Temperature dependence of ultrasonic velocity using diffuse fields; Implications for measurement of stress

It was reported several years ago that the coefficient, partial derivative InV / partial derivativeT of temperature dependence of ultrasonic velocity, varied with stress. Values reported for this variation, partial derivative (2) InV / partial derivativeT partial derivative sigma, were sufficiently large to suggest that the effect could be used for the nondestructive inference of stress. The precision required was, however, prohibitive. Here we report measurements of a quantity equivalent to partial derivative InV/partial derivativeT, a quantity that can be measured with great precision and in a manner robust enough to wan-ant revisiting the issue. We show that the temperature dependence of ultrasonic velocity manifests in diffuse fields as signal dilation or compression. Because signals have enormous ages (up to 100 msec in some cases, corresponding to travel distances of hundreds of meters) and because shifts may be measured to within nanoseconds, variations with temperature may be quantified with high precision. Signals are found to dilate in accord with prior estimates based on the known temperature dependence of ultrasonic velocities. Signals are found to distort in accord with the known difference in the temperature dependence of longitudinal and shear waves. The dilation was found, however, to be independent of applied stress; we have not been able to replicate the large coefficients partial derivative (2) InV / partial derivativeT partial derivative sigma reported elsewhere.