• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.137-146
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• 2019

The ultrasonic phased arrays are used for treating tumors in the human body by the focus control of the acoustic pressure at the desired position. The magnitude and phase of the surface acoustic pressure in each ultrasonic transducer is controlled by the magnitude and phase of the applied voltage to it. In this paper, the relationship between the applied voltage and the surface acoustic pressure of the ultrasound transducer is modelled, and the desired voltage is realized by PWM technique. The validity of the proposed method is verified by computer simulation of the focus control of a ultrasonic phased array composed of 61 ultrasonic transducers.

• Journal of Applied Reliability
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• v.17 no.3
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• pp.236-245
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• 2017

Purpose: There is no established inspection system for composite wind blade during the fabrication stage even though the blades are one of the most important part at wind generation system, but phased array ultrasonic testing method has been continuously studied about wind turbine blade with composite. When wind turbine blade with complex shape by phased array probe is inspected, it is necessary to study for system keeping constant pressure using pressure device. Methods: In this paper, we propose constant pressure device for inspecting wind turbine blade by phased array ultrasonic test method. Design of the device controller is based on Hunt-Crossley model. We evaluate reliability of phased array ultrasonic inspection result that applicated constant pressure device. Result: Defect indication is precise and its error is small when constant pressure mechanism based on Hunt-Crossley model was used. Conclusion: When inspection is progressed using constant pressure mechanism, the reliability of composite wind blade inspection can be improved.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.231-234
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• 2002

Ultrasonic machining technology has been developed over recent years for the manufacture of cost-effective and quality-assured precision parts for several industrial application such as optics, semiconductors, aerospace, and automobile. Ultrasonic machining process is an efficient and economical means of precision machining of ceramic materials. The process is non-thermal, non-chemical and non-electric and hardly creates changes to the mechanical properties of the brittle materials machined. This paper describes the characteristics of the micro-hole of $\textrm{Al}_2\textrm{O}_3$ by ultrasonic machining with tungsten carbide tool. The effects of various parameters of ultrasonic machining, including abrasives, machining force and pressure, on the material removal rate, hole quality, and tool wear presented and discussed. The ultrasonic Machining of micro-holes in ceramics has been under taken and the machining mechanism in the ultrasonic machining of ceramics based on the fracture-mechanics concept has been analyzed.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.9 no.1
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• pp.25-30
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• 2013

The periodic inspection of piping and pressure vessels welds in nuclear power plant has to provide reliable result related to weld flaws, such as location, maximum amplitude response, ultrasonic length, height and finally the nature or flaw pattern. The founded flaw in ultrasonic inspection is accepted or rejected based on these data. Specially, the amplitude of flaw response is used as basic parameter for flaw sizing and it may cause some deviation in length sizing result. Currently the ultrasonic inspections in nuclear power plant components are performed by specific inspection procedure which describing inspection technique include inspection system, calibration methodology and flaw characterizing. To perform ultrasonic inspection during in-service inspection, reference gain should be established before starting ultrasonic inspection by the requirement of ASME code. This reference gain used as basic criteria to evaluate flaw sizing. Sometimes, a little difference in establishing reference gain between calibration and field condition can lead to deviation in flaw sizing. Due to this difference, the inspection result may cause flaw sizing error. Therefore, the objective of this study is to compare and evaluate the ultrasonic amplitude difference between air filled and water filled pipe in nuclear power plant. Additionally, the accuracy of flaw sizing is estimated by comparing both conditions.

• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.578-595
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• 2020

Submarine pressure hulls must withstand high hydraulic pressure and be free of defects. To improve the precision of defect detection, we herein examined different probes for optimal defect assessment by applying the Phased Array Ultrasonic Testing (PAUT) method. Two sets of probe design parameters were selected by considering pressure hull characteristics and analyzed through modeling. PAUT probes were applied, and defect assessment results were compared based on ultrasonic signals of various simulated defects in specimens designed to be the same as actual pressure hulls. The final selected design parameters for the submarine probe, which were designed to minimize the grating lobe of wave interference effect and improve the ultrasonic resolution of pressure hull welds, were identified through the experiment. The improvement in the probe's ability to detect defects in a pressure hull was verified. Furthermore, the accuracy of defect length measurement was improved, enhancing the applicability of the technique.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.5 no.1
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• pp.20-24
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• 2009

There is extensive tubing pipe in the nuclear power plant under high temperature and pressure. Erosion and corrosion defects are expected on this tubing pipe due to environmental and mechanical factors. In this study, Guided Ultrasonic Wave technique was applied to detect defects. The technique explores the advantages of the Guided Ultrasonic Wave method that inspects along the wall of the pipe and can travel long distances, providing rapid collection of data. This paper presents a case study of the Guided Ultrasonic Wave testing of 3/8" tubing pipe. This study offers to understand detected signals through correlation between amplitude and depth of defects.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.4
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• pp.41-47
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• 2000

In this study, the purpose finds out the best welding conditions for bonding of electric wire by ultrasonic welding. The material was plastic-insulating low-voltage-cabels for automobiles. The experiment varied the values of welding time and welding pressure and fixed the values of amplitude and energy. With the facts, the best condition for ultrasonic welding to achieve bonding exactly is gained according to the size of the cross-sectional area of the cable, and the adhesive intensity is greatly influenced by the variables of welding time and welding pressure. Also when the welding time and welding time and welding pressure increase as the cross-sectional areas of the cable increase the welding result in gained exactly.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.121.1-121.1
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• 2014

Recently, much attention has been given to plasma production under liquid and its applications [1]. However, most of plasma production techniques reported so far utilize high voltage dc, ac, rf or microwave power [2], where damage to discharge electrodes and small discharge volume are remained issues. As an alternative of plasma production method under liquid, we have proposed pulsed microwave excited plasma using slot antenna, where damage to the slot electrode can be minimized and plasma volume can be increased. We have also reported improvement of treatment efficiency with use of reduced-pressure condition during the discharge [3]. To realize low pressure conditions in liquid, various alternative technique can be considered. One possible technique is simultaneous injection of microwave power and ultrasonic wave. Ultrasonic wave induces pressure fluctuation with the wave propagation and is so far used for cavitation production in the water. We propose utilization of reduced pressure induced by ultrasonic cavitation for improvement of the plasma production. Correlation between the plasma production and the ultrasonic power will be discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1229-1237
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• 2003

The production of hydrogen fuel depends basically on the water electrolysis. The ultrasonic effects the decrease of the overpotential in a water electrolysis. A study on the overpotential which activates the hydrogen production is the core to elevate the hydrogen production efficiency on the principle. A pressure sensor system by a new idea is developed and applied. Solutions are 4 kinds of KOH concentration such as 0%, 10%, 20%, and 30%. Two frequency bands of the ultrasonic transducer are 28kHz and 2MHz. The directions of ultrasonic forcing are the vertical direction and the horizontal direction. The temperatures are two states, i.e., no constant and constant. Experiments are carried out sequentially in order in three cases of no ultrasonic forcing, ultrasonic forcing, and ultrasonic discontinution. In results, it is clarified that the ultrasonic effects the decrease of overpotential to elevate the efficiency of hydrogen production.

• The Journal of the Acoustical Society of Korea
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• v.29 no.2
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• pp.91-96
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• 2010

To improve the limit of efficiency of squeezing oil in a conventional method, which seeds are compressed simply, the adoptability of the additional energy by the ultrasonic wave was investigated experimentally. As the results, using the ultrasonic vibration from the Langevin-type transducer, the efficiency was increased up to 25 %, whereas the conventional method has 15% efficiency. To investigate the additional pressure by the ultrasonic wave, the acoustic impedance of the sample and the vibration velocity of the transducer were measured. Although the amplitude of the ultrasonic is about 2.8 % of the compression pressure, the efficiency is increased a lot as mentioned above because the pressure is changed according to ultrasonic period.