Search | Korea Science

Park, Sungwoo
- Journal of the Computational Structural Engineering Institute of Korea
- /
- v.35 no.2
- /
- pp.101-107
- /
- 2022
This study proposes the deconvolution method for the nanoindentation test results of geopolymer employing the Gaussian mixture model. Geopolymer has been studied extensively as an alternative construction material because it emits relatively lower CO₂ compared to ordinary Portland cement. Geopolymer is made of aluminosilicate and alkaline solution, and the Si/Al molar ratio affects its mechanical properties. Previous studies revealed that the Si/Al molar ratio of 1.8~2.0 results in the highest compressive strength, and the Si/Al molar ratio over 1.8 degrades the compressive strength of geopolymer severely; however the reason for the compressive strength degradation is still unclear. To understand the effect of the Si/Al molar ratio on the geopolymer structure, this study exploits the nanoindentation. The phase deconvolution of the indent modulus data is successful using the Gaussian mixture model, and it is observed that the Si/Al molar ratio alters the homogeneity of the geopolymer. Geopolymer becomes more homogeneous up to an Si/Al molar ratio of 1.8 at which geopolymer exhibits the highest compressive strength. The examination of this study is assumed to be adopted as evidence of strength degradation by the Si/Al ratio higher than the optimum value.
https://doi.org/10.7734/COSEIK.2022.35.2.101 인용 PDF KSCI

Trandinh, Long;Ryu, Yong-Moon;Kang, Woo-Jong;Cheon, Seong-Sik
- Composites Research
- /
- v.24 no.2
- /
- pp.9-13
- /
- 2011
,In this paper, the symmetric axis parameter method, which was proposed to identify defects, dislocations and stacking fault, with perfect structures in the zinc-blende materials, was introduced as a way to distinguish between elastic and plastic deformation. LAMMPS, a molecular dynamics programme of Sandia National Laboratories, was used to perform nanoindentation simulation on silicon, a zinc-blende material. Defects in silicon (111) under spherical indentation showed the threefold pattern and the slip system in the form of ring crack. Also simulation results show good agreement with experimental results and existing theoretical analyses.
https://doi.org/10.7234/kscm.2011.24.2.009 인용 PDF KSCI

Kim, J.;Park, J.W.;Kim, Y.S.;Lee, S.S.
- Proceedings of the Korean Society for Technology of Plasticity Conference
- /
- 2003.05a
- /
- pp.111-115
- /
- 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.
PDF

Lee, H.J.;Ko, S.G.;Kim, J.H.;Hur, S.;Lee, E.S.;Jeong, J.H.
- Proceedings of the KSME Conference
- /
- 2003.11a
- /
- pp.1921-1926
- /
- 2003
Nano-imprint technology has been vigorously studied by many researchers for it is one of the most promising technologies for manufacturing the pattern with its critical dimension below 100nm. In the nano-imprint technology, nano patterns are transferred on a polymer film and the transferred patterns are used as an etch mask to define the designed patterns on a substrate or a metal layer. To this end, it is important to keep the residual thickness of the imprinted polymer film uniform. In this study, a novel measurement technique to measure the residual thickness of films is proposed based on nanoindentation theory. This technique has advantages of saving time and measuring the residual thickness of highly-localized portions in comparison with other techniques, but has limitation of requiring calibration process.
PDF

Trandinh, Long;Ryu, Yong-Moon;Cheon, Seong-Sik
- Composites Research
- /
- v.24 no.3
- /
- pp.17-24
- /
- 2011
The EAM simulation of nanoindentation was performed to investigate misfit dislocation slip in the Ag/Cu. The film layer, whose thickness in the range of 2-5nm, was indented by a spherical indenter with the N$\'{o}$se-Hoover thermostat condition. The simulation shows that the indentation position relative to misfit dislocation (MFD) has the effect on the dislocation, glide up or cross slip, for Ag film layer thickness less than 4 nm. Elastic energy variation during MFDs slip was revealed to be a key factor for the softening of Ag/Cu. The critical film layer thickness was evaluated for each case of Ag/Cu according to the spline extrapolation technique.
https://doi.org/10.7234/kscm.2011.24.3.017 인용 PDF KSCI