Reliability of rail transverse flaw detection by means of an embedded ultrasonic based device

Hajar Benzeroual,Alia Zakriti,Abdellatif Khamlichi,A Khamlichi

doi:10.1051/matecconf/201819100005

Hajar Benzeroual, Alia Zakriti + Show 2 more

Open Access

https://doi.org/10.1051/matecconf/201819100005

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Abstract

The main causes of train derailment are related to rail defects such as head surface defects, horizontal defects, vertical longitudinal split defects, star cracks at colt holes and diagonal crack in web. The most adverse form of these defects consists of transverse flaws that are either opened or internal. These flaws are developed generally in a plane which is orthogonal to the rail direction. Detection of these defects is essential in order to improve security of rail roads and to prevent catastrophic failures. Most of the inspection techniques of rails relay on eddy currents, electromagnetic induction and ultrasounds. Unlike some conventional inspection tests based on contact excitation probes that roll on the rail head, this work deals with theoretical analysis of an integrated contact-less system based on ultrasound waves. Generation of these waves was performed by using a non-ablative laser source. A rotational laser vibrometer was used to perform reception of the echoes. Through finite element modelling of the rail system under specific ultrasound excitation of the rail head, detection of transverse rail flaws was studied. Reliability of defect detection was then assessed by considering various sources of perturbations.

Highlights

Railways traffic is currently increasing and speed of modern trains is augmenting considerably
The amplitude of y-velocity at sensors locations (Si, i=1,2,3,4), as shown in Figure 3, was obtained at the time instant t f = 45ms. This was performed for both defect free rail and rail having a transverse like defect
Detection is based on variation of these amplitudes as the device crosses a defected zone

Summary

Introduction

Railways traffic is currently increasing and speed of modern trains is augmenting considerably. Maintenance of rails has become a major challenge in order to assure sufficient safety of this mean of transportation to the occurrence of accidents. This task requires preventing rail failure which is known to yield catastrophic derailments with lots of casualties and huge economic loss [1]. Ultrasonic waves are waves having the form of very short pulses that are generated at the rail surface [3] and centred on a chosen work frequency. These frequencies range from 0.1MHz up to 50MHz. Ultrasonic waves propagate in the rail structure under various dispersion patterns. When crossing an internal flaw, these waves produce echoes that can be sensed to determine some indications about the defect [4,5,6,7]

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