Stress-induced changes in the velocity of guided waves

This paper describes a series of experiments to evaluate the stress-induced changes in the wave speed (acousto-elastic effect) of guided waves. Pulsed ultrasonic waves having frequencies ranging from 0.1 to 5 MHz are introduced through variable wedges into rectangular bars machined from the head of railroad rail. The bars are stressed axially, in tension or compression, causing changes in the velocity of propagation of the various wave modes. The speed changes are measured by a pulse-overlay technique. Application to the measurement of longitudinal stress in rail is discussed.