Research On Dynamic Models And Dynamic Characteristics Of Several Typical Rack Vehicles

Vehicles require greater forward traction and braking capabilities when traveling on ramp sections than straight sections,resulting in the generation of gear rail vehicles traveling on rack railways（Cog railways）.Rack railways lay a steel structure track similar to a rack between the rails on both sides of an ordinary railway track,and form a gear-rack meshing system with the drive gears equipped on the bogie of a rack vehicle.The gear-rack meshing force is used to supplement or replace the insufficient wheel/rail adhesion when the vehicle goes uphill.There are many types of gear-rack systems,and their equipped gear-rack systems are therefore diverse.Due to their structural differences and unique installation methods,different gear-rack systems introduce different dynamic disturbances to rack vehicles during operation,resulting in different dynamic characteristics of rack vehicles.Therefore,it is necessary to analyze the dynamic characteristics of rack vehicles with different gear-rack systems.Based on the analysis of the generation mechanism of gear-rack meshing excitation,considering the impact of gear-rack meshing,four typical rack vehicles dynamic models,two types of Strub system,double row teeth Abt system,and Locher system are established based on vehicle coupling dynamics,and the models are experimentally verified;Using the established model,analyze the gear-rack meshing behavior of rack vehicles operating on ramp meshing sections,and explore the impact of line irregularities on gear-rack meshing errors of rack vehicles;On this basis,the wheel/rail action and vehicle acceleration of the rack vehicle are studied,and the dynamic response of each component of the rack vehicle and the dynamic characteristics of the entire vehicle are analyzed,providing theoretical support for the selection,design,and safe operation and maintenance of the mountainous rack railway in China.Firstly,based on the mechanical structures of four typical rack vehicles:coaxial Strub gear-rack system,double row teeth Abt gear-rack system,different axles Strub gear-rack system,and Locher gear-rack railway system,a gear gear-rack meshing model and a rack vehicle dynamics model are established based on gear system dynamics and vehicle coupling dynamics,and a line irregularity model is established.Then,a numerical integration solution method for the model is given,the experimental verification of the model was carried out,and it was found that the established dynamic model of the rack vehicle was reliable.Secondly,using the established gear-rack meshing model,the gear-rack meshing forces,time-varying meshing stiffness,meshing characteristics and the meshing center distance error of the gear-rack system for four typical rack vehicles are analyzed respectively.There are multiple impacts on the gear-rack meshing force of the coaxial Strub gear-rack system and the double row teeth Abt gear-rack system with gears connected to axles,the maximum value of the gear-rack meshing force of the coaxial Strub gear-rack system is 29.8 k N;The meshing stability of the gear-rack system of the coaxial Strub gear-rack system,the double row teeth Abt gear-rack system,the different axle Strub gear-rack system is poor,and the meshing impact is more obvious;The vertical vibration amplitude of the gears in the coaxial Strub gear-rack system,the double row teeth Abt gear-rack system and the different axle Strub gear-rack system is maintained at0.18 mm,with a main vibration frequency of 3.9 Hz,and their gear time history curve waveforms are similar.It can be considered that the vibration laws of the gear-rack in the three vertical meshing arrangements are consistent;The gear-rack meshing center distance error of the Locher gear-rack system fluctuates most smoothly,while the gear-rack meshing center distance error of the coaxial Strub gear-rack system and the double row teeth Abt gear-rack system fluctuates greatly due to line irregularities,with a maximum value of 0.037 m.Then,using the rack vehicle dynamic model,the dynamic responses of the wheelsets,frames,and carbodies of four typical rack vehicles were studied and compared.It was found that rack vehicles of the coaxial Strub gear-rack system and the double row teeth Abt gear-rack system have significant impacts due to the large unsprung mass and the large vertical vibration of the wheelset,with a maximum amplitude of 0.002 mm and an acceleration of 32 mm·s^-2.The wheelset vertical acceleration of the rack vehicles in the different axis Strub gear-rack system changes relatively smoothly,and the wheelset vibration frequency of the rack vehicles in each gear-rack system is 3.9 Hz;The rack vehicle bogie frame and the gear-rack system are directly elastically connected with each other.The vibration of the bogie frame and the carbody is large,with a maximum amplitude of 0.13 mm for the bogie,a maximum vibration acceleration of 97 mm·s^-2,a maximum vibration value of 0.063 mm for the carbody,and a maximum vibration acceleration of 0.33 m·s^-2;The influence of the Locher gear-rack meshing system on the dynamic response of each component of a gear rail vehicle is almost zero.Finally,the wheel/rail interaction performance,vehicle operation safety,and running smoothness of rack vehicles operating at different speeds on different slopes were studied.Through comparative analysis,the corresponding gear-rack systems for the rack vehicles with the best and worst dynamic performance were obtained.When the rack vehicles of the coaxial Strub gear-rack system,the double row teeth Abt gear-rack system,and the different axle Strub gear-rack system are running,their wheel/rail interaction performance is significantly affected by the gear-rack meshing excitation.The double row teeth Abt gear-rack system rack vehicles are most affected,with the maximum wheel/rail vertical force reaching 51.47 k N,and the axle lateral force reaching 1309 N.The wheel/rail vertical force of the rack vehicles decreases with the increase of the line slope,increase with the increase of operating speed;The operational safety of the rack vehicles of the coaxial Strub gear-rack system,the double row teeth Abt gear-rack system,and the different axle Strub gear-rack system is significantly affected by the gear-rack meshing excitation,while the rack vehicles of the Locher gear-rack system are almost not affected.The wheel unloading rate of the rack vehicles of the double row tooth Abt gear-rack system are the largest,The wheel unloading rate of each rack vehicle shows an increasing trend with the increase of line gradient and operating speed;The rack vehicle stability of the different axle Strub gear-rack system is the worst.When the line gradient is 200‰and the operating speed is 30 km/h,the maximum carbody vertical acceleration is 0.33m·s^-2,with a stability index of 1.32.The operation stability of the rack vehicles of the coaxial Strub gear-rack system and the double row teeth Abt gear-rack system becomes better as the line gradient increases,The stability index of the rack vehicles of the different axle Strub gear-rack system and the Locher gear-rack system becomes worse as the line slope increases.