A Novel Method for Estimating the Neutral Temperature of Continuously Welded Rail

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.