Ultrasound measurements of segmental temperature distribution in solids: Method and its high-temperature validation

• A new method for measuring the temperature distribution in solids is proposed.
• The method is non-invasive in pulse-echo implementation.
• It can be used to characterize a broad range of temperatures.
• The temperature distribution can be measured in real time.
• Suitable for use in extreme environments, in which conventional sensors fail.
• An attractive choice when probe insertion is undesirable, difficult, or impossible.

A novel approach that uses noninvasive ultrasound to measure the temperature distribution in solid materials is described and validated in high-temperature laboratory experiments. The approach utilizes an ultrasound propagation path with naturally occurring or purposefully introduced echogenic features that partially redirect the energy of an ultrasound excitation pulse back to the transducer, resulting in a train of echoes. Their time of flight depends on the velocity of ultrasound propagation, which changes with temperature distribution in different segments of the propagation path. We reconstruct segmental temperature distributions under different parameterizations. Several parameterizations are discussed, including piecewise constant and piecewise linear, and the parametrization that requires that the estimated temperature profile satisfies an appropriate heat conduction model. The experimental validation of the proposed approach with an alumina sample shows that even with simple parameterizations, the temperature profile is correctly captured with an accuracy that may be comparable to that of the traditional pointwise sensors. The advantages of the approach are discussed, including its suitability for real time and non-destructive temperature measurements in extreme environments and locations inaccessible to the traditional insertion sensors.