series,Timoshenko-beam and flexible spring,respectively.By comparing the dynamic responses and performance parameters of the proposed models and tests under different service conditions,the results show that the proposed nonlinear mechanical models can accurately reflect the performance of suspension components under different service conditions.(4)According to the complex service conditions such as different ambient temperatures,line conditions and operating mileage,the vehicle system dynamics models under different service conditions are constructed based on the service performance models of suspension components and the corresponding service boundary conditions.The difference of dynamic response of suspension components,vehicle vibration response and dynamic performance index between traditional modeling method and refined modeling method of suspension components is analyzed,and the vehicle dynamic behavior under different service conditions such as ambient temperature,line conditions and operating mileage is further studied.The results show that the response of suspension components and vehicle dynamics indexes are significantly deteriorated with the decrease of ambient temperature or the increase of wheel-rail excitation and service mileage.(5)Considering the factors such as long-term operation of vehicles and environmental temperature changes,a multi-objective and multi-boundary optimization matching method for vehicle suspension parameters is proposed.The suspension parameter optimization model is established by taking the comprehensive dynamic performance as the objective function and the limit value of dynamic index as the boundary condition.The optimized suspension parameters matching scheme obtained by the model has excellent dynamic performance under different service conditions.