Study On The Technologies Of The Damage Monitoring On The Railway Key Parts

With the planning and rapid construction of domestic and international railway networks,the safety inspection and state monitoring technology of railway infrastructure construction is of great significance for ensuring the safety of railway network transportation.The traditional on-board inspection equipment of the current in-service cannot monitor the full-scale of the rail,especially the damage in the waist and bottom of the railway,will lead to missed inspection,misdetection and failure to evaluate rail track correctly.In this study,through combining with ultrasonic guided wave technology and structural health monitoring,the damage monitoring for web,base and key parts of rail tracks were studied,and the quantitative of damage length and localization analysis of damage were realized.In order to solve the measurement difficulties in damage detection caused by the dispersion of ultrasonic guided waves in complex rail structures,this study drew the dispersion curves of rail structure.the propagation characteristics of the ultrasonic guided waves at different excitation frequencies and different propagation distances were analyzed with the finite element simulation method through considering the number of modes,modal aliasing,crosstalk influence,modal attenuation et al The appropriate monitoring frequency and propagation distance were selected.Based on these,the relevant experimental system was built and tested.The quantitative analysis of the crack length at rail base and the positioning imaging method of damage in the rail web region were studied.For details:Established a three-dimensional finite element simulation model of 60 rail and turnout tip rails,analyzed the influence of modal aliasing of ultrasonic guided waves on the measurement results under different excitation frequencies and different detection distances in the rail web,the appropriate excitation frequency is selected.On this basis,a three-dimensional simulation model containing cracks of different lengths was established.The relationship between the crack length of the rail base and the correlations between the signals in the time and frequency domain is further analyzed.Designed the WSN-based structure health monitoring experiment system,and the ultrasonic guided wave signals with different lengths of simulated damage were collected through field test to verify the theory.Results show that the changes of the crack length at rail base are more obviously in the time domain than in the frequency domain.The crossing correlation coefficient of the signal in the time domain is more suitable for quantitative analysis of damage.According to the propagation characteristics of ultrasonic guided waves with different propagation distances at different excitation frequencies in the rail web,the sensor array method of the rail web region was designed to determine the excitation frequency of the monitoring signal,and the sensor array was arranged at the rail web region.Inductive multi-reception mode,collected the guided signals of the multi-channel excitation-sensing path.Combining with the damage probability imaging technique,analyzed the characteristics of time domain signal cross-correlation,spectral amplitude difference and relative time-shift damage factor of scatter signal are analyzed theoretically.A damage probability imaging method based on multi-damage factor fusion method was proposed,which was analyzed by finite element simulation.The experimental results show that the method can clearly and intuitively locate the damage and obtain higher positioning accuracy than the single damage factor,which provides a study for the regional monitoring of the actual rail web damage.