• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 금형가공 심포지엄
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• pp.68-75
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• 2002

Most of numerical analyses for injection molding have been based on the Hele Shaw's approximation: two-dimensional flow analysis. In some cases, that approximation causes significant errors due to loss of geometrical information as well as simplification of the flow characteristics along the thickness direction. The present work covers numerical analyses of injection molding using three-dimensional solid elements. The accuracy of the analysis results has been verified through some numerical examples in comparison with the classical shell-based approach. The proposed approach are then applied to predict product defects and to improve flow characteristics for a precision electronics part. In addition, design of experiment has been utilized in order to find the optimal process conditions for better product quality.

• International Journal of Aeronautical and Space Sciences
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• 제13권4호
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• pp.446-457
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• 2012

Aeroelastic analysis of an aircraft with a high aspect ratio wing for medium altitude and long endurance capability was attempted in this paper. In order to achieve such an objective, various structural models were adopted. The traditional approach has been based on a one-dimensional Euler-Bernoulli beam model. The structural analysis results of the present beam model were compared with those by the three-dimensional NASTRAN finite element model. In it, a taper ratio of 0.5 was applied; it was comprised of 21 ribs and 3 spars, and included two control surfaces. The relevant unsteady aerodynamic forces were obtained by using ZAERO, which is based on the doublet lattice method that considers flow compressibility. To obtain the unsteady aerodynamic force, the structural mode shapes and natural frequencies were transferred to ZAERO. Two types of unsteady aerodynamic forces were considered. The first was the unsteady aerodynamic forces which were based on the one-dimensional beam shape; the other was based on the three-dimensional FEM model shape. These two types of aerodynamic forces were compared, and applied to the foregoing flutter analysis. The ultimate goal of the present research is to analyze the possible interaction between the rigid-body degrees of freedom and the aeroelastic modes. This will be achieved after the development of a reliable nonlinear beam formulation that would validate the current results as well as enable a thorough investigation of the nonlinearity. Moreover, such analysis will allow for an examination of the above-mentioned interaction between the flight dynamics and aeroelastic modes with the inclusion of the rigid body degrees of freedom.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권3호
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• pp.253-257
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• 2005

By using a coupled circuit, time-stepping, two-dimensional finite element method (2-D FEM), the performance of a stand-alone permanent-magnet synchronous generator (PMSG) with inset rotor can be computed without involving the classical two-axis model. The effects of interpolar air gap length and armature resistance on the load characteristics are investigated. It is shown that the interpolar flux density, and hence the amount of voltage compensation, is affected by magnetic saturation. Validity of the coupled circuit and field analysis is confirmed by experiments on a prototype generator. The machine exhibits an approximately level load characteristic when it is supplying an isolated unity-power-factor load.

• Geomechanics and Engineering
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• 제14권5호
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• pp.479-489
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• 2018

In this paper, a comparative study of the effects of soil modelling on the interaction between tunnelling in soft soil and adjacent piled structure is presented. Several three-dimensional finite element analyses are performed to study the deformation of pile caps and piles as well as tunnel internal forces during the construction of an underground tunnel. The soil is modelled by two material models: the simple, yet approximate Mohr Coulomb (MC) yield criterion; and the complex, but reasonable hardening soil (HS) model with hyperbolic relation between stress and strain. For the former model, two different values of the soil stiffness modulus ($E_{50}$ or $E_{ur}$) as well as two profiles of stiffness variation with depth (constant and linearly increasing) were used in attempts to improve its prediction. As these four attempts did not succeed, a hybrid representation in which the hardening soil is used for soil located at the highly-strained zones while the Mohr Coulomb model is utilized elsewhere was investigated. This hybrid representation, which is a compromise between rigorous and simple solutions yielded results that compare well with those of the hardening soil model. The compared results include pile cap movements, pile deformation, and tunnel internal forces. Problem symmetry is utilized and, therefore, one symmetric half of the soil medium, the tunnel boring machine, the face pressure, the final tunnel lining, the pile caps, and the piles are modelled in several construction phases.

• Structural Engineering and Mechanics
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• 제48권6호
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• pp.757-774
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• 2013

An integrated simulation tool for multilayer stepped pyramidal structures is presented. The tool, based on a semi-analytical mathematical strategy, is able to calculate the temperature distributions and thermal stresses at the interfaces between the layers of such structures. The core of the thermal solver is the analytical simulator for power electronic devices, DJOSER, which has been supplemented with a mechanical solver based on the finite-element method. To this end, a new ele-ment is proposed whose geometry is defined by its mean surface and thickness, just as in a plate. The resulting mechanical model is fully three-dimensional, in the sense that the deformability in the direction orthogonal to the mean surface is taken into account. The dedicated finite element code developed for solving the equilibrium problem of structures made up of two or more superimposed plates subjected to thermal loads is applied to some two-layer samples made of silicon and copper. Comparisons performed with the results of standard finite element analyses using a large number of brick elements reveal the soundness of the strategy employed and the accuracy of the tool developed.

• Structural Engineering and Mechanics
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• 제54권1호
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• pp.69-85
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• 2015

In this paper, a receding contact problem for an elastic layer resting on two quarter planes is considered. The layer is pressed by a stamp and distributed loads. It is assumed that the contact surfaces are frictionless and only compressive traction can be transmitted through the contact surfaces. In addition the effect of body forces are neglected. Firstly, the problem is solved analytically based on theory of elasticity. In this solution, the problem is reduced into a system of singular integral equations in which contact areas and contact stresses are unknowns using boundary conditions and integral transform techniques. This system is solved numerically using Gauss-Jacobi integral formulation. Secondly, two dimensional finite element analysis of the problem is carried out using ANSYS. The dimensionless quantities for the contact areas and the contact pressures are calculated under various distributed load conditions using both solutions. It is concluded that the position and the magnitude of the distributed load have an important role on the contact area and contact pressure distribution between layer and quarter plane contact surface. The analytic results are verified by comparison with finite element results.

• 대한기계학회논문집A
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• 제38권2호
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• pp.167-175
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• 2014

가동중검사 동안 가압중수로 압력관에서 탐지된 베어링 패드 프레팅 결함, 이물질 프레팅 결함 등 체적결함에 대해서는 CSA N285.8-05 에 따라 탄성 응력집중계수 수식을 이용하여 피로균열 및 수소지연균열이 개시되는 것을 평가하여야 한다. CSA N285.8-05 에는 이물질 프레팅 결함에 대해서는 선형파괴역학 기반한 개략적인 수식만이 제시된다. 본 연구에서는 이러한 이물질 프레팅 결함에 대해 2 차원 유한요소 해석과 일부 수정된 Kinectrics 사의 공학적 절차를 통해 이물질 프레팅 결함의 기하학적 특성이 좀더 상세히 고려된 탄성 응력집중계수 수식을 도출하였다. 도출된 수식을 적용한 결과와 3 차원 유한요소 해석 결과를 비교한 결과, 도출된 수식은 유한요소 해석과 잘 일치하는 결과를 얻을 수 있음을 확인하였다.

• 대한치과보철학회지
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• 제35권4호
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• pp.627-646
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• 1997

In order to find the degree of osseointegration at bone-implant interface of clinically successful implants, models including the 3.75mm wide, 10mm long screw type $Br{\aa}nemark$ implant as a standard and cylinder, 15mm long, 5.0mm wide, two splinted implants, and implants installed in various cancellous bone density were designed. Also, the amount of load and material of prostheses were changed. The stress and minimum contact fraction were analyzed on each model using three-dimensional finite element method(I-DEAS and ABAQUS version 5.5). The results of this study were as follows. 1. 10mm long, 3.75mm diameter-screw type implant had $36.5{\sim}43.7%$ of minimum contact fraction. 2. Cylinder type implant showed inferior stress distribution and higher minimum contact fraction than screw type. 3. As implant length was increased, minimum contact fraction was increased a little, however, maximum principal stress was decreased. 4. Implants with a large diameter had lower stress value with slightly higher minimum contact fraction than standard screw type. 5. Two splinted implants showed no change of minimum contact fraction. 6. The higher bone density, the lower stress value. 7. The material of occlusal surface had no effect on the stress of the bone-implant interface.

• 한국지리정보학회지
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• 제12권3호
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• pp.21-34
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• 2009

홍수 시 흐름은 기본적으로 2차원 흐름으로서 이 때 하천 흐름의 수위와 유속 분포는 1차원 하천 모형으로 적절한 결과를 도출하기 어렵다. 이에 본 연구에서는 GIS를 이용하여 낙동강의 합류점에 대한 2차원 유한요소망을 구축하고 RMA-2모형을 이용하여 모의를 수행하였다. 이를 위해 모형의 매개변수들이 해석결과에 미치는 영향을 검토하였으며, 모형의 적용성을 검토하기 위해 금호강 합류부에 대해 흐름해석을 실시하고 검증하였다. 또한 하천의 단면 변화에 따른 흐름변화를 판단하기 위하여 과거 단면과 최근 단면에 대해 모의를 실시하고 비교 검토하였다. 그 결과 합류부에 대한 2차원 모형의 적용성을 검증하고 단변변화의 영향이 수위에 미치는 영향을 확인하여, 향후 합류부 처리, 하구부 처리, 제방축조 등에 효율적으로 활용될 수 있을 것으로 판단된다.

• 한국해안해양공학회지
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• 제15권3호
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• pp.159-166
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• 2003

본 연구에서는 천해 파랑 계산에 널리 사용되어지고 있는 확장형 완경사 방정식과 계산 효율은 같게 유지하면서 Laplace방정식을 직접 풀 수 있는 유한 요소 모형에 대해서 연구하였다. 기존의 확장형 완경사 방정식을 사용하는 경우와 같은 계산효율을 유지하기 위하여 파동장을 수심방향으로 1층인 유한요소로 나누고, 요소내의 포텐셜을 수면에 위치한 절점에 대한 포텐셜만으로 표시하도록 한 후, Galerkin 기법을 적용하여 수치모형을 구성하였다. 요소 내 수평방향에 대해서는 통상의 보간함수를 채택하였으며, 수심방향에 대해서는 진행파의 수심방향 거동인 함수를 사용하여 보간함수를 구성하였다. 모형의 개발은 우선 연직 2차원 문제를 대상으로 하였다. 개발된 모형의 검증을 위하여 연직 2차원에서의 파랑 반사 및 전달문제에 적용한 결과, 개발된 유한 요소 모형은 계산상의 효율면에서나 해의 정확도 면에서 기존의 확장형 완경사 방정식에 기초한 모형과 같은 수준을 보임을 확인하였다.