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11 June 2002 Advances in health monitoring of railroad tracks
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Air-coupled ultrasonic testing is gaining increasing attention in a variety of NDE applications that can benefit from non-contact probing and ease of transducer positioning. The main focus of this paper is the assessment of an air- coupled ultrasonic method for the inspection of railroad tracks focusing on the detection of internal defects. It is shown that resonant standing waves can be successfully generated in the rail cross-section to alleviate the challenges associated with the large acoustic impedance mismatch between air and steel. The effectiveness of the resonance concept is demonstrated in through-transmission laboratory testing of the rail head, web and head flange aimed at the detection of longitudinal defects. A pitch- catch configuration potentially effective for the detection of transverse defects in the head flange is also demonstrated. The suitability of the air-coupled ultrasonic method for field use is discussed with particular attention to the achievable inspection speed. Feasibility results are also presented from the measurement of flexural (guided) vibrations in rails. These vibrations propagate long distances and could therefore be well-suited for long-range testing.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
John D. McNamara and Francesco Lanza di Scalea "Advances in health monitoring of railroad tracks", Proc. SPIE 4702, Smart Nondestructive Evaluation for Health Monitoring of Structural and Biological Systems, (11 June 2002);

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