The application of long range ultrasonic testing (LRUT) for examination of hard to access areas on railway tracks

Following a number of severe accidents caused by rail breaks, there has been a significant improvement in NDT methods for the detection of rail head defects. However, current NDL methods are limited in their ability to detect defects in the rail foot, especially in the side edges away from the region directly below the web. Long Range Ultrasonic Lesting (LRUT) is proposed as a complimentary inspection technique to examine the foot of rails, especially in track regions where corrosion and associated fatigue cracking is likely, such as at level crossings. The focus of this study is to demonstrate the ability of using LRUT to examine inaccessible railway tracks areas for corrosion and fatigue cracking. In this paper, the properties of guided waves in the three different parts of the rail section (head, web and foot) are examined and their capability to detect defects in each part is explored. The purpose of this work is to develop suitable arrays of transducers able to generate selected guided wave modes in rails which will allow a reliable long range inspection of the rail. This investigation has being carried out using Finite Element Analysis (FEA) as well as experimental trials. The findings have shown that ultrasonic guided waves can propagate in rails with the ability to detect common type of defects. The emphasis of the work is on the foot since currently applied NDT methods are less effective in this region. Nevertheless, work has been also carried out in the web and the head in order to develop a cost effective and global inspection solution.