• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 2001년도 The Seoul International Simulation Conference
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• pp.373-379
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• 2001

There is a big issue to generate 3D hexahedral finite element (FE) model, since a process to divide the whole domain into several simple-shaped sub-domains is required before generating a continuous mesh with mapped mesh generators. In general, it is nearly impossible to set up proper division numbers interactively to keep mesh connectivity between sub-domains on a complicated arbitrary-shaped domain. If mesh continuity between sub-domains is not required in an analysis, this complicated process can be omitted. Element-free Galerkin method (EFGM) can accept discontinuous meshes, which only requires nodal information. However it is difficult to choose a reasonable influenced domain in moving least squares scheme with non-uniformly distributed nodes in discontinuous FE models. A new FE scheme fur discontinuous mesh is proposed in this paper by applying improved EFGM with some modification to derive FE approximated function in discontinuous parts. Its validity is evaluated on linear elastic problems.

• Journal of Mechanical Science and Technology
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• 제19권7호
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• pp.1424-1431
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• 2005

In this study, head injury by impact force was evaluated by numerical analysis with 3-dimensional finite element (FE) model. Brain deformation by frontal head impact was analyzed to evaluate traumatic brain injury (TBI). The variations of head acceleration and intra-cranial pressure (ICP) during the impact were analyzed. Relative displacement between the skull and the brain due to head impact was investigated from this simulation. In addition, pathological severity was evaluated according to head injury criterion (HIC) from simulation with FE model. The analytic result of brain damage was accorded with that of the cadaver test performed by Nahum et al.(1977) and many medical reports. The main emphasis of this study is that our FE model was valid to simulate the traumatic brain injury by head impact and the variation of the HIC value was evaluated according to various impact conditions using the FE model.

• Safety and Health at Work
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• 제12권4호
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• pp.544-545
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• 2021

The article by Tae-Gu Kim et al. conducted elastic FE modeling, which was inappropriate for fracture of elastic-plastic chain material (11.3% of elongation). FE analysis results and the findings in the fracto-graphic analysis did not tally but contradicted each other. The article identified "incorrect installation"/bending forces as the root cause while FE results of the chain under bending forces showed very low stresses at fracture locations but the highest stress in the middle of shank of the chain. The article's "step-like topographies indicating the fracture due to bending moment rather than uniaxial tension" lacked scientific support. The load value carried by each chain section under bending/incorrect installation was only half of that under tension, thus the article using same load value in FE simulation comparison for bending and tension was incorrect. The real cause of the chain fracture was likely improper checking the lifted load or/and using the wrong chain with much lower safety working load.

• Composites Research
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• 제34권6호
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• pp.337-344
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• 2021

본 연구에서는 복합재료 팬 블레이드 도브테일 요소의 인장하중에 따른 점진적 파손거동을 유한요소 시뮬레이션을 통한 수치적 연구를 수행하고, 인장시험을 통하여 정확도를 검증한다. 도브테일 요소는 터보 팬 엔진의 팬 블레이드를 디스크와 결합시키는 조인트의 하나로, 통상 티타늄 등의 금속 재료로 제작되나 경량화 등의 이유로 복합재료의 적용이 연구되고 있다. 하지만 복합재료를 이용한 팬 블레이드 제조과정에서 드롭오프 플라이(Drop-off ply), 수지 포켓(resin pocket) 등의 제조 결함이 필연적으로 발생한다. 이러한 제조 결함이 복합재료 팬 블레이드 도브테일 요소에 미치는 영향을 확인하기 위해 유한요소모델을 이용한 수치해석을 수행하여 예측 결과와 인장시험 결과를 비교 분석한다. 이때 층간분리(delamination) 거동을 모사 가능한 응집영역 모델을 적용하였다. 결론적으로, 열 잔류응력 및 두께방향 압축하중에 의한 계면 물성 강화 효과를 고려하여 유한요소 해석결과와 시험결과 간의 높은 상사성을 얻을 수 있었다.

• 소성∙가공
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• 제26권2호
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• pp.95-100
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• 2017

In this study, the method of process design for side forming of a tooth part used for a component of automobile transmission was suggested using FE-simulations. To develop the side forming for the tooth part, in this paper, the shape factors of B.T.Pin was considered as design parameters. The shape factors of B.T.Pin were selected to be the round of pin, reinforced angle and reinforced length. Based on FE simulation results, appropriate shape factor without causing any defects was selected. In addition, to increase the strength of pin, the combination of shape factor having minimum stress after side forming was selected using FE-simulation. In addition, with design of a die set, cold side forming of the tooth part was experimented to estimate effectiveness of the designed B.T.Pin. From experiments, it was found that the tooth part with complete formation of the tooth was obtained without making any forming defects and punch fracture.

• 한국정밀공학회지
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• 제24권11호
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• pp.44-51
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• 2007

Condenser tubes are mainly produced by precision extrusion with a porthole die and are used in the flow pass of refrigerant cooling systems in automobiles. The recent technical trend of condenser tube requires the tube to be of more multi cellizing, high strength and small size, and to increase the heat transfer area and heat efficiency. Hence, this paper is shown that the results of FE-simulation are in good agreement with the experimental ones. Finally, the extrusion die shape is proposed through analysis of FE-simulation and performance of trial extrusion. Chamber shape dimension and initial temperatures of die is adjusted analysis results. And the possibility of extrusion is estimated that forming load, welding pressure and stress analysis of die in this paper. The validity of simulated results was verified into extrusion experiments on the condenser tubes.

• 소성∙가공
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• 제23권3호
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• pp.164-170
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• 2014

To predict the deformation and fracture during tube expansion using the finite element (FE) method, a material model is considered that incorporates the damage evolution due to the deformation. In the current study, a Rice-Tracey model was used as the damage model with inclusion of the hydrostatic stress term. Since OFHC Cu is not significantly affected by strain rate, a Hollomon flow stress model was used. The material parameters in each model were obtained by using an optimization method. The objective function was defined as the difference between the experimental measurements and FE simulation results. The parameters were determined by minimizing the objective function. To verify the validity of the FE modeling, cross-verification was conducted through a tube expansion test. The simulation results show reasonable agreement with the experiments. The design for a minimum diameter of expansion tube using the FE modeling was verified by a simplified tube expansion test and simulation results.

• 한국전기전자재료학회논문지
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• 제23권3호
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• pp.240-244
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• 2010

The surface segregation and surface order near the order-disorder phase transition of FeCo alloy was studied through Monte Carlo simulation of an Ising type model Hamiltonian. The results showed that the proper choice of Hamiltonian parameters could reproduce the recent observation of surface order above the transition temperature and that the field term played dominant role.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.213-216
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• 2008

Sled test id widely used to evaluate the performance of occupant's safety system in frontal crash environment without having to conduct a full-scale crash test. Steel bar breaking system is used to generate deceleration profile which is experienced by passengers in frontal crash. In this study, deformation analyses of steel bars were conducted using a commercial FE code. Several guidelines were proposed to improve the accuracy of simulation.

• 소성∙가공
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• 제16권1호
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• pp.25-30
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• 2007

The present study covers an integrated simulation method to evaluate optical performance of an aspheric plastic lens by connecting a finite element (FE) analysis of injection molding with a ray tracing simulation. Traditional ray tracing methods have based on the assumption that the optical properties of a lens are homogeneous throughout the entire volume. This assumption is to a certain extent unrealistic for injection-molded plastic lenses because material properties vary at every point due to the injection molding effects. To take into account the effects of the inhomogeneous optical properties of the molded lens, a new.ay tracing scheme is proposed in conjunction with a FE analysis of the injection molding. A numerical scheme is developed to calculate ray paths on every element layer with more realistic information of the refractive indices which can be obtained through the FE analysis. This information is then used to calculate the ray paths based on the FE mesh of which nodal points have unique index values. The proposed tracing scheme is implemented on the tracing of an aspheric lens, and its validity is ascertained through experimental verification.