• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 춘계학술대회 논문집
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• pp.47-51
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• 1996

Unsteady-state temperature distributions and thermal deformations of a spindle system are studied in this paper. Three dimensional model is built for analysis, and the amount of heat generation of bearing and the thermal characteristic values including heat transfer coefficient are estimated. Temperature distributions and thermal deformations of a model are analyzed using the finite element method and the termal boundary values. Numerical results are compared with the measured data. The results show that thermal deformations and temperature distributions of a high precision spindle system can be reasonably estimated using the three dimensional model and the finite element method.

• 한국지능시스템학회논문지
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• 제19권2호
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• pp.230-235
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• 2009

본 논문은 3차원구조물의 유한요소해석을 위한 자동 유한요소 생성에 관한 것으로 퍼지이론과 버블요소 생성기법, 상용 솔리드모델러로 구성되어진다. 새로운 요소생성과정은 (a) 해석모델인 형상모델링 정의, (b) 버블생성, 그리고 (c) 요소생성으로 이루어진다. 형상모델링에는 상용 솔리드모델러를 이용하였으며 버블은 각 지점에서의 버블간격함수에 의해 생성되어진다. 버블간격 함수는 지식처리수법에 의해 조절되어 진다. 요소생성을 위해서는 기본적으로 데로우니방법을 도입하였다. 이러한 3차원 구조물에 대한 유한요소의 자동생성은 해석을 위해 큰 잇점이 있다. 실제적인 현 시스템의 효용성을 검증하기위해 3차원 형상에 대한 예를 제시하였다.

• The Journal of Advanced Prosthodontics
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• 제10권2호
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• pp.138-146
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• 2018

PURPOSE. The purpose of this study was to analyze the effects of the splinted implant prosthesis in a reconstructed mandible using three-dimensional finite element analysis. MATERIALS AND METHODS. Three-dimensional finite element models were generated from a patient's computed tomography data. The patient had undergone partial resection of the mandible that covered the area from the left canine to the right condyle. The mandible was reconstructed using a fibula bone graft and dental implants. The left mandibular premolars and molars remained intact. Three types of models were created. The implant-supported prosthesis was splinted and segmented into two or three pieces. Each of these models was further subcategorized into two situations to compare the stress distribution around normal teeth and implants. Oblique loading of 300 N was applied on both sides of the mandible unilaterally. The maximum von Mises stress and displacement of the models were analyzed. RESULTS. The stress distribution of the natural mandible was more uniform than that of the reconstructed fibula. When the loading was applied to the implant prosthesis of reconstructed fibula, stress was concentrated at the cortical bone around the neck of the implants. The three-piece prosthesis model showed less uniform stress distribution compared to the others. Displacement of the components was positively correlated with the distance from areas of muscle attachment. The three-piece prosthesis model showed the greatest displacement. CONCLUSION. The splinted implant prosthesis showed a more favorable stress distribution and less displacement than the separated models in the reconstructed mandible.

• 대한치과보철학회지
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• 제49권3호
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• pp.222-228
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• 2011

연구 목적: 이 연구의 목적은 삼차원 유한요소 분석법을 이용하여 무치악 구개결손 환자에 사용되는 폐쇄장치의 응력 및 변위를 측정하고 이를 총의치 모형과 비교하는 것이다. 연구 재료 및 방법: 무치악 환자의 컴퓨터단층촬영 영상을 기반으로 구개 중앙에 상악절제술 후 발생한 결손부를 가지는 무치악 상악모형과, 무치악 3차원 유한요소 모형을 제작하였다. 각각의 모형에 적합한 총의치와 폐쇄장치를 제작하고 좌측 소구치와 구치 부위에 200 N의 수직하중을 가하였다. 3차원 유한요소 분석법을 이용하여 두 모형에서 보철물과 잔존 상악골조직의 von Mises 응력값과 변위량을 측정하였다. 결과: 두 모형 모두 하중을 가한 쪽의 피질골에서 최대 von Mises 응력 값이 관찰되었다. 총의치 모형의 피질골에서 가장 높은 값은 2.73 MPa 이었으며 폐쇄장치 모형의 피질골에서 가장 높은 값은 2.69 MPa 이었다. 보철물의 조직면에서도 높은 응력값이 관찰되었다. 최대 변위량은 폐쇄장치에서 총의치보다 더 높은 값이 관찰되었다. 결론: 폐쇄장치는 총의치에 비해 교합력 전달 면에서 불리했고, 더 큰 변위량이 관찰되어 상악절제술을 받은 무치악 환자의 보철치료 시 해부학적 지식에 바탕을 둔 정확한 인상채득과 보철치료 원칙의 적용이 고려되어야 한다.

• Coupled systems mechanics
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• 제2권4호
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• pp.389-410
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• 2013

Three-dimensional Lagrangian fluid finite element is applied to seismic response analysis of an oil storage tank with a floating roof. The fluid element utilized in the present analysis is formulated based on the displacement finite element method considering only volumetric elasticity and its element stiffness matrix is derived by using one-point integration method in order to avoid volumetric locking. The method usually adds a rotational penalty stiffness to satisfy the irrotational condition for fluid motion and modifies element mass matrices through the projected mass method to suppress spurious hourglass-mode appeared in compensation for one-point integration. In the fluid element utilized in the present paper, a small hourglass stiffness is employed. The fluid and structure domains for the objective oil storage tank are modeled by eight-node solid elements and four-node shell elements, respectively, and the transient response of the floating roof structure or the free surface are evaluated by implicit direct time integration method. The results of seismic response analyses are compared with those by other method and the validation of the present analysis using three-dimensional Lagrangian fluid finite elements is shown.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.62-67
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• 2002

It has been shown that the vibrational response of a tire can be represented by a set of decaying waves, each associated with a particular cross-sectional mode shape in the region near the contact patch. Thus, it can be concluded that tires can be effectively modeled as lossy waveguides. It has also been shown that the sound radiation from tires is mainly from the region close to the contact patch. In consequence, it may be computationally efficient to analyze tire vibration and sound radiation in the region close to the contact patch by using a hybrid finite element model in which the cross-section of a tire is approximated by 2-D finite elements while an analytical wave solution is assumed in the circumferential direction of the tire. In this article. a hybrid finite element was formulated based on a composite shell model. The dispersion relations for sample structures obtained by using the hybrid FE model were then compared with those obtained by using a full, three-dimensional FE model. It has been shown that the FE analysis made using the hybrid 2-D finite elements yields results in close agreement with the three-dimensional model.

• 한국농공학회논문집
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• 제57권5호
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• pp.43-49
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• 2015

Most of agricultural structures located in seashore could not avoid rapid deterioration of concrete because chloride-ion and $CO_2$ gradually penetrate into concrete. However, since most of models can be able to describe the phenomenon of penetration by using one or two dimensional models based on finite difference method (FDM), those modes can not simulate the real geometry and it takes a lot of computational time to complete even the calculation. To overcome those weaknesses, three dimensional numerical model considering time dependent variables such as surface concentration of chloride and diffusion coefficient of domain based on finite element method (FEM) was suggested. This model also included the neutralization occurred by the penetration of $CO_2$. Because the model used various sizes of tetrahedral mesh instead of equivalent rectangular mesh, it reduced the computational time to compare with FDM. As this model is based on FEM, it will be easily extended to execute multi-physics simulation including water evaporation and temperature change of concrete.

• 소성∙가공
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• 제5권1호
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• pp.55-60
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• 1996

In the finite element analysis of metal forming processes the updated Lagrangian approach has been widely and effectively used to simulate the non-steady state problems. however some difficulties have arisen from abrupt flow change as in extrusion through square dies. In the present work an ALE(arbitrary Lagrangian-Euleria) finite element formulation for deforma-tion analysis are presented fro rigid-viscoplastic materials. The developed finite element program is applied to the isothermal analysis of square die extrusion of a square section. The computational results are compared with those by the updated Lagrangian finite element analysis.

• 한국도로학회논문집
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• 제15권1호
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• pp.103-110
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• 2013

PURPOSES: The objective of this study is to analyze and evaluate the behavior of orthotropic steel bridge deck pavement using three-dimensional finite element analysis and full-scale wheel load testing. METHODS: Since the layer thickness and material properties used in the bridge deck pavement are different from its condition, it is very difficult to measure and access the behavior of bridge deck pavement in the field. To solve this problem, the full-scale wheel load testing was conducted on the PSMA/Mastic bridge deck pavement and the deflection of bridge deck and horizontal tensile strain on top of pavement were measured under the loading condition. Three-dimensional finite element analysis was conducted to predict the behavior of bridge deck pavement and the predicted deflection and tensile strain values are compared with measured values from the wheel loading testing. RESULTS: Test results showed that the predicted deflections are 10% lower than measured ones and the error between predicted and measured horizontal tensile strain values is less than 2% in the critical location. CONCLUSIONS: The fact indicates that the proposed the analysis is found to be accurate for estimating the behavior of bridge deck pavements.

• 소성∙가공
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• 제1권1호
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• pp.52-65
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• 1992

In this study a new simplified three-dimensional numerical method and the associated computer program have been developed to simulate the non-axisymmetric extrusion processes. The two-dimensional rigid-plastic finite element method under the generalized plane-strain condition is combined with the slab method. To define the die geometry for a non-axisymmetric extrusion. area mapping technique was used. Streamlined die surface was used to minimize the total extrusion pressure. Extrusion of square, hexagonal and 'T' section from round billet have been simulated and experimented with a model material. The computed results were in good agreement with the experiments in cross-sectional grid distortion. Computational results will be valuable for designing tool geometries and corresponding processes.