• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1807-1812
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• 2007

A bulge testing system was developed to measure mechanical properties of thin film materials. A bulge pressure test system for pressurizing the bulge window of the film and a micro out-of-plane ESPI(Electronic Speckle Pattern Interferometric) system for measuring deflection of the film were included in the testing system developed. For the out-of-plane ESPI system, whole field speckle fringe pattern, corresponding to the out-of-plane deflection of the bulged film, was 3-dimensionally visualized using 4-bucket phase shifting algorithm and least square phase unwrapping algorithm. The bulge pressure for loading and unloading was controlled at a constant rate. From the pressure-deflection curve measured by this testing system, ain-plane stress-strain curve could be determined. In this study, elastic modulus of an electrolytic copper film 18 ${\mu}m$ was determined. The modulus was calculated from determining the plain-strain biaxial elastic modulus at the respective unloading slopes of the stress-strain curve and for the Poisson's ratio of 0.34.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1315-1320
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• 2003

The thermal expansion coefficient, which causes the micro failure at the interfacial state of thin films is necessary to consider for proper designing MEMS. The effect of temperature on the coefficient of thermal expansion(CTE) of $SiO_2$ and $Si_3N_4$ film was investigated. Thermal strain induced by mismatch of CTE between substrate and thin film continuously measured with resolution-improved electronic speckle pattern interferometry(ESPI). The thermal stress induced by mismatch of CTE derivate through thermal strain. The thermal expansion coefficients of thin film were calculated with the general equation of CTE and thermal stress in thin films, and it confirmed that CTE of $SiO_2$changed from $0.25{\times}10^{-6}/^{\circ}C$ to $1.4{\times}10^{-6}/^{\circ}C$ with temperature increasing from 50 to $600^{\circ}C$

• 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.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.6
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• pp.119-126
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• 2004

The welding characteristics of Inconel 600 Alloy using a continuous wave Nd:YAG laser are experimentally investigated. The major process parameters studied in the present laser welding experiment were the positions of focus, laser power and travel speed of laser bean We measured the fusion zone size and its shape using an optical microscope for the observation of cross-sectional area. We performed two tests regarding the tension and the micro hardness for welding quality estimation. Then we measured residual stress in welds by electronic speckle pattern interferometry(ESPI). In conclusion the optimum butt welding process parameters were 0.5mm focus position, 1.6kW laser power, 1m/min travel speed and 5.5$\ell$/min assist gas discharge.