• 한국생산제조학회지
• /
• 제8권4호
• /
• pp.106-111
• /
• 1999

This study discusses a non-contact optical technique electronic, electronic speckle pattern interferometry(ESPI) that is well suited for in-plane and out-of-plane deformation measurement Used as specimen which has the boundary condition of two clamped parallel edges composite material AS4/PEEK[30/-30/90]s was analyzed by ESPI to determined the characteristics of tensile and vibration. These are quantitativly compared with the result of FEM analysis. Finally the results of this study are briefly summarized as follows : (1) In the in-plane strain analysis by comparison of theoretical results with experimental results qualitatively we confirmed that measurement errors are within 3 % in case of accuracy (2) From comparison of experimental vibration modes with numerical vibration mode shapes by the FEM analysis quantitatively we confirmed that vibration mode measurement by the ESPI has high accuacy.

• 한국정밀공학회지
• /
• 제19권3호
• /
• pp.66-72
• /
• 2002

Electronic Speckle Pattern Interferometry (ESPI) has been recently developed and widely used because it has advantage to be able to measure surface deformations of engineering components and materials in industrial areas with non-contact. The speckle patterns to be formed with interference and scattering phenomena can measure not only out-of-plane but also in-plane deformations, together with the use of digital image equipment to process the informations included in the speckle patterns and to display consequent interferogram on a computer monitor. In this study, the experimental results of a canti-levered plate using ESPI were compared with those obtained from the simple beam theory. The ESPI results of the canti-levered plate analyzed by 4-step phase shifting method are close to the theoretical expectation. Also, out-of-plane displacements of a spot welded cacti-levered plate were measured by ESPI with 4-step phase shifting technique. The phase map of the spot welded cacti-levered plate is quite different from that of the canti-levered plate without spot welding.

• 한국정밀공학회지
• /
• 제26권7호
• /
• pp.65-72
• /
• 2009

Laser interferometry is widely used as a measuring system in many fields because of its high resolution and its ability to measure a broad area in real-time all at once. In conventional laser interferometry, for example out-of-plane ESPI (Electronic Speckle Pattern Interferometry), in plane ESPI, shearography and holography, it uses PZT or other components as a phase shift instrumentation to extract 3-D deformation data, vibration mode and others. However, in most cases PZT has some disadvantages, which include nonlinear errors and limited time of use. In the present study, a new type of laser interferometry using a laser diode is proposed. Using Laser Diode Sinusoidal Phase Modulating (LD-SPM) interferometry, the phase modulation can be directly modulated by controlling the laser diode injection current thereby eliminating the need for PZT and its components. This makes the interferometry more compact. This paper reports on a new approach to the LD (Laser Diode) Modulating interferometry that involves four-frame phase shift method. This study proposes a four-frame phase mapping algorithm, which was developed to have a guaranteed application, to stabilize the system in the field and to be a user-friendly GUI. In this paper, the theory for LD wavelength modulation and sinusoidal phase modulation of LD modulating interferometry is shown. Using modulating laser and research of measurement algorithm does comparison with existent ESPI measurement algorithm. Algorithm measures using GPIB communication through most LabVIEW 8.2. GPIB communication does alteration through PC. Transformation of measurement object measures through modulating laser algorithm that develops. Comparison of algorithm of modulating laser developed newly with existent PZT algorithm compares transformation price through 3-D. Comparison of 4-frame phase mapping, unwrapping, 3-D is then introduced.

• 한국생산제조학회지
• /
• 제8권4호
• /
• pp.79-86
• /
• 1999

Electronic Speckle Pattern Interferometry(ESPI) is a powerful tool to measure the vibration mode shape and resonance frequency for modal analysis. As for ESPI this method is very suited for full-field measurement of objects in industrial areas because the interferograms are recorded with a video camera and evaluated in real-time with a computer. In this study We performed experiments at the same constraint conditions as disk brake of the practical vehicle as far as possible and obtained the resonance frequencies and vibration mode shapes by using time-averaged ESPI at once. Finally to assure the expetimental results by time-averaged ESPI we also compare those with results obtained by Laser Doppler Vibrometer and obtained good agreement.

• 한국정밀공학회지
• /
• 제12권10호
• /
• pp.40-49
• /
• 1995

This paper presents the performance and problems in analysis method and testing system of Electronic Speckle Pattern Interferometry (ESPI) method, in measuring two - dimensional in-plane displacement. The anyalysis result of measurement by ESPE is quite comparable to that tof measurement by strain gauge method. This implies that the method of ESPE is a very effective tool in non-contact two-dimensional in-plane strain analysis. But there is a controversal point, measurment error. This error is discussed to be affected not by ESPE method itself, but by its analysis scheme of the interference fringe, where the first-order interpolation has been applied to the points of strain measured. In this case, it is turned out that the more errors would be occurred in the large interval of fringe. And so this paper describes a computer method for drawing when the height is available only for some arbitrary collection of points. The method is based on a distance-weighted, last- squares approximation technique with the weight varying with the distance of the data points.

• 한국산학기술학회논문지
• /
• 제1권1호
• /
• pp.23-26
• /
• 2000

스폿용접은 겹침판을 끼우고 가압상태의 전극 사이에 단시간의 대전류를 흘려, 전류가 집중하는 전극 직하의 모재 저항발열과 전극 및 모재의 열전도를 이용해서 판과 판의 접촉부에 안정한 용융부를 형성하는 압접법이다. 스폿용접으로 대표되는 저항용접법의 특징은 작업속도가 빠르고. 대량 생산적인 성격이 강하다는 점이다. 그러나, 용접부의 점검이 중요함에도 불구하고 용접부의 직접 감시가 곤란하여 적절한 검사 방법이 확립되지 않은 결점이 있다. 최근 제조공정 중에 실시간으로 스폿 용접부를 비파괴적인 방법을 이용하여 응력 및 변형상태를 체크하고. 결합을 검출할 수 있는 방법이 강력히 요구되고 있는 실정이다. 스폿 용접부페 광학적으로 레이저 빔을 조사하여 렌즈에 의해 결상되면 결상면상에 작은 입자모양의 반점이 생긴다. 이 반점을 스페클이라 하며 이 스페클에 의해 만들어진 불규칙한 반점모양을 스페클 패턴이라 한다. 이러한 현상은 레이저 빔이 가간섭의 성질을 지니고 있으므로 조사영역에서는 랜덤하지만 시간적으로 정상적인 위상관계에 있는 다수의 광파가 간섭함으로서 발생하는데 이와 같은 줄무늬 간격을 PC 프로그램으로 계산하여 응력을 측정한다. 따라서 본 연구에서는 레이저를 이용한 전자처리식 스페클 패턴 간섭법(ESPI)으로 스폿 용접부의 응력 및 변형률을 측정하여 스트레인 게이지법과 비교 고찰한 결과, ESPI법이 유용함을 알 수 있었으며. 이 방법을 생산 공정에 적용함으로서 생산성 및 품질 향상을 기할 수 있다고 판단된다.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제5권4호
• /
• pp.439-450
• /
• 2005

Thermal deformation of Digital Television effect friction noise directly. However there was no methods to find and to solve the thermal friction noise which is huge problem in Digital Television In this study, to figure out occurrence cause of friction noise of the product, we measured thermal deformation of the product to organize a triggering device united with Laser Doppler Vibrometer(LDV) which turned occurrence moment of thermal friction noise into a possibility to measure. In conclusion, we could offer an effective information of design, and ensured ESPI(Electronic Speckle Pattern Interferometry) measure technique which is more detailed than the past way.

• 한국정밀공학회지
• /
• 제18권5호
• /
• pp.90-97
• /
• 2001

An electronic speckle pattern interferometry (ESPI) system for measuring tensile properties under micro-tensile testing has been developed. The system consists of an optical system and an image processing system. In the optical system, optical components for measurement of in-plane deformation are arranged on the path of He-Ne laser. In the image processing system, the window-based program for acquiring speckle pattern interferometric image was developed and deformation in a small specimen is continuously evaluated during the test. Using this system, tensile strain of copper foil was measured during tensile testing. Tensile specimen had the thickness and width of 22 and 500 ${\mu}{\textrm}{m}$, respectively. Tensile properties, including the elastic modulus, yielding strength and tensile strength, of the copper were evaluated and also plastic exponent and coefficient in the Ramberg-Osgood relationship were evaluated from the stress-strain curve.

• 한국정밀공학회지
• /
• 제24권12호
• /
• pp.104-110
• /
• 2007

Internal defects are mainly caused by a corrosive action and degradation in the pipe used in a nuclear power plant or factory. The ESPI method have the many advantages when compared with conventional method. The advantage are the area measurement ability at one time and non-contact measurement ability in the real-time. In this paper, we studied on the measurement of a internal defect by using out of plane ESPI technique. Here, we compared the experimental results using out of plane ESPI with the FEM results.

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