| With the continuous development of high-speed railroads in China,the operating speed and mileage of moving trains continue to increase.Wheel-rail contact fatigue and wear phenomenon gradually emerge,wheel polygon wear problem also commonly exists in the operation site.The polygonal wheel wear will deteriorate the wheel-rail contact relationship and make the wheel-rail force surge,which will have a serious impact on the safety and stability of the train.Gear transmission as a critical method of transmitting power to the moving vehicle.It has the advantages of constant power transmission,strong load-bearing capacity and high transmission efficiency.However,the gears are often under severe working conditions such as high speed and heavy load,which are not only affected by the periodic meshing excitation of the gears,but also by the polygonal shape of the wheels and the uneven excitation of the road.Fatigue failure and gear failure can easily occur,affecting the safety of train operation.Most studies only consider the wheel polygons alone or the gearing excitation on the dynamics of the moving train,but rarely consider the impact of wheel polygons and gearing excitation on the moving train system at the same time.However,the effects of both gearing excitation and wheel polygon excitation on the system cannot be ignored.Therefore,it is necessary to carry out research on the dynamics of the moving vehicle under the combined effect of wheel polygons and internal excitation of the gearing system,and reveal the influence law of the wheel polygon order and wave depth amplitude after considering the gearing system,which has more general guidance significance for ensuring the safety of train operation.The main research works include.(1)Based on the multi-body dynamics theory,the moving mark point technique and the sliced helical gear stiffness solution calculation method are established in the dynamics software to establish the dynamic model of the moving train considering the gearing excitation,and the model is compared with the traditional model and the wheel polygon working condition is considered.The traditional method of moving a moving car model is to give initial speed and maintain a uniform speed.In contrast,the method used in the operation of the model car considering gearing is to provide torque to the motor rotor and transfer the power to the wheel pairs to drive the car through the gearing system,which is more in line with the actual situation.(2)Through theoretical and simulation comparisons,it is verified that the model considering the gearing system can simulate the axle load transfer phenomenon in the actual working conditions,and the operational quality and operational stability of each model are compared and analyzed.The results show that the model considering the gearing system has less error in the axle weight transfer simulation and is closer to the reality.The modulation frequencies of the gear and polygon appear in the spectrogram,indicating that the two excitations interact with each other and have some coupling effect.The gearing excitation has a certain influence on the operating quality and operating stability,and the excitation cannot be neglected.(3)The effect of wheel polygons on wheel operating quality,operating stability,and operating smoothness is investigated in depth in the time and frequency domains using a dynamics model considering a gear train.The results show that the wheel polygon excitation has a greater effect on the wheelset vibration acceleration and wheel-rail vertical force,and a smaller effect on the smoothness of operation.The maximum value of wheel-rail vertical force after considering the gearing excitation is larger,which has better safety performance when studying the safety limits of wheel polygons.(4)The time-varying meshing stiffness of the gears with cracks is derived from the sliced helical gear stiffness solution calculation model and input to the dynamics model.The effects of the gear transmission system with cracked gears on the dynamic performance of the moving vehicle are investigated by time and frequency domain curves,and the patterns of dynamic meshing forces at different gear crack depths are analyzed using statistical indicators such as rms,kurtosis,and shapefactor.The results show that the cracked gear transmission system has less influence on the wheelset vibration acceleration and wheel-rail vertical force.The effect on dynamic meshing force is more obvious.When polygon and crack excitation exist at the same time,the effect of the cracked gear transmission system on dynamic meshing force is more significant. |
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