• Journal of the Korean Society for Precision Engineering
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• v.13 no.2
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• pp.84-93
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• 1996

Non-destructive inspection techniques using laser have been broading their application areas as well as growing their measurement skills together with the rapid development of circumferential technology like fiber optics, computer and image processing. The ESPI technique is already on the stage of on-line testing with commercial products in developed country nations. Especially, this technique is expected to be applied to the nuclear industry, automobile and aerospace because it is proper for the vibration measurement and it can be applied to objects of a high temperature. This paper describes the use of the ESPI system for measuring vibration patterns on the reflecting objects. Using this system, high-quality Jo fringes for identifying mode shapes are displayed. A bias vibration is introduced into the reference beam to shift the Jo fringes so that fringe shift algorithms can be used to determine vibration amplitude. Using this method, amplitude fields for vibrating objects were obtained directly from the time-average interferograms recorded by the ESPI system.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.93-100
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• 2008

Laser interferometry is widely used as a measuring system in many fields because of its high resolution and 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 3D 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 Modulating interferometry that involves four-buckets phase shift method. This study proposes a four-bucket 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. Four-bucket phase mapping algorithm is then introduced.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.516-521
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• 2000

Most of studies, using ESPI method, have handled tension, thermal and vibration analysis, and is limited to isotropic materials. However, tension and vibration simultaneously are loaded in real structure. Also, almost study using ESPI method is locally limited to the analysis on the isotropic materials and a few studies on the anisotropic materials have reported. Existing methods, such as the accelerometer method and FEA method, to analyze vibration have some disadvantages. Using the accelerometer method that is generally used to analyze vibration phenomena, it is impossible to analyze vibration on the oscillating body and one can observe no vibration mode shape during experiment. In case of the FEA method, it is difficult to define boundary conditions correctly if the shape of a body tested is complex, and one can just obtain vibration mode shapes on the peak amplitude in each modes. In this study, plane plate of stainless steel(STS304), isotropic material, that is used as structural steel is analyzed about vibration characteristics under tension. Also, in the study of stainless steel, the characteristics of composite material(AS4/PEEK) used as high strength structural material in aircraft is evaluated about vibration under tension, and studies the effect of tension on vibration.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.542-543
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• 2012

Coherent diffraction imaging (CDI) method using hard x-ray at 5.46 keV was applied to study assembly of Ni and Ni oxide nano structures formed on a Si3N4 membrane. Density distribution of Ni nano-particles was obtained quantitatively with about 15 nm lateral resolution by reconstructing images from the speckle diffraction pattern. In addition, reconstructed images of nickel oxide particles indicated that Ni atoms diffuse out during the oxidation process leaving pores inside the nickel oxide crust. Furthermore, we recognize that really weak phase object, less than 5 nm thickness of Ni residues, can be reconstructed due to the reference particles. We achieved quantitative information of nanometer sized materials and demonstrate the effect of reference particles by using hard x-ray coherent diffractive imaging method.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.240-245
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• 2004

Tensile properties of hard coating material, TiN, were evaluated using micro-tensile testing system. TiN has been known as a hard coating material commonly used today. Micro-tensile testing system consisted of a micro tensile loading system and a micro-ESPI(Electronic Speckle Pattern Interferometry) system. Micro-tensile loading system had a maximum load capacity of 500mN and a resolution of 4.5 nm in stroke. TiN thin film $1{\mu}m$ thick was deposited on the Si wafer pre-deposited of $Si_3N_4$ film substrate by the closed field unbalanced magnetron sputtering (CFUBMS) process. Three kinds of micro-tensile specimen with the respective width of $50{\mu}m$, $100{\mu}m$ and $500{\mu}m$ were fabricated by MEMS process. The mechanical properties including tensile strength and elastic modulus were determined using the micro-tensile testing system and compared by those obtained by nano-indentation

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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• pp.485-490
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• 2010

Recently, environment problems have effects on the electronic equipments. Security problems are presented. For security reasons, it is necessary to study electronic equipments. In this paper, we handle the Elasticity modulus on the polymer insulator by UV irradiation. The types of material are used in this experiment, is the EPDM (Ethylene Propylene Diene Monomer). For increasing the reliability, real material specimens are used. For this study, we used ESPI (Electronic speckle pattern interferometry), UTM (Universal thesting machine) device, Accelerated weathering tester. Through this measurement, we evaluated how much UV irradiation has effect on polymer insulator and how long does it take to change the polymer insulator. Also this paper will give a help in electronic industry and the method of measuring the insulator elasticity modulus of polymer could be utilized in life estimation and replacement time of the products of electronic equipment that is used in real industrial fields.

• Journal of the Korean Society of Safety
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• v.23 no.5
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• pp.30-34
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• 2008

To evaluate the mechanical properties of in-service materials, tensile properties measurement using small-scaled specimen has been carried out. Tensile testing specimens with various dimensions, including standard and sub-size specimen specified in ASTM and ISO and small-scaled specimen, were prepared. Tensile strain in small-scaled specimen was measured using micro-ESPI system set up in this study. This system was used in the specimen with the parallel length of 2 mm and in subsequently measuring the strain under tensile loading. From each type of tensile specimen, stress-strain curves were determined. The dimension effect of the tensile properties was investigated comparing the tensile results obtained from standard specimens and small-scaled specimens. It was shown that the tensile strength for the small-scaled specimen is lower by 15% than those for the standard specimen.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.1
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• pp.59-66
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• 2013

The measuring of internal defects of objects using the shearography has many advantages. It is a non-contact and non-destructive method and It has a real time measurement speed and no constraints of object shape. Compared to ESPI(Electronic Speckle Pattern Interferometry), Shearography has a very low error rate by vibration and air turbulence. So shearography provides possibilities of industrial application. In this paper, Image processing algorithm that is measurement of out-of-plane deformation using the shearography is proposed by developed using the LabVIEW 2010 and measurement result of out-of-plane ESPI and Shearography are compared quantitatively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.930-933
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• 2005

Non-destructive inspection techniques using laser have been breading their application areas as well as growing their measurement skills together with the rapid development of circumferential technology like fiber optics. computer and image processing The ESPI technique is already on the stage of on-line testing with commercial products in developed country nations. Especially, this technique is expected to be applied to the nuclear industry, automobile and aerospace because it is proper for the vibration measurement and it can be applied to objects of a high temperature. This paper describes the use of the ESPI system for measuring vibration patterns on the reflecting objects. Using this system, high-quality Jo fringes for identifying mode shapes are displayed. A bias vibration is introduced into the reference beam to shift the Jo fringes so that fringe shift algorithms can be used to determine vibration amplitude. Using this method. amplitude fields for vibrating objects were obtained directly from the time-average interferometer recorded by the ESPI system.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.54-63
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• 2006

Enhancement methods of sensitivity to in-plane strain measurement by micro-ESPI(Electronic Speckle Pattern Interferometry) technique were proposed using TiN and Au thin films. Micro-tensile strain over the micro-tensile specimens, prepared in micro-scale by those films, was measured by micro-tensile loading system and micro-ESPI system developed in this study. The subsequent measurement of in-plane tensile strain in the micro-sized specimens was introduced using the micro-ESPI technique, and the micro-tensile stress-strain curves for these films were determined. To enhance the sensitivity to measurement of in-plane tensile strain, algorithms of the phase estimation by using curve fitting of inter-fringe and the discrete Fourier Transform with object-induced dynamic phase shifting were developed. Using these two algorithms, the micro-tensile strain-stress curves were generated. It is shown that the algorithms for enhancement of the sensitivity suggested in this study make the sensitivity to measurement of the in-plane tensile strain increase.