| The train running on the track and track constitute a coupled vibration system.The interaction between the train and track is realized by wheel-rail contact.Under the action of earthquake,the wheel flange can contact with rail easily,and the wheel can even climb onto the top surface of rail.At the same time,wheel-rail two-point even multi-point contact often occurs.At this case,the wheel-rail contact relationship can’t meet the Hertz contact hypothesis.The traditional Hertz contact theory can’t accurately describe the above complex wheel-rail contact relationship.In view of this,aiming at the wheel-rail contact relationship under earthquake,this thesis proposes wheel-rail non-Hertz contact algorithm considering multi-point contact and the influence of wheelset yaw,and applies it to the analysis of vehicle-track system vibration under earthquake.The main research work and conclusions are as follows:(1)Considering the influence of the wheelset yaw,the geometric relationship of wheel-rail contact is solved by using trace line method,and the wheel-rail gap function is determined by the wheel-rail motion state.Then,the shape and size of wheel-rail contact spot are calculated by using virtual penetration method.The wheel-rail multi-point contact is judged and determined by combining the position relationship of calculated contact spots.(2)Taking the Kalker’s variational method as the standard,the accuracy of Hertz contact theory and the KP method(a typical non-Hertz contact simplified algorithm)in solving wheel-rail contact spot and normal contact force in large range of wheelset’s transverse displacement is compared.The results show that the relative error of the KP method is under 5%,and its calculation accuracy is better than that of the Hertz contact theory as a whole.Thus,the KP method is more suitable for the analysis of vehicle-track system vibration under earthquake.(3)Aiming at the shortcomings of the KP method in calculating wheel-rail multi-point contact,an improved KP method considering the interaction effect of each contact spot in multi-point contact is proposed,and the accuracy of the improved KP method is verified by examples.Considering the influence of wheelset yaw on the shape of wheel-rail contact spot and the distribution of contact stress,an improved KP method considering wheelset yaw is proposed,and the verification shows that the improved KP method meets the requirements of calculation accuracy.(4)Taking the track irregularity as excitation,the analysis model for vibration of vehicle-ballastless track system considering wheel-rail multipoint contact relationship under earthquake is established.The vibration characteristics of vehicle-ballastless track system under earthquake are analyzed.The influence of earthquake intensity on train running safety is studied.The cases of wheel-rail two-point contact and train derailment under earthquake are analyzed respectively.The improved KP method and the analysis model for vibration of vehicle-ballastless track system under earthquake proposed in this thesis provide an effective means for analyzing the derailment characteristics of running train under earthquake. |
