A method of in situ measurement of an acoustoelastic constant (L) of a railway rail, using an ultrasonic wedge sensor to measure a stress-free (unloaded) time-of-flight (t.sub.0) in the vertical direction of the rail. Next, a vertical load of known load value is applied to the rail. While the vertical load is applied, the ultrasonic wedge sensor is used to measure a stressed time-of-flight value. The difference between the stress-free and the stressed time-of-flight is calculated to obtain a time-of-flight difference value (Δt). Based on the load value, the stress-free time-of-flight value, and the time-of-flight difference value, the acoustoelastic constant, L, may be calculated. The wedge sensor may be further used to measure the (stressed) horizontal time of flight, and a time-of-flight difference value in the horizontal direction may be used to measure longitudinal stress.
Xin Chen; Adam C. Cobb; Douglas R. Earnest; Keith A. Bartels