Research On Vibration Characteristics Of Tooth Root Crack Fault In Gear Transmission System Of Heavy Haul Locomotive

With the rapid development of heavy haul railway in China,increasing axle load and expanding train formation are effective ways to relieve the pressure of heavy haul railway transportation.However,a problem is proposed,that is,the traction and braking power required will also be increased while the axle load or the number of freight car marshalling are increased.Therefore,the development of high-power heavy-haul locomotives has become the inevitable direction of heavy-haul freight development in China.However,as a vital device for locomotive to transmit traction and braking moment to draw the train move or stop along the railway line,the dynamic load of gear transmission system increases with the increasing of locomotive traction/braking power which could easily cause faults in gear transmission system,accidents affecting normal operation such as parking,even initiate derailment accidents and resulting in significant economic losse.Thus,accurately monitoring the running condition of locomotive gear transmission system,improving the success rate of fault diagnosis and farthest avoiding safety accidents are urgent.Meanwhile the vibration characteristics of locomotive induced by fauty gear transmission system are often covered by vibration signals generated by various complex exciting sources,especially the incipient fault characteristics.Consequently,proposing the corresponding fault feature extraction and diagnosis methods is of great significance to improve the efficiency of heavy haul train transportation,as well ensure the safety of train operation and reduce accidents.Based on the summary and analysis of the research on dynamics of gear transmission system,faulty gear transmission system and locomotive dynamics considering the coupling effect of gear transmission system at home and abroad.A spatial heavy-haul locomotive dynamic model considering the tooth root crack in gear transmission is established by using multi-body dynamics and the vibration characteristics induced by tooth root crack under the complex wheel/rail excitation are further studied in this paper.Firstly,only considering torsional vibration of spur gear transmission system,a lumped parameter dynamic model of spur gear transmission system based on analytical computing model of time varying meshing stiffness,namely,“slice method” and the moved Marker technique provided by SIMPACK is established.While the lumped parameter dynamic model of spur gear transmission system established by SIMPACK 225 force element and the dynamic model of spur gear transmission system established by finite element method are also be used to verify the availability of the first model in high speed and low speed conditions.Besides,two indicators of gear dynamic transmission error and dynamic meshing force are used during the verification.Result shows that,the established model based on analytical computing model of “slice method” and the moved Marker technique provided by SIMPACK could be better used in dynamic characteristic analysis of gear transmission compare to the second dynamic model.After that,the time varying meshing stiffness of locomotive gear transmission with appearance of tooth root crack under different crack depth are obtained by using the “slice method”.Based on the aforementioned lumped parameter dynamic modeling method of gear transmission and multi-body dynamic theory,the locomotive gear transmission dynamic model with appearance of tooth root crack is established as well the heavy haul locomotive dynamic model with considering the fault gear transmission system.The dynamic response of locomotive system is calculated by using the established model.Result shows that,Time-domain response signal of locomotive system is difficult to reflect vibration characteristics caused by tooth root crack,while frequency spectrum response of locomotive system could reflect vibration characteristics caused by tooth root crack and the track random irregularity excitation can strongly mask the vibration characteristics caused by the root crack,especially the incipient tooth root crack fault.Finally,the evolution law of vibration characteristics caused by tooth root crack failure at different depths are analyzed.The dynamic response of locomotive under steady state operation is analyzed by using frequency spectrum analysis method.Additionly,Angular Synchronous Averaging is adopted to analyze the dynamic response of locomotive during the whole process of acceleration and constant operation speed,the fault characteristics of tooth root crack under corresponding operation conditions are obtained.Result shows that,In frequency domain response,the amplitude of fault vibration characteristics caused by tooth root crack increases with the depeening of crack.The angular synchronous averaging method can effectively improve the signal-to-noise ratio of fault vibration signal,and has a good effect on extracting the fault vibration characteristics of locomotive system induced by tooth root crack.