• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.11
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• pp.2088-2092
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• 2011

The accelerated thermal aging of CSPE(chloro sulfonate polyethylene) of test cables were carried out for the period equal to 10, 20 and 30 years in air at $100^{\circ}C$, respectively. The CSPE cables(TAIHAN electric wire Co. Ltd) which installed in nuclear power plant for three years were used as starting materials. Condition monitering methods of the accelerated thermal aging of CSPE cables were estimated through indenter modulus and OIT(oxidation induction time) of IEC 62582, and those were newly estimated through volume electrical resistivity, ultrasound reflection time, density, FE-SEM(field emission scanning electron microscopy), XPS(x-ray photoelectron spectroscopy), EDS(energy dispersive spectroscopy), and WD-XRF(wavelength dispersive x-ray fluorescence). A new condition monitoring methods of the accelerated thermal aging of CSPE cables were generally coincident with trend of indenter modulus expect EDS, XPS and XRF. A volume electrical resistivity among new condition monitoring methods of the accelerated thermal aging of CSPE cables is excellent. It is considered that life-time of CSPE cable can be predicted through volume electrical resistivity, if CSPE jacket was aged for period such as more than 20 years.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.216.2-216.2
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• 2013

Nano-indenter는 팁을 박막 표면으로부터 일정 깊이까지 일정한 비율로 힘을 팁에 인가하여 그에 따른 박막의 반응을 in-situ로 확인하기 위하여 고안된 장치이며, 박막은 물론 나노 구조물까지 다양한 범위에서 기계적 특성을 분석하기 위하여 사용되고 있다. 이 연구에서는 유전체 및 확산방지막으로 사용되는 Hf을 rf magnetron sputter로 증착하였으며 이때 Ar 가스와 함께 $N_2$ 가스의 혼합 비율을 다르게 하여 HfN을 증착하였다. 질소 분압에 따라 증착된 HfN 박막은 고온중에서 질소의 영향을 확인하기 위하여 $800^{\circ}C$로 질소 분위기에서 20분간 열처리하여 이후 박막의 nano-mechanical 특성을 nanoindenter를 사용하여 확인하였고 최대 압입력을 250 ${\mu}N$으로 고정하였다. 측정결과 고온 열처리후 HfN 박막은 증착시 질소 분압이 0%에서 5%로 증가함에 따라 surface hardness는 8.6 GPa에서 8.1 GPa로 elastic modulus는 123.7 GPa에서 134 GPa로 각각 변화되는 것을 확인할 수 있었다. 특히, 질소 분압이 2.5%로 증착된 HfN 박막은 열처리후 박막 표면의 물리적 특성이 깊이 방향으로 층을 이루고 있어 nano-indenter 압입시 다수의 pop-in이 나타남을 확인하였다.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.484-490
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• 2021

Instrumented indentation testing has been widely used for residual stress measurement. The Knoop indentation is mainly selected for determining anisotropic mechanical properties and non-equibiaxial residual stress. However, the measurement of equibiaxial stress state and compressive residual stress on a specimen surface using Knoop indentation is neither fully comprehended nor unavailable. In this study, we investigated stress conversion factors for measuring Knoop indentation on equibiaxial stress state through indentation depth using finite element analysis. Knoop indentation was conducted for specimens to determine tensile and compressive equibiaxial residual stress. Both were found to be increased proportionally according to indentation depth. The stress field beneath the indenter during each indentation test was also analyzed. Compressive residual stress suppressed the in-plane expansion of stress field during indentation. In contrast, stress fields beneath the indenter developed diagonally downward for tensile residual stress. Furthermore, differences between trends of stress fields at long and short axes of Knoop indenter were observed due to difference in indenting angles and the projected area of plastic zone that was exposed to residual stress.

• Structural Engineering and Mechanics
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• v.85 no.5
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• pp.621-633
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• 2023

The major objective of this paper is to study the receding contact problem between two functional graded layers under a flat indenter. The gravity is assumed negligible, and the shear moduli of both layers are assumed to vary exponentially along the thickness direction. In the absence of body forces, the problem is reduced to a system of Fredholm singular integral equations with the contact pressure and contact size as unknowns via Fourier integral transform, which is transformed into an algebraic one by the Gauss-Chebyshev quadratures and polynomials of both the first and second kinds. Then, an iterative speediest descending algorithm is proposed to numerically solve the system of algebraic equations. Both semi-analytical and finite element method, FEM solutions for the presented problem validate each other. To improve the accuracy of the numerical result of FEM, a graded FEM solution is performed to simulate the FGM mechanical characteristics. The results reveal the potential links between the contact stress/size and the indenter size, the thickness, as well as some other material properties of FGM.

• Journal of the Korean Vacuum Society
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• v.18 no.2
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• pp.97-101
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• 2009

In the modem semiconductor industry, the progress that consumes the most capital and labor is cleansing process. Cleansing process is to remove impurities that can affect the operation of the device and deteriorate its function. Especially, Photoresist (PR) progress that etches the device always requires cleansing at the end of the progress. Also, HDI-PR (High-Dose Ion-implanted Photoresist) created from PR progress is difficult to remove. Thus, in modem IC cleansing, many steps of cleansing are used, including dry and wet cleansing. In this paper, we suggested to combine existing dry-cleansing and wet-cleansing, each represented by plasma cleansing and stripper solution, as Plasma Liquid-Vapor Activation (PLVA). This PLVA method enhances the effect of existing cleansing solution, and decreases the amount of solution and time required to strip. We stripped HDI-PR by activated solution and measured surface hardness and Young's modulus by Nano-indenter. Nano-indenter is the equipment that determines the hardness and the modulus of elasticity by indenting nano-sized tip with specific shape into the surface and measuring weight and z-axis displacement. We measured the change of surface hardness and Young's modulus before and after the cleansing. As a result, we found out that the surface hardness of the sample sharply decreased after the cleansing by plasma-activated PR stripper solution. It can be considered that if physical surface-cleansing process is inserted after this, more effective elimination of HDI-PR is possible.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.4
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• pp.61-64
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• 2003

The fractography was used to observe the stress profile on a single ion-exchanged glass. In the processing, the temperature was varied during the ion exchange, and then the stress profile on the single ion-exchanged glass was shifted from glass surface to slightly below the glass surface. The hackle mark and mirror surface were varied according to process conditions, and the glass strength was increased with increasing the number of hackle markers. In case of breaking the stress profile by using indenter, the breaking property was similar to the annealed glass.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1030-1035
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• 2003

The nanoimprint lithography technology makes higher density of semiconductor device and larger capacity of storage media. In this technology the induced damage while detaching polymer pattern from mold should be minimized. In order to analyze the problem, the basic knowledge of adhesion between the polymer and the mold is required. In this study a contact experiment of polyisobutylene specimen with spherical steel tip and polyisobutylene bead tip was conducted using nano indenter. During the contact experiment with various loading rate under load control the contact behavior of viscoelastic material was measured, i.e., the load and displacement between the tip and the specimen were measured. The data was analyzed by HBK model to obtain the stress intensity factor of contact edge and the contact radius as a function of time. Also the adhesion energies between steel/polyisobutylene and polyisobutylene/polyisobutylene were obtained employing the analysis of the crack of viscoelastic material by Schapery.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.12
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• pp.1357-1365
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• 2009

In this study, we enhance the numerical approach of Lee et al.$^{(1)}$ to spherical indentation technique for property evaluation of hyper-elastic rubber. We first determine the friction coefficient between rubber and indenter in a practical viewpoint. We perform finite element numerical simulations for deeper indentation depth. An optimal data acquisition spot is selected, which features sufficiently large strain energy density and negligible frictional effect. We then improve two normalized functions mapping an indentation load vs. deflection curve into a strain energy density vs. first invariant curve, the latter of which in turn gives the Yeoh-model constants. The enhanced spherical indentation approach produces the rubber material properties with an average error of less than 3%.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.5
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• pp.708-713
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• 2012

The indented geometry for rockwell hardness indenter has been configured by using Confocal Laser Scanning Microscopy (CLSM). For this purpose, the CLSM can be well suited to construct the three-dimensional indented volume from the indented surface by rockwell hardness tester. Furthermore, the height data of HEI(height encoded image) by CLSM must be acquired at first and converted to indented surface later. And the indented surface patterns enable us to predict the indenter shape and volume. This volume can be used to study the rockwell hardness model as a volume parameter. As a result, the technique performed in this study by combining the CLSM with compensation technique is an excellent one to obtain the geometries of indented surfaces over a wide range of surface resolution in a micro scale. And it can be used for micro volume calculation.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.1
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• pp.27-32
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• 2004

The diamond-like carbon (DLC) films were deposited on the Si (100) wafer by a rf-PECVD method as a function of the mixture rate of methane-hydrogen gas and bias voltage. The bonding structure and mechanical properties of these deposited DLC films were investigated using FT-IR, Raman, and nano-indenter. The deposition rates of DLC films increased with increased flow rate of methane in the gas mixtures and increased bias voltage. The $sp^3/sp^2$ bonding ratio of carbon in thin film and the hardness increased with increasing flow rate of hydrogen in the gas mixtures and increasing bias voltage.