Figure 5. LURI software. The defect type UIC 213 is identified in one of the rail sections. Results obtained with P-scan Lite: A battery-operated system based on contact transducers was additionally developed for rail inspection. The system consists of a standard ultrasonic P-scan Lite  system mounted on a flexible rail car. The main advantage of this system is its four channels to acquire ultrasonic data and its relative low weight. Results from a rail piece with small artificial flaws are shown in Fig. 6. Several defects are seen in the figure. The uppermost signal identifies a crack in a bolthole (UIC 235), and below a horizontal flaw (UIC 232) in the web at 85 mm depth is seen clearly. Finally a flaw in the head (UIC 212) at 20 mm depth is displayed by a cross-mark.
Figure 6. P-scan Lite for rail inspection.
Conclusion: An automatic Laser Ultrasonic system for Rail Inspection (LURI) has been developed and tested on a railroad line containing man-made structural defects. LURI is mounted on a specially designed railroad vehicle and allows detection of defects on the running surface of the rail, as well as horizontal and vertical flaws in the railhead. At present, LURI provides rail integrity information up to speed of 40 km/h (25 mph) interrogating both the running surface and the body of the head of the rail. Several critical rail defects were found and identified during the field test of the LURI-system. The results of the test confirm appropriateness of the developed concept of rail flaw detection and open up possibilities for further development.
Acknowledgements: The authors would like to thank Banedanmark for consultations and help in carrying out the field tests of the LURI system.