Characteristics of high-temperature equipment monitoring using dry-coupled ultrasonic waveguide transducers.

Dry-coupled ultrasonic waveguide transducers enable the long-term monitoring of the critical mechanical components working in high temperature environment. In these systems, waveguide units are applied to isolate the vulnerable piezoelectric elements from the harsh measurement zones. However, the disturbance cannot be overcome, which may arise from inevitably temperature fluctuation and the indirect measurement in long term monitoring. In the present research, a high temperature experimental system using dry-coupled ultrasonic waveguide transducers is investigated. The disturbances caused by this measurement system are studied in the heating period, holding period and cooling period, respectively. Moreover, the correlations between the group velocities, dispersion curves, signal amplitudes, waveforms under temperature variations are investigated. At last, the dispersion characteristics of the shear horizontal wave in high temperature stainless steel plate are analyzed. This work strives to pave a solid foundation for the application of SH waves to online monitoring of high-temperature equipment using dry-coupled ultrasonic waveguide transducers.