• Journal of the Korean Society for Precision Engineering
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• v.32 no.10
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• pp.911-916
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• 2015

In the nano/micro scale, material properties are dependent on the size-scale of a structure. However, conventional micro-scale tensile tests have limitations to obtain reliable values of nano-scale material properties owing to residual stress and elastic slippage in the gripping/aligning process. The indenter-driven nano-scale tensile test provides prominent advantages simple testing device, high-quality nano-scale metallic specimen with negligible residual stress. In this paper, two-types of specimens (a specimen with multi-testing parts and a specimen with a single-testing part) are discussed. Focused ion beam (FIB) is employed to fabricate a nano-scale specimen from a thin nickel film. Using the specimen with a single-testing part, we obtained a nano-scale stress-strain curve of electroplated nickel film.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.30-34
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• 2008

The transfer assembly (or transfer printing) technique is a promising method for fabricating multi-scale structures on various substrates including semiconductors and polymers, and has been applied to fabrication of flexible devices with superior performance to conventional organic flexible devices. The mechanical behaviors of the structures fabricated by the transfer assembly is a very important information for design and reliability evaluation purpose, but the measurement of the behaviors is difficult since their critical-dimensions are very tiny. In this study, Au films with nano-scale thickness were fabricated on a silicon substrate and their mechanical properties were measured using micro-tensile test. The Au films on the silicon substrate were then transferred to a PDMS substrate using the transfer assembly technique. Self-assembled monolayer (SAM) with a thiol group was used to enhance the transfer of Au films, and the mechanical behaviors were characterized using wrinkle-based test. The test results from micro-tensile and wrinkle-based test are compared to each other, and their implication to the transfer assembly technique is discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.220-224
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• 2005

The technology trend of Flat Panel Display (FPD) equipments have been demanded that there are compact and multi-function. Therefore, nano/micro scale patterned on polymeric materials of Back Light Unit (BLU) in Liquid Crystal Display (LCD) that has been investigated. This paper describes a series of Horizontal Type Micro Tensile Tester that were carried out to investigate the load strain distance performance of typical polymeric material sheets. The polymeric materials film that micro size shaped specimens for tensile test are used by Cold-Isostatic-Press (CIP). Test equipment is Horizontal type Micro Tensile Tester that is presented to measure the micro scale mechanical property of thin film for FPD. This paper presents which easy testing tools measure for micro patterned on polyethylene (PET) specimens.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.503-504
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• 2006

Determination of elastic properties of nano-scale materials using nano-indentation tests is well established, but that of plastic properties is not yet clear. This paper presents a method to extract plastic properties from nano-indentation test, together with results from detailed elastic-plastic FE analysis. It shows that the plastic properties determined from this method are not unique, in the sense that a number of different plastic properties can give the same load-displacement response from nano-indentation test. possible ways to overcome such problems are discussed.

• Journal of the Korean Geotechnical Society
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• v.28 no.7
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• pp.55-65
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• 2012

Total reduction factor that is used when calculating allowable tensile strength of geogrids is made by multiplying the installation damage reduction factor ($RF_{ID}$), chemical degradation reduction factor ($RF_D$), and creep reduction factor ($RF_{CR}$) etc. In case of a model estimating allowable tensile strength considering reduction factor over the short-term tensile strength of geogrids, it has a limit of not considering interaction force between reduction factors. Junction strength comes to be reduced by installation damages or chemical degradation in the same way as tensile strength. Single junction test method cannot properly test damaged samples and shows large deviations as it does not consider scale effect. Besides, regarding calculating shear strength, no reasonable study on reduction factors was conducted yet. Therefore, in this study, reduction factors that may affect the long-term performance of geogrids were revaluated considering various conditions and accurate long-term allowable tensile strength was calculated considering interrelation between reduction factors. Creep results after installation damage and chemical resistance test showed lower value than calculated value according to GRI GG-4. After the installation damage test and the chemical resistance test, the reduction factor of junction strength was less than that of tensile strength. Shear strength before and after installation damage showed no change or increase.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.208-212
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• 2009

The nano-clay is widely used in polymer-nanocomposites due to the high aspect ratio, heat resistance and nano-scale dimension. In recent researches, the thermal and mechanical properties of polyurethane foam were improved with introducing the nano-clay. In this study, we describe the influence of ultrasonic treatment and content of nano-clay on properties of polyurethane foam. The nano-clay/polyurethane foam were characterized using their recovery time, compressive deflection, cell morphology and tensile test. The ultrasonic treatment was very effective for dispersion of nano-clay. Moreover, we found that introducing over 3 wt% of nano-clay bring the decrease of properties due to the poor dispersion. Expecially, ultrasonically treated 20A/polyurethane foam(1 wt%) showed greatly improved properties, such as homogeneous cell size and good dimension stability. We expect that our results could be applied to insulating materials for construction.