The application of Long Range Ultrasonic Testing (LRUT) to inspect railway tracks Carmen Campos Castellanos Yousef Gharaibeh NDT Technology Group TWI
Contents MonitoRail Project overview Rail industry need and market potential Limitation of current inspection methods. Project challenges Long range ultrasonic testing (LRUT) The application of guided waves as an inspection technique. Previous work Deformation shape of guided waves. Investigation of different excitation conditions. Experimental trials Conclusion and Future work.
MonitoRail project overview MONITORAIL: Long range inspection and condition monitoring of rails using guided waves Partly funded by the FP7 programme (Research for the benefit of SMEs) over two years Project manager: Carmen Campos Castellanos -TWI Ltd Jackweld
Rail industry need & market potential Recent advances in inspection and NDT techniques have drastically reduced the incidence of rail breaks. However, a residual number of rail breaks still occurs Rail breaks England, Wales and Scotland (source: Network rail)
Limitations of the existing NDT techniques Limitation in terms of reliability of defect detection (e.g. internal defects) Inspection speed Maintenance is carried out in difficult conditions and often at night Inspection can be risky and dangerous operation Can not cover the whole section of the rail (constraints in detecting defects in the rail foot)
Current inspection method RSU Tyre 70 Degree Probe Coverage 37 Degree Probe Coverage 0 Degree Probes Coverage 0 Degree Probe 37 Fw Degree Probe 70 Rev G, C & F Degree Probes 70 Fw G, C & F Degree Probes 37 Rev Degree Probe
Limited defect sensitivity in the foot Possible Not Possible Not Possible Currently there is no method to detect foot defects other than those directly beneath the web of the rail. Detection of defects in the rail head and web will also be investigated in order to provide a cost effective solution.
Project objectives To inspect critical areas where the probability for defects is high and there is limited access to carry out the conventional NDT techniques. To inspect long lengths of rail track from a limited number of access points. To achieve full volumetric coverage of the rail. To develop a cost efficient technique for condition monitoring. To extend the life of the rail through early repairs of rail tracks.
Project challenges Accessibility Environmental conditions: Rain/snow Temperature -20 to 60 Celsius degrees. Interface to rail engineering/ operation staff Existing features on the rail attenuates the signal
LRUT- Ultrasonic Guided Waves 0 20 Hz 20 khz 1GHz Infra sound Audible sound Ultrasonic Hyper sonic Frequency Much lower frequency than conventional ultrasonics Equivalent to Lamb waves Use a wave guide - a regular cross section Complex due to large number of wavemodes
Conventional Vs LRUT Conventional Transducer Flange Localised Inspection Weld Metal loss Teletest Tool Metal loss Guided Wave Flange 100% Inspection Weld Metal loss Metal loss
Adopting Guided waves as Long Range Ultrasonic Inspection technique
Railway track cross sectional surface (BS113A) 69.9mm Head 35.9mm 158.75mm Web 86.7mm 11.11mm Foot 139.7mm
Dispersion Curves (modelling results) Y Gharaibeh, et all Investigation of the behaviour of selected ultrasonic guided wave modes to inspect rails for long-range testing and monitoring Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, pp. 225: 311 (2011)
Different possible wave modes for different sections in the railway track. Sole existence in each section in the railway track. Similar vibration patterns. Displacement in the entire section suggests 100% coverage of the cross sectional surface of the railway track. Y Gharaibeh, et all Investigation of the behaviour of selected ultrasonic guided wave modes to inspect rails for long-range testing and monitoring Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit, pp. 225: 311 (2011)
Wave mode characterisation (Dispersion Curves in the foot)
Wave mode (F7) characterisation Displacement distribution across the width of the foot of F7 wave mode Deformation shape of the F7 wave mode
Wave mode (F4) characterisation Displacement distribution across the width of the foot of F4 wave mode Deformation shape of the F4 wave mode
Wave mode (F2) characterisation Displacement distribution across the width of the foot of F2 wave mode Deformation shape of the F2 wave mode
Investigating different excitation conditions
Excitation of F2 scenario 1
Excitation of F2 scenario 2
Excitation of F2 scenario 3
Experimental trials TWI rail feature free Birmingham University rail features: weld and clips
TWI sample -Transducer arrangement
Surface preparation and Sensor attachment
Defect addition
Defect detection sensitivity Time Domain Signal 6 5 Amplitude (mv) 4 3 2 Dead Zone 1 0 0 300 500 1,000 1,500 2,000 2,500 3,000 Time (us) (a) 6 Time Domain Signal Amplitude (mv) 5 4 3 2 Dead Zone defect 2mm 1 0 0 300 500 1,000 1,500 2,000 2,500 3,000 Time (us) (b) 6 Time Domain Signal Amplitude (mv) 5 4 3 2 Dead Zone defect 4mm 1 0 0 300 500 1,000 1,500 2,000 2,500 3,000 Time (us)
Birmingham University rail sample
Work plan To determine the effect in the wave mode propagation caused by common rail features such as clips and welds. To identify responses due to the rail features and to monitor the signal over time in order to detect any significant change over time that might indicate the presence of a defect. This work is still in progress.
Conclusion The characteristics of ultrasonic guided waves in the rail complex geometrical profile have been identified A suitable wave mode with full volumetric coverage in has been identified for each section of the rail. F2 has been selected as the wave mode most suitable to inspect the foot An improved excitation/reception conditions has been proposed. Defect detection sensitivity test have been conducted Experimental validations of the models are in progress
Future work Improving of the quality of the propagated wave by using: Minimise coherent noise. Apply phase delay. Apply signal weighting technique. Enhanced signal to noise ratio. Further experimental validations using Railway track with feature free specimen Railway track with clamps mounted on the specimen. Further signal processing analysis is needed. Investigate exisiting wave modes in the rail head with respect to the problem definition.
MONITORAIL acknowledgement MONITORAIL is collaboration between the following organisations: TWI Ltd, Vermon SA, OpenPattern, Aerosoft S.p.A, Jackweld Ltd, Network Rail Infrastructure Ltd, Cereteth and Brunel University. The Project is co-ordinated and managed by TWI Ltd. and is partly funded by the EC under the Collaborative project programme- Research for SMEs & Research for SME Associations. Grant Agreement Number. 26219. Jackweld
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