• 한국항공운항학회지
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• 제18권4호
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• pp.59-66
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• 2010

Aerospace structures need high stability and long life because many personal injuries can result from an accident and securing structural integrity for various external environments is more important than any other thing. So first of all we must prove the destruction properties for operating environment, have prediction technology about damage evolution and life, and develop an economical non-destructive technology capable of detecting structure damage. Acoustic emission (AE) have no need of artificial environment like ultrasonic inspection or radio fluoroscopy to emit a certain energy, is a testing technique using seismic signal resulting from interior changes of solids, and enables to observe if any fault is appeared and it grows seriously or not while running. In this study we suggest the method of structural integrity evaluation for aerospace structures through the acoustic emission technique, for which a model plane was manufactured and an actual operation test was conducted.

• 한국전기전자재료학회논문지
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• 제18권10호
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• pp.960-964
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• 2005

In this paper, we dealt with a partial discharge(PD) measurement method that has been accepted as an effective and non-destructive technique to estimate insulation performance of low-voltage electric and electronic devices. The PD measurement system Is composed of a coupling network, a low noise amplifier, and associated electronics. h shielded box Is adopted to make a better measurement environment against around noise. A low cut-off frequency of the coupling network estimated by a sinusoidal wave input was 125 kHz (-3 dB). Calibration tests on laboratory set-up have shown that the PD measurement system has a stable sensitivity of 10 mV/pC. In an application test oil a low-voltage three phase Induction motor (5 HP), we could detect 0.53 pC level of partial discharge at the applied voltage of AC 650 $V_{peak}$.

• 한국추진공학회지
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• 제12권2호
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• pp.40-47
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• 2008

초음파를 이용한 추진기관의 접착 계면 검사는 결함 검출 능력과 경제성이 우수하다고 알려져 있다. 하지만, 추진기관의 접착 구조는 다중 계면이므로 송신 펄스와 수신 펄스의 시간 간격이 짧아서 반사 신호의 분리가 어렵기 때문에 초음파의 신호 분석에는 많은 시간과 노력이 소요된다. 이런 이유로 추진기관의 초음파시험은 연소관과 내열재 사이의 미접착 결함과 같이 극히 제한된 영역에 대해서만 자동화 시스템으로 수행하고 있다. 본 논문에서는 기존의 초음파시험으로 검출이 불가능했던 라이너와 추진제 미접착 결함을 초음파의 공진 현상과 램파 특성을 이용하여 검출하는 새로운 기법에 대해 기술하였다.

• Architectural research
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• 제22권1호
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• pp.23-31
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• 2020

This study aims to verify a method for accurately estimating the sizes of the column, slab, and beam members of concrete structures using the impact echo method, which is a nondestructive testing method. The concrete specimens are designed and fabricated with six single-layer frame specimens composed of columns, slabs, and beam members based on three strengths of 24, 30, and 40 MPa. To estimate the sizes of the members according to the member types of concrete structures, the experiment was performed using the impact echo method. As a result of estimating the sizes of the concrete column members using the impact echo method, the error rate is 2.9%. As a result of estimating the depth of the concrete beam members, the error rate is 9.7%. And, as a result of estimating the thickness of the concrete slab members, the error rate is 2.4%. These results confirmed that quality control of the members of concrete structures is possible by estimating their sizes using a non-destructive testing method.

• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2008년도 춘계 학술발표회 논문집
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• pp.179-183
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• 2008

콘크리트에서의 손상 검증법은 비파괴 시험법을 주로 이용한다. 이러한 비파괴시험법은 다양한 센서를 이용하지만, 대부분의 손상을 검사하는 방법은 육안으로 확인한다. 비파괴 시험법에서 가속도계를 이용하여 철근 콘크리트 부재 내부의 불규칙한 균열 손상을 측정하기에는 철근의 방향성과 경계조건으로 어려움이 많다. 본 연구에서는 3축 가속도센서를 이용하고 탄성파를 가진하여, 콘크리트 부재 내부에 철근의 배치방향에 따른 영향 검토와 강도가 저하된 부재의 손상을 검토하기 위한 기초적 연구이다.

• 한국생산제조학회지
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• 제20권5호
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• pp.564-569
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• 2011

The current establishment of city gas piping polyethylene (PE) tube used as bonding state or part of the health or safety of fusion is very important. A part of these fusion methods to determine the soundness of the short-term trials and long-term tests can be largely classified. Typical tests include short-term strength, tensile strength, impact strength, compressive strength, resiliency and compression. Polyethylene (PE) pipes installed in the domestic terms of overall penetration rate of 45% has been used. However, polyethylene (PE) pipes have reliability problems, and these occurs mostly in part by defective welding. Therefore, the test is necessary for safety. Non-destructive methods (ultrasonic testing) are difficult to be used. Therefore, Polypropylene copolymer (PP-C), polypropylene homopolymer (PP-H), and polyethylene (PE) pipe are used. Fusion of these materials is necessary in these field however, its technical, and basic research has not been studied well. In this research, short-term strength of welding parts, its tensile strength, hardness, fatigue, and microstructure have been analyzed to find the optimum process conditions to improve mechanical properties.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.55-59
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• 2007

초음파를 이용한 추진기관의 접착 계면 검사는 결함 검출 능력과 경제성이 우수하다고 알려져 있다. 하지만, 추진기관의 접착 구조는 다중 계면이므로 송신 펄스와 수신 펄스의 시간 간격이 짧아서 반사 신호의 분리가 어렵기 때문에 초음파의 신호 분석에는 많은 시간과 노력이 소요된다. 이런 이유로 추진기관의 초음파시험은 연소관과 내열재 사이의 미접착 결함과 같이 극히 제한된 영역에 대해서만 자동화 시스템으로 수행하고 있다. 본 논문에서는 기존의 초음파시험으로 검출이 불가능했던 라이너와 추진제 미접착 결함을 초음파의 공진 현상과 램파 특성을 이용하여 검출하는 새로운 기법에 대해 기술하였다.

• Computers and Concrete
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• 제19권5호
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• pp.467-475
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• 2017

The purpose of this study is to establish a prediction model for the electrical resistivity ($E_r$) of self-consolidating concrete by using waste LCD (liquid crystal display) glass as part of the fine aggregate and then, to analyze the results obtained from a series of laboratory tests. A hyperbolic function is used to perform nonlinear multivariate regression analysis of the electrical resistivity prediction model, with parameters such as water-binder ratio (w/b), curing age (t) and waste glass content (G). Furthermore, the relationship of compressive strength and electrical resistivity of waste LCD glass concrete is also found by a logarithm function, while compressive strength is evaluated by the electrical resistivity of non-destructive testing (NDT). According to relative regression analysis, the electrical resistivity and compressive strength prediction models are developed, and the results show that a good agreement is obtained using the proposed prediction models. From the comparison between the predicted analysis values and test results, the MAPE value of electrical resistivity is 17.0-18.2% and less than 20%, the MAPE value of compressive strength evaluated by $E_r$ is 5.9-10.6% and nearly less than 10%. Therefore, the prediction models established in this study have good predictive ability for electrical resistivity and compressive strength of waste LCD glass concrete. However, further study is needed in regard to applying the proposed prediction models to other ranges of mixture parameters.

• 제어로봇시스템학회논문지
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• 제2권3호
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• pp.236-241
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• 1996

This paper presents a new eddy current testing system for inspecting tubes of steam generator in nuclear power plant. The proposed system adopted embedded expert system concept to automate tasks of the inspection such as inspection planning and flaw signal interpretation, and integrated all the tasks into a client/server type computing architecture using database management system. Therefore, human factor errors occurred during inspection could be minimized and the inspection data could be transferred in real-time. As a result, we can increase the level of inspection confidence and the productivity of a personal inspector. A prototype of the proposed system has been developed for 5 years and the test operation has been performed in domestic nuclear power plants.

• 한국정밀공학회지
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• 제31권2호
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• pp.165-170
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• 2014

Reproducibility of injection molding machines are studied at the study of this time. We applied computer aided engineering program so it could generate clamping force, about 1,500 kN, to the nozzle center part of flex link in tie-bar and at this time, we made sure condition of stress distribution and transformation quantity in flex link. The result of computer aided engineering transformation quantity was confirmed that transformation of top area was 247~257 kN and bottom areas was 273~279 kN and also was confirmed that the stresses are distributed in a range of 57~750 $N/mm^2$ from top to the bottom of the surface. This time we could confirm the condition of transformation quantity and stress distribution by enforcing the previously used structure analysis of flex link. And we utilized the reference data to establish important point of section for non destructive test overhaul.