• 한국광학회지
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• 제15권5호
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• pp.405-408
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• 2004

나뉜 렌즈를 사용하는 스펙클 전단 간섭계로 전단링(shear)에 따라 변형을 가하지 않은 상태에서 물체에 대한 동일한 두 장의 스펙클그램 쌍들을 제작하여, 이중 스펙클 기법을 사용함으로서 전단량에 따라 이 전단간섭계의 측정한계를 구하였다. 이 측정한계는 기존의 방법으로 얻어지는 값과 잘 일치함을 알 수 있었다.

• 한국기계가공학회지
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• 제20권4호
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• pp.39-48
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• 2021

In this paper, an in-plane deformation measuring system using a dual-beam shear interferometer was constructed to measure the in-plane deformation of the measuring object. The in-plane deformation of the object was quantitatively measured according to the load and surface treatment conditions of the object. We also verified the reliability of the proposed technique by simultaneously performing the technique with an electronic speckle pattern interferometry system (ESPI), which is another laser application measurement technology. Digital shearography directly measures the deformation gradient or strain components and has the advantages of being full-field, noncontact, highly sensitive, and robust. It offers a much higher measurement sensitivity compared with noncoherent measurement methods and is more robust and applicable to in-field tests.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2003년도 학술대회지
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• pp.215-223
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• 2003

Viscosity index improver (VII) is one of the major additives to the modern multigrade lubricants for the viscosity stability against temperature rise. However, it causes shear thinning effects which make the film thickness lessened very delicately at high shear rate $(over\;10^5\;s^{-1})$ of general EHL contact regime. In order to exactly verify the VII's performance of viscosity stability at such high shear rate, it is necessary to make the measurement of EHL film thickness down to $\~100nm$ with fine resolution for the preliminary study of viscosity control. In this work, EHL film thickness of VII added lubricant is measured with the resolution of $\~5nm$, which will give very informative design tool for the synthesis of lubricants regarding the matter of load carrying capacity at high shear rate condition.

• Korea-Australia Rheology Journal
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• 제15권3호
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• pp.117-124
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• 2003

Elastohydrodynamic lubrication (EHL) film is measured under the condition of viscosity index improver added to base oil. In-situ optical contact method using the interference principle make the measuring resolution of ~5 nm possible and enables the measuring range all over the contact area of up to ~300 $\mu\textrm{m}$ diameter. What is more important to the developed method by the author is that the measurement of EHL film thickness is possible in the range from 100 nm to 2 $\mu\textrm{m}$, which is the regime of worst contact failures in precision machinery. Viscosity index improver (VII) is one of the major additives to the modem multigrade lubricants for the viscosity stability against temperature rise. However, it causes shear thinning effects which make the film thickness lessened very delicately at high shear rate (over $10^5 s^{-1}$) of general EHL contact regime. In order to exactly verify the VIIs performance of viscosity stability at such high shear rate, it is necessary to make the measurement of EHL film thickness down to ~100 nm with fine resolution for the preliminary study of viscosity control. In this work, EHL film thickness of VII added lubricant is measured with the resolution of ~5 nm, which will give very informative design tool for the synthesis of lubricants regarding the matter of load carrying capacity at high shear rate condition.

• 비파괴검사학회지
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• 제20권1호
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• pp.27-32
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• 2000

본 논문에서는 고출력 펄스 Nd:YAG 레이저를 이용해서 원반형 시편의 한쪽 면에서 초음파를 발생시키고 반대 면에서 피드백 제어에 의해서 안정화된 마이켈슨 간섭계를 이용하여 열탄성 영역에서의 초음파를 검출하였다. 이론식에 의해서 계산된 열탄성 영역에서의 초음파 변위 파형이 실험에서 얻어진 파형과 유사한 것을 확인하였고, 특히 종파와 횡파의 음속이 접촉식 트랜스듀서를 이용하여 펄스-에코법으로 측정한 음속과 거의 일치하는 것을 확인하였다. 레이저 초음파를 이용한 응용예의 하나로 원반형 시편을 노 안에 넣고 음속을 계측한 결과 온도의 증가에 따라 음속이 감소하는 것을 확인하였다.

• 비파괴검사학회지
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• 제34권2호
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• pp.165-170
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• 2014

수평횡파(SH-wave)는 배관과 같은 박판 구조물에서 판파 모드로 전파하고 분산성이 단순하여 구조물의 건전성 평가에 유용하다. 전자기초음파탐촉자(EMAT)는 비접촉식으로 자석과 코일 배열을 조절하여 수평횡파를 발생하기 용이하다. 따라서 수평횡파 전자기초음파탐촉자(SH-EMAT)를 이용한 자동화 검사 시스템은 박판 구조물 건전성 감시에 매우 유용하다. 하지만 발전설비 또는 자동화 장비 등에서는 전자기노이즈가 상당히 많이 발생하고 EMAT 수신 센서는 전자기노이즈에 취약한 면이 있다. 광섬유 센서는 빛을 이용하여 전자기노이즈 환경에서 매우 유용하게 활용될 수 있다. 본 연구에서는 이러한 환경적 제약을 고려하여 광섬유 패브리-페롯 간섭계(FFPI)를 SH-EMAT으로 발생되는 초음파의 수신용 센서로 제안하였다. 평판시험편에서 SH-EMAT의 신호를 FFPI 센서를 이용하여 수신하고 이 신호에 대한 분석을 하였다. 제안된 FFPI 센서가 EMAT으로 가진된 SH wave의 신호를 명료하게 수신할 수 있음을 확인하였다.

• 대한기계학회논문집A
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• 제28권9호
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• pp.1408-1414
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• 2004

The use of flip-chip technology has many advantages over other approaches for high-density electronic packaging. ACF (anisotropic conductive film) is one of the major flip-chip technologies, which has short chip-to-chip interconnection length, high productivity, and miniaturization of package. In this study, thermal fatigue lift of ACF bonding flip-chip package has been predicted. Elastic and thermal properties of ACF were measured by using DMA and TMA. Temperature dependent nonlinear hi-thermal analysis was conducted and the result was compared with Moire interferometer experiment. Calculated displacement field was well matched with experimental result. Thermal fatigue analysis was also conducted. The maximum shear strain occurs at the outmost located bump. Shear stress-strain curve was obtained to calculate fatigue life. Fatigue model for electronic adhesives was used to predict thermal fatigue life of ACF bonding flip-chip packaging. DOE (Design of Experiment) technique was used to find important design factors. The results show that PCB CTE (Coefficient of Thermal Expansion) and elastic modulus of ACF material are important material parameters. And as important design parameters, chip width, bump pitch and bump width were chose. 2$^{nd}$ DOE was conducted to obtain RSM equation far the choose 3 design parameter. The coefficient of determination ($R^2$) for the calculated RSM equation is 0.99934. Optimum design is conducted using the RSM equation. MMFD (Modified Method for feasible Direction) algorithm is used to optimum design. The optimum value for chip width, bump pitch and bump width were 7.87mm, 430$\mu$m, and 78$\mu$m, respectively. Approximately, 1400 cycles have been expected under optimum conditions. Reliability analysis was conducted to find out guideline for control range of design parameter. Sigma value was calculated with changing standard deviation of design variable. To acquire 6 sigma level thermal fatigue reliability, the Std. Deviation of design parameter should be controlled within 3% of average value.