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Detection of Transverse Defects in Rails Using Noncontact Laser Ultrasound
* 1 , 1 , 2
1  Systems of Communication and Detection Laboratory
2  National School of Applied Sciences of Tetuan


Rail inspection is required and aims at ensuring safety and preserving the availability of railway infrastructure. According to the statistics published by world railroad administrations, the transverse fissure appearing in railhead is the principal cause of rail accidents. These particular defects are initiated inside the railhead. Detection of these cracks has always been challenging to perform as defect signature remains mostly small until the defect size reaches a significant value. Early detection of transverse like defects constitutes then a real challenge to improve the security of railways and to prevent catastrophic failures. Most of the inspection techniques of rails relay on eddy currents, infrared thermography, and ultrasounds. Inspection tests have been conducted conventionally by using contact excitation probes that roll on the railhead. Modern inspection methods use contact-less devices such as those relying on laser excitation of the rail and air-coupled acoustic sensors for echo reception. The present work deals with the theoretical analysis of an integrated contact-less system for rail diagnosis, which is based on ultrasounds. The generation of these waves is performed through non-ablative laser sources. Rotational laser vibrometry was used to achieve the reception of the echoes. Detection of flaws in the rail was monitored by considering special ultrasound wave signal based indicators. Finite element modeling of the rail system was performed, and transverse defect detection of the rail was analyzed.

Keywords: Rail; Transverse fissure; Ultrasounds; Contact-less system; Rotational laser vibrometry.