Continuous Welded Rail (CWR) practice is used in modern railroads to alleviate maintenance issues associated with joints and to improve ride quality. The absence of expansion joints, however, leads to long rail segments that are prone to the development of longitudinal thermal stresses that may cause track buckling, or rail pull-apart. A critical parameter in the susceptibility of the track to failure due to thermal loading is the Rail Neutral Temperature. This parameter is the temperature at which the rail is stress free. Rail stress management practices depend on the knowledge of the total net stress in the rail and the RNT. Current in-situ rail stress measurement techniques are destructive and disruptive of service. A new non contacting, nondestructive methodology is under development at the University of South Carolina for RNT and longitudinal stress measurements. The method is based on stereo vision image acquisition and Digital Image Correlation (DIC) for acquiring the full field shape, deformation and strain measurements taken during a thermal cycle. The thermal cycle can be natural or induced. This paper discusses the effects of the way the rail is heated on the RNT and stress measurements.

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