Ultrasonic studies of anisotropy in cold-worked layer of used rail

Abstract

The upper 3–5 mm of rail becomes severely cold worked with the regular passage of trains. Previous work has shown that the shear wave velocity in this upper layer is actually reduced by ∼ 10%. One of the most likely sources of this velocity reduction is the presence of a material texture in the upper region. In order to investigate the wave propagation properties of this upper region, several wafers of material, ∼ 4 mm thick, were removed from used and new rail. These wafers were removed from positions at different orientations relative to the longitudinal axis of the rail. Each wafer was secured in a device that permitted a 350° rotation of a pair of shear wave transducers propagating through the thickness of the samples. Transducer centre frequencies were above 10 MHz. The observed shear wave velocity change is compared to predicted changes for several textures observed in steel. A pattern exists indicating that a texture does exist in the cold-worked layer. Steel used for rail normally has a carbon content of 0·67–0·82%.