钢轨螺孔伤损激光声磁检测系统研究

Research on laser-EMA ultrasonic detection system for the defects of rail screw hole

为检测钢轨螺孔伤损,根据激光声磁技术的基本原理和钢轨螺孔伤损检测的特点,建立了钢轨激光声磁检测系统。通过检测钢轨无伤损螺孔和有上裂伤损螺孔的对比实验,表明本系统能准确检测螺孔上裂伤损。通过小波阈值去噪技术对激光声磁信号进行处理,在保留原始信号各种特征的同时大大提高了信噪比(SNR)。实验结果表明,本文方法无需耦合剂,对钢轨表面状况要求低,可实现钢轨螺孔伤损非接触、快速和准确的检测。

With the increase of the railway load and running speed,the probability of the rail screw hole defects increases and can cause serious damage to the rail operation safety.The traditional nondestructive testing（NDT）is not suitable for the rail development of testing needs nowadays,so we need to develop a new method to test the defects of the rail screw holes.The laser-electro magnetic acoustic（EMA）testing system of rail is designed based on the basic principles of the laser-EMA ultrasonic technique and the characteristics of the rail nondestructive testing.The comparison experiments are conducted by using the laser-EMA to test the screw hole,and the results show that the method can precisely find the upward tilted cracks.From the laser-EMA signal processed based on wavelet threshold denoising,it could be seen that the signal to noise ratio is greatly improved and all characteristics of the original signal are remained,thus the signal processed by the wavelet threshold denoising will be convenient for the damage identification and features extraction.Experimental results show that this method doesn′t need coupling medium and good surface conditions,and could realize non-contact,rapid scanning and precise inspection to the rail screw holes.