• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.703-708
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• 2006

The cantilever beam with nonlinearity has many dynamic characteristics of nonlinear vibration. Nonlinear terms of a flexible cantilever beam include inertia, spring, damping, and warping. When the beam is given basic harmonic excitation, it shows planar and nonplanar vibrations due to one-to-one resonance. And when the one-to-one resonance occurs, the flexible beam shows different behaviors in those vibrations. For the one-to-one resonance occurring in each mode, the phase value of the planar vibration is different from that of the nonlinear vibration. This paper investigates the phase change and the phase difference between such planar and nonplanar vibrations which are caused by one-to-one resonance.

• 한국소음진동공학회논문집
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• 제17권1호
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• pp.48-54
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• 2007

The cantilever beam with nonlinearity has many dynamic characteristics of nonlinear vibration. Nonlinear terms of a flexible cantilever beam include inertia, spring, damping, and warping. When the beam is given basic harmonic excitation, it shows planar and nonplanar vibrations due to one-to-one resonance. And when the one-to-one resonance occurs, the flexible beam shows different behaviors in those vibrations. For the one-to-one resonance occurring in each mode, the phase value of the planar vibration is different from that of the nonlinear vibration. This paper investigates the phase change and the phase difference between such planar and nonplanar vibrations which are caused by one-to-one resonance.

• 대한기계학회논문집B
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• 제23권7호
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• pp.893-900
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• 1999

Measuring temperature with ultrasonic wave apparatus is desirable in the cue of gas below $300^{\circ}$ because of the fact that the temperature of gas is the function of only sound velocity. In this study, being used a heatable wind channel and a blower. the variation of temperature is observed in accordance with flow rate(air velocity). The frequency modulation method is used to measure the temperature which is varying in hot air flow up to $100^{\circ}$. The length changed in the position of ultrasonic sensors is considered. Also. the effects of air velocity at the same temperature and various facing angles of ultrasonic sensors are considered. As a result of this study. it has been found that the temperature in gas flow is correctly measured regardless of both the distance of ultrasonic sensors and the variation of air velocity. and that there is just a little influence of facing angles.

• 대한안전경영과학회지
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• 제4권2호
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• pp.1-10
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• 2002

In order to protect the head, baseball helmet must to have proper strength and to absorb the kinetic energy. The purposes of this study are to validate whether the helmet have the protecting ability or not. We performed three kinds of experiment to know about the this ability. To find out the limit of displacement at 4 points(front, rear, right side, and left side), the static load by magnetic dial gauges were used, and to validate the ability of absorption, drop tests were peformed from 0.5 and 1.0 meter. Futhermore, we calculated natural frequency of the helmets by the principle of Lissajous Diagram and we performed FEM(Finite Element Method) analysis. From the results of these experiments, we found that the displacement of helmet was largest at rear point and it was smallest at left-side point(ear-covered part). The ability of absorption was better at the left-side point than the other points.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.529-532
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• 2003

In this paper, the discharge characteristics of silent discharge chamber with 2mm and 3mm gap spacings were investigated. Dielectric of $Al_2O_3$ was embedded in the cylindrical type of discharge chamber. It was known that V-I and P-V characteristics depend strongly on the charge transportation characteristics, and in the low frequency silent discharge mode of operation, discharge voltage was always sustained to Vd, irrespective of applied voltage.

• 한국압력기기공학회 논문집
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• 제10권1호
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• pp.75-81
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• 2014

A simulation of eddy current testing has been utilized for predicting the signal characteristics to the various defects and developing the probes. Especially, CIVA which is a simulation tool dedicated to nondestructive testing has a good accuracy and speed, and provides a three-dimensional graphical user interface for improved visualization and familiar data displays consistent with NDE technique. Although internal validations have been performed by the CIVA software development specialists, an independent validation study is necessary for the accuracy assessment of the software prior to practical use. For this purpose, in this study, eddy current testing signals of ASME FBH calibration standard tube for bobbin probe were simulated using CIVA and the results were compared to the experimental inspected signals based on the relationship between each flaw signal in terms of amplitude and phase, and the shape of the Lissajous curve. And then we verified the accuracy of the simulated signals and the possible range for simulation. Overall, there is a good qualitative agreement between the CIVA simulated and experimental results in the absolute and differential modes at the two inspection frequencies.

• 대한기계학회논문집A
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• 제28권12호
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• pp.2004-2011
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• 2004

The applicability of the ultrasonic C-scan inspection is restricted due to the deterioration of mechanical properties of specimen during the test. Therefore, the aim of this research is applied to Eddy Current (EC) test substitute for the C-scan inspection in CFRP tube containing defects. This research is to evaluate the EC signals for the inspection of CFRP tube containing various circular hole defects (20% to 100% depth to the specimen thickness) using the unloading specimen and radial loading specimen. This study was considered the following points; 1) Analysis of EC signals for the inspection of saw-cut defect and circular hole defect, 2) The evaluation of defect depths and EC signals relationship. 3) Variation of EC signal owing to the radial load. In conclusions, the high frequency such as 300∼500 kHz made it possible to the inspection of 40% to 100% defects. Particularly, in case of 20% defect, the EC signal was not detected due to the noise of micro-crack and delamination. While the depth of the hole defects were decreasing, the difference of the phase angle between unloading specimen and radial loading specimen was gradually increasing.

• 한국광학회지
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• 제2권1호
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• pp.20-25
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• 1991

홑 결모양 빛살이 도파되는 광섬유와 두 결모양 빛살이 도파되는 광섬유를 스러지는 들 결합(evanescent field coupling)을 써서 두 결모양 빛살($LP_{01}, LP_{11}$)이 도파되는 광섬유에서 $LP_{11}$ 결모양 빛살만 뽑아 내었다. 이 $LP_{11}$ 결모양 빛살이 도파되는 광섬유에 짝짓게 세 개를 제작해 두 개는 결합시켜 $LP_{11}$결모양 빛살 광섬유 공진고리 간섭계를 구성 하였다. 구성된 간섭계의 출력 광섬유의 짝짓게판과 프리즘 츨력 짝짓게를 결합시켜 광섬유로부터 방사 결모양 빛살을 뽑아 내어 도파되는 결모양수를 조사하였다. 외부 섭동이 간섭계 고리에 가해질 때 프리즘 출력 짝짓게에서 나온 방사 결모양 빛살의 변화와 출력끝에서 나온 방사 빛살모양의 변화를 조사하였다. $LP_{11}$ 결모양 빛살의 edit 두 반구에 광 다이오우드 2개를 놓아 빛살을 받아 오실로스코우프에 입력시켜 Lissajous 모양을 만들어 그 궤도에서 돌아가는 방향으로 위상변화의 증가 혹은 감소되는 방향을 알 수 있다.

• 비파괴검사학회지
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• 제31권5호
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• pp.552-559
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• 2011

전자기유도(electromagnetic induction) 현상을 이용한 비파괴진단기법으로서 최근까지 와전류탐상기법, 교류장측정기법, 자속누설검사기법, 그리고 원격장검사기법 등이 개발되어 활용되고 있다. 이 기법 중 와전류탐상기법은 오늘날 발전설비, 화학, 조선 및 군수설비 등의 열교환기 전열관 비파괴검사에 널리 적용되고 있다. 와전류탐상검사 시스템의 구성은 기능별로 와전류신호 합성 모듈, 아날로그 모듈, 디지털 신호처리를 위한 아날로그-디지털 변환 모듈, 전원공급장치 및 신호취득 평가 프로그램 등으로 구성되며, 선행 연구(I)에서는 다중채널방식의 와전류탐상검사 시스템의 구성 요소 중 1차로 와전류신호 합성 모듈, 아날로그 모듈을 설계 개발하였으며, 2차로 와전류 신호 취득 평가 프로그램을 개발하였다. 2차 연구에서 개발한 와전류 신호취득 평가 프로그램의 운영체제는 "Windows 7"로서 국내 사용자를 위해 최적화 하였으며, 주요 특징은 검사자가 "setup wizard"를 이용하여 검사에 필요한 검사 조건 및 변수를 용이하게 설정하고 이를 이용하여 신호취득 및 평가를 수행할 수 있다. 본 논문에서는 개발된 와전류신호 수집 및 평가 프로그램의 구성과 각 기능을 설명하고자 한다.

• 비파괴검사학회지
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• 제30권2호
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• pp.155-161
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• 2010

전자기유도(electromagnetic induction) 현상을 이용한 비파괴진단기법으로 최근까지 와전류탐상기법, 교류장측정기법, 자속누설검사기법, 그리고 원격장검사기법 등이 개발되어 활용되고 있었다. 이 기법중 와전류탐상기법은 오늘날 발전설비, 화학, 조선 및 군수설비 등의 열교환기 전열관 비파괴검사에 널리 적용되고 있다. 와전류탐상검사 시스템의 구성은 기능별로 와전류신호 합성 모듈, 아날로그 모듈, 디지털 신호처리를 위한 아날로그-디지털 변환 모듈, 전원공급장치 및 신호취득 평가 프로그램 등으로 구성되며, 본 연구에서는 다중채널방식의 와전류탐상검사 장치(하드웨어) 개발에 필요한 구성 요소중 1차적으로 와전류신호 합성 모듈, 아날로그 모듈을 설계 개발하였다. 본 연구에서 개발한 와전류탐상검사 장치의 특정은 주파수영역 및 시간영역 다중화 방식에 의한 최대 4개 주파수의 동시 적용이 가능한 다중채널장치이다. 와전류신호 합성 모듈, 아날로그 모듈을 구성하는 각 회로에서 와전류신호 발생, 변조, 전처리, 변조 및 신호 디스플레이를 위한 신호가 적절하게 처리되어 최종적으로 와전류신호 평가에 필수적인 리사쥬신호가 임피던스 평면 내에 디스플레이 되는 것을 확인하였다.