| ABSTRACT: | LONG RANGE INSPECTION OF RAIL USING GUIDED WAVES Ð FIELD EXPERIENCE
P Cawley1, MJS Lowe1, B Pavlakovic2, M Evans2, K Vine2, and P Wilcox2
1Department of Mechanical Engineering, Imperial College, London United Kingdom; 2Guided Ultrasonics
Ltd, Ravenshead, Nottingham United Kingdom
Ultrasonic techniques have been used for many years for the inspection of rail. These measurements can
detect the presence of a wide variety of defects but there are practical difficulties with the technology. While
large transverse cracks of the type likely to cause catastrophic failure can be detected, the large, critical
defects can be masked by large numbers of small, surface defects along the length of the rail. It would be
very useful to be able to determine reliably the largest defect size in a length of rail. Also alumino-thermic
welds are difficult to inspect due to the typical defect orientation and the attenuation of the weld material.
Guided waves provide a very attractive solution to these problems; they travel along the rail, for tens or
hundreds of metres, and are partially reflected by any defects which are present. They are particularly
sensitive to vertical defects and they are used at relatively low frequency so they are not significantly
attenuated by weld material. The authors have developed a practical inspection tool based on guided wave
measurements. This paper presents the results of laboratory measurements backed up by finite element
predictions of reflections from different features. This is followed by the results of a set of field trials
covering the inspection of plain rail and features such as alumino-thermic and flash butt welds, level
crossings and switch blades.
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