In both high speed and freight rail systems, the modern construction method is Continuous Welded Rail (CWR). The purpose of the CWR method is to eliminate joints in order to reduce the maintenance costs for both the rails and the rolling stock. However, the elimination of the joints increases the risk of rail breakage in cold weather and buckling in hot weather. In order to predict the temperature at which the rail will break or buckle, it is critical to have knowledge of the temperature at which the rail is stress free, namely the rail Neutral Temperature. The University of California at San Diego (UCSD) has developed an innovative technique based on non-linear ultrasonic guided waves, under Federal Railroad Administration (FRA) research and development grants for the non-destructive measurement of the Neutral Temperature of CWR. Through the licensing of this technology from UCSD and under the sponsorship of the FRA Office of Research and Development, a field deployable prototype system has been developed and recently field-tested at cooperating railroad properties. Three prototype systems have been deployed to the Burlington Northern Santa Fe (BNSF), AMTRAK, and the Union Pacific (UP) railroads for field testing and related data acquisition for a comprehensive evaluation, with respect to both performance and economy of operation. This paper summarizes the results of these field tests, as compared to well-established techniques such as VERSE and strain gages.

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