Guided Wave Propagation as a Measure of Axial Loads in Rails

Guided wave propagation has been proposed as a means to monitor the axial loads in continuously welded railway rails although no practical system has been developed. In this paper, the influence of axial load on the guided wave propagation characteristics was analyzed using the semi-analytical finite element method, extended to include axial loads. Forty modes of propagation were analyzed up to a maximum frequency of 100 kHz. The sensitivity of the modes to axial load or changes in elastic modulus was formulated analytically and computed. In practice, by using separation of signals in time it would only be possible to separate the mode with the greatest group velocity over a reasonable distance. It was found that the influence of axial load on the wavelength of such a mode should be measureable. However, the influence of changes in the elastic modulus due to temperature is expected to be an order of magnitude larger. In order to develop a practical measurement technique it would be necessary to eliminate or compensate for this and other influences.