Abstract
Guided wave technique could be a possible method for monitoring components working in high temperature above 350 °C. However, this would require the design of an appropriate waveguide bar to transmit the wave, so that its sensing part is not influenced by the high temperature. In the present study, the shape of waveguide bars is designed based on the analysis of wave source characteristics. The critical frequency-width and frequency-thickness products of waveguide bars are analyzed theoretically and numerically to transmit the zeroth shear horizontal wave SH0* in bars. The results show that waveguide bars can cut off all the other wave modes when their frequency-thickness products are smaller than the critical value fd*, and frequency-width products are not smaller than the critical value fw*. Six waveguide bars are designed and fabricated based on the design criteria, and an experiment system is set up to check their work performance. The testing results indicate that the wave signals of the SH0* mode propagate clearly in waveguide bars, and cut off all the other modes when the frequency-thickness products and frequency-width products of the bars meet the design criteria. It is also demonstrated that the dependency of the experimental group velocity of each waveguide bar on frequency is in good agreement with the numerical result. High-temperature experiments also validate the reliability of the designed waveguide bars. Therefore, the critical frequency-thickness product and frequency-width product can be the basis for the design of the waveguide bars.
Highlights
High temperature components are applied comprehensively in aerospace and process industries.Many researchers have suggested that monitoring the structural health of components with permanently installed transducers is a useful way to maintain their safety [1,2,3,4,5,6,7,8,9]
In order to introduce ultrasonic wave technology into high-temperature components monitoring to improve their security, the waveguide bars have been designed to transmit the wave so that the to improve their security, the waveguide bars have been designed to transmit the wave so that the sensing part is not influenced by high temperature
According to wave source characteristics analysis, sensing part is not influenced by high temperature
Summary
High temperature components are applied comprehensively in aerospace and process industries. Many researchers have suggested that monitoring the structural health of components with permanently installed transducers is a useful way to maintain their safety [1,2,3,4,5,6,7,8,9]. The financial consequences of prolonged operational shutdowns have previously aroused strong interest in developing ultrasonic transducers that can operate at elevated temperatures above 350 ◦ C for a long time. Hou et al [11] have directly deposited thick piezo films onto high temperature structures. The attachment procedure for these transducers is intricate and time-consuming, requiring several deposition steps and subsequent poling to achieve robust attachment. None of them have achieved ideal results for high temperature longtime usage
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