Technical Reports

On-line High-speed Rail Defect Detection

  • 01
  • Oct
  • 2004
AUTHOR: F. Lanza di Scalea, I. Bartoli, P. Rizzo, and J. McNamara
KEYWORDS: Transverse cracks, ultrasonic guided waves, non-contact ultrasonic testing, laser ultrasonics, air-coupled sensors, continuous Wavelet transform, discrete Wavelet transform, signal de-noising, Finite Element Modeling, automatic defect classification
ABSTRACT: This report presents the results of phase 2 of the project “On-line high-speed rail defect detection” aimed at improving the reliability and the speed of current defect detection in rails. Ultrasonic guided waves, traveling in the rail running direction, were examined for this task. The advantages of this approach include: the inherent sensitivity to transverse-type cracks even in the presence of surface shells , the potential for extremely high testing speed, and the ease of field deployment since the sensors can be positioned at distances as far as 3.5 inches from the rail surface. Two methods of implementation were investigated. The first method used an impact hammer for wave generation and air-coupled sensors for wave detection. This setup proved effective for detecting “large” (>15% H.A.) transverse cracks at frequencies below 50 kHz. The second method used a pulsed laser for wave generation. This setup proved effective for detecting “small” (<15% H.A.) transverse surface-breaking cracks as shallow as 1 mm at frequencies between 100 kHz and 600 kHz. The inspection ranges (distance covered in one test) were substantially larger than current methods.
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