FBG Ultrasonic Detection And Experimental Research On The Bottom Of Pointed Rail Damage

Turnouts are the necessary equipment for trains to divert or get over the tracks,which are an important part of the railway.As the turnouts always sustain the impact of trains,the turnouts are tend to crack and even break.However,the existing ultrasonic detection technology cannot monitor the bottom of the turnouts effectively.In recent years,some scholars have used ultrasound guided waves to perform damage detection on the bottom of the rail.Nevertheless,the piezoelectric or electromagnetic ultrasonic transducers have complex structures and are subject to electromagnetic interference.The ultrasonic detection technology has more advantages,which is high sensitivity,anti-electromagnetic interference and so on.In this paper,ultrasonic detection based on FBG and experimental research on the rail-track rail damage are carried out.The main research contents are as follows:Firstly,the literature search and analysis were carried out on the current detection methods of ballast damage and the current research status of FBG ultrasonic inspection.The deficiencies of existing inspection technologies are discovered.Combined with the advantages of the FBG ultrasonic detection method,this method is used to detect the damage the ballast tract bottom.Transient state of the ultrasonic guided wave in the steel plate was analyzed by the transient dynamics in ANSYS.Meanwhile,the propagation characteristics of Lamb waves in cracked steel plates is simulated.These simulations is regard as as a theoretical basis for the following use of FBG ultrasonic technology to detect the crack damage of steel plate.Establishing the model of turnouts with SolidWorks,applying the vertical modal 50kHz ultrasonic excitation at the bottom and the wasit of the switch rail,we proved that the ultrasonic exciation can be used to detect the damage of the tongue rail.For the FBG ultrasonic testing,the design of ultrasound sensor is a very critical factor.Considerating the poor mobility of direct-attached fiber grating sensors,we design a portable fiber grating ultrasonic sensor.Packaging with PDMS,this material is better for the ultrasound transmission performance,we using the role of pinhole structure in strain amplification of FBG.The performance of the new structure is simulated using finite element with ANSYS.The experimental results show that the new FBG ultrasonic sensor can perceive ultrasound well.The primary experiment and simulated damage experiment of the FBG ultrasonic detection technology on steel plate.The effects of ultrasonic modes,excitation frequency and crack width on the detection of fiber gratings were experimentally studied.It also verifies the feasibility of the fiber grating optical inspection technology in the damage detection of the steel plate.The test was conducted on the track rail at the bottom of the turnout.In the experiment,the best detection frequency and the detect distance of the method is determined.It is verified that the FBG ultrasonic detection method can realize the detection of crack damage at bottom of rails under the effect of ultrasonic wave of 60kHz.The end is the summation of the project situation.We also analyze the limitation in current study;propose area need for improvement and point out the aspects to be further studied.