| Summary: | 碩士 === 長庚大學 === 機械工程研究所 === 88 === The main purpose of this study is to fulfill the need for a real-time testing method at the elevated temperature to improve efficiency and to reduce cost saving of the production process. In this study a set of instrument was designed to protect the ultrasonic transducer from any damage by the heat from the heated surroundings and to provide a medium for propagation of ultrasonic waves. Through this medium the ultrasonic waves produced by the transducer can propagate to the heated specimens and the nondestructive ultrasonic testing (UT) can be carried out.
In this study, a water-coupling method was successfully developed to protect the transducer from the heat conducted from the specimens which were heated to temperature as high as 250oC. By using commonly used industrial ultrasonic devices, defects deep inside the heated steel plates were readily detected. In designing the water-coupling device, the convenience and practicability in field testing was also considered. The result of this study not only can significantly reduce construction cost and production time, but also provide a novel and feasible technique to conduct UT to specimens at the elevated temperature. This study has effectively improved the signal-to-noise ratio. When a side-drilled hole 3mm in diameter in a steel plate was tested, S/N ratio was 4.3 when the wave propagation path was 141.4 mm. The maximum wave propagation path to clearly detect the aforementioned as long as was192.3 mm and the S/N ratio was 2.2.
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