Improvement Of ANCF Cable Element Theory And Application In Rail Vehicle Dynamics

Higher speed is the eternal theme of rail transit development.With the continuous increase of railway operation speed in my country,higher technical requirements are put forward for the dynamic performance of high-speed trains.The coupling relationship between pantograph and catenary determines whether the train can obtain electric energy continuously and effectively during operation.The vehicle-track coupling relationship affects the safety and stability of the train.Absolute Nodal Coordinate Formulation(ANCF)can analyze the dynamic behavior of complex structures.In order to analyze the dynamics of rail vehicles at high speed more accurately and efficiently,this thesis will conduct the following research based on the ANCF method.(1)The classical ANCF cable element model was introduced.The characterization method of the cable element configuration was given,and the kinetic energy,strain energy,load and generalized force of the cable element ware calculated.The common constraints in the cable structure ware modeled,the dynamic equation of the cable element system was deduced based on the Lagrangian method,and the numerical solution method was given.(2)A variable-length ANCF cable element model was established on the basis of the classical ANCF cable element.The configuration description method of the cable element in the time-varying system was given.The dynamic equation of the cable element was derived by using the arbitrary Lagrangian-Eulerian(ALE)method,which extends the application of the Lagrangian method to the variable mass system.A segmented and smooth length control model was proposed based on the step function.The accuracy of the variable-length cable element model was verified by a simulation example.(3)A form-finding method for catenary based on variable-length ANCF cable element model was proposed.In the proposed method,the equivalent model of catenary was established based the variable-length ANCF cable element model;the cable element length variation model was established with the tension of the contact wire and messenger wire and the spatial location of the dropper point as the control targets.The model reconstruction process was completed based on the integral method and the split-mode method.The accuracy and effectiveness of the form-finding method ware verified by simulation and comparison with the results in the literature.(4)A moving ANCF cable element model was established.Considering the propagation characteristics of track vibration,this thesis introduces the concept of moving control body,which reduces the long-distance vehicle-track coupling problem to the vehicle-track coupling problem in the moving control body.Based on the ANCF theory,the method proposed in this thesis establishes the mechanical model of the cable element in the moving state,and deduces the dynamic equation.The accuracy of this method in the analysis of vehicle-track coupling dynamics is demonstrated by simulation calculations and comparison with the modal superposition method.