Measurement of acoustoelastic and third-order elastic constants for rail steel

Measurements of the stress‐induced changes in ultrasonic wave speeds in several samples of steels typically used in railroad rails are presented. All of the five possible relative changes in wave speeds for an initially isotropic material subjected to a uniaxial state of stress have been determined and agree to within the limits of accuracy of the measurement with the second‐order theory of Hughes and Kelly. The third‐order elastic constants are calculated from the acoustoelastic data.