• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.484-488
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• 1997

Three-dimensional finite element analyses were used to compare the stress distribution and the stability of the fixation among seven different tibial components and to investigate the effect due to implant materials in total knee arthroplasty. The components included an intact tibia(Type I), Cemented Cobalt-Chromium tibial tray implanted with a PMMA cemented Co-Cr stem(Type II), Cemented Co-Cr tibial tray with a uncemented Co-Cr stem(Type III), Cemented Ultra High Molecular Weight Polyethylene (UHMWPE) tibial tray with a cemented UHMWPE stem (Type IV), Cemented UHMWPE tray with a uncemented UHMWPE stem(Type V), Cemented Co-Cr tray without a stem(Type VI), and Cemented UHMWPE tray without a stem(Type VII). Uncemented components were assumed to have complete bony in growth and a rigid state of fixation between component and bone. The interface between bone/cement/component of cemented components was also assumed to be fully bonded. Bi-condylar forces were applied. The results indicated that Uncemented stem components provided lower bone stress shielding and stress concentration. The UHMWPE tray and stem component showed better agreement with the intact tibia than the Co-Cr Alloy tray and stem components. If the implant tray can be fixed firmed without a stem, Cemented PE tray without a stem(Type VII) may be recommended to give the best characteristics in the sense of stress distribution and stability.

• Explosives and Blasting
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• v.23 no.2
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• pp.23-35
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• 2005

Excavation of an opening in a saturated porous rock may lead to the development of pore pressure around the opening due to the redistribution of initial rock stresses. The built-up of pore pressure, in turn, may affect the mechanical behavior of rock mass and give the different pattern of stress distribution around the opening from that of the case where the coupling is neglected. In this study, the short time response of an opening excavated in saturated ground under anisotropic initial stress conditions was investigated numerically. Not on the wall of opening but at a short distance from the wall, the tangential stresses were peak during the short period after excavation when the hydro-mechanical coupling is considered.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.932-938
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• 2001

This study is concerned with the shape optimization of stem for the artificial hip prosthesis with unbonded cement mantle. The artificial hip prosthesis with unbonded cement mantle allows a stem to slip on cement mantle because of polished stem surface. Unbonded cement mantle type has several advantages compared with bonded cement mantle type, for example, small micro motion, preventing stress shielding and so on. In this study, 2-dimensional axisymmetric model was developed with considering characteristics of unbonded cement mantle. Moreover, optimal shape of stem was obtained by using feasible direction method. The objective of this optimization is maximizing supported vertical loading. The slip motion and stresses of stem, cement mantle and bone is used for constraints. The optimal shape which obtained by this study has slope of 0.15 in proximal part and maintains the width about 5mm in distal part In addition, simplified 3-dimensional analysis which applying optimal shape is carried out. The result of 3-dimensional analysis showed that optimal shape has some advantages for cement mantle stress. However, more realistic 3-dimensional analysis which including bending effect, complex geometries etc. is needed in further research.

• Journal of Technologic Dentistry
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• v.33 no.1
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• pp.55-61
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• 2011

Purpose: In this study, FEM(Finite Element Method) and bending strength test was conducted using normal implant and porous implant for the mechanical estimation of porous dental implant made by SLM method. Methods: Mechanical characteristics of PI(porous implant) and NI(normal implant) applied distributed loads(200N, 500N) were observed through FEM analysis. And each bending strength was gotten through bending test using MTS(Mechanical Test System, Instron 8871). Results: The result of FEM analysis was observed that stress difference between upper and surface of PI was 12 times, while NI was 2 times. The result of bending test was observed that bending strength of PI was lower than NI. we made a decision about this result that cross-sectional area of NI was larger than the PI. Conclusion: The stress shielding ability of porous implant was better than normal implant through result of FEM analysis. And bending strength of porous implant was lower than NI. We think that cause of this result was difference of cross-sectional area.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.11
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• pp.1929-1932
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• 2008

In case of a line-to-ground fault at transmission lines, a portion of fault current will flow into the earth through the footings of the faulted tower causing electrical potential rise nearby the faulted tower footings. In this situation, any buried pipelines or structures nearby the faulted tower can be exposed to the electrical stress by earth potential rise. Although many research works has been conducted on this phenomena, there has been no clear answer of the required separation distance between tower footings and neary buried pipeline because of its dependancy on the soil electrical charactersics of the concerned area and the faulted system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1996.11a
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• pp.27-41
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• 1996

In this study the heat transfer and fluid flow of the molten pool in stationary gas tungsten arc welding using argon shielding gas were investigated. Transporting phenomena from the welding arc to the base material surface, such as current density, heat flux, arc pressure and shear stress acting on the weld pool surface, were taken from the simulation results of the corresponding welding arc. Various driving forces for the weld pool convection were considered, self-induced electromagnetic, surface tension, buoyancy, and impinging plasma arc forces. Furthermore, the effect of surface depression due to the arc pressure acting on the molten pool surface was considered. Because fusion boundary has a curved and unknown shape during welding, a boundary-fitted coordinate system was adopted to precisely describe the boundary for the momentum equation. The numerical model was applied to AISI 304 stainless steel and compared with the experimental results.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1591-1593
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• 1996

The experimental study was carried out to investigate the effects of metallic particulate filler on the mechanical properties and the thermal properties of epoxy resin system filled with Cu powder. As Cu contents increased, the tensile strength, surface hardness and $T_d$ decreased. $T_g$ increased and decreased at 300 phr. $E_d$ decreased and increased at 200 phr, because the thermal conducting path of filler was formed and dissipated thermal stress.

• Journal of Welding and Joining
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• v.16 no.2
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• pp.64-72
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• 1998

This study aims a investigating the effect of volume fraction of chromium carbide phase(VFC) of hardfaced iron/chromium alloys on fracture toughness. The alloys were deposited twice on a mild steel plate using self-shielding flux cored arc welding process. In order to examine VFC effect, different VFC (0.28∼0.62) were employed by changing the Cr and C content, while the ratio of Cr/C was fixed in the range of 5.7∼6.6. Fracture toughness was constant as increasing VFC because fracture surface was developed in the eutectic phase which was growing parallel with introduced sharp notch in the hypoeutectic alloys, but fracture toughness did not decreased in spite of increasing volume fraction of coarse primary chromium carbide phase which was easily craced at the low stress because the growth direction of chromium carbide phase were more irregular as increasing VFC in the hypereutectic alloys.

• Journal of the Korean Ceramic Society
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• v.33 no.2
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• pp.203-213
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• 1996

In this study the subcritical crack growth behavior in an Al2O3-SiCw composite has been investigated using in situ fracture technique of applied moment double cantilever beam (AMDCB) specimens indside an SEM. This technique allows the detailed observation of whisker and grain bridging in the crack wake region. The experimental results indicated that the KI-a curve was deviated from the conventional powder law form and that the existed a region where the rate of microcrack growth was decreased with increasing the externally applied stress intensity factor. This behavior could be explained by arising crack growth resistance i.e. R-curve behavior which was associated with crack shielding due to whisker and grain bridging. The R-curve was also analyzed from the KI-a curve data in order to quantify the bridging effect in the Al2O3-SiCw composite.

• 연구논문집
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• s.33
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• pp.157-165
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• 2003

New titanium alloys with a low elastic modulus have been developed for biomedical applications to avoid the stress shielding effect of the artificial prosthesis. The newly developed alloys contained the transition elements like Zr, Hf, Nb, Ta which were non-cytotoxicity elements and $\beta$ stabilizers. In the present paper the elastic moduli of Ti-xM containing Zr, Hf, Nb, Ta were evaluated by measuring the acoustic velocity (PEG). The effectiveness of the alloying elements for lowering the elastic modulus was investigated. In addition, the dominant factors for the low modulus were discussed. Ta was the most effective in lowering the elastic modulus of the alloys. The effectiveness of Hf was not acceptable for decreasing the elastic modulus. The dominant factor was the lattice parameter for Zr, and the poisson's ratio for Nb, Ta, respectively.