01206828

Component

http://www.trb.org/Publications/Blurbs/163903.aspx

In an effort to overcome some of the issues associated with ultrasonic wheel inspections, some research groups, including the University of California, San Diego (UCSD), are investigating ultrasonic guided waves for rail inspections. There are several reasons for this. First, guided waves propagate along, rather than across the rail, and are thus ideal for detecting the critical transverse defects (TDs). Second, guided waves increase the inspection coverage (length of rail inspected at once) thereby relaxing limits on the achievable speed. Third, since guided waves penetrate a finite depth of the rail surface, they can travel underneath shelling and still interact with internal defects allowing for their detection. Fourth, since guided waves travel in the mid-frequency range, between 20 kHz and 1 MHz, they can penetrate alumino-thermic welds, hence potentially targeting weld cracks/discontinuities. The advantages of guided waves come with the difficulty in managing their complicated propagation behavior. UCSD has utilized a semianalytical finite element (SAFE) method that combines theoretical and numerical formulations to allow the study of high-frequency guided waves in rails in a computationally efficient manner. These studies have allowed an optimized design of the rail defect detection prototype. The UCSD/FRA prototype uses non-contact means of generating and detecting the guided waves in the rail. The solution of choice is a combination of laser and air-coupled sensors, which were first proposed in 2000 for noncontact rail probing. The prototype also uses a statistical pattern recognition algorithm for detecting and classifying defects. The uniqueness of this algorithm is that it does not require previous knowledge of defects (i.e. it does not require a “training” phase as in neural network-based classificators), and it is hence very practical. This algorithm was successfully tested in the field with excellent results. This paper describes first SAFE models of guided waves in rails. It then discusses the status of the UCSD/FRA rail defect detection prototype including the results of the last field tests performed in March 2008.

01206823

English

pp 285-296

2010-7

Transportation Research Circular

Joint International Light Rail Conference: Growth and Renewal

Web

Figures (5) ; Photos (3) ; References (17) ; Tables (1)

Algorithms; Defects; Field tests; Flaw detection; Inspection; Maintenance of way; Pattern recognition systems; Prototypes; Railroad tracks; Ultrasonic waves

Guided wave inspection

Maintenance and Preservation; Public Transportation; Railroads; Terminals and Facilities; I22: Design of Pavements, Railways and Guideways

TRIS, TRB

Oct 7 2010 3:40PM

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