Abstract
On railroad tracks, in order to improve a riding comfortability and a noise suppression, the introduction of long rail is advanced in recent years. However, because a long rail is concluded on the long section, the elasticity of the rail accompanying a temperature change is restrained and consequently an axial stress generates. In case of the big axial stress, there is a possibility of causing a buckling and a tension fracture in railroad rail. In this study, we carried out the basic examination for applying a surface SH-wave acoustoelastic method to the stress measurement as an axial stress management of railroad long rails. This method is able to measure the stress of metallic materials nondestructively, even if the initial value, an acoustic anisotropy by the texture, is unknown. A T-type surface SH-wave sensor was improved for the railroad rail and the residual stress measurement in a 50 kgN rail being used for long rails of conventional lines was tried. As the result, it was demonstrated that this sensor was able to measure the residual stress nondestructively by comparing with a strain gage testing. Moreover, in order to measure the axial stress of a long rail, the side of head of the rail has been found out as a suitable measurement point which is unaffected by residual stress. On the other hand, considering the effect of thickness of the rail, it was found that the axial stress in a railroad long rail would be able to measure accurately by compensating acoustoelasticity coefficient.
