Traditionally, railroad track is installed so that rails that are welded together into strings longer than 400 feet experience no longitudinal thermal force at rail temperatures of 90 to 115 degrees °F. This rail temperature at which the thermal force is zero is commonly referred to as the rail's neutral temperature. Rail at temperatures higher than the neutral temperature are in a state of compression, and in cooler temperatures are in tension. Except for the textbook case of a perfectly straight rail, these longitudinal forces must be reacted along the length of the rail via friction and the rail fasteners. A new device is designed to exploit changes in vibration of the rails within these fastenings and yield a non-destructive estimate of the installed neutral temperature. This paper will report on various on-track tests conducted at the Transportation Technology Center, Inc. (TTCI) in Pueblo, CO. This behavior was first noted empirically, without a background engineering mechanics outline. Similarly, this paper will follow the same evolution. After presentation of test data, engineering explanations will follow using theory and mechanical modeling.
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