• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.355-358
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• 2003

To estimate the residual stresses in the thin film and surface coatings, combined method based on nanoindentation and finite element (FE) analysis was developed. A simple equation for estimating the residual stress was composed of the hardness and the parameters which can be driven from the nanoindentation loading and unloading behaviors. FE analysis on the nanoindentation procedure under the various residual stress levels was performed to determine the parameters that included in the equation. The equation showed a good coincidence between the estimated residual stresses and those for the FE analysis. Thus the proposed method was considered as a useful method for estimating the residual stresses in the thin film without stress free specimen.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.111-115
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• 2003

Nanoindentation is simply an indentation test in which the length scale of the penetration is measured in nanometres rather than microns or millimetres, the latter being common in conventional hardness tests. Three-dimensional molecular dynamics simulations have been conducted to evaluate the nanoindentation test. Molecular dynamics simulations were carried out on single crystal copper by varying crystal orientations to investigate nano-behavior of material beneath an indenter in nanoindentation. Morse potential function was used as an interatomic force between indenter and thin film. The result of the simulation shows that crystal orientation significantly influenced the slip system, dislocation nucleation and dislocation behavior.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.63-68
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• 2005

The nanoindentation technique is widely used to investigate the mechanical properties of nano-microscale materials. The nanoindentation method for assessing mechanical properties at low loads and shallow depths is already well established fur the characterization of thin films as well as bulk materials. In this study, we evaluated residual stress in DLC and Au thin films usign nanoindentation technique with a new stress-relaxation model. Moreover, We suggest a composite hardness equation and quantify the magnitude of hardness increase by using an equation based on the interface hardness and the interface thickness, derived by comparing results derived from this equation and those determined in nanoindentation tests. Finally, We present an indentation size effect (ISE) model that extends the available contact depth for ISE application down to several tens of nanometers by considering the tip bluntness effect.

• Journal of the Korean Ceramic Society
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• v.46 no.1
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• pp.116-121
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• 2009

The constituent phases in Ti($C_{0.7}N_{0.3}$)-xWC-20Ni (wt%, x=5, 15, 25) cermets were characterized using nanoindentation in conjunction with observation of microstructure. The microstructure of cermet is composed of hard phase and binder phase, which gave rise to a wide range of hardness distribution when nanoindentation was carried out on the polished surface of cermets. Because of the inhomogeneous nature of cermet microstructure, observation of indented surface was indispensable in order to separate the hardness of each constituent phase. The measured values of hardness using nanoindentation were ${\sim}14\;GPa$ for the binder phase and ${\sim}24$ to 28 GPa for the hard phase, of which nanoindentation hardness was decreased with the addition of WC into Ti($C_{0.7}N_{0.3}$)-Ni system. In addition, the nanoindentation hardness of Ni binder phase was much higher than reported Vickers hardness, which could result from confined deformation of binder phase due to the surrounding hard phase particles.

• Journal of the Korean Ceramic Society
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• v.45 no.9
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• pp.518-523
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• 2008

The mechanical properties of silicon carbide deposited by chemical vapor deposition process onto a graphite substrate are studied using nanoindentation techniques. The silicon carbide coating was fabricated in a chemical vapor deposition process with different microstructures and thicknesses. A nanoindentation technique is preferred because it provides a reliable means to measure the mechanical properties with continuous load-displacement recording. Thus, a detailed nanoindentation study of silicon carbide coatings on graphite structures was conducted using a specialized specimen preparation technique. The mechanical properties of the modulus, hardness and toughness were characterized. Silicon carbide deposited at $1300^{\circ}C$ has the following values: E=316 GPa, H=29 GPa, and $K_c$=9.8 MPa $m^{1/2}$; additionally, silicon carbide deposited at $1350^{\circ}C$ shows E=283 GPa, H=23 GPa, and $K_c$=6.1 MPa $m^{1/2}$. The mechanical properties of two grades of SiC coating with different microstructures and thicknesses are discussed.

• Journal of Ocean Engineering and Technology
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• v.28 no.4
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• pp.338-344
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• 2014

The purpose of this study was to evaluate the dispersion degree of particles using a nanoindentation test for titanium oxide nanoparticles/epoxy resin nanocomposites. Thus, the effects of the particle size and weight fraction, dispersion agent, and position of the sample on the modulus and degree of particle dispersion in the nanocomposites were investigated. As a result, the dispersion degree of large particles was found to be better than that of smaller particles in composites. It could be found that the aggregation or agglomeration of small particles with large surface energy occurred more easily in nanocomposites because of the large specific surface area. The moduli of the upper side of the film-shaped sample obtained from a nanoindentation test were low scattering, while the values for the bottom side were high scattering. Thus, the dispersion situation of the nanoparticles on the upper side of film-shaped samples could be considered to be better than that for the bottom side. This could be concluded due to the non-uniform nanoparticle dispersion in the same sample. The modulus obtained from nanoindentation test increased slightly with the content of nanoparticles and increased with the indented depth for the same sample. The latter is presumably due to the increase in the accumulated particles facing the indenter with the indented depth. The nanoindentation test was found to be a useful method to evaluate the dispersion status of nanoparticles in nanocomposites.

• Korean Journal of Materials Research
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• v.14 no.6
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• pp.436-442
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• 2004

Elastic and plastic deformation behaviors of the high purity aluminum and the silica glass were studied using nanoindentation and finite element analysis(FEA) techniques. Berkovich- and cone-type indenters were used for the nanoindentation test. Deformation behaviors and nanoindent profiles of elastic, elastic-plastic or plastic materials were clearly visualized by FEA simulation. Effects of the penetration depth and strain hardening on the deformation behavior were examined. Pile-up and sink-in behaviors were studied by using FEA technique. Degree of pile-up or sink-in was found to be a function of the ratio of elastic modulus to yield strength of materials. FEA was found to be an effective method to study deformation behaviors of materials under nanoindentation, especially in the case when pile-up or sink-in phenomena occurred.

• Interaction and multiscale mechanics
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• v.6 no.3
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• pp.301-316
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• 2013

The influence of indenter geometry on nanoindentation was studied using a static molecular dynamics simulation. Dislocation nucleation, dislocation locks, and dislocation movements during nanoindentation into Al (001) were studied. Spherical, rectangular, and Berkovich indenters were modeled to study the material behaviors and dislocation activities induced by their different shapes. We found that the elastic responses for the three cases agreed well with those predicted from elastic contact theory. Complicated stress fields were generated by the rectangular and Berkovich indenters, leading to a few uncommon nucleation and dislocation processes. The calculated mean critical resolved shear stresses for the Berkovich and rectangular indenters were lower than the theoretical strength. In the Berkovich indenter case, an amorphous region was observed directly below the indenter tip. In the rectangular indenter case, we observed that some dislocation loops nucleated on the plane. Furthermore, a prismatic loop originating from inside the material glided upward to create a mesa on the indenting surface. We observed an unusual softening phenomenon in the rectangular indenter case and proposed that heterogeneously nucleating dislocations are responsible for this.

• Journal of the Korean Ceramic Society
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• v.38 no.4
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• pp.365-369
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• 2001

플라즈마 화학증착법(PECVD)에 의해 실리콘 (100) 기판 위에 3C-SiC막을 증착하였다. 증착반응시 유입가스비, R$_{x}$[=CH$_4$/(CH$_4$+H$_2$)]에 따른 증착막의 결정성에 대해 검토하였다. 증착된 3C-SiC막의 결정성은 R$_{x}$ 값이 감소할수록 더욱 향상되었으며, 형성된 결정상은 (111) 면으로 최대의 우선배향성을 가졌다. Nanoindentation 방법을 이용하여 3C-SiC막의 압입깊이에 따른 경도 및 탄성계수를 측정하였으며, 유입가스비(R$_{x}$)의 변화에 따라서 막의 경도 및 탄성계수가 뚜렷이 변화하였다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.77-80
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• 2006

Structural phase transformations of silicon during nanoindentation were investigated in detail at the atomic level. The molecular dynamics simulations of nanoindentation on the (100), (110) and (111) surface of single crystalline silicon were simulated, and this supported the theoretical prediction of the anisotropic behavior of structural phase transformations. Simulations showed that microscopic aspects of phase transformation varied according to the crystallographic orientation of the contact surface and were directly linked to the slip system.