242. THERMAL STRESS AND BUCKLING DETECTION IN RAIL BY NON-DESTRUCTIVE ULTRASONIC TESTING

Department: Structural Engineering
Faculty Advisor(s): Francesco Lanza di Scalea
Award(s): Department Best Poster

Primary Student
Name: Claudio Nucera
Email: cnucera@ucsd.edu
Phone: 858-534-5279
Grad Year: 2012

Abstract
The use Continuous Welded Rail (CWR) has increased dramatically in the last decades because it reduces maintenance costs and, at the same time, increases life time of track components and the comfort of passengers. Compared to traditional jointed tracks, a critical feature of CWR is the almost total absence of expansion joints to accommodate seasonal thermal variations. This lack of joints and consequent rail thermal stresses can result in derailments because of buckling in hot weather (sun-kinks) and breakage in cold weather (pull-apart). These reasons emphasize the importance of collecting periodically reliable information on the level of stress acting in the rail to ensure safety of operation in CWR. In June 2008 the University of California, San Diego (UCSD), under the sponsorship of a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, began work to develop a technique for in-situ measurement of stress and detection of incipient buckling in CWR. The method under investigation is based on nonlinear features of ultrasonic guided waves. A large-scale full rail track (70 feet in length) has been constructed at UCSD?s Powell Structural Laboratories, the largest laboratories in the country for structural testing, to validate the CWR stress measurement and buckling detection technique under rail heating conditions well controlled in the laboratory. The results of these tests are expected to lead to the development of a prototype for NT/incipient buckling detection that can be used either in motion or in a stationary manner. The present work entails the description of the theoretical framework of nonlinear guided wave propagation in CWR and reports the results obtained from the aforementioned unique large-scale test track and from some nonlinear Finite Element simulations developed at UCSD to corroborate theoretical predictions and experimental findings.

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