• Journal of Ocean Engineering and Technology
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• v.21 no.1 s.74
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• pp.59-63
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• 2007

The thin film of indium tin oxide (ITO) was prepared using the inclination opposite target type DC magnetron sputtering equipment onto the glass substrate at room temperature, using oxidized ITO with In2O3 and SnO2in a weight ratio of 9:1. The elastic modulus and hardness of the ITO thin films, prepared at different deposition conditions, were determined through anano-indentation experiment. The work pressure was varied from $2.6{\times}10-1\;to\;8.3{\times}10-1Pa$. The results show that the variation of work pressure during film deposition could vary significantly, according to the elastic modulus and hardness of the ITO thin films. It also can be seen that a minimum value exists in the film resistivity for the ITO thin films, prepared according to the variation of work pressure. However, the ITO film produced at room temperature had a microstructure in which a X ray diffraction peak is not clear, regardless of the work pressure.

• Journal of Power System Engineering
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• v.18 no.4
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• pp.104-111
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• 2014

In this study, EH36 is thick steel plate, which welded by auto $CO_2$ gas welding machine, has been applied on offshore filed. The specimen was examined by indentation tester and it was measured for fracture toughness at $18^{\circ}C$, $0^{\circ}C$, $-20^{\circ}C$ and $-45^{\circ}C$ by low temperature chamber, respectively. The absorbed energy was got on same temperature by Charpy impact tester. The weld surface was observed for watch of changed crystalline structure by optical microscope, and fracture surface of impact test specimen were observed by scanning electron microscope(SEM).

• Journal of the Korean Ceramic Society
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• v.56 no.1
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• pp.37-48
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• 2019

The objective of this research is to analyze the fracture toughness of pure and silica co-doped yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) bioceramics containing 0.1 and 0.2 wt.% of alumina, and sintered at a temperature of $1500^{\circ}C$. Because of the relatively easy preparation of the test specimens and the high speed of testing, the Vickers indentation fracture (VIF) technique is more frequently used to evaluate the fracture toughness of biomaterials and hard biological tissues. The Young's modulus and hardness values were obtained by means of nanoindentation and indentation methods. The fracture toughness values of 3Y-TZP bioceramics were calculated and analyzed using 15 equations related to the VIF technique, and loadings of 49.03 and 196.13 N with a Vickers diamond. For validation, the results were compared with fracture toughness values obtained by the single-edge laser-notch beam (SELNB) method with an almost atomically sharp laser-machined initial notch.

• Journal of the Korean Ceramic Society
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• v.33 no.3
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• pp.339-347
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• 1996

Mechanical properties(flexural strength hardness fracture toughness) of alumina ceramics were evaluated. Alumina products of four companies were selected and three of those were made in Korea and one of those was made in Japan. The large differences according to manufacturing companies had resulted from flexural strength and weibull modulus which had a wide ranges of 300 to 400 MPa and 5 to 15 respectively. Critical indenstation load which could be neglected the effect of elastic recovery was about 9.8N and Vickers' hardness were about 15 GPa. Fracture toughnesses were evaluated by IF and ISB method. It was more preferable to the average at one indentation load that fracture toughness were obtained from the slope of the relationship between indentation load and crack length in IF method and between indentation load and fracture load in ISB method and fracture toughness was about 4 MPa·m1/2.

• Composites Research
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• v.14 no.3
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• pp.42-50
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• 2001

Modeling of damage initiation in singly oriented ply (SOP) Fiber Metal Laminate (FML) under concentrated loading conditions was studied. The finite element method (FEM) base on the first order shear deformation theory is used for th\ulcorner modeling of damage initiation in SOP FML. The failure indices (FI) of the fiber prepreg and the metal laminate were calculated by using the Tasi-Hill failure criterion and the Miser yield criterion, respectively. To verify the present method, the failure analysis was conducted under uniaxial loading and cylindrical bending, then the analysis under concentrated load was conducted. The results show that the analysis is reasonable. An indentation test was conducted to compare a damage initiation load with a calculated FI. The test was conducted under two side clamped conditions to study the fiber orientation effect. Indentation curve was fitted using the Hertz equation and a damage initiation load is defined that the point which deviate the fitted curve from the real indentation curve. The damage initiation loads were obtained under various fiber orientations and compared with calculated FIs. The experiment was well matched with calculated FI. This results shows that the present method is suitable for the damage initiation modeling of SOP FML.

• Journal of the Korean institute of surface engineering
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• v.51 no.4
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• pp.197-201
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• 2018

Dynamic nano-indentation method was applied to characterize thin electroformed Ni-P layers. The Ni-P layers were produced in a sulphamic acid bath at $50^{\circ}C$ in $0.02A/cm^2$ for 10-60 minutes. The chemical analyses by XRD and EDX showed that the Ni-P layers were very fine grains with mainly $Ni_3P$ with Ni. The surface roughness determined by atomic force microscopy increased with thickness, which was relative to the surface morphology. The nano-hardness and the stiffness of the thin Ni-P layers with thickness of 1.9, 6.2 and $7.5{\mu}m$ were 5.52, 6.52 and 6.77 [GPa] and 56.7, 76.2 and 108.0 [${\mu}N/nm$], respectively. The elastic modulus of the Ni-P layer increased with thickness such as 37.29, 54.50 and 78.76 [GPa], respectively. The surface roughness of the electroplated Ni-P layers with diverse thickness was 8.66, 18.56 and 35.22 [nm], respectively. The enhanced nano-mechanical properties were related to mainly residual stress of the Ni-P layers.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.415-424
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• 2014

The carrying capacity of existing concrete structures is evaluated by the measured data from displacement and strain gauges for given loads and the results of numerical analysis that are compared with the measured ones. Consequently, this process could be accomplished in doing the direct measurement of residual stress on existing concrete. This study is concerned with the development of IITC (Instrumented Indentation Technique for Concrete) system which is based on the experimental stress analysis technique using non-destructive test method to evaluate the residual stress of concrete structures depending on the types of applied loadings in analysing indentation load - indentation depth curve derived experimentally on concrete surface. As a result, in this paper, almost all of systematized H/W and S/W were newly developed to estimate the residual stresses of concrete structures. Thus, the creation of new experimental equations for deriving residual stresses and automatical calculations of residual stresses using the empirical formula can lead to evaluate the structural resistances conveniently in the structures from construction phase to maintenance stage.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.2
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• pp.125-130
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• 2008

A spherical indentation has been proposed as a nondestructive method of measuring local residual stress field in laser-voided joints. The apparent yield strengths interpreted from the spherical indentation data of as-welded cutting wheel were compared with the intrinsic yield strengths measured at nearly equivalent locations in annealed wheel. Their difference along the distance from the welding line is welding stress distribution because the intrinsic yield strength is invariant regardless of the elastic residual stress. The spherical indentations show that the laser-welded diamond cutting wheel displays a 10 min-wide distribution of the welding residual stress and has peak compressive and tensile stresses in the shank and tip regions, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.17-28
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• 2012

In this study, we suggest a method for material property evaluation by dual-triangular pyramidal indenters using the reverse analysis. First, we demonstrated that load-displacement curves of conical and triangular pyramidal indenters are different for the same material. For this reason, an independent research on the triangular pyramidal indenter is needed. From FE indentation analyses on various materials, we then investigated the relationships among material properties, indentation parameters and load-displacement curves. From this, we established property evaluation formula using dual-triangular pyramidal indenters having two different half-included-angles. The approach provides the values of elastic modulus, yield strength and strain-hardening exponent within an average error of 3% for various materials.

• Tribology and Lubricants
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• v.37 no.6
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• pp.240-245
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• 2021

Ceramic coatings with high hardness and excellent chemical stability have been successfully applied to various machine elements, tools, and implants. However, in the case of monolayer coating on soft substrates, a high-stress concentration at the interface between the coating and the substrate causes delamination of the coating layer. Recently, to overcome this problem, multilayer coatings with a metal layer with a low modulus of elasticity added between the ceramic and the substrate have been widely applied. This study presents the third part of a recent study and focuses on the effect of the number of coating layers on the Brinell hardness of multilayered coating with TiN/Ti, following the two previous studies on a new Brinell hardness test method for a coated surface and on the influence of substrate and coating thickness. Indentation analyses are performed using finite element analysis software, von Mises stress and equivalent plastic strain distributions, load-displacement curves, and residual indentation shapes are presented. The number of TiN/Ti layers considerably affect the stress distributions and indentation shapes. Moreover, the greater the number of TiN/Ti layers, the higher is the Brinell hardness. The stress and plastic strain distributions confirm that the multilayer coatings improve the wear resistance. The results are expected to be used to design and evaluate various coating systems, and additional study is required.