Defects Detection Of Rail With Finite Element Laser Ultrasonic Technology

Rail non-destructive testing technology is widely used for the detection of rail defects.However,the coupling agent is required to detect defects in this technology,which will affect the accuracy of the detection.Laser ultrasound technology not only has the advantages of conventional ultrasound,but also has the characteristics of no couplant and abundant wave modes.Therefore,it is of great significance to apply laser ultrasound technology to the detection of rail defects.Therefore,this article mainly uses laser ultrasound technology to detect rail Defects.Firstly,the thermo-elastic coupling equation is established based on the principle of laser ultrasonic testing technology,and the thermo-elastic coupling equation in the form of finite element is established in combination with the principle of finite element.The correctness of this model is verified by analyzing the relationship between theoretical calculations and the obtained echo signals.Because laser ultrasound is not sensitive to the width of defects,an interlaced laser ultrasound imaging technique is proposed.Based on the actual rail tread defect information,the established model defects are improved.The laser is used to stimulate the two sides of the rail tread and receive it on the same side.The received one-dimensional data containing the defect information is registered and fused to obtain the complete defect.The image not only has sharp edges but also high resolution,so that the detected defects can be quantitatively analyzed.Subsequently,the effect of changing laser-related parameters on defect detection was studied.By changing parameters such as laser energy,pulse width,and laser beam lateral width,the amplitude and spectrum of the echo data containing defect information were analyzed,and the defect is imaged in combination with the interlaced imaging technology.It is concluded that the laser energy and pulse width can change the intensity of laser ultrasound and make the detected defects more obvious,changing the lateral width of the laser spot can not only change the intensity of the ultrasound,but also the spectral components of the laser-excited ultrasound,so it is more sensitive to defects and easier to detect.Finally,the laser ultrasonic detection finite element model of rail defects was modified to the rail bottom defect finite element model.The grid bottom analysis and defect location analysis were performed to detect the rail bottom defects.Finally,the depth of the rail bottom defects was detected,the relationship between laser ultrasonic surface wave and defect depth is obtained.