Residual Stress Measurements in Rails by Neutron Diffraction

Abstract

The relatively new technique of neutron strain scanning has several unique advantages over most traditional methods of measuring internal strains. It is non-destructive and, in principle, measurements can be made and repeated at any point in any direction within a sample. In practice its range of its application is limited in thick section samples, such as long lengths of rail, by neutron beam attenuation. In such cases it is often necessary to reach a compromise between what is ideally preferred by engineers for use in stress analysis calculations and what it is practical or economic to measure using the technique. Examples are given of how neutron strain scanning may be applied, in a cost effective manner, to the problem of the measurement of residual stresses in railway rails. Results are presented of representative longitudinal, transverse and vertical stresses measured down the centre-lines of rail sections and of stress contours measured in rail heads. The data are of sufficient quality and quantity to be used to validate theoretical calculations and reveal details of the residual stress distributions in rails not obtainable by other methods.