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허인재(In Jae Heo),김진오(Jin Oh Kim) 한국소음진동공학회 2022 한국소음진동공학회 논문집 Vol.32 No.2
This study deals with the ultrasonic propagation characteristics according to the wall in a linear waveguide combined with an ultrasonic sensor for distance measurement. The purpose is to reduce the wall reflection by a rough surface because the wave reflecting on a smooth wall of the waveguide would interfere with straightly travelling wave. Wedges were designed on the waveguide wall. Ultrasonic wave propagation in a linear waveguide with the wedged wall was analyzed by finite elements, and the magnitude of the wave signals was evaluated according to the wedge angle for distance measurement. Experiments were carried out and the analysis results were verified by comparison. Wedge angle maximizing the wave signal magnitude was obtained.
백병주(Byung Ju Baek),허인재(In Jae Heo),김진오(Jin Oh Kim) 한국소음진동공학회 2021 한국소음진동공학회 논문집 Vol.31 No.3
This paper deals with the in-plane and out-of-plane vibrations of piezoelectric disc transducers, which are the main elements of ultrasonic sensors. In disc-type piezoelectric transducers, the fundamental mode is a radial mode, and the in-plane vibration of radial motion is coupled with the out-of-plane vibration of the axial motion. We developed an in-plane vibration theory, which was reported earlier, and theoretically analyzed the out-of-plane vibration and verified the theory by finite element analysis. We experimentally measured and compared the natural frequencies and verified the analysis results. In addition, we established a theoretical equation for the vibration distribution, which shows a bell-shape for the out-of-plane vibration in the thickness direction for the fundamental mode, as well as a theoretical equation of the natural frequency, which is inversely proportional to the radius.
안병호(Byeong Ho An),허인재(In Jae Heo),김진오(Jin Oh Kim) 한국소음진동공학회 2021 한국소음진동공학회 논문집 Vol.31 No.1
This paper describes a method to shorten the minimum detectable distance of an ultrasonic sensor in a liquid-level meter. The minimum detectable distance, which is limited by the number of ultrasonic transmission pulses and the ringing of the vibration plates in the sensor, needs to be shortened by an appropriate method. The purpose of this research is to improve the proximal measurement capability by combining the ultrasonic sensor for a liquid-level meter with a waveguide. Flat- and wedged-wall-type waveguides were designed and finite-element analysis was performed for ultrasound transmission and reception. Experiments were conducted for the distance and water level measurements by using the ultrasonic sensor combined with a waveguide. The results of the finite-element analysis and experiments showed that the wedged-wall-type waveguide produced reasonable measurements of the distance in the proximal range. We confirmed the improvement of the proximal-measurement capability of an ultrasonic level meter, thus shortening the minimum detectable distance by combination with a waveguide.
김령연(Ryeong Yeon Kim),허인재(In Jae Heo),김진오(Jin Oh Kim) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
This study deals with piezoelectric transducers of disc and ring types for an ultrasonic sensor, and compares the analyses results of vibration distributions. Since the directivity of ultrasound generated at an ultrasonic sensor depends on the uniformity of vibration distribution on a sensor housing disc, it is necessary to identify the vibration distribution in order to design a sensor with improved ultrasonic propagation performance. The vibration distributions of piezoelectric disc and ring transducers were compared on the basis of the theoretical and finite element analysis results. In the vibration distribution of the first mode the non-uniformity appeared 80% for a piezoelectric disc and 60% for a piezoelectric ring.