Maintenance is a vital part of the system approach: appropriate and timely maintenance forms an integral part of the system approach that needs to be adopted by railways if they are to meet the demanding challenges being put upon them

International Railway Journal, Sept, 2005 by Jay Jaiswal

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The need to assess accurately the internal propagation of RCF cracks led to the development of variants of eddy-current-based techniques that measure the penehated length of crack. However, the complexity of the crack network makes accurate measurement difficult.

Although train-mounted eddy current systems are being evaluated in Germany, their accuracy for detection and measurement of RCF cracks has yet to be demonstrated. Furthermore, such techniques do not necessarily capture all the characteristics of RCF cracks such as their linear density and angle, and the position of initiation on the head in relationship to primary running bands.

Train-borne track inspection has until recently been restricted to ultrasonic testing and measurement of track geometry. The recent introduction of the New Measurement Train (NMT) by Network Rail (NR), Britain, and Archimede by Italian Rail Network (RFI) represent a significant technical advance as they incorporate laser measurement of rail profile and video imaging of the rail and track components. Research is being undertaken by Corus, Oxford Lasers, and University of Exeter (with guidance from NR, Heathrow Express, and London Underground and part financial support from the British government), to enable an objective and consistent assessment of the rail-wheel contact band and visible rail head defects such as RCF cracks through innovative image acquisition and Intelligent Image Analysis (IIA).

A reliable inspection technique is needed to monitor parameters related to the rail-wheel interface to enable informed decisions for renewal and maintenance. This would help to reduce the very high cost of managing RCF.

Vast quantities of video data are now being collected on several European networks, but resolution is not sufficient to resolve RCF cracks and none of the systems address motion blur adequately. Furthermore, analysis of the data is restricted to either visual assessment or the use of basic image analysis techniques based on comparison with standard images. Although such techniques will identify the overall maintenance work requirements, the real benefits will come from a deeper analysis of the data from the whole network to extract trends and correlations between asset condition and track and traffic characteristics.

The project should create a step change in the cost-effective inspection of the rail head condition with increased safety. It aims to deliver:

* an enhanced image acquisition system using pulsed laser illumination technology to eliminate motion blur and thereby resolve features such as RCF cracks

* IIA techniques using standard software capable of rapid off-line processing will provide a cost-effective way of conducting reliable and consistent analysis of vast quantities of inspection data

* measurements of key features of rail-wheel contact, such as variation in the width and location of the running bands and the size, angle, distribution and frequency of RCF cracks, which will improve the understanding of track degradation and provide earlier warnings for appropriate planned maintenance intervention, and a significant cost saving by minimising manual inspection and eliminating erroneous placement of emergency speed restrictions or rail renewal.