The Study Of Ultrasonic Guided Wave Propagation Mode And Defects Detection Method In Rail Based On COMSOL

As the rapid development of rail transport,maintenance of rail has become a focus problem.Researchers have found that ultrasonic guided wave is preferred method in detection of rail.The character of acoustic propagation in rail and detection of defects has become a research hotspot in recent years.In this paper,the simplified model of rail can deduce the corresponding theory and through FEM of COMSOL and verify feasibility of complete rail.To simulate the real situation and to ascertain the influence factors of the characteristic of acoustic wave propagation in rail,in this paper,we create the model of piezoelectric sound source to simulate the acoustic sound of incident angle,conversion efficiency of piezoelectricity and displacement,et.These factors are how influence acoustic wave propagation.Secondly,combining with user-defined mesh,the paper analyze rail of the characteristic of time domain,frequency domain and the characteristic frequency.Through the simulation results,get the best trigger frequency of the sound source in rail,and determine the optimal installation location of ultrasonic transducer based on the vibration modes.Finally,the paper can provide theoretical guidance for the ultrasonic guided wave testing through creating APP.Instead of the conventional method,in this paper,the conventional method which is using the boundary simulate the acoustic source is replaced by the model of piezoelectric sound source.This method makes simulation results becoming real.The paper combines the feature of multi-physics field to analyze characteristic of acoustic wave propagation in rail.Using the analysis of thermal stress to verify deformation of rail in different temperature,obtain relation curve of acoustic amplitude versus temperature through statistic simulation results.Combining with acoustic-structure coupling module of COMSOL solve characteristic of acoustic wave propagation in air domain,respectively,in time domain and in frequency domain.And according to the conclusion of simulation,we present method of ultrasonic guided wave detection of defects and verify it through experiment.The comparison of experiment and simulation shows that there are two similar results,which are resonant frequency and ratio of piezoelectric conversion.The result shows that the defect of 15 mm radius in rail head should use the ultrasonic guided wave testing of greater than 40 kHz to see obvious damping.To the defect,radius of less than 6 mm,using ultrasonic guided wave of level of kHz can't test effectively.And according to the result of the defect of depth 75mm and width 2mm in the center of rail,the comparison of experiment and simulation shows that the acoustic damping is more obvious if the width of crack is more than 2 mm in time domain.In frequency domain,the result shows that around the frequency of 30 kHz and 40 kHz are suit to detect crack,but using around the frequency of 45 kHz to detect crack is not good.This result illustrates that detect cracks and defects to need matched frequency of ultrasonic guided wave.The experiment of thermal stress versus acoustic amplitude shows that both are same trends.But compared with simulation result,the real situation is fluctuant and the influence factors are complex.According to the above results,the simulation can analyze damping of acoustic amplitude,resonant frequency of ultrasonic transducer,acoustic propagation in thermal stress and ultrasonic guided wave detecting defects.