The most important inspection of any rail is visual inspection that is increasingly being replaced by automated vision techniques (cameras). A fundamental challenge is to detect failed track components and rail defects automatically from the captured images. These methods do not apply for non visible rail that is embedded in the street or in a concrete track bed. This is the motivation to develop techniques that are able to detect rail defects that are not visible (internal or covered by the rail embedment material). Therefore, this paper presents a novel non-destructive technique for the assessment of the structural integrity of embedded girder rails. More specifically, the focus lies on the detection of rail foot corrosion. The developed technique is based on the measurement of the vibration response up to a frequency of 120 kHz, upon impact excitation of the rail. The advantage of high-frequency analysis is that the high-frequency range is relatively unaffected by global properties of the system, but rather by the presence of small defects and local changes in the geometry. Measurements on rail samples with different extents of corrosion have been tested in a laboratory environment. The measurements indicate that rail foot corrosion increases the damping of the measured response signal. Based on these results, three analysis techniques for rail foot corrosion detection are proposed; resonant peak count, damping ratio determination and cepstrum analysis. In a second phase, measurements on an operation tramway network are performed to translate the results obtained on rail samples to an actual situation with rails embedded in the pavement. Although the embedment significantly influences the measured response, it is demonstrated that using the three analysis techniques it is possible to distinguish between three grades of rail foot corrosion; no/light corrosion, corrosion and heavy corrosion.
A non-destructive high-frequency technique for internal structural integrity assessment of embedded girder rails
2012
14 Seiten, 14 Bilder, 4 Quellen
Conference paper
English
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