Coupling pressure of an ultrasonic transducer excitation under the action of a loading device.

Ultrasonic thermal excitation can be regulated by coupling pressure conditions that indirectly influence the excitation effect. This study evaluated the effects of coupling pressure conditions on concrete microcracks detection through ultrasonic thermal excitation testing. Concrete microcracks were subjected to coupling tests, and two coupling pressure conditions were applied to the stimulation. A finite element simulation model was used to quantify the coupling pressure excitation, and the differences in temperature rises due to the coupling pressure conditions were analyzed. The study indicates the addition fluctuations in coupling pressure under the direct loading excitation could be neglected; while the coupling pressure increases by about 53% under the aluminum alloy sleeve loading excitation, and the fluctuation increases with the initial coupling pressure. The excitation effects of the tests are influenced by the coupling pressure condition, which will be weak if the perturbation of coupling pressure is great and changes drastically. Analysis suggests the drastically varying coupling pressure leads to substantial changes in the transducer's equivalent resistance and the output efficiency of the piezoelectric transducer decreases. It emphasizes the importance of controlling the perturbation of coupling pressure and provides research ideas to enhance the detection efficiency. [ABSTRACT FROM AUTHOR]