The Analysis On Random Vibration And Dynamic Reliability Of Rail Transit System

With its comprehensive advantages such as the high speed, large transportcapacity, low energy consumption, light pollution, less occupation of the land, highsafety and comfort performance, the rail transit has been developed rapidly all overthe world. The train speed has been improved greatly in China by following andstudying the technology abroad, building new fast Passenger Dedicated Line andstrengthening technological alteration of existing railway. However, the correspondingproblems like the interaction forces between trains and tracks, the safety and comfortof the running train, the reliability of tracks are even more conspicuous and theseproblems still lack enough theoretical research and engineering practice in China.Therefore, the study on the dynamic interaction between trains and tracks is one of thebasic research subjects to meet the need of achieving great-leap-forward developmentof railway in China.On the foundation of the domestic and abroad technical development of therailway, the vehicle and tracks are regarded as a whole system in this thesis. Based onthe vehicle dynamics and the track dynamics, using the random vibration spectralanalysis and numerical integrate method, using the dynamic simulation softwareADAMS, a new method is proposed in this thesis to analyze the dynamic reliabilityand the fatigue reliability of rails and study the dynamic characteristics of thevehicle-track system and the safety and comfort of the running train.The validity and perfection degree of the vehicle-track coupling dynamics modelplays a decisive role in the dependability and accuracy of the simulation result. Afour-axle rolling stock dynamics model is set up in this thesis according to thecharacteristics of the running train and the actual instance of the track. In this model,the rolling stock is regarded as the multiple rigid body system, in which vertical androlling motion for car body and bogie and vertical motion for wheel sets areconcerned; rails are modeled as Euler beams laid on elasticity supports, in which thecut-off mode number is 30; sleepers and discrete ballast blocks are modeled as rigidbodies. In total, there are 154 DOF in the whole vehicle-track system. In the processof using ADAMS/Rail, the rolling stock model is relatively more perfect than before,in which all kinds of movements of car body, bogie and wheel sets and various sortsof non-linear factors in vehicle suspension system are fully considered, and the DOFof vehicle totaled up to 86. The wheel/rail interaction is the connection between therolling stock and the track, and the wheel/rail non-linear elastic contact model is used in the simulation, which corresponds to the facts.The evaluation standards of the dynamic safety and comfort of the vehicleinfluence the quality and economy of track directly. The dynamic evaluation index ofthe rolling stock and track are summed up in this thesis such as the verticalacceleration of car body, lateral acceleration of car body, reduction rate of wheel load,wheel/rail vertical force, wheel/rail lateral force and derailment coefficient etc.The reliability method is a major developmental trend in the field of structuraldesign. Converting the deterministic design method into reliability design method isnot only in the direction of the railway technology development in our country, butalso can meet the needs of current railway transportation. The rail is an importantcomponent of track structures. The method for calculating the dynamic reliability ofrail is discussed in this thesis, and the sensitivity analysis is done for some importantparameters such as elastic modulus of cushion, vertical stiffness of bed, discretestiffness of sub grade, overcrossing limit and train speed etc. From this, the reasonablevalues of the parameters are able to ascertain, and then the entirety optimization of thetrack structures can be carried out.Fatigue is an ancient and basic problem of the track structures. The fatiguetheory is applied to analyze the dynamic reliability of structures in this thesis. Monte-Carlo method is used to predict the fatigue life of rails, and some correspondingadvices are put forward to control the damage of rails.