Research On The Effect Of Typical Service Defects Of High-speed Railway Track On Wheel-Rail Dynamic Contact Posture

The construction technology of high-speed railway in China has reached the world-class level,but it still faces great challenges in the aspects of operation safety and long-term service performance.Due to the high-speed,high-frequency,and repeated impacts and vibrations of the wheel and rail,many abnormal defects of the ballastless track have emerged.Track defects are closely related to the wheel-rail contact status under the operating conditions of high-speed railways.In order to grasp the relationship between the wheel-rail contact status and track structure service defects under high-speed train movement,and then accurately assess the service capacity of high-speed railways.This article relies on National Natural Science Foundation of China "High-precision structured light-based high-speed railway wheel-rail dynamic contact posture detection system" project,based on vehicle-track coupling dynamics,multi-body dynamics,finite element and other related theories.The dynamic analysis models of vehicle-ballastless track considering different types of track defects were established respectively.The changes of wheel-rail contact posture parameters under four typical track service defects are calculated,and further combined with the analysis of the safe operation of high-speed vehicles,obtained the safety limits of different contact posture parameters,and finally gave the track service defect identification method based on the wheel-rail contact posture information.The main contents are as follows:(1)A refined model of vehicle-track coupling dynamics considering track short-wave defects and medium-long-wave defects is establishedFor track short-wave service defects,a three-dimensional high-speed wheel-rail transient rolling contact mesoscopic finite element model is established based on finite element theory,which is used to accurately solve the wheel-rail contact posture information under rail welds and corrugation defects.For long-wave service defects in the track,a macro-dynamic analysis model of the vehicle-ballastless track is established based on the multi-body dynamics theory,which is used to simulate and calculate the track slab seam-off and the upwarp defects and the lower wheel-rail contact posture information.(2)The effect of high-speed railway short-wave service defects on wheel-rail contact posture is studiedThe law of the influence of high-speed rail weld defects on the wheel-rail contact posture: when the weld wavelength is constant,the wheel-rail vertical force,contact patch area,contact patch longitudinal axis length,wheelset sink and float,wheelset roll angle and other parameters follow the wave depth of the weld increases approximately linearly;the wheel-rail contact patch area has a good consistency with the change law of the wheel-rail vertical force,and the weld defects on one side has little effect on the wheel-rail contact state on the other side.When the weld wave depth is constant,the contact patch area and the longitudinal axis length of the contact patch decrease with the increase of the weld wavelength;the parameters such as the amount of wheelset ups and downs and the wheel-to-side roll angle increase approximately linearly with the increase of the weld wavelength.The law of the influence of high-speed rail corrugation defects on the wheel-rail contact posture: the contact patch area and longitudinal axis length of the corrugated side fluctuate periodically with the corrugated geometry,and the corrugated defects on one side has little effect on the contact state of the other side.When the corrugation wave depth is constant,the wheel-rail force and contact patch area reach the maximum when the corrugation wavelength is 80 mm.When the wave wavelength is constant,the wheel-rail force,the contact patch area,and the longitudinal axis length of the contact patch all increase approximately linearly with the increase of wave depth.(3)The effect of long-wave service defects on high-speed railway tracks on wheel-rail contact posture is studiedThe law of the influence of seam-off defects of high-speed railway track slab on wheel-rail contact posture: when the seam-off length is fixed,the wheel-rail vertical force,wheelset ups and downs,rail vertical dynamic displacement,contact patch area,and contact patch longitudinal axis length all follow the amount of seam separation increases;the change law of the contact patch area and the longitudinal axis length of the contact patch is consistent with the change law of wheel-rail force;the ups and downs of wheelset and the dynamic displacement of the rail show a strong linear change with the increase of seam separation.When the depth of the track seam-off is constant,the wheel-rail vertical force,the amount of ups and downs of the wheelset,the vertical dynamic displacement of the rail,the area of the contact patch,and the longitudinal axis length of the contact patch all reach the maximum when the length of the seam-off is two plates;the wheel set ups and downs and the variation dynamic displacement of the rail along the longitudinal direction of the track is basically the same as the wavelength of the seam-off.The influence law of high-speed railway track slab upwarp defects on wheel-rail contact posture: when the upwarp range is fixed,the wheel-rail vertical force,contact patch area,and contact patch longitudinal axis length all increase with the increase of the amount of upwarp;the peak value of the vertical dynamic displacement of the rail increases approximately linearly with the increase of the amount of upwarp.When the amount of upwarp is constant,the wheel-rail vertical force,contact patch area,and longitudinal axis length of the contact patch all increase with the increase of the upwarp range;due to the influence of the closing of the seam from the bottom of the plate,the upwarp range is larger,the amount of wheelset ups and downs does not change significantly;the vertical displacement of the rail increases with the increase of the upwarp range,and the distribution of the vertical displacement along the longitudinal direction of the track can reflect the range of the upwarp.(4)Track safety assessment and the methods of defects identification based on wheel-rail contact posture information is studiedBased on the change law of the following car safety indicators and the analysis results of the wheel-rail contact posture for different track defects,the maximum seam separation and upwarp camber of the track slab should not exceed 8mm;the maximum rail weld wave depth should not exceed 0.2mm;For corrugation defects,the wavelength80 mm should be repaired in time,the wave depth should be controlled within 0.1mm.According to the corresponding relationship between different posture parameters and wheel load shedding rate,the change rate of the contact patch area cannot exceed 0.5;the change rate of the longitudinal axis length of the contact patch cannot exceed 0.3;the safety limit of the ups and downs of the wheelset is 9.6mm;the vertical displacement of the rail safety limit is 10 mm.Track defects identification method based on contact posture: For the seam-off defects,the characteristic parameters of the defects can be analyzed according to the change rule of the wheel set ups and downs and the dynamic displacement of the rail;for the upwarp defects,the change rule of the dynamic displacement of the rail can be more intuitively evaluated;for weld defects,analyze the wavelength according to the frequency bandwidth of the contact patch area,and then identify the wave depth according to the corresponding relationship between the area of the contact patch and the wave depth of the weld;for corrugated defects,analyze the wavelength according to the dominant frequency of the contact patch area,and then judge the wave depth through the corresponding relationship between the contact patch area and the corrugation wave depth.