Study On Fault Mechanism And Diagnosis Method Based On Locomotive Transmission System Dynamics Model

With the continuous improvement of locomotive speed,higher requirement of the stability and operating safety of locomotive is proposed.Especially,during the long operation of locomotive,under the influence of complex wheel-rail excitation,the locomotive axle box bearing,gear,locomotive wheel and other key parts are prone to spalling,pitting and other failures.In the early stage of failure development,the vibration response of gear and bearing caused by failure is very weak,and it is very difficult to extract failure features under the complex wheel-rail interference noise.So firstly,the interaction of bearing-wheel and gear is considered in this paper,the finite element dynamic model of locomotive transmission system is established.Secondly,according to the different failures of the key parts such as gears,bearings and wheel sets.The vibration response characteristics and failure mechanism of the system are analyzed.Finally,the characteristic extraction method of locomotive failure signal under the action of complex and strong interference is studied.A set effective method is proposed.The details are as follows:The coupling relation of gear-bearing-wheel is considered,the finite element dynamic model of locomotive transmission system is established,the natural frequency and modal response characteristics of the system under different speed conditions are solved.At the same time,the influence of wheel-rail creep force on system response is considered,the finite element vibration response of locomotive transmission system is solved by using incremental iterative method,and the established transmission system model can be used to study the positive problem of gear-bearing-wheel failure response mechanism.Based on locomotive transmission system dynamic model,under the different local surface failure,the gear time-varying meshing stiffness characterization equation,bearing contact force equation and wheel contract force equation are constructed.Then,the equations are embedded into the dynamic model of locomotive transmission system.The dynamic response characteristics and power transfer rule under different failure are studied.At the same time,the response characteristics of the system under the composite failure are studied.When there is weak failure in system,in order to explore the dynamic characteristics of system,the dynamic response mechanism and influencing factors of gear-bearing failure are studied.By simplifying the gear-bearing-wheel model of locomotive transmission system,the analytical solution of the model is obtained.For the gear node model,the steady-state response solution and the response characteristics of the system under unbalanced force are studied.For the bearing node failure,the influence of different failure sizes,wheel-rail forces and bearing clearances on the weak response of bearing failure is analyzed.The relative transient solution is proposed,which can effectively represent the weak change of system response caused by bearing failure.Finally,when there is failure in wheel,the response characteristics and system energy distribution characteristics of gear and bearing failure are studied.Affected by complex wheel-rail excitation,bearing failure characteristics are easily submerged and difficult to extract.In view of this problem,the characteristic extraction method of bearnng weak failure signal is studied.Through the system dynamics model,the resonance response characteristics of failure signal and the source of noise interference are analyzed.Then,through the time domain autocorrelation processing and the envelope demodulation method based on frequency domain correlation kurtosis,frequency band and bandwidth method of the wavelet filtering center are optimized,the failure signal characteristics under strong interference are extracted.Finally,a series of experiments are carried out on the DF4B testing bed,and experimental results verify the effectiveness of the proposed method.The extraction method of complex failure features under complex disturbance is studied.The frequency domain correlation kernel method for square envelope spectrum is proposed.The representation of periodic failure characteristics is analyzed by use of composite failure simulation signals.The traditional frequency domain correlation kurtosis method can not identify characteristics of repeated failure shocks under the strong interference.However,the amplitude of the square envelope spectrum of a signal can be quantitatively characterized by using the frequency-domain correlation kernel method.In other words,the spectrum is generated by correlative kernel values in frequency domain,which can identify the optimal frequency band range and demodulate a single failure feature.Simulation and experimental results show that this method can effectively overcome the influence of multiple complex disturbances and accurately extract failure feature signal.In this paper,the nonlinear finite element dynamic model of locomotive transmission system under complex and strong disturbance is established.The dynamic vibration response characteristics and response mechanism under local failure of the system are studied,and the failure diagnosis method of locomotive transmission system is proposed.The research in this paper will have center theoretical guidance meaning and applied vale for dynamic simulation and failure extraction of locomotive transmission system.