Study On Polygonization Wear Mechanism Of High-speed Train Wheels

The high-speed railway has been developed explosively in China in recent years.When the vehicle runs at a high speed,the wheel tread usually works in a comparatively hard environment which leads to a series of problems.The polygonal wear of the wheel is one of the most prominent problems.Polygonal wear refers to the regular harmonic wear along the wheel circumference,and its amplitude is usually small.However,such a small irregularity can cause very large dynamic forces due to the high running speed.Besides,its frequency is relatively high,usually between 550 Hz and 600 Hz.Thus,the vehicle track structure is prone to fatigue damage once the polygonal wear happens.The wheel polygon has become an urgent problem to be solved which affects the safety and economy of the high-speed railway system.However,the formation and development mechanism of the wheel polygon is not yet completely clear.This work aims at the mechanism of the wheel polygon wear,and adopts experiment and simulation to quantitatively calculate and qualitatively analyze the formation and development process of wheel polygons.The specific works and the main conclusions are listed as follows:(1)Various field tests were carried out on the wheel polygonal wear.It is found that the polygonal wear is frequency-fixing.The vibration characteristics of the vehicle track structure with the wheel polygon are analyzed,and the wheel polygon is mainly related to the vertical vibration of the track structure.The modal analysis of the rail shows the local vibration mode of the rail is consistent with the characteristic frequency of the polygon.The data show that the wavelength of the rail local mod is slightly longer than two-thirds of the wheelbase.(2)The rigid-flexible dynamics model of the vehicle–track coupling system is established.The flexibility of the frame,axle box,wheelset and track are considered in the model,and the model is verified by experimental data.(3)An improved wheel–rail contact algorithm applied to polygonal wear calculation is proposed.The algorithm can consider the non-Hertzian characteristics of contact patch as well as the yaw angle of the wheelset.The algorithm is verified by the program CONTACT.Finally,the contact algorithm is applied to the wheel polygonal wear calculation.(4)The formation mechanism of polygons is explained.The excitation,local vibration modal resonance and the wheel periodic wear procedure are analyzed.As for the excitation,it is found that a small wheel defect can cause the excitation with integer multiples of the rotation frequency,and can also initialize the wear phase.The relationship of the track wavelength and the frequency is introduced to explain the wheel polygonal frequency.Finally,a rail vibration induced wheel polygon mechanism is described.(5)The wheel polygon development process is analyzed by simulation.It is found that there are phase differences between the wheel–rail contact solution and the wheel polygon wave.The wheel variation of speed will change the phase difference between the wear distribution and the polygon wave,as a result,the wheel polygon development trend will be dominated by the running speed.(6)Finally,a method based on track vertical vibration displacement and deep learning algorithm is proposed to monitor the wheel polygon online in the high-speed train system.The model was trained and validated with simulated rail vibration data,and the feasibility of the method was initially verified.