• Advances in biomechanics and applications
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• 제1권4호
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• pp.253-267
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• 2014

The human head is identified as the body region most frequently involved in life-threatening injuries. Extensive research based on experimental, analytical and numerical methods has sought to quantify the response of the human head to blunt impact in an attempt to explain the likely injury process. Blunt head impact arising from vehicular collisions, sporting injuries, and falls leads to relative motion between the brain and skull and an increase in contact and shear stresses in the meningeal region, thereby leading to traumatic brain injuries. In this paper the properties and material modeling of the subarachnoid space (SAS) as it relates to Traumatic Brain Injuries (TBI) is investigated. This was accomplished using a simplified local model and a validated 3D finite element model. First the material modeling of the trabeculae in the Subarachnoid Space (SAS) was investigated and validated, then the validated material property was used in a 3D head model. In addition, the strain in the brain due to an impact was investigated. From this work it was determined that the material property of the SAS is approximately E = 1150 Pa and that the strain in the brain, and thus the severity of TBI, is proportional to the applied impact velocity and is approximately a quadratic function. This study reveals that the choice of material behavior and properties of the SAS are significant factors in determining the strain in the brain and therefore the understanding of different types of head/brain injuries.

• 한국해양공학회지
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• 제34권6호
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• pp.481-488
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• 2020

Composite materialsuch as glass-fiber reinforced plastic and carbon-fiber reinforced plastic (CFRP) shows anisotropic property and have been widely used for structural members and outfitings of ships. The structural safety of composite structures has been generally evaluated via finite element analysis. This paper presents a technique for updating the finite element model of anisotropic beams or plates via natural frequencies. The finite element model updates involved a compensation process of anisotropic material properties, such as the elastic and shear moduli of orthotropic structural members. The technique adopted was based on a discrete genetic algorithm, which is an optimization technique. The cost function was adopted to assess the optimization problem, which consisted of the calculated and referenced low-order natural frequencies for the target structure. The optimization process was implemented with MATLAB, which includes the finite element updates and the corresponding natural frequency calculations with MSC/NASTRAN. Material properties of a virtual cantilevered orthotropic beam were estimated to verify the presented method and the results obtained were compared with the reference values. Furthermore, the technique was applied to a cantilevered CFRP beam to successfully estimate the unknown material properties.

• Journal of the Korean Wood Science and Technology
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• 제42권4호
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• pp.367-375
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• 2014

삼차원 솔리드 유한요소 방법을 이용한 목재 거동 해석을 보다 효율적으로 손쉽게 활용하기 위하여, 이에 필요한 목재재료모델 생성 방법을 개발하였다. 2단선형 탄소성이방성 이론에 근거하여 목재의 주요 세 방향 즉, 섬유, 방사 및 접선방향의 구성방정식을 정의하였다. 목재재료상수 결정의 단순화를 위하여 방사방향과 접선방향의 특성을 섬유직각 방향으로 통합하고, 요구되는 총 27개의 재료입력상수를 방향별 탄성계수와 항복응력, 그리고 프와송 비를 포함하는 6개의 독립상수로 단순화하였다. 개발된 목재재료모델을 이용하여 북미 더글라스 퍼 압축시험에 대한 삼차원 유한요소 모델을 개발하고 주요 세 방향에 대한 실험 측정치들과 시뮬레이션 결과를 비교하였다. 성공적인 모델해석 결과를 얻었으며, 이를 바탕으로 향후 진척되어야 할 연구개발 방향과 예상되는 문제점들을 논의하였다.

• 한국전산구조공학회논문집
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• 제24권4호
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• pp.383-389
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• 2011

본 논문에서는 통계적인 방법을 이용하여 점탄성 제진재인 합성고무의 물성에 대한 변동성을 평가하는 방법을 제안하고 측정데이터를 이용하여 합성고무에 대한 평가를 수행하고 합성고무로 이루어진 고무 마운트에 대한 동특성 해석을 수행하였다. 고무 물성의 불확실성 인자로는 외기 온도의 변화와 실험 데이터의 오차 및 점탄성 물질모델의 오차를 고려하였다. 고무는 분수차 미분모델로 표현되었고, 온도의 영향은 비선형 이동계수모델을 도입하여 복소계수로 나타내어 동강성과 감쇠를 표현하였다. 이러한 물성모델을 바탕으로 고무에 대한 물성 실험데이터와 물성계수의 확률밀도함수 사이에 정의된 우도함수를 최대화하는 통계적 보정방법을 이용하여 물성모델의 물질계수들에 대한 변동성을 추정하였다. 합성고무로 이루어진 제진용 고무 마운트에 대하여 유한요소모델을 이용하여 동특성을 계산하였다. 동특성의 계산시 추정된 물성의 통계값을 적용하고 몬테카를로 해석을 통하여 동강성의 변동성을 살펴서 그 변동성이 매우 큼을 확인하였다.

• 한국건설순환자원학회논문집
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• 제10권4호
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• pp.443-449
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• 2022

섬유보강 콘크리트 제조 시 감섬유 대체재료로서 선반 스크랩을 활용하는 것이 효과적이다. 왜냐하면, 선반 스크랩은 철강 제품의 부산물로서 경제적일 뿐만 아니라 강섬유의 조성과 매우 유사하기 때문이다. 본 연구의 목적은 선반 스크랩 보강 모르타르의 압축강도 및 인장거동을 평가한 후 인장거동에 대한 재료모델을 제안하는 것이다. 이를 위하여 물-결합재비 30 % 및 40 %에 각각에 대하여 선반 스크랩을 총 부피비의 1.5 %를 혼입한 선반 스크랩 보강 모르타르를 제작한 후 압축강도 및 인장거동 등의 역학적 특성을 평가하였다. 또한 선반 스크랩 보강 모르타르의 실험 결과를 바탕으로 인장거동에 대한 재료모델을 제안하였으며, 제안한 모델은 실험 결과와 비교적 잘 일치하는 것으로 나타났다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2000년도 추계학술대회 및 정기총회
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• pp.275-278
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• 2000

This paper focuses on a performance analysis model for optimizing the freight terminal design and layout using AutoMod simulator and numerical analysis. We developed a model to analyze the freiht terminal performance per unit time and the material handling cost based on both throughput and waiting due to conjestion. We developed computer program for this model and some sample results by both numerical method and AutoMod simulator are compared.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 제4회 압출 및 인발가공 심포지엄
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• pp.1-12
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• 2001

In cold forging of piston-pin for automobile parts, the flow defect appears by the dead metal zone. This appearance evidently happens in products with a thin piercing thickness for the dimension accuracy and the decrease of material loss. The best method that can prevent flow defect is removing dead metal zone. The purpose of this study is to investigate the material flow behavior of forward-backward extruded piston-pin through the relative velocity ratio and the stroke control of upper moving punch & container using the flow control forming technique. The finite element simulations are applied to analyse the flow defect, then the results are compared with the plasticine model material experiments. Finally, the model experiment results are in good agreement with the FE simulation ones.

• 품질경영학회지
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• 제35권4호
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• pp.61-66
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• 2007

The performance of a building material degrades as time goes by and the failure of the material is often defined as the point at which the performance of the material reaches a pre-specified degraded level. Based on a stochastic deterioration model, a performance based service life prediction method for building materials and components is developed. As a stochastic degradation model, a gamma process is considered and lifetime distribution and service life of a material are predicted using the degradation model. A numerical example is provided to illustrate the use of the proposed service life prediction method.

• 터널과지하공간
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• 제6권4호
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• pp.298-305
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• 1996

Grouting technique is frequently used where a tunnel structure is passing through the shallow overburden area or where the thickness of hard rock above the tunnel is rather thin. However, engineering background on design process of the grout reinforcement does not seem to be fully understood until now. Mechanics of composite material is, therefore, introduced in this study to investigate the orthotropic material properties of the composites containing soil(or rock) and grouting material. These orthotropic material properties can be used to represent the reinfocement effects quantitatively. The model developed in this study is next applied to a typical tunnel structure and the grouting effect is analyzed numerically. The idea used in this study can be expanded to a situation where a pipe roofing or a forepoling technique is adopted and a simplified design procedure, similar to the model model introduced in this study, can be developed.

• 소성∙가공
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• 제9권5호
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• pp.533-538
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• 2000

This study has been carried out to develop a CRT die using hot forging. The conventional CRT die made by casting has defects such as void and inclusion. These defects of the cast die make micro-spots on the surface of the CRT which affect the quality of the final product. So, a hot forging process is developed to avoid these defects of CRT die by the model material test and the rigid-plastic FEM. Firstly, model material tests are carried out with plasticine billets in order to investigate the material flow pattern in the die cavity and to get the reasonable initial values for designing the preform in the FE simulation. And then a finite element analysis has been performed to Predict the preform and the forging load of a CRT die. We also suggest an integrated die-set which combines two die-sets into one die-set to save manufacturing time and cost in case of similar die-size.