Analyzing the Development of Rail Defects Based on Results of Multichannel Periodic Testing

Abstract

Systems for nondestructive testing (NDT) of rails are multichannel and concurrently use several methods, including ultrasonic, magnetic flux leakage (MFL), visual, and others. Periodic inspection of rails does not allow easily monitoring the condition of rails and tracking the trend in the development of defects simultaneously through multiple (up to 14) channels based on several parameters of ultrasonic- and magnetic-testing signals. We propose approaches to developing a generalized (integral) parameter that takes into account the main characteristics of signals from defects concurrently through all testing channels (methods). Using this parameter, we have analyzed the development of various defects in the rail head during repeated (up to 17 times) inspections. As expected, longitudinal defects in the head develop over a rather long (up to 4 years) period of time. At the same time, transverse cracks, most dangerous due to the likelihood of a sudden break in the rail, develop quite rapidly (0.5–4 months). Attention is drawn to the significant instability of ultrasonic flaw-detection signals during repeated monitoring and to regular changes in magnetic-testing signals. It is shown that it is possible to monitor the development of rail defects and take proactive measures for the timely removal of dangerous defects. The proposed approaches can be used in monitoring the development of defects in other fields of NDT.