• 대한치과보철학회지
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• 제44권5호
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• pp.526-536
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• 2006

Statement of problem : Use of fiber composite technology as well as development of nonmetal implant prosthesis solved many problems due to metal alloy substructure such as corrosion. toxicity, difficult casting, expensiveness and esthetic limit. After clinical and laboratory test, we could find out that fiber-reinforced composite prostheses have good mechanical properties and FRC can make metal-free implant prostheses successful. Purpose : The purpose of this study is to evaluate the flexural strength of implant fixed prosthesis using fiber reinforced composite. Material and methods : 2-implant fixture were placed in second premolar and second molar area in edentulous mandibular model, and their abutments were placed, and bridge prostheses using gold, PFG, Tescera, and Targis Vectris were fabricated. Tescera was made in 5 different designs with different supplements. Group I was composed by 3 bars with diameter 1.0mm and 5 meshes, 2 bars and 5 meshes for Group II, 1 bar and 5 meshes for Group III, and only 5 meshes were used for Group IV. And Group V is composed by only 3 bars. Resin (Tescera) facing was made to buccal part of pontic of gold bridge. All of gold and PFG bridges were made on one model, 5 Targis Vectris bridges were also made on one model, and 25 Tescera bridges were. made on 3 models. Each bridge was attached to the test model by temporary cement and shallow depression was formed near central fossa of the bridge pontic to let 5 mm metal ball not move. Flexual strength was marked in graph by INSTRON. Results : The results of the study are as follows. The initial crack strength was the highest on PFG. and in order of gold bridge Tescera I, Tescera II, Targis vectris, Tescera IV, Tescera III, and Tescera V. The maximum strength was the highest on gold bridge, and in order of PFG, Tescera I, Tescera IV Tescera II, Targis vectris, Tescera III, and Tescera V. Conculsions : The following conclusions were drawn from the results of this study. 1. Flextural strength of implant prosthesis using fiber reinforced composite was higher than average posterior occlusal force. 2. In initial crack strength, Tescera I was stronger than Tescera V, and weaker than PFG. 3. Kinds and number of auxillary components had an effect on maximum strength, and maximum strength was increased as number of auxillary components increased. 4 Maximum strength of Tescera I was higher than Targis vectris, and lower than PFG.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 제7회 단조 심포지엄
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• pp.105-112
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• 2002

A new grid-based approach is presented for automatic generation of hexahedral meshes for simulation of plastic deformation in metal forming. In this approach, special enveloping schemes are applied, to eradicate the sources of the degenerate elements that may appear in a generated mesh. The schemes are described in detail, along with a complete procedure for mesh generation. The capability of the approach to deal with an arbitrary, 3-D process geometry is demonstrated through application to a selected forming problem.

• 한국표면공학회지
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• 제49권6호
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• pp.575-579
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• 2016

The metal mesh films with thickness of 1.0, 1.5, $2.0{\mu}m$ were prepared by photolithography using Ag, Al, and Cu metals. Every metal films were showed C(111) preferred orientation and Ag showed the lowest resistivity and followed by Al and Cu. The transmittance of almost films were higher than 90%. But, the Ag film with thickness of $2.0{\mu}m$ was delaminated during photolithography process due to low adhesion. So, Cu and Ti metal films were introduced under Ag film to improve adhesion property. The Cu film showed higher adhesion properties compared to Ti film. Furthermore, the Ti films that deposited on Ag film showed higher acid resistance.

• 대한기계학회논문집A
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• 제30권9호
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• pp.1078-1085
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• 2006

Many studies have been focused on how to manufacture ultra light metal structures and optimize them. In this study, we introduced a new idea to make sandwich panels with quasi-Kagome truss cores. First, metal sheets with a peculiar pattern of slits were expanded to be meshes, they are crimped into a triangular wave pattern, and then one third of struts were bent reversely to be quasi-Kagome trusses. Finally, two face sheets were bonded on the upper and the lower sides. The bending strength was estimated through elementary mechanics for the sandwich specimens with two kinds of face sheet the results of estimation were compared with the those of finite element analyses and experiments.

• 반도체디스플레이기술학회지
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• 제13권1호
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• pp.83-90
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• 2014

Using a ray tracing simulation, we have investigated the moir${\acute{e}}$ and starburst phenomena of touch screen panels (TSPs) based on opaque metallic grids (square, hexagonal, and random grids). It is demonstrated that employing a random metal mesh is the most effective way to suppress the moir${\acute{e}}$ and starburst phenomena at the same time. At high crossing angles between metal mesh of TSPs and black matrix (BM) of displays, however, a random metal mesh brings in stronger moir${\acute{e}}$ phenomenon than a square metal mesh due to point defects. Though the square metal mesh suppresses the moir${\acute{e}}$ effect substantially at high crossing angles, yet it results in the strongest starburst patterns. We have also provided the simulation scheme that can capture the moir${\acute{e}}$ and starburst patterns observed experimentally and useful design guidelines for metal grids.

• 소성∙가공
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• 제16권7호
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• pp.538-548
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• 2007

In this paper, a novel approach which enables rapid die surface modification for sheet metal forming process is proposed. In this method an implicit surface which interpolates a given set of control points and displacement constraints is generated to compute the displacements at arbitrary points located on die surface. The proposed method does not depend on the underlying surface representation type and is affected neither by its complexity nor by its quality. In addition, the domain decomposition method is introduced in order to treat large surface model. The global domain of interest is divided into smaller domains where the problem can be solved locally. And then the local solutions are combined together to obtain a global solution. In order to verify the validity and effectiveness of the proposed method, various surface modifications are carried out fur three kinds of die surface model including polygonal surface composed of triangular and rectangular meshes, polynomial surface and NURBS surface.

• 소성∙가공
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• 제1권1호
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• pp.95-103
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• 1992

The plane strain analysis for simulating the stretch/draw forming operation with an arbitrarily-shaped tool profile is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-normal, which compatibly describes arbitrary tool surfaces and FEM meshes without depending on the explicit spatial derivatives of tool surfaces. The linear line elements are used for depicting the formed sheet, based on membrane approximation. The FEM formulation is tested in the sections of automotive inner panel and two-side draw-in. Not only the excellent agreement between measured and computed strains is obtained in the stretched section, but also the numerical stability of formulation is verified in the draw-in section.

• 한국대기환경학회지
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• 제22권1호
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• pp.35-41
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• 2006

The steel foundries with electric arc furnaces handling metal scraps have recently gained an attention as a potential source of dusts. The present study focuses on the analysis of dust emissions and removals during furnace charging and melting processes by commercial CFD software named FLUENT. A body fitted grid system consisting of 880,000 meshes was first generated by Gambit for the electric arc furnace with the capacity of 60 ton/cycle and then FLUENT was invoked to solve the corresponding NavierStokers equation for the momentum, temperature and dust concentration. The entire processes from metal charging to metal melting were simulated to investigate the unsteady behaviors of fluid flows and dust concentrations. The model simulation results showed that as the top of the electric arc furnace opened for metal charging, hot plumes bursted out from the furnace rose strongly by buoyance and escaped mostly through the main hood. Therefore, the capacity of main hoods determined the vent efficiency in the metal charging process. As the furnace was closed after the metal charging and the metal melting processes was followed, the hot flow stream stretching from the furnace to the main hood was dissipated fast and the flow from the inlet of the bottom of the left hand side to the main and monitoring hoods constituted the main stream. And there was only a slow flow in the right hand side of the furnace. Therefore, the dust concentrations were calculated higher in the left hand side of the furnace, which was consistent with observations.

• 멤브레인
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• 제17권3호
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• pp.174-183
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• 2007

본 연구는 압연공정을 이용하여 금속망 만을 사용하여 금속막을 제조하는 과정과 금속망과 금속분말을 사용하여 금속막을 제조하는 과정에 대해 연구했다. 금속망 압연과정에서 선택된 금속망은 각각 10%, 20% 그리고 30%의 감소율로 압연했다. 이 압연공정은 망 wire의 지름을 변화시키거나 망의 단면적의 감소를 통해 망의 공경 크기를 감소시킨다. 압연된 금속망의 여과율은 압연시키지 않은 금속망의 여과율과 거의 동일한 여과율을 보였으며 금속막의 공경크기 분포 또한 더 균일했다. 금속망 위에 금속분말 층을 제조하는데 있어 분말 접합제로서 PVA를 사용하였으며 1시간 동안 $100^{\circ}C$에서 금속분말 층을 건조시키고 진공에서 3시간 동안 $1000^{\circ}C$에서 소결시키는 방법이 높은 공경 밀도와 균열이 없는 금속망 위에 금속분말 층을 형성하는 최적 조건이었다. 소결 전 30%감소율을 가지는 금속망에 대해 금속분말 층 형성에 압연공정을 적용할 경우 여과율이 약 $0.7{\mu}m$인 금속막이 성공적으로 제조되었다.

• 대한기계학회논문집
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• 제18권8호
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• pp.2113-2122
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• 1994

The 3-D FEM analysis for simulating the stamping operation of planar anisotropic sheet metals with arbitrarily-shaped tools is introduced. An implicit, incremental, updated Lagrangian formulation with a rigid-viscoplastic constitutive equation is employed. Contact and friction are considered through the mesh-normal, which compatibly describes arbitrary tool surfaces and FEM meshes without depending on the explicit spatial derivatives of tool surfaces. The consistent full set of governing relations, comprising equilibrium equation and mesh-normal geometric constraints, is appropriately linearized. The linear triangular elements are used for depicting the formed sheet, based on membrane approximation. Barlat's non-quadratic anisotropic yield criterion(strain-rate potential) is employed, whose in-plane anisotropic properties are taken into account with anisotropic coefficients and non-quadratic function parameter. The planar anisotropic finite element formulation is tested with the numerical simulations of the stamping of an automotive hood inner panel and the drawing of a hemispherical punch. The in-plane anisotropic effects on the formability of both mild steel and aluminum alloy sheet metals are examined.