• Journal of Welding and Joining
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• 제19권1호
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• pp.40-48
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• 2001

An ultrasonic test method, as a nondestructive test is applied to ensure the clad interface quality assessment. According to the reference codes and standards, not only korea Industrial Standard(KS) but also American Society for Testing and Materials (ASTM) Standard, ultrasonic examination procedures use the pulse-echo, A-scan, back reflection signal drop method and/or side drilled reference hole used to establish the acceptance criteria of clad material test. But the variety of bonding materials and sizes makes it difficult to produce the reference blocks, or thus the criteria. In order to overcome these practical difficulties, new ultrasonic testing criterion is suggested. In this new method, the theoretical interface reflection signal amplitude level is calculated and suggested as an acceptance criteria with the back reflection signal set to 100% FSH(Full Screen Height) which is based on acoustic impedance mismatch at the clad interface for the explosive clad ultrasonic inspection. Applicability of suggested criterion, for the explosive clad Fe-Naval Brass with different bonding quality is confirmed to the pre-existed KS and ASTM specifications and verified by using SEM (Seanning Electron Microscope) micrograph. The results obtained by the suggested method is more conservative than the results according to the KS B 0234 and ASTM A 578 specifications The suggested method could be applicable to any other combination of explosive clad ultrasonic inspection.

• 제어로봇시스템학회논문지
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• 제9권9호
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• pp.707-713
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• 2003

We investigate the ultrasonic gas flow meter for the measurement of gas volume quantity, which passing through pipe, using the transit time difference method. We have designed a receiving system of an ultrasonic signal and hardware system of a flow meter Also, we have designed an experimental system for the characteristic test and calibration of a gas flow meter system. We have developed an ultrasonic gas flow meter, which has a measurement uncertainty within $\pm$ 1.7 %. For the test, we have compared our system with a difference pressure type flow meter for a few months in the real field. Through the test, we have confirmed that our system have a good reliability and durability. Also, we have confirmed that our system follows very well the variation of gas volume quantity, which was measured by a difference pressure type flow meter.

• Nuclear Engineering and Technology
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• 제36권1호
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• pp.12-23
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• 2004

In the present study a new measurement technique has been developed, which uses an ultrasonic transmission signal in order to identify the vertical two phase flow pattern. The ultrasonic measurement system developed in the present study not only provides the information required for the identification of vertical two phase flow patterns but also makes real time identification possible. Various vertical two phase flow patterns such as bubbly, slug, churn, annular flow etc. have been accurately identified with the present ultrasonic measurement system under atmospheric condition. In addition, the present test apparatus can practically simulate the ultrasonic propagation characteristics under high temperature and high pressure systems. Therefore, it is expected that the present ultrasonic flow pattern identification technique could be applicable to the vertical two phase flow systems under high temperature and high pressure conditions.

• 전자공학회논문지SC
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• 제43권4호
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• pp.60-66
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• 2006

장비를 사용해서 해양자원을 탐사하고 개발하기 위해서 수중초음파 통신은 유용한 수단이 된다. 이러한 응용을 위해서는 정보전달 및 원격제어가 필수적인데, 해양환경에서 다양한 형태의 노이즈가 발생하여 제어의 효율성과 수중통신의 신뢰성이 저하 되고 있다. 그래서 기존의 방법은 하드웨어적인 방법으로 제어정보를 수신하고 이를 반복적으로 기준 정보와 비교하는 방법을 사용하고 있어 제어신뢰성이 중요시되는 시스템에서는 효율성이 떨어지고 있다. 따라서 본 연구에서는 해양환경 변화에 따른 영향이 없이 초음파 신호를 인식할 수 있는 수중 초음파신호 검출성능 향상 알고리듬을 제안하려 한다. 제안하는 알고리듬의 적합성을 시뮬레이션을 통하여 확인하였다.

• Journal of Biosystems Engineering
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• 제38권3호
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• pp.192-198
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• 2013

Purpose: Methods for non-destructive estimation of product quality have been reported in various industrial fields, but the application of ultrasonic techniques for the agricultural products of potatoes, pears, apples, watermelons, kiwis and tomatoes etc. have been rarely reported since the application of a contact-type ultrasonic transducer in agricultural products is very difficult. Therefore, this study sought to determine the firmness of apples using non-contact ultrasonic techniques. Methods: For this experiment, an ultrasonic experimental tester using a non-contact ultrasonic transducer was created, and a signal processing program was used to analyze the acquired ultrasonic reflected signal. Also, a universal testing machine was used to measure firmness parameters of the apples such as bioyield strength, a firmness factor, after the ultrasonic tests had been performed. Results: Six distance correction factors were calculated to obtain consistent values of ultrasonic properties regardless of the distance between the transducer and the surface of the subject. We developed prediction models of the bioyield strength using the distance correction factors. Conclusions: The optimum prediction model of the bioyield strength of apples using a non-contact ultrasonic technique was a multiple regression model ($R^2=0.9402$).

• 제어로봇시스템학회논문지
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• 제12권6호
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• pp.580-584
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• 2006

Material information for environment may be useful to accomplish mobile robot localization. A procedure to classify a set of indoor materials (glass, steel, wood, aluminum and concrete) with the reflected signal of ultrasonic sensor is proposed in this paper. The main idea is to use material-specific reflection characteristics for the recognition of material type. To achieve the classification task, we modeled reflected signal as a maximum amplitude with respect to distance. In this way, we can generate echo signal models for the given materials and these models are used to compare with the current sensor reading. The experimental results show that the proposed method may give material information during map building task of mobile robot.

• Journal of Welding and Joining
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• 제22권5호
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• pp.32-37
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• 2004

Application of bonding by adhesives can be found in many industries, particularly in advanced technological domains such as aeronautical and space, automobile and electronics industries. Periodic inspection with conventional ultrasonic NDE techniques is capable of indicating the presence and possible location of crack. Continuous ultrasonic attenuation monitoring has potential to supply information. This article discusses the use of pulse-echo ultrasonic testing for the inspection of adhesive bonds between metal sheets. The method is based on the measurement of the reflection coefficient at the metal/adhesive interface. By means of a control experiment it is shown that Quantitative Nondestructive Evaluation in Adhesive Joints are evaluated together with Ultrasonic Testing and Fracture Testing.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.456-458
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• 1995

This paper describes a diagnosis of power transformers by on-line detection of ultrasonic signals. Partial discharge in power transformer generates ultrasonic signals. The trend of the ultrasonic signal number can be measured when partial discharge is generated in HV Winding. The trend of the ultrasonic signal number could easily be distinguished by taking moving average. The insulation failure due to partial discharge in transformers can be predicted based in the trend analysis of the number of ultrasonic signals caused by partial discharge.

• 한국철도학회논문집
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• 제5권2호
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• pp.55-60
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• 2002

This study proposes the post-processor simulator construction of ultrasonic signal for integrity evaluation of railway truck. For these purposes, the ultrasonic signals for defects(crack) of weld zone in frames are acquired in the type of time series data and echo strength. The detection of the natural defects in railway truck is performed using the characteristics of echodynamic pattern in ultrasonic signal. The constructed post-processor simulator agree fairly well with the measured results of test block(defect location, beam propagation distance, echo strength, etc). Proposed post-processor simulator construction of ultrasonic in this study can be used for the integrity evaluation of railway truck.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제3B권4호
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• pp.173-178
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• 2003

The rotational force of ultrasonic motors is able to get from the frictional force of elliptical vibration by contact between rotor and stator. Generally, ultrasonic motors are suitable for driving at resonant frequencies of about 20∼80［KHz］. The driving characteristics of ring type ultrasonic motors are the object of this study. A two-phase driving signal is delivered to the tested ultrasonic motor, which has a $90^0$ phase difference respectively with both sine and cosine voltage waveforms. The driving frequency is almost equal to the mechanical resonant frequency for the proper operation, and the driving signal is supplied by the two-phase parallel resonant inverter. The validity of the proposed driving method is verified by experimental results with stable operation.