• 한국전산구조공학회논문집
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• 제14권3호
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• pp.317-327
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• 2001

이 논문에서는 이동식 지보를 이용한 MSS공법에 의해 건설되는 콘크리트 교량의 설계 모멘트를 산정하기 위한 관계식을 제안하고 있다. 각 시공 단계에 따른 시간 의존적 거동해석을 통해 교량의 부재력 변화와 처짐 변화를 고찰하였으며 변위와 하중조건을 토대로 한 지배방정식을 구성한 후 복잡한 장기 거동 해석 없이 탄성 해석 결과를 토대로 설계 부재력과 임의의 시간 경과 후 모멘트 변화를 예측할 수 있는 관계식을 구성하였다. 나아가 다양한 예제 해석을 통해 제안한 관계식의 적용성을 검증하였으며 모멘트 포락선을 토대로 보다 합리석인 설계 부재력의 산정 방안을 소개하였다.

• The Journal of Advanced Prosthodontics
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• 제7권6호
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• pp.475-483
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• 2015

PURPOSE. The objective of this study was to evaluate the influence of various cement types on the stress distribution in monolithic zirconia crowns under maximum bite force using the finite element analysis. MATERIALS AND METHODS. The models of the prepared #46 crown (deep chamfer margin) were scanned and solid models composed of the monolithic zirconia crown, cement layer, and prepared tooth were produced using the computer-aided design technology and were subsequently translated into 3-dimensional finite element models. Four models were prepared according to different cement types (zinc phosphate, polycarboxylate, glass ionomer, and resin). A load of 700 N was applied vertically on the crowns (8 loading points). Maximum principal stress was determined. RESULTS. Zinc phosphate cement had a greater stress concentration in the cement layer, while polycarboxylate cement had a greater stress concentration on the distal surface of the monolithic zirconia crown and abutment tooth. Resin cement and glass ionomer cement showed similar patterns, but resin cement showed a lower stress distribution on the lingual and mesial surface of the cement layer. CONCLUSION. The test results indicate that the use of different luting agents that have various elastic moduli has an impact on the stress distribution of the monolithic zirconia crowns, cement layers, and abutment tooth. Resin cement is recommended for the luting agent of the monolithic zirconia crowns.

• 한국항해학회지
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• 제24권1호
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• pp.85-95
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• 2000

In the country where the population concentrates in the metropolis with the narrow land, development of the ocean space is necessary. Recently, mega-float offshore structure has been studied as one of the effective utilization of the ocean space. And very large floating structures are now being considered for various applications such as floating airports, offshore cities and so on. This very large structure is relatively flexible compared with real floating structures like large ships. when we estimate dynamic responses of these structures in waves, the elastic deformation is important, because vertical dimension is small compared with horizontal. And it is necessary to examine the effect of ocean wave external force received from the natural environment. In this study, the mat-type large floating structure is made to be analytical model. And the analysis of the dynamic response as it receives regular wave is studied. The finite element method is used in the analysis of structural section of this model. And the analysis is carried out using the boundary element method in the fluid division. The validity of analysis method is verified in comparison with the experimental result in the Japan Ministry of Transport Ship Research Institution. In order to know the characteristics of the dynamic response of the large floating structures, effects of wavelength, bending rigidity of the structure, water depth, and wave direction on dynamic response of the floating structure are studied by use of numerical calculation.

• 전력전자학회논문지
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• 제2권1호
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• pp.26-32
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• 1997

본 논문에서는 자동차나 항공기에서 많이 사용되고 있는 고속 솔레노이드 밸브의 플런저형 솔레노이드에 대한 설계기술을 확보하기 위하여, 수치해석을 통해 플런저의 이동시간에 대해 설계 파라메타들이 미치는 영향 및 솔레노이드의 동작특성을 검토하였다. 솔레노이드의 형상이 원통형이므로 축대칭원통좌표계를 이용하였고, 특히 전자기적 부분의 이론 해석시 와전류에 의한 영향을 고려하였으며, 가정자로법에 의해 퍼미언스를 계산하여 해석에 활용하였다. 구해진 파라메타의 해석 결과를 참고로 하여, 파라메타 값을 약간씩 변화시켜서 시간에 따른 플런저의 변위, 전류, 흡인력과의 관계등 동특성을 재해석하는 과정을 반복하여 최적치를 도출하였다. 도출된 최적치를 사용한 모의실험결과 플런저 이동시간은 1.8[ms] 정도의 고속이 됨을 알 수 있었다.

• 한국의류학회지
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• 제31권1호
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• pp.77-84
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• 2007

The purpose of this study was to investigate and to compare the performances of silicone laminated materials sold for swimming cap in market, to get the basic data for product development. We selected 4 specimens and tested their air permeability, waterproofness and breathability. We also tested the physical and mechanical properties of the specimens using KES system. Silicone-laminated material was not bursted on high hydraulic pressure since silicone membrane gave waterproofness while PU/Polyester substrate gave elasticity. It didn't have air permeability and breathability at all. Any toxic materials such as Formaldehyde, Deldrin, PCP, Amin, TDBPP were not detected in silicone-laminated material and other materials. Silicone-laminated material had higher stretchability with the low force but it had lower elastic recovery and shape stability comparing to PU laminated material. It had lower flexibility than PU laminated material. It had lower unrecoverable amount in shearing direction. Friction coefficient was higher in silicone-laminated material than PU laminated material due to its surface stickiness. It was compressed easily and its compression resiliency was higher with compared to PU laminated material.

• Tribology and Lubricants
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• 제27권6호
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• pp.326-331
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• 2011

The purpose of this paper is to analyze and discuss the effects of surface roughness by comparing the elastohydrodynamic lubrication(EHL) analysis of smooth surface and rough surface as the ball bearing. In order to do this, The average flow model is adapted for the interaction of the flow rheology of lubricant and surface roughness. The average Reynolds equation and the related flow factor which describes the coupled effects of surface roughness and flow rheology, the viscosity-pressure and density-pressure relations equations, the elastic deformation equation, and the force balance equation are solved simultaneously. The results show that effects of surface roughness on the film thickness and pressre distribution should be considered especially in EHL contact problems.

• Steel and Composite Structures
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• 제33권3호
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• pp.463-472
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• 2019

Initial thermo-elastic and steady state creep deformation of a rotating functionally graded simple blade is studied using first-order shear deformation theory. A variable thickness model for cantilever beam has been considered. The blade geometry and loading are defined as functions of length so that one can define his own blade profile and loading using any arbitrary function. The blade is subjected to a transverse distributed load, an inertia body force due to rotation and a distributed temperature field due to a thermal gradient between the tip and the root. All mechanical and thermal properties except Poisson's ratio are assumed to be longitudinally variable based on the volume fraction of reinforcement. The creep behaviour is modelled by Norton's law. Considering creep strains in stress strain relation, Prandtl-Reuss relations, Norton' law and effective stress relation differential equation in term of effective creep strain is established. This differential equation is solved numerically. By effective creep strain, steady state stresses and deflections are obtained. It is concluded that reinforcement particle size and form of distribution of reinforcement has significant effect on the steady state creep behavior of the blade.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.804-809
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• 2008

In this study, the cooling performance of a C/C composite material structure with metallic cooling tubes fixed by elastic force without chemical bonding was evaluated experimentally using combustion gas in a rocket combustor. The C/C composite chamber was covered by a stainless steel outer shell to maintain its airtightness. Gaseous hydrogen as a fuel and gaseous oxygen as an oxidizer were used for the heating test. The surface of these C/C composites was maintained below 1500 K when the combustion gas temperature was about 2900 K and heat flux to the combustion chamber wall was about 9 $MW/m^2$. No thermal damage was observed on the stainless steel tubes which were in contact with the C/C composite materials. Results of the heating test showed that such a metallic-tube-cooled C/C composite structure is able to control the surface temperature as a cooling structure(also as a heat exchanger), as well as indicating the possibility of reducing the amount of the coolant even if the thermal load to the engine is high. Thus, application of the metallic-tube-cooled C/C composite structure to reusable engines such as a rocket-ramjet combined cycle engine is expected.

• Structural Engineering and Mechanics
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• 제20권4호
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• pp.451-463
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• 2005

Structural members commonly employed in marine and off-shore structures are usually fabricated from plates and shells. Collision of this class of structures is usually modeled as plate and shell structures subjected to dynamic impact loading. The understanding of the dynamic response and energy transmission of the structures subjected to low velocity impact is useful for the efficient design of this type of structures. The transmissions of transient energy flow and dynamic transient response of these structures under low velocity impact are presented in the paper. The structural intensity approach is adopted to study the elastic transient dynamic characteristics of the plate structures under low velocity impact. The nine-node degenerated shell elements are adopted to model both the target and impactor in the dynamic impact response analysis. The structural intensity streamline representation is introduced to interpret energy flow paths for transient dynamic response of the structures. Numerical results, including contact force and transient energy flow vectors as well as structural intensity stream lines, demonstrate the efficiency of the present approach and attenuating impact effects on this type of structures.

• Structural Engineering and Mechanics
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• 제40권2호
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• pp.257-277
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• 2011

In this paper the geometrically nonlinear continuum plate finite element model, hitherto not reported in the literature, is developed using the total Lagrange formulation. With the layerwise displacement field of Reddy, nonlinear Green-Lagrange small strain large displacements relations (in the von Karman sense) and linear elastic orthotropic material properties for each lamina, the 3D elasticity equations are reduced to 2D problem and the nonlinear equilibrium integral form is obtained. By performing the linearization on nonlinear integral form and then the discretization on linearized integral form, tangent stiffness matrix is obtained with less manipulation and in more consistent form, compared to the one obtained using laminated element approach. Symmetric tangent stiffness matrixes, together with internal force vector are then utilized in Newton Raphson's method for the numerical solution of nonlinear incremental finite element equilibrium equations. Despite of its complex layer dependent numerical nature, the present model has no shear locking problems, compared to ESL (Equivalent Single Layer) models, or aspect ratio problems, as the 3D finite element may have when analyzing thin plate behavior. The originally coded MATLAB computer program for the finite element solution is used to verify the accuracy of the numerical model, by calculating nonlinear response of plates with different mechanical properties, which are isotropic, orthotropic and anisotropic (cross ply and angle ply), different plate thickness, different boundary conditions and different load direction (unloading/loading). The obtained results are compared with available results from the literature and the linear solutions from the author's previous papers.