• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.405-408
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• 2004

In this paper, we used a split-lens speckle shear interferometer using a double speckle interferometer, which enables continuous measurement of the deformation. We made two identical specklegrams corresponding to an object. With this method we could detect the measuring limits of the deformation for various shears. This experimental results showed that the measuring limits of a split-lens speckle shear interferometer are similar to the measuring limits of a double exposure speckle interferometer.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.5
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• pp.19-23
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• 2004

최근 산업의 고도화와 함께 초고온, 방사선노출 등과 같은 극한환경에서 사용되는 구조물과 MEMS 와 같은 미소 구조물(Hicrostructure)이 많아지고 있으며, 이들의 변형해석을 위한 기존의 접촉식 기법들은 그 한계를 극복해야 할 필요가 있다 해결방안으로 레이저를 이용한 비접촉 측정방식이 많은 발전을 해오고 있으며, 특히, 스페클간섭법(Speckle inteferometry)기반의 변형해석 기술이 가장 뛰어난 기술로 인정받고 있다. 스페클간섭법은 컴퓨터 화상처리기술에 힘입어 전자처리 스페클간섭법(Electronic Speckle Pattern Interferometry : ESPI)으로 발전을 하고 있으며, 자동차와 같은 대형구조물의 변형해석에서 MEMS 구조물과 같은 미소구조물 변형해석까지 그 적용범위가 매우 넓다. 본 논문에서는 ESPI 를 이용한 변형해석분야의 국내외 기술현황 및 적응사례, 발전방향를 소개하였다.(중략)

• Journal of Mechanical Science and Technology
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• v.18 no.9
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• pp.1493-1499
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• 2004

This paper describes the speckle shearing interferometry, a non-destructive optical method, for quantitative estimation of void defect and monitoring separation defect inside of a pneumatic tire. Previous shearing interferometry has not supplied quantitative result of inside defect, due to effective factors. In the study, factors related to the details of an inside defect are classified and optimized with pipeline simulator. The size and the shape of defect can be estimated accurately to find a critical point and also is closely related with shearing direction. The technique is applied for quantitative estimation of defects inside of a pneumatic tire. The actual traveling tire is monitored to reveal the cause of separation and the starting points. And also unknown void defects on tread are inspected and the size and shape of defects are estimated which has good agreement with the result of visual inspection.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.2
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• pp.564-574
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• 1996

This paper describes as Electronic Speckle Pattern Interferometry system which has been designed for measuring vibration patterns and quantitative measurement of vibration amplitude fields by using the time average method on a object. Visbility of fringe patterns is more improved by using the phase stepping and frame average method to reduce speckle and electric noise. And a bias vibration is introduced into the reference beam to shift the $\frac{2}{0}$ fringes so that fringe shift algorithms can be used to determine vibration amplitude. The experimental results are compared to those of the FFT analyzer and the FEM model analysis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.356-361
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• 1996

Nowadays, Electronic Speckle Pattern Interferometry is a well established measuring technique with a wide range of industrial applications, particularly in the fields of deformation measurement and vibration analysis. Comparing with holographic inteferometry, it has some attractive features, which are rapid recording and reconstruction, satisfiable automation etc. Time-average ESPI was used to provide vibration mode shape of an object whose vibration amplitude is given as a fringe pattern. However, it is not possible to determine the direction of motions of a point on the object at any given time, because time-average method does not give any information about the phase of vibration. A better technique is stroboscopic method which can measure the amplitude and phase of vibrating surface. In this paper, loudspeakers were tested by these two methods and the mode shape and amplitude of vibration were visualized. As measured results, we can assume that these techniques will be applied directly in the loudspeaker industry.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.11
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• pp.37-43
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• 2007

• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.22-28
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• 2006

• Current Optics and Photonics
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• v.7 no.4
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• pp.337-344
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• 2023

Three-point bending is the main method for measuring the elastic modulus of a thin plate. Although various displacement transducers may be used to measure the bending, these are single-point measurements, and it is difficult to eliminate the error caused by eccentric load and shear force. Error-correction models for the elastic modulus of quartz glass using digital speckle interferometry are proposed for eccentric load and shear force. First, the positional misalignment between maximum deflection and load is analyzed, and the error caused by eccentric load is corrected. Then, the additional displacement caused by shear force at different positions of the quartz glass plate is explored. The effect of shear deformation is also corrected, by measuring two points. Since digital speckle interferometry has the advantage of full-field measurement, it can simultaneously obtain deflection data for multiple points to realize error correction. Experimental results are presented to demonstrate that the proposed model can effectively correct the measurement error of the elastic modulus.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.2
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• pp.149-154
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• 2012

The size and distribution of welding residual stress and welding deformation in welding structures have an effect on various sorts of damage like brittle failure, fatigue failure and stress corrosion cracking. So, research for this problem is necessary continuously. In this study, non-destructive technique using laser electronic speckle pattern interferometry, plate of welding specimen according to the external load on the entire behavior of residual stress are presented measurement techniques. Once, welding specimen force tensile loading, using electronic speckle pattern interferometry is measured. welding specimen of base metal and weld zone measure strain from measured result, this using measure elastic modulus. In this study, electronic speckle pattern interferometry use weld zone and base metal parts of the strain differences using were presented in residual stress calculated value, This residual stress value were calculated by numerical calculation. Consequently, weld zone of modulus high approximately 3.7 fold beside base metal and this measured approximately 8.46 MPa.

• Nuclear Engineering and Technology
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• v.48 no.1
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• pp.259-267
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• 2016

Most manufacturing processes, including welding, create residual stresses. Residual stresses can reduce material strength and cause fractures. For estimating the reliability and aging of a welded structure, residual stresses should be evaluated as precisely as possible. Optical techniques such as holographic interferometry, electronic speckle pattern interferometry (ESPI), Moire interferometry, and shearography are noncontact means of measuring residual stresses. Among optical techniques, ESPI is typically used as a nondestructive measurement technique of in-plane displacement, such as stress and strain, and out-of-plane displacement, such as vibration and bending. In this study, ESPI was used to measure the residual stress on the welded part of butt-welded American Society for Testing and Materials (ASTM) A36 specimens with $CO_2$ welding. Four types of specimens, base metal specimen (BSP), tensile specimen including welded part (TSP), compression specimen including welded part (CSP), and annealed tensile specimen including welded part (ATSP), were tested. BSP was used to obtain the elastic modulus of a base metal. TSP and CSP were used to compare residual stresses under tensile and compressive loading conditions. ATSP was used to confirm the effect of heat treatment. Residual stresses on the welded parts of specimens were obtained from the phase map images obtained by ESPI. The results confirmed that residual stresses of welded parts can be measured by ESPI.