• 열처리공학회지
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• 제31권4호
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• pp.180-186
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• 2018

High temperature flow behaviors of Fe-Cr-Mo-V-W-C tool steel were investigated using isothermal compression tests on a Gleeble simulator. The compressive test temperature was varied from 850 to $1,150^{\circ}C$ with the strain rate ranges of 0.05 and $10s^{-1}$. The maximum height reduction was 45%. The dynamic softening related to the dynamic recrystallization was observed during hot deformation. The constitutive model based on Arrhenius-typed equation with the Zener-Hollomon parameter was proposed to simulate the hot deformation behavior of Fe-Cr-Mo-V-W-C steel. An artificial neural network (ANN) model was also developed to compare with the constitutive model. It was concluded that the ANN model showed more accurate prediction compared with the constitutive model for describing the hot compressive behavior of Fe-Cr-Mo-V-W-C steel.

• 한국측량학회지
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• 제31권2호
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• pp.173-180
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• 2013

본 논문에서는 근접 사진측량을 이용한 모형말뚝 선단부 주변의 지반 변형 측정 방법에 대하여 연구하였다. 모형 토조에 말뚝을 단계적으로 관입하여 말뚝 주변에서 지반 변형이 발생하는 크기 및 궤적을 근접 사진측량으로 모니터링 하는 방법을 제시하였다. 토조에 설치된 평면 기준점을 셀프캘리브레이션 번들조정에 활용 가능하도록 가로 3장 및 세로 1장의 사진으로 구성하고, 정확하고 효율적인 사진측량을 위해 필요한 기준점 및 타겟점 영상 좌표 자동 독취, 그리고 토조 환경에서 필요한 토조 빛 굴절 등을 해결하기 위한 방법론을 제시하여 실험을 통해 검증하였다. 실험 결과, 말뚝 관입 단계에 따라 기준점 및 타겟점의 영상좌표를 자동으로 추출 가능하였고 토조 굴절이 고려된 번들조정을 통해 자동화된 지반 변형 측정이 가능하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.343-350
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• 2005

A constitutive model was implemented in ABAQUS code. The constitutive equation can model the behavior for overall range of strain level from small to large deformation, which is based on anisotropic hardening rule and total stress concept. The formulation includes (1) finite strain formulation on the basis of Jaumann rate, (2) implicit stress integration and (3) consistent tangent moduli. Therefore the mathematical background was established in order that large deformation analysis can be performed accurately and efficiently with the anisotropic constitutive model. In the large deformation analyses, geometric nonlinearity was considered and the result of analyses with the proposed model was compared with that of Mises model for the overall strain range behavior.

• 소성∙가공
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• 제10권5호
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• pp.383-388
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• 2001

In describing the plastic deformation behaviour of ultrafine-grained materials, a phase mixture model in which a polycrystalline material is regarded as a mixture of a crystalline phase and a grain boundary phase has been successful. The deformation mechanism for the grain boundary phase, which is necessary for applying the phase mixture model to polycrystalline materials, is modelled as a diffusional flow of matter along the grain boundary. A constitutive equation for the boundary diffusion creep of the boundary phase was proposed, in which the strain rate is proportional to (stress/grain siz $e^{2}$). The upper limit of the stress of the boundary phase was set to equal to the strength to the amorphous phase. The proposed model can explain the strain rate and grain size dependence of the strength of the grain boundary phase. Successful applications of the model compared with published experimental data are described.

• Structural Engineering and Mechanics
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• 제6권1호
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• pp.63-76
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• 1998

This paper presents dynamic responses of structures with sliding base which limits the translation of external loads from ground excitation. A discrete element model based on the discontinuous deformation analysis method is proposed to study this sliding boundary problem. The sliding base is simulated using sets of fictitious contact springs along the sliding interface. The set of contact spring is to translate friction force from ground to superstructure. Validity of the proposed model is examined by the closed-form solutions of an idealized mass-spring structural model subjected to harmonic ground excitation. This model is also applied to a problem of a three-story structural model subjected to the ground excitation of 1940 El Centro earthquake. Analyses of both sliding-base and fixed-base conditions are performed as comparisons. This study shows that using this model can simulate the dynamic response of a sliding structure with frictional cut-off quite accurately. Results reveal that lowering the frictional coefficient of the sliding joint will reduce the peak responses. The structure responses in little deformation, but it displaces at the end of excitation.

• 한국기계가공학회지
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• 제10권2호
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• pp.124-129
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• 2011

The thick plate produced by rolling process is used as the basic members of a ship structure. In this paper, we present a setup model to control the asymmetric factors causing plate bending in the upper or lower direction during rolling. A series of finite element analysis are conducted to predict the relationship between various asymmetric factors and plate bending. The setup model is developed by regressing the relationship to the linear equations with several non-dimensional parameters. The setup model is verified by a pilot rolling test and applied to actual rolling conditions. Results show that the model is substantial to predict the asymmetric deformation in the plate rolling process.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.121-126
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• 2003

This paper is concerns with the development of the formulae to predict deformation of curved plate due to line heating. For this purpose thermal elasto-plastic analysis has been carried out for both flat and curved plate models with varying parameters which affect the result of line heating. based on the results of numerical analysis, the formulae for predicting angular deformation has been derived through the regression analysis, which. It has been seen that the present model well agrees with the numerical analysis results and can reflect the curvature effect of plate to be heated. This paper ends with some comments on this formulae.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제2권2호
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• pp.127-132
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• 2002

In this paper, a new method for displaying a surface deformation is proposed using the fuzzy model. In the proposed method, it is enough that only one rule is added to the fuzzy model to display a surface deformation. Furthermore, designer can easily determine which parameters should be used and how much they should be changed in order to alter shapes as they want. The proposed method is, thus, a simple, but effective technique that can also be applied to real time operation. The results of the computer simulation are also given to demonstrate the validity of the proposed algorithm.

• 소성∙가공
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• 제22권1호
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• pp.11-16
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• 2013

Despite its importance the control of roller leveling has primarily relied on the operator's experience and on operation tables. In order to effectively eliminate various shape defects, the optimal leveling condition for a specific mode of plate deformation needs to be determined as well as a careful evaluation as to whether or not the condition is still appropriate for other modes or not. A numerical model, which considers both computation efficiency and accuracy, has been developed. The variations of residual stress are studied according to the entry and the delivery intermeshes, respectively. The camber deformation decreases linearly as the entry intermesh increases. In contrast the curl deformation does not vary directly with the entry intermesh. Therefore, the optimum intermesh values need to be determined in order to simultaneously minimize both the camber and the curl deformation.

• Structural Engineering and Mechanics
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• 제24권1호
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• pp.31-50
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• 2006

This paper deals with the mechanical behaviour of the thin-walled cylindrical air-spring shell (CAS) made of rubber-textile cord composite (RCC) subjected to different types of loading. An orthotropic hyperelastic constitutive model is presented which can be applied to numerical simulation for the response of biological soft tissue and of the nonlinear anisotropic hyperelastic material of the CAS used in vibroisolation of driver's seat. The parameters of strain energy function of the constitutive model are fitted to the experimental results by the nonlinear least squares method. The deformation of the inflated CAS is calculated by solving the system of five first-order ordinary differential equations with the material constitutive law and proper boundary conditions. Nonlinear hyperelastic constitutive equations of orthotropic composite material are incorporated into the finite strain analysis by finite element method (FEM). The results for the deformation analysis of the inflated CAS made of RCC are given. Numerical results of principal stretches and deformed profiles of the inflated CAS obtained by numerical deformation analysis are compared with experimental ones.