| Rack railway is a kind of rail transit system with long history and good application prospect,especially suitable for mountain rail transit and mountain scenic spot tourism.The significant advantage of rack railway lies in its ability to climb hills,which can supplement the deficiency of wheel-rail adhesion through gear and rack engagement or directly use gear and rack engagement to drive trains to run safely and reliably on large ramp lines.Many mountain scenic spots and mountainous areas in the middle and west of China have the environmental conditions and practical demands for the construction of rack railway,and it will become an important supplement of Chinese railway.However,there is no built rack railway line in China,the interaction mechanism between rack railway train and track has not been proved yet,and there is a lack of relevant methods and theories for rack railway system design.Therefore,it is of great theoretical significance and engineering value to study the dynamics of rack railway.In this thesis,based on the analysis and summary of different systems and application examples of rack railway,the dynamics model of rack railway vehicle was established based on multibody dynamics theory,and the dynamic performance of rack railway guiding equipment(RRGE)was studied.At the same time,an analytical calculation method of time-varying meshing stiffness of gear and rack based on potential energy principle was proposed,and the correctness of the proposed method was verified by comparing with the calculation results of 225 force element method in Simpack and finite element method.Based on the established model,the dynamic meshing excitation of rack and gear was considered in detail,and the influence of line slope and driving speed on the dynamic characteristics of the gear rail vehicle system was analyzed during climbing,and the influence of different rack railway bogie arrangement on the dynamic performance index of gear rail vehicle was explored.Firstly,the finite element software Abaqus was used to establish the dynamics model of RRGE.Based on this model,the dynamic interaction simulation analysis of the system in the process of gear entry was carried out,and the dynamic response law of structural stress and vibration response of the RRGE under the influence of different parameters was studied,and the gear splitting effect of the RRGE was evaluated.The studied results indicate that as the increase of the supporting spring preload,the rotating speed of the gear will be increased to the value that matching the train speed more promptly.And generally the vibrations and dynamic stress of the synchronous section of the RRGE will be greater,while both the vibrations and dynamic stress of the entry section and the vibration of the calibration section will be smaller.As the increase of the initial rotating speed of the gear up to the train speed,the vertical vibration of the synchronous section varies little in general,and the longitudinal vibration will be decreased,indicating that it is better to set the initial rotating speed of the gear equal to the train speed.The faster the speed of vehicle passing through the RRGE,the worse the gear splitting effect of the RRGE,and the more obvious the impact effect of gear on the entry section and the calibration section.In the calculated speed of 5 to 10 km/h,it is recommended that the speed of rack railway vehicle is 5 km/h or less than 5 km/h.After that,the theoretical calculation method for meshing stiffness of gear and rack was established,and considering the dynamic meshing excitation of gear and rack and the random non-smooth excitation of track.Based on the established model,the influence of rack matrix deflection deformation on the dynamic response of the rack railway vehicle system was investigated,the influence law of the slope and speed on the dynamic performance of the rack railway vehicle was obtained,and the safety and smoothness of the rack railway vehicle were analyzed.The results show that the proposed analytical calculation method can accurately obtain the meshing stiffness changes caused by rack matrix deflection deformation,and the calculated results are in good agreement with the finite element method.And the dynamic meshing force of gear and rack and angular acceleration of gear are increase with the increase of line slope and vehicle speed.In the speed range of 10 to 35 km/h analyzed in this thesis,the derailment coefficient of each wheelset and the vehicle body spering index all meet the relevant standard requirements.Finally,the dynamic response of rack railway system under two different bogie arrangement schemes was compared,the dynamic results of wheel-rail interaction such as wheel-rail force and wheelset acceleration were obtained,and the running safety and smoothness of rack railway train were analyzed.Result shows that,the dynamic responses of wheel-rail vertical force,wheel-rail lateral force and wheelset vibration acceleration of gear-rack drive wheelsets are larger than those of wheel-rail drive wheelsets.The wheel unloading rate of the two bogie arrangement schemes is less than the limit 0.65.And when the rack railway train climbs the slope,there is obvious axle load transfer phenomenon.At the same time,on the climbing line,the difference of coupler 3 between the two bogie arrangement schemes is obvious,that is,the coupler force in scheme B is about 4.5 times that in scheme A. |
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