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

Abstract

It was reported several years ago that the coefficient, ∂ ln V/∂T of temperature dependence of ultrasonic velocity, varied with stress. Values reported for this variation, ∂2 ln V/∂T∂σ, 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 ∂ ln V/∂T, a quantity that can be measured with great precision and in a manner robust enough to warrant 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 vel...