| The high speed and heavy load of the railway locomotive will cause the internal temperature of the gearbox to rise rapidly,which will affect the gear meshing stiffness and tooth surface friction.At present,most of the research on gear system ignores the influence of temperature.This paper takes the locomotive gear transmission system as the research object.In the gearbox,comprehensive consideration is given to the friction of the tooth surface,the temperature change inside the gearbox,the tooth side clearance and other factors,while considering the external effect of load fluctuations caused by wheel/rail adhesion.The dynamic model of the locomotive gear system with gear crack is established,and the vibration characteristics and response characteristics of the crack fault are analyzed,as well as the stability of the gear system.The tooth surface contact and the tooth surface flash temperature are calculated based on the Hertz contact and the Block flash temperature formula.Firstly,the relative sliding speeds of the two meshing tooth surfaces are calculated.The flash temperature temperature,tooth profile deformation and tooth surface friction factor are obtained in different meshing zones by the flash temperature formula and the thermal deformation formula.At the same time,the variation of flash temperature under different input speeds is analyzed.The Weber method of the equivalent cantilever beam model is used to calculate the time-varying meshing stiffness.The tooth root crack and the indexing circle crack are added to the model respectively,and the meshing stiffness of the crack-containing gear is obtained.Considering the stiffness caused by the flash temperature and the time-varying meshing stiffness,it is substituted into the system model.The dynamic response of the system under healthy gear and different root crack conditions are analyzed from the time and frequency response fields.The influence of crack depth on the dynamics of the locomotive gear system and the impact response of the crack on the locomotive gear system are obtained.Thus,the dynamic response characteristics of the cracked gear system are obtained.The input speed is changed under the same crack depth condition,and the dynamic response characteristics of the locomotive gear system are analyzed.The optimal speed range of crack detection is proposed,and the corresponding relationship between the maximum amplitude range of the side frequency and the rotational speed is established.Finally,a multi-scale method is used to obtain a first approximate solution of the crack-containing gear system.The results are basically the same as those calculated by the previous numerical method.At the same time,the response characteristics of the main resonance and 1/3 harmonic resonance of the system are analyzed,and the stability interval is obtained and the parameters response(damping,stick-slip rate,stiffness harmonic amplitude,internal and external load,crack,etc.)are analyzed.The analysis results show that the crack propagation has great harm to the stability of the system.At the same time,the crack will amplify the instability of other parameters.Through the multi-scale solution of the system homogeneous equation,the stability interval of the locomotive running speed is obtained,which provides reference and guidance for the locomotive operation. |
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