• Coupled systems mechanics
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• 제9권2호
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• pp.125-145
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• 2020

In this paper, we present a 3D thermo-hydro-mechanical coupled discrete beam lattice model of structure built of the nonisothermal saturated poro-plastic medium subjected to mechanical loads and nonstationary heat transfer conditions. The proposed model is based on Voronoi cell representation of the domain with cohesive links represented as inelastic Timoshenko beam finite elements enhanced with additional kinematics in terms of embedded strong discontinuities in axial and both transverse directions. The enhanced Timoshenko beam finite element is capable of modeling crack formation in mode I, mode II and mode III. Mode I relates to crack opening, mode II relates to in-plane crack sliding, and mode III relates to the out-of-plane shear sliding. The pore fluid flow and heat flow in the proposed model are governed by Darcy's law and Fourier's law for heat conduction, respectively. The pore pressure field and temperature field are approximated with linear tetrahedral finite elements. By exploiting nodal point quadrature rule for numerical integration on tetrahedral finite elements and duality property between Voronoi diagram and Delaunay tetrahedralization, the numerical implementation of the coupling results with additional pore pressure and temperature degrees of freedom placed at each node of a Timoshenko beam finite element. The results of several numerical simulations are presented and discussed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.988-991
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• 2001

Plastically deformed layer influences the mechanical property of the mechanical element such as creep hardening, microscopical crack and stress corrosion destruction. Therefore, the property so called the surface integrity has to be considered, and the machined surface including plastic deformation, distribution of stress has to be conducted quantitatively. This paper explains the orthogonal cutting, and made an orthogonal cutting model using the finite element method, then analyzed cutting power, plastic deformation of workpiece. It introduces the developed subsequent recrystallizations technique for measurement of the plastic strain of machined surface, and verified the technique.

• 한국기계가공학회지
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• 제2권3호
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• pp.69-75
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• 2003

Plastically deformed layer influences the mechanical property of the mechanical element such as creep hardening, microscopical crack and stress corrosion destruction. Therefore, the property so called the surface integrity has to be considered, and the machined surface including plastic deformation, distribution of stress has to be conducted quantitatively. This paper explains the orthogonal cutting, and made an orthogonal cutting model using the finite element method, then analyzed cutting power, plastic deformation of workpiece. It introduces the developed subsequent recrystallizations technique for measurement of the plastic strain of machined surface, and verified the technique.

• 산업기술연구
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• 제9권
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• pp.109-117
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• 1989

In the finite element analysis of semiconductor devices analysis, the solution often be diverged due to the numerical instability of discretized equations. To overcome this problems, a noble finite element code which guarantees a successful convergence is developed. The factor of divergence in the current continuity equation of semiconductor governing equations is derived using stability test and an adaptive mesh refine scheme is introduced to eliminates the divergence properties. A test calculation of GaAs MESFET model reveals that the proposed scheme has a robust self-convergence property and is suitable for the semiconductor devices analysis.

• Elastomers and Composites
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• 제41권1호
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• pp.40-48
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• 2006

고무는 금속 및 플라스틱 재료와 달리 작은 하중에서도 큰 변형이 발생되며, 높은 변형 구간에서 탄성특성을 보이는 특징이 있다. 특히 충격흡수 특성이 금속 및 플라스틱보다 우수하므로 제진 및 충격 완충구조물로 널리 활용되고 있다. 충격하중을 받는 고무 구조물의 특성을 평가하기 위하여 자유 낙하형 충격시험기를 이용하여 충격실험을 실시하였으며, ABAQUS/Explicit를 이용하여 유한요소 해석을 수행하였다. 고무의 동강성은 충격펄스의 최대변형량과 충격지속시간으로부터 얻어진 진폭과 주파수를 적용하여 동특성 시험을 수행하고 WLF모델을 적용하여 높은 주파수 대역의 동강성을 예측하였다. 실험을 실시한 $0.3{\sim}l.5J$의 충격에너지 영역에서는 고무의 경도가 증가되면 충격흡수율이 감소되며, 충격에너지가 커질수록 충격흡수율은 감소하는 경향을 나타내었다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제26권2호
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• pp.108-120
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• 2022

We considered qualitative behaviour of the generalization of Einstein's model of Brownian motion when the key parameter of the time interval of free jump degenerates. Fluids will be characterised by number of particles per unit volume (density of fluid) at point of observation. Degeneration of the phenomenon manifests in two scenarios: a) flow of the fluid, which is highly dispersing like a non-dense gas and b) flow of fluid far away from the source of flow, when the velocity of the flow is incomparably smaller than the gradient of the density. First, we will show that both types of flows can be modeled using the Einstein paradigm. We will investigate the question: What features will particle flow exhibit if the time interval of the free jump is inverse proportional to the density and its gradient ? We will show that in this scenario, the flow exhibits localization property, namely: if at some moment of time t₀ in the region, the gradient of the density or density itself is equal to zero, then for some T during time interval [t₀, t₀ + T] there is no flow in the region. This directly links to Barenblatt's finite speed of propagation property for the degenerate equation. The method of the proof is very different from Barenblatt's method and based on the application of Ladyzhenskaya - De Giorgi iterative scheme and Vespri - Tedeev technique. From PDE point of view it assumed that solution exists in appropriate Sobolev type of space.

• 소성∙가공
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• 제3권1호
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• pp.120-132
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• 1994

Strip drawing of strain-hardening, viscoplastic materials with damage is analyzed by a rigid plastic finite element method. A process model is formulated using two state variables, one for strain hardening from slip dominated plastic distortion and the other for damage from growth of microvoids. Application of the model to aluminum strip drawing is given via implementation in a consistent penalty finite element formulation. The predicted density changes as a result of void growth are compared to those from experiments reported in the literature. The effects of drawing conditions such as drawing speed and die angle on the mechanical property chages are studied.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.215-222
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• 2007

Coating of Hot-dip galvannealed steel consists of various Fe-Zn intermetallic compounds. Since the coating is hard and there for is very brittle, the surface of steel sheet is easy to be ruptured during second manufacturing processing. This is called as powdering. In addition, forming equipment might be polluted with debris by powdering. Therefore, various research have been carried out to prohibit powdering fur improving the quality of GA steel. This paper carried out finite element analysis combined with damage model which simulate the failure of local layer of hot-dip galvannealed steel surface during v-bending test. Since the mechanical property of intermetallic compound was unknown exactly, we used the properties calculated from measurements. The specimen was divided into substrate, coating layer and interface layer. Local failure at coating layer or interface layer was simulated when elemental strain reached a prescribed strain.

• 대한기계학회논문집A
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• 제35권12호
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• pp.1563-1571
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• 2011

본 연구에서는 인간중이의 소리전달특성 계산을 위한 유한요소모델을 개발하였다. 이소골의 형상을 얻기 위하여 한국인 사체에서 추출한 측두골을 마이크로 CT 촬영하여 3 차원 입체모델로 변환하였다. 유한요소모델은 이소골, 고막, 인대와 근육 등을 포함하여 구성하였다. 유한요소모델을 이용하여 고막에서 등골족판까지의 응답함수를 계산한 후 측정값을 갖는 선행연구와 비교하였고 그 결과 10 kHz 주파수 대역까지 소리전달특성을 잘 표현하고 있음을 보였다. 또한 유한요소 모델을 구성하는 주요 물성인자의 변화에 대한 소리전달특성의 변화를 살피고 침등골관절의 강성값이 중이의 소리전달특성에 큰 영향을 미침을 보였다.

• 디지털산업정보학회논문지
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• 제10권3호
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• pp.1-9
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• 2014

The inverse Rayleigh model distribution and Rayleigh distribution model were widely used in the field of reliability station. In this paper applied using the finite failure NHPP models in order to growth model. In other words, a large change in the course of the software is modified, and the occurrence of defects is almost inevitable reality. Finite failure NHPP software reliability models can have, in the literature, exhibit either constant, monotonic increasing or monotonic decreasing failure occurrence rates per fault. In this paper, proposes the inverse Rayleigh and Rayleigh software reliability growth model, which made out efficiency application for software reliability. Algorithm to estimate the parameters used to maximum likelihood estimator and bisection method, model selection based on mean square error (MSE) and coefficient of determination($R^2$), for the sake of efficient model, were employed. In order to insurance for the reliability of data, Laplace trend test was employed. In many aspects, Rayleigh distribution model is more efficient than the reverse-Rayleigh distribution model was proved. From this paper, software developers have to consider the growth model by prior knowledge of the software to identify failure modes which can helped.