• Journal of rehabilitation welfare engineering & assistive technology
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• v.4 no.1
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• pp.15-21
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• 2010

Ultrasonic wave stimulator need estimation of quality and security of safety by courtesy call about malfunction or side effect. Need a standard of test method for estimation of safety and performance in type test before marketing or removal examination after marketing for this. In this paper, studied standard of test method for estimation of essential electrical safety and performance for ultrasonic wave stimulator.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.1
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• pp.64-69
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• 2008

In order to detect the internal defects which occur in welding parts of pressure vessel and structures, radiographic testing and ultrasonic testing is applied. However, because of the risks of radiation exposure and film processing, radiographic testing takes a relatively long time to verify the test results and it has affected in the production process. Typically, the manual ultrasonic testing is not easy to reproduce the result and it is highly dependent on the tester's skills. The TOFD technique, one of the automatic ultrasonic testings is spreading alternatively. This research describes the comparing test results by applying radiographic testing and TOFD technique to a mock-up specimen incruding the flaws. The TOFD technique will contribute to improve the objective reliability of the ultrasonic technique.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.3
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• pp.307-312
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• 2001

Ultrasonic signals from Charpy impact test specimen have been analyzed in order to evaluate the integrity of reactor pressure vessel. Base and weld metal that were extracted from reactor vessel doting plant outages according to the schedule of the surveillance test required by the related regulations have been used and the ultrasonic test parameters including velocity, attenuation, etc. showed a close correlations with the amount of neutron irradiation for base metal, relatively homogeneous materials. This result showed certain possibility where a nondestructive method could be used to predict the fluence of the Irradiation due to neutron in nuclear reactor vessel materials.

• Journal of the Korean Wood Science and Technology
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• v.43 no.4
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• pp.486-493
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• 2015

The ultrasonic nondestructive test (NDT) was applied to deck in-service to inspect and evaluate the performance of decking materials using ultrasonic pulse velocity. First, the measuring method between direct and indirect method according to transducer arrangement was studied. Second, the ultrasonic pulse velocity of decks in-service was compared with the passage of time. Finally, the change of ultrasonic pulse velocity was evaluated to expect service life of decking materials. The results of comparison between direct and indirect method was statistically insignificant and the ratio of direct to indirect method was 1.02. 1.05 respectively. The ultrasonic pulse velocity of decks in-service was decreased as the passage of time and the linear relationship in the ultrasonic pulse velocity to passage of time was found. From the results, The ultrasonic NDT will be helpful as an efficient method of on-site management of decks in-service.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.2
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• pp.46-53
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• 2004

Ultrasonic testing method has been developed to evaluate flaw of adhesive layers in blast tube for the reliability of the rocket nozzle. The ultrasonic reflection from the interface between the steel sheet and the epoxy adhesive is measured with a high-frequency Pulse-echo setup in order to identify contact debonding and missing adhesive in epoxy layer between steel and FRP layers. The steel sheet is resonated by low-frequency ultrasound, and the gap size underneath the measuring location is estimated from the resonance responses. For practical application in industry an automated testing system has been developed where the proposed approach is implemented. The performance of the proposed approach has been verified by actual measurement of gap sizes from the cross-sections of cut specimens using an optical microscope.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.230-237
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• 2003

Ultrasonic testing method has been developed to evaluate adhesive layers in blast tube for the reliability of the rocket. The main objective of the present work was to find debonding and missing adhesive in epoxy layer between steel and FRP layers. In this approach, the ultrasonic reflection from the interface between the steel sheet and the epoxy adhesive is measured with a high-frequency pulse-echo setup in order to identify contact debonding and missing adhesive. Then, the steel sheet is excited to resonance by low-frequency ultrasound, and the gap size underneath the measuring location is estimated from the resonance responses. For practical application in industry an automated testing system has been developed where the proposed approach is implemented. The performance of the proposed approach has been verified by actual measurement of gap sizes from the cross-sections of cut specimens using an optical microscope.

• Proceedings of the KIEE Conference
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• 2007.11c
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• pp.194-196
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• 2007

댐 및 저수지 운영시 가장 중요한 센서 중의 하나인 수위계는 댐의 수문조작에 있어 직접적으로 연관되기 때문에 수위계의 특성이 잘 관리될 필요가 있다. 따라서 수위 측정에 널리 사용되고 있는 부자식, 초음파식, 그리고 레이다식 수위계에 대한 특성시험이 가능하도록 수위계 표준 시험 장치를 개발하였고, 이를 이용하여 레이다식 수위계와 초음파식 수위계에 대하여 수위에 따른 특성시험을 실시하여 각 수위계에 대한 특성을 상호 비교 분석하고자 한다.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.281-282
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• 2007

댐 및 저수지 운영시 가장 중요한 센서 중의 하나인 수위계는 댐의 수문조작에 있어 직접적으로 연관되기 때문에 수위계의 특성이 잘 관리될 필요가 있다. 따라서 수위 측정에 널리 사용되고 있는 부자식, 초음파식, 그리고 레이다식 수위계에 대한 특성시험이 가능하도록 수위계 표준 시험장치를 개발하였고, 이를 이용하여 레이다식 수위계와 초음파식 수위계에 대하여 수위에 따른 특성시험을 실시하여 각 수위계에 대한 특성을 상호 비교 분석하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.781-785
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• 2015

In this study, a newly developed ultrasonic fatigue test was performed for durability assessment of polyoxymethylene engineering plastic, which has a high crystallization rate and degree of crystallization. Fatigue strength of POM (polyoxymethylene) was performed on a piezoelectric UFT developed by Mbrosia Co., Ltd(1), operating at a high frequency of 20 kHz. The test results showed a fatigue limit of 5.0~6.0 MPa under fatigue testing at R = -1, 20kHz; and, electron microscopy revealed the size effect by risk volume and fractured dimple structure after the coalescence of micro-voids through the crazing effect, which occurs during the failure of a polymer.

• Journal of the Korean Society for Nondestructive Testing
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• v.14 no.2
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• pp.83-89
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• 1994

It is important for an ultrasonic testing to know the sound pressure field and the directivity of ultrasonic waves propagating in a solid. The directivity of ultrasonic wave is closely related to the sensitivity, the scanning pitch, the arrangement of angle probe, and the defect kind in ultrasonic testing. This paper describes on the directivity measurement of ultrasonic wave using ultrasonic wave visualization method. The directivity of the shear wave emitted from the angle probes were constant during propagation. The difference of directivity was existed between 2MHz and 4MHz angle probes. The centers of directivity were located backward from the incident poing and inside of the angle probe and were not changed during the wave propagation.