| With the gradual upgrading of railway rolling stock equipment in China,,there are many problems appeared,the problems such as fatigue failure of box structure and gear tooth,wear of tooth surface and so on are appeared when the traction gear transmission system which is as the key part of locomotive power transmission is in operation pose innovative challenges for the design of key parts.How to conduct reliable and efficient dynamic behavior analysis of locomotive coupling system on the premise of fully mastering the mechanism of structural coupling vibration,and at the same time,how to predict the fatigue life of key components based on dynamic behavior analysis is a necessary means to improve the competitiveness of China's railway rolling stock design.Based on the specific requirements of the research and development of modern railway vehicles,this doctoral dissertation aims to develop effective dynamic response behavior and fatigue research and numerical methods for the complex locomotive coupling system through the time-domain and frequency-domain random vibration analysis methods of locomotive coupling system are studied.According to the current research situation of the dynamic model of locomotive gear transmission system,further integration is carried out to realize the dynamic response analysis of the gear-motor suspension-locomotive coupling system.In view of the low efficiency of the existing methods to calculate the random stress of the structure,based on the development of the corresponding rail vehicle random vibration analysis platform-RVRAP system for in-depth expansion a special analysis module of the locomotive coupling system including the locomotive gearbox and other main components is established,considering the different suspension modes,so as to realize the high efficiency analysis of the dynamic stress and the prediction of the fatigue life of the key component.The results based on the two methods can provide reasonable and reliable external boundary conditions for further study of locomotive traction gear transmission system.The specific research contents are as follows:(1)The dynamic model of spur gear and helical gear for locomotive are established consider the locomotive gear transmission system as the research object,and then the dynamic model of axle suspension and frame suspension locomotive system are established according to the different suspension modes of locomotive traction motor.Finally,A dynamic analysis model of spur and helical gear-axle suspension and frame suspension locomotive coupling system with DOF of 62 and 86 are established by combine the dynamic theory of gear transmission system and vehicle system dynamics and considering the time-varying characteristics of gear transmission system.(2)The Runge-Kutta method is improved in solving the dynamic equation of the periodic time-varying system.According to the characteristics of the sub block matrix of the state space matrix and the external load vector,the solving steps are optimized and the solving process is simplified.The matrix operation involved in the solving process is transformed from the overall matrix operation to the sub block matrix operation,so as to reduce a large number of unnecessary matrices.In the process of operation,the memory of computer is reduced,and the efficiency of Runge-Kutta method is improved.Through numerical verification,the improved method can reduce the calculation time by 50% on the premise of ensuring the accuracy.(3)The acceleration response of each component of the gear-axle suspension and frame suspension locomotive coupling system are calculated considering the internal gear meshing excitation and external wheel rail random excitation based on the dynamic model of gearlocomotive coupling system by using the improved Runge-Kutta method to study the dynamic behavior of the locomotive gear transmission system in the whole vehicle environment under the external excitation and internal excitation.The vibration response of each degree of freedom of axle suspension and frame suspension locomotives can be divided into low-frequency vibration and high-frequency vibration.The low-frequency vibration is mainly caused by the external wheel rail random excitation,and the frequency range is consistent with the wheel rail excitation frequency.The high-frequency vibration is mainly caused by the meshing stiffness time-varying characteristics of the gear pair,and the gear meshing frequency is the basic frequency.The effect of external wheel rail random excitation on the vertical acceleration of driven gear(wheel set)of axle suspension locomotive increases by 41%,and causes random vibration of traction gear transmission system.The application of helical cylindrical gear has obvious effect on improving the high-frequency vibration of various structures of locomotive system.The maximum reduction of vibration amplitude is 50%,but there is no effect on the low-frequency vibration of the structure,and which can cause the high-frequency vibration of the driving and driven gears on the lateral direction.When the axle suspension locomotive is driven by the helical cylindrical gear,the lateral degrees of freedom of the wheel set and the traction motor are coupled with the vertical,longitudinal degrees of freedom and the rotational degrees of freedom of the driving and driven gears,when the vehicle speed reaches more than 110km/h,the gear meshing frequency will gradually produce double frequency resonance with the coupling lateral natural frequency of traction motor and wheel set,the high frequency excitation of gear meshing axial force has a strong effect on the degrees of freedom of the traction gear transmission system of the axle suspension locomotive.With the increase of running speed,the effect of external wheel rail random excitation on gear meshing force of frame suspension locomotive is gradually strengthened,while the effect of internal excitation of gear is gradually reduced,and the random characteristics of gear meshing force is gradually strengthened.(4)The application field of RVRAP system is extended from the traditional railway vehicle random vibration analysis method to the railway locomotive coupling system,and the main components including locomotive gearbox are established.The locomotive gear coupling dynamic system model considering different suspension modes of traction motor is established,which made the system could applicable for the random vibration analysis of locomotive system.The random vibration response of a two-axle locomotive in China is calculated and compared with the results of time domain method of multi rigid body dynamic model.The relative errors of frame,wheelset(driven gear)and traction motor(driving gear)vibration are controlled within 7%,13% and 13%.The trend of acceleration power spectrum curve of each DOF is basically the same,and the wave peak distribution is basically the same.The feasibility,applicability and efficiency of the method based on PEM for random vibration analysis of locomotive coupling system are verified,the vibration response of the driving and driven gears of the locomotive coupling system caused by the wheel rail random excitation which is obtained by PEM can provide reasonable the source of external random excitation of for further study of the locomotive traction gear.The influence of structural elasticity on the vibration of gearbox is studied.Considering the influence of structural elasticity on the vertical and lateral response of gearbox,the change rates are 20% and 6% respectively.(5)Based on the random vibration analysis method of locomotive finite element coupling system of RVRAP system,combined with structural random stress calculation method and structural random fatigue frequency domain method,the application field of RVRAP system is extended to realize efficient and direct analysis of random fatigue of key components of locomotive system.The finite element model of locomotive gearbox under 1000 frequency points is calculated,the model scale is 507079 nodes,and the total time is only 70 seconds to get the random stress results.The random stress response standard deviation cloud map of the key component is drawn,through the cloud image,the overall response of the random stress of different parts of the structure under the random excitation of the wheel and rail can be visually observed to determine the weak parts of the structure which are prone to fatigue damage.Accurate fatigue life analysis of the gearbox is evaluated,less than 150 seconds in total.The minimum life of the gearbox is 5.3997 million km. |
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