Eddy Current Thermography for Rail Inspection

Abstract

With the tendency of the railway transportation into heavy haul, more frequent usage of rail tracks and increased axle load, the problem of surface damage and fatigue is dominant on rails. Rolling contact fatigue (RCF), which leads to crack formation in rail track heads, is becoming a growing concern in the transportation industry. It occurs on or very close to the rail head surface, and is a significant cause of rail failure. The detection of cracks in RAILS is a critical requirement in the Railway industry. Cracks, if undetected will lead to rail fractures and consequently may lead to catastrophic accidents. Thus with the development and operation of high speed trains, condition based maintenance and monitoring becomes an important approach for the improvement of reliability and safety of rail transportation. Eddy Current Thermography (ECT) is an emerging NDT method especially for conductive material like rails which combines the advantages of eddy current testing and IR Thermography. Due to electrical conductivity, thermal conductivity and high permeability of rails, ECT is very suitable for its damage detections. This technology describes an inspection methodology which utilizes scanning induction Thermography in which coil is excited by a high frequency alternating current and induced eddy current are generated in sample placed near the coil. The thermographic camera is arranged to capture data indicative of a thermal response resulting from the flow of electrical current through the copper coil which scans the rail track. A computer system is configured to process the data from the thermographic camera to generate an indication of a presence of a discontinuity in the rails.

Recent advances in wheel-rail RCF and wear testing

“…The PEC has been used in the railway domain as a complementary system and/or together with ultrasonic testing [41,[87][88][89]. Some of the recent developments of such a testing system are reported by several researchers and companies [90][91][92][93][94][95][96][97][98][99].…”

Scanning inductive thermography using a µ-bolometer and a visual camera

“…Inductive thermography is a standardized NDT method, which is used for detection of surface defects in metal parts 1,2 . In recent years, the usage of inductive thermography for testing railway rails and turnout sections has also been investigated [3][4][5][6] . Short pulses from an inductor heat the component by a few degrees (∆T<10 K) and an infrared camera records the changes in the surface temperature before, during and after those pulses.…”

Inductive Thermography as Non-Destructive Testing for Railway Rails

“…In the last few years the new technique of inductive thermography has been developed, which has a high potential for automated rail inspection [11][12][13][14]. In the case of inductive thermography, the specimen to be tested is heated with a short inductive heating pulse, usually in the range of 0.1-1 s. The applied excitation frequency is in the range of 100-200 kHz, whereby in ferro-magnetic steel the induced eddy current penetrates only up to about 0.03 mm below the surface.…”