• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 춘계학술대회 논문집(한국공작기계학회)
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• pp.155-161
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• 2001

Currently knowledge of strain in welds has mainly been obtained from strain gaging method; that is directly attaching most of the material to the gage. The very few non-contact method are still in the early stage. One of the non-contact methods is by the use of the laser that has high-level of the accuracy for the measurement, and this laser also has excellent characteristics on which many studies for its applications are focused throughout the many fields. The dissertation is on the measurement of the strain caused by the characteristics and the temperature changes of the TIG welded zone which is used with 3D ESPI system that is functionally modified through the laser ESPI system. This system employed the aluminum sheet-metal which are mainly used for the steel plate such as for the electronics, chemistry, food instrument and electronic appliances.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.235-238
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• 2001

Deformation phase can be obtained by using Least-Square Fitting. In extraction of phase values, Least-Square Fitting is superior to usual method like as 2, 3, 4-Bucket Algorithm. That can extract almost noise-free phase and retain 2$\pi$discontinuities. But more fringe in phase map, 2$\pi$ discontinuities is destroyed when that is filtered and reconstruction of deformation is not reliable. So, we adapted Least-Square Fitting using an isotropic window in dense fringe. using Sine-Cosine filter give us perfect 2$\pi$discontinuities information. We showed the process and result of extraction of phase map and filtering in this paper.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.239-242
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• 2001

Electronic Speckle Pattern Interferometry(ESPI) was proposed in the 1970's as a method of producing the interferogram without using traditional holographic technique. ESPI is more faster than Holography method, because the interferometric image is recorded and updated by the video camera every 1/30 second and whold-field inspection possibly. In this study using a non-contact optical technique that is suited for in-plane and out-of-plane deformation measurement. Thin plate with crack was analyzed by ESPI to determine the characteristics of vibration mode shape and natural frequency. Also, results of the experiment were compared with Finite Element Method(FEM).

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.295-298
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• 1997

Recycl ing of PP/EPR based bumper coated with polyester urethane paint has been per formed by chemical decoating method. Electronic Speckle Pattern Interferometry (ESP11 has been applied to characterize the deformation of polyolef in based bumper. In additon, physical properties and processability of recycled materials have been investigated by dynamic mechanical thermal analysis, impact test and melt flower index measurement. The results show that the deformation ratio of recycled material is higher than that of virgin one. The morphological change of EPR, degree of distribution and dispersion during the recycling process seem to be the most important factor for the deformation and the mechanical properties of recycled materials. The experimental results obtained show that ESPI is very powerful technique to study the thermal mechanical property of polyolefin bumper system.

• 한국정밀공학회지
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• 제8권4호
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• pp.41-54
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• 1991

Laser speckle photography-one of the Laser speckle measurement methods which, recently, are used widely in various science, and engineering applications are succesfully used in the non-contact measurement of In-plaane displacement. In this study, automated measurement and analysis are tried in the laser speckle photo- graphy method using a video camera, computer control and processing, and a X-Y positioning table driven by computer controlled stepping motor. The experiment was compared with the theorecial strain and stress data from finite element method. The result showed that displacement, strain and stress can be measured more accurately and conveniently by using this approach.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.911-914
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• 2003

The non-contact laser measurement system what can be used for the vibration analysis of structures is discussed. There are few systems using laser speckle interferometer for vibration analysis. One of these systems is the Electronic Speckle Pattern Interferometer (ESPI). With ESPI system, one can obtain the vibration mode shape qualitatively and the maximum vibration amplitude quantitatively of the structure at each resonance frequency. In this paper, the phase-shifting ESPI system with stroboscopic illumination for measuring vibration mode shapes is constructed and the operating software is programmed. The results are compared with that of commercial ESPI system.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1059-1062
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• 2003

Micro-tensile testing system has been developed and micro-tensile tests for copper foil have been carried out. The system consisted of a micro tensile loading system and a micro-ESPI system for measuring strain. The loading system has a maximum loading capacity of 50N and a stroke resolution of 4.5nm. Stress-strain curves for the electro-deposited copper foil with the thickness of 18$\mu\textrm{m}$ were obtained, and tensile properties, including elastic modulus, yielding strength and tensile strength, were determined. The tensile properties obtained under three different conditions of testing speed showed a dependency on the speed.

• 한국정밀공학회지
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• 제24권7호
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• pp.69-74
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• 2007

The paper proposes a new sonic resonance test for a elastic modulus measurement which is based on time-average electronic speckle pattern interferometry(TA-ESPI) and Euler-Bernoulli equation. Previous measurement technique of elastic constant has the limitation of application for thin film or polymer material because contact to specimen affects the result. TA-ESPI has been developed as a non-contact optical measurement technique which can visualize resonance vibration mode shapes with whole-field. The maximum vibration amplitude at each vibration mode shape is a clue to find the resonance frequencies. The dynamic elastic constant of test material can be easily estimated from Euler-Bernoulli equation using the measured resonance frequencies. The proposed technique is able to give high accurate elastic modulus of materials through a simple experiment set up and analysis.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 춘계학술대회 논문집
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• pp.251-254
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• 2003

In recent years, shearogrpahy has significantly improved capabilities In the areas of unbend and separation detection in tires. Although shearography has many advantages fur qualitative evaluation, the technique remains the problem of quantitative analysis of inside defects, because shearography needs several effective factors including the amount of shearing, shearine direction and induced load, which exist as barrier for the quantitative analysis of inside defects. Since the factors are highly dependent on inspectors skill and also affect the in-situ workability. The factors were optimized and the size of cracks inside of pipeline and tire has been quantitatively determined.

• 대한전자공학회논문지
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• 제20권3호
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• pp.1-5
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• 1983

레이저 다이오드를 사용한 광섬유 아나로그 영상신호 전송 시스템에서 기존 노이즈(short thermal noise 등) 이외에 광섬유내의 스페클 현상에 기인한 모달 노이즈를 확인하기 위하여 시스템 선형성의 degradation를 여러 종류의 광함유에 따라 조사하고, 그 결과 다중 모드 광섬유 시스템에서 모달 노이즈 영향은 N.A(numerical apperture)와 core 반경의 크기 및 대역폭에 관계됨을 확인하였다. 모달 노이즈를 고려한 고품질 영상신호 전송 시스템을 실현키 위한 방법으로는 단- 모드 광섬유를 사용하든지, 레이저 다이오드의 coherence time를 감소시킬 수 있는 변조기술을 개발해야 됨을 알았다.