• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.233-235
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• 2007

Finite element analysis was conducted for cold roller leveler to verify numerical model of roller leveler developed by POSTECH. On-line model of roller leveler was developed to predict rapid and precise roll intermesh of roller leveler in thick plate mill. The cold roller leveler in thick plate mill was analyzed using MARC & MENTAT and the results are compared with the results of numerical model of roller leveler calculated by POSTECH.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.163-165
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• 1996

In the PIC simulation of plasma, the fields are commonly calculated on uniform spatial grids using FDM. But, FDM has a difficulty in modeling a complex shaped model. FEM has a good flexibiblity in treating a complex shape, so that we calculated the field by using FEM not FDM. In this paper, the plasma between plane-to-plane electrodes was simulated using FEM and FDM. Comparing the results of those two methods told us that FEM is also valid as a calculating method in PIC plasma simulation. In order to verify the use of FEM, the discharge of rod-to-plane was simulated. There was not a little distortion of the electric field between the electrodes due to the distribution of space charges.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.363-368
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• 2004

Maglev vehicles, which are levitated and propelled by electromagnets, often run on elevated guideways comprised of steel, aluminum and concrete. Therefore, an analysis of the dynamic interaction between the Maglev vehicle and the guideway is needed in the design of the critical speed, ride, controller design and weight reduction of the guideway. This study introduces a dynamic interaction simulation technique that applies FEM. The proposed method uses FEM to model the elevated guideway and the Maglev vehicle, which is different from conventional studies. Because the proposed method uses FEM, it is useful to calculate the deformation of the elevated guideway, the dynamic stress, and the motion of the vehicle. By applying the proposed method to an urban transit Maglev vehicle, UTM01, the dynamic response is simulated according to velocity increase and can be reviewed again. From the result of the study, we concluded that FEM simulation of the dynamic interaction between the maglev vehicle and the guideway is possible.

• 전기학회논문지
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• 제56권12호
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• pp.2103-2108
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• 2007

This study investigates the dynamic characteristics of Synchronous Reluctance Motor (SynRM), with segmental rotor structure, using finite element method in which the moving mesh technique is considered. The focus of this paper is the efficiency of on-line parameter identification system for position sensorless control of a SynRM considering saturation and iron loss. Comparisons are given with angle of the observer and those of proposed FEM & Preisach model of synchronous reluctance motor, respectively. The position sensorless control using identified motor parameters is realized, and the efficiency of the on-line parameter identification system is verified by experimental results.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.416-421
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• 2004

Off-line feedrate scheduling is presented as the advanced technology to regulate cutting forces at the desired level through change of feedrates. In rough cutting, the feedrate scheduling aims at reducing the machining time, which is the most important factor for better productivity. Thus, the largest force which can avoid breakage of tool shank and tooth is a reference force for feedrate scheduling in rough cutting. In this paper, a calculation method of the reference cutting force for feedrate scheduling is developed. This model calculates rupture plane of tooth using the FEM analysis of a tool and computes the reference force using the transverse rupture strength of a tool. Experiments validate that the presented feedrate scheduling model reduced machining time drastically and regulate cutting forces at the reference cutting force.

• Steel and Composite Structures
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• 제20권6호
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• pp.1237-1257
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• 2016

The paper concerns analysis of effects of shrinkage of slab concrete in a steel-concrete composite deck of a through truss bridge span. Attention is paid to the shrinkage alongside the span, i.e., transverse to steel-concrete composite cross-beams. So far this aspect has not been given much attention in spite of the fact that it affects not only steel-concrete decks of bridges but also steel-concrete floors of steel frame building structures. For the problem analysis a two-dimensional model is created. An analytical method is presented in detail. A set of linear equations is built to compute axial forces in members of truss girder flange and transverse shear forces in steel-concrete composite beams. Finally a case study is shown: test loading of twin railway truss bridge spans is described, verified FEM model of the spans is presented and computational results of FEM and the analytical method are compared. Conclusions concerning applicability of the presented analytical method to practical design are drawn. The presented analytical method provides satisfactory accuracy of results in comparison with the verified FEM model.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.45-45
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• 2010

This paper discusses the simulation and LI(light impulse) test of the shieldless vacuum interrupter concept. The shields of vacuum interrupter play an important role in absorbing the metal vapor. But shield distort the electric field distribution of inner vacuum interrupter. Therefore, the insulation efficiency will improve. if shield of vacuum interrupter inside does not exist. As a result, FEM simulation show that improve distribution of electrical field and equi-potential line. But LI test result dissimilar to FEM simulation result. Shieldless vacuum interrupter model lower BIL(breakdown impulse light) than vacuum interrupter have installed shield. Because conditioning process occurred metal vapor. This paper compared that FEM analysis and LI test of installed shield model and shieldless model.

• Computers and Concrete
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• 제25권2호
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• pp.181-192
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• 2020

Nowadays, steel fiber reinforced concretes (SFRCs) are widely used in practical applications. Significant experimental research has thus been carried out to determine the constitutive equations that represent the behavior of SFRCs under multiaxial loadings. However, numerical modelling of SFRCs via FEM has been challenging due to the complexities of the implementation of these constitutive equations. In this study, following the literature, a plasticity model is constructed for the behavior of SFRCs that involves the Willam-Warnke failure surface with the relevant evolution laws and a non-associated flow rule for determining the plastic deformations. For the precise (yet rapid) integration of the constitutive equations, an explicit substepping scheme consisting of yield intersection and drift correction algorithms is employed and thus implemented in ABAQUS via UMAT. The FEM model includes various material parameters that are determined from the experimental data. Three sets of parameters are used in the numerical simulations. While the first set is from the experiments that are conducted in this study on SFRC specimens with various contents of steel fibers, the other two sets are from the experiments reported in the literature. The response of SFRCs under multiaxial compression obtained from various numerical simulations are compared with the experimental data. The good agreement between numerical results and the experimental data indicates that not only the adopted plasticity model represents the behavior of SFRCs very well but also the implemented integration scheme can be employed in practical applications of SFRCs.

• Structural Engineering and Mechanics
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• 제81권3호
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• pp.379-394
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• 2022

Shallow footings usually belonged to the category of thick plate structures. For accurate analysis of thick plates, the contribution of out-of-plane components of the stress tensor should be considered in the formulation. Most of the available shallow footing models are based on the classical plate theories, which usually neglect the effects of the out-of-plane stresses. In this study, a mixed-field plate finite element model (FEM) is developed for the analysis of shallow footings rested on soil foundations. In addition to displacement field variables, the out-of-plane components of the stress tensor are also assumed as a priori unknown variables. For modeling the interaction effect of the soil under and outside of the shallow footings, the modified Vlasov theory is used. The tensionless nature of the supporting soil foundation is taken into account by adopting an incremental, iterative procedure. The equality requirement of displacements at the interface between the shallow footing and soil is fulfilled using the penalty approach. For validation of the present mixed FEM, the obtained results are compared with the results of 3D FEM and previous results published in the literature. The comparisons show the present mixed FEM is an efficient and accurate tool for solving the problems of shallow footings rested on subsoil.

• Interaction and multiscale mechanics
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• 제1권1호
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• pp.1-31
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• 2008

The present paper presents multiscale modelling via coupling of the discrete and finite element methods. Theoretical formulation of the discrete element method using spherical or cylindrical particles has been briefly reviewed. Basic equations of the finite element method using the explicit time integration have been given. The micr-macro transition for the discrete element method has been discussed. Theoretical formulations for macroscopic stress and strain tensors have been given. Determination of macroscopic constitutive properties using dimensionless micro-macro relationships has been proposed. The formulation of the multiscale DEM/FEM model employing the DEM and FEM in different subdomains of the same body has been presented. The coupling allows the use of partially overlapping DEM and FEM subdomains. The overlap zone in the two coupling algorithms is introduced in order to provide a smooth transition from one discretization method to the other. Coupling between the DEM and FEM subdomains is provided by additional kinematic constraints imposed by means of either the Lagrange multipliers or penalty function method. The coupled DEM/FEM formulation has been implemented in the authors' own numerical program. Good performance of the numerical algorithms has been demonstrated in a number of examples.