• Journal of the Korean Society for Precision Engineering
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• v.18 no.5
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• pp.90-97
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• 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.

• 한국가시화정보학회:학술대회논문집
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• 2005.12a
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• pp.40-45
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• 2005

Velocity and density distributions of a high-speed and initial $CO_{2}$ jet flow have been analyzed simultaneously by a developed three-dimensional digital speckle tomography and a particle image velocimetry(PIV). Three high-speed cameras have been used for tomography and PIV since a shape of a nozzle for the jet flow is asymmetric and the initial flow is fast and unsteady, The speckle movements between no flow and $CO_{2}$ jet flow have been obtained by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays for density gradients. The three-dimensional density fields for the high-speed $CO_{2}$ jet flow have been reconstructed from the deflection angles by a real-time tomography method and the two-dimensional velocity fields have been calculated by a PIV method simultaneously and instantaneously.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.29-33
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• 2004

This paper presents ESPI system for the measurement of thermal expansion coefficient of STS430 up to 1,000$^{\circ}C$. Existing methods, strain gauge and moire have the limitation of contact to object and do not supply the coefficient up to 800$^{\circ}C$. There needs to measure the data up to 800$^{\circ}C$, because heat resistant materials have high melting temperature up to 1,000$^{\circ}C$. In previous studies related to thermal strain analysis, the quantitative results are not reported by ESPI at high temperature, yet. In-plane ESPI and vacuum chamber for the reduction of air turbulence and oxidation are designed for the measurement of the coefficient up to 1,000$^{\circ}C$and speckle correlation fringe pattern images are processed by commercial image filtering tool-smoothing, thinning and enhancement- to obtain quantitative results, which is compared with references data. The comparison shows two data are agreed within 4.1％ blow 600$^{\circ}C$ however, there is some difference up to 600$^{\circ}C$. Also, the incremental ratio of the coefficient is changed up to 800$^{\circ}C$. The reason is the phase transformation of STS430 probably begins at 800$^{\circ}C$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.226-230
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• 2001

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 spekle patterns to be formed with interference phenomena of scattering phenomena measure the out-of-plane deformations, together with the use of digital image equipment to process the informations included in the speckle patterns and the 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-0of-plane displacements of a spot welded canti-levered plate were measured by ESPI with 4-step phase shifting technique. The phase map of the spot welded canti-levered plate is quite different from that of the canti-levered plate without spot welding.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.3
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• pp.66-72
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• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.93-96
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• 2000

This study discusses a non-contact optical technique, phase shifting electronic speckle pattern interferometry, that is well suited for a deformation measurement. However, the phase shifting method has difficulties for determinating a deformation quantitatively beacuse of the characteristics of arctan function. In order to solve this problem, phase unwrapping methods has been studied during the last few years. In this study, using phase unwrapping based on line by line scanning phase shifted fringe patterns are studied to determinate a deformation quantitatively. Also least square fitting method is applied to reduce noise and improve image resolution.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.114-122
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• 1994

ESPE(Electonic-Speckle-Pattern-Interferometry) is very useful method for measuring In-plane displacement. Using the CW-Laser and Image processing system, it is possible to measure displacement and strain. Unlike traditional straingauge or moire' method, ESPI method requires no special surface preparation or attachments and can be measured In-plane displacement with no contact and real time. In this experimental specimen was loaded in paralled with loadcell, which provided loading step. The specimen was sheet plate, which was attached straingauge in x-y direction. In this study provides an example of how ESPI has been used to measure two dimensional displacement and strain distribution in this specimen. The results measured by ESPI compare with the data which was measured straingauge method in tensile testing at 1 ton range.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.1
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• pp.23-26
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• 2000

In spot welded joint. Electronic Speckle Pattern Interferometry(ESPI) method using the Model 95 Ar laser a video system and an image processor was applied to measure the stress Unlike traditional strain gauges or Moire method, ESPI method has no special surface preparation or attachments and can be measured in-plane displacement with non-contact and real time. In this experiment, specimens are loaded in parallel with a load cell. The specimens are made of the cold rolled steel sheet with 1mm thickness, are attached strain. gauges. This study Provides an example of how ESPI has been used to measure stress and strain inspecimen. The results measured by ESPI are compared with the data which was measured by strain gauge method under tensile testing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.330-333
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• 2002

This study Presents improvement of Precision in the non-contacted laser application measuring techniques. The phase map of deformation obtained by phase shifting method in Electronic Speckle Pattern Interferometry displays the wrapped image by the arctangent function, which is a characteristic of 4-step phase shifting method. To obtain deformation distribution from the results, the wrapped phase map is processed by an unwrapping method. But a previous method cannot apply discontinuous object as like plate with a circular hole to obtain precious deformation distribution To solve this problem, new algorithm is developed and the result is compared with previous method.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.3
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• pp.52-57
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• 1997

Electronic Speckle Pattern Interferometry(ESPI) using the Model 95 Ar. laser, a video system and an image processor was applied to the in-plane displacement measurements. Unlike traditional strain gauges or Moire method, ESPI method requires no special surface preparation or attachments and can be measured in-plane displacement with no special surface preparation or attachments and can be measured in-plane displacement with no contact and real time. In this experiment specimen was loaded in parallel with a loadcell. The specimen was the cold rolled steel sheet of 2mm thickness, which was attached strain gauges. The study provides an example of how ESPI have been used to measure strain displacement in this specimen. The results measured by ESPI compare with the data which was measured by strain gauge method in tensile testing.