• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.229-234
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• 1994

The major objective of the present paper is to estabilish finite element simulation technique in order to further analyze the shearing process. For this the ductile fracture criterion and element kill method are used in the present work. It is postulated that a fracture initiation is based on the magnitude of local effective strain. The features of sheared surface are easily observed by the element kill method. The simulation results are compard with existing experimental results. It is found that the results of the present work are close agreement with the existing results.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.271-277
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• 1994

The fatigue crack opening behavior is analyzed using finite element method. Because extremely fine mesh subdivision is required when using constant stress constant strain triangular element, this study uses conventional two dimensional eight node isoparametric elements. Since plasitc zone size is similar to crack propagating length per each load cycle because of relatively large element size, a new analysis model that a crack propagates every two load cycle is suggested. the opening load and crack opening displacement can be obtained accurately by this method.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.765-772
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• 1996

Objectives of this study were to develop an application method of a numerical retina using the finite element model and to investigate the performance of image features extraction in comparison to the textural analysis. Using a plant community of radish sprouts, excellent resolution of the finite element retina was revealed. The sensitivity analysis of the finite element retina from engineering point of view was discussed. The importance of sensitivity analysis of the finite element retina was pointed out in terms of extraction of effective image features of plant community . Technical details of maximizing the sensitivity of the finite element retina to populated plant canopy were also discussed.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.458-460
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• 1998

The drum level control is initiated by 1-element manual control, and then the control mode is changed to 1-element automatic control mode. Finally, the drum level control is changed to 3-element automatic control mode by the logic based on pre-defined threshold of main steam flow. In terms of plant automation, the automatic 1-element control mode is required from the start-up of boiler. In this paper, the fuzzy controller is adopted for automatic 1-element control of drum level from start-up. It is suggested that the fuzzy controller is used in 1-element control, and the fuzzy-PI cascade controller is used in 3-element control. Finally, the validity of suggested control scheme is shown via simulation.

• Structural Engineering and Mechanics
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• v.37 no.6
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• pp.633-648
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• 2011

This paper investigates the aspect-ratio locking of the isoparametric 8-node quadrilateral (QUAD8) element. An important finding is that, if finite element solution is carried out with in exact arithmetic (i.e., with no truncation and round off errors), the locking tendency of the element is completely avoided even for aspect-ratios as high as 100000. The current finite element codes mostly use floating point arithmetic. Thus, they can only avoid this locking for aspect-ratios up to 100 or 1000. A novel method is proposed in the paper to avoid aspect-ratio locking in floating point computations. In this method, the offending terms of the strain-displacement matrix (i.e., $\mathbf{B}$-matrix) are multiplied by suitable scaling factors to avoid ill-conditioning of stiffness matrix. Numerical examples are presented to demonstrate the efficacy of the method. The examples reveal that aspect-ratio locking is avoided even for aspect-ratios as high as 100000.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.258-265
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• 1998

Application of the flat shell element with drilling D.O.F to linear buckling analysis of thin-walled structures is presented in this paper. The shell element has been developed basically by combining a membrane element with drilling D.O.F. and Mindlin plate bending element. Thus, the shell element possesses six degrees-of-freedom per node which, in addition to improvement of the element behavior, permits an easy connection to other six degrees-of-freedom per node elements(CLS, Choi and Lee, 1995). Accordingly, structures like folded plate and stiffened shell structure, for which it is hard to find the analytical solutions, can be analyzed using these developed flat shell elements. In this paper, linear buckling analysis of thin-walled structures like folded plate structures using the shell elements(CLS) with drilling D.O.F. to be formulated and then fulfilled. Subsequently, buckling modes and the critical loads can be output. Finally. finite element solutions for linear buckling analysis of folded plate structures are compared with available analytic solutions and other researcher's results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.120-128
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• 2002

In order to analyze shell structures more accurately and effectively, a hybrid 4-node quadrilateral shell element is formulated. The element includes the frilling degrees of freedom and the independent parameter terms of the stress resultants are appropriately selected to overcome some of the shortcomings of the standard 4-node quadrilateral elements. In order to show the accuracy and convergent characteristics of the proposed shell element, three numerical examples are analyzed and the results are compared with the existed. As a result of this study, following conclusions are obtained. (1)Analysis results by the proposed element are less sensitive to the element geometric distortion. (2)The proposed element does not produce any spurious zero-energy modes

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.169-176
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• 2002

This paper is concerned with development of an enhanced quadratic Mindlin plate bending element. The behavior of the proposed plate element is further improved by the coupled use of non-conforming displacement modes, the selectively reduced integration scheme, and the assumed shear strain fields. The improvement may be attributable to the fact that the merits of these improvement techniques are merged in the formation of the new element in a complementary manner. The proposed quadratic finite element passes the patch tests, does not show spurious mechanism, and does not produce shear locking phenomena even with distorted meshes. It is shown that the element produces reliable solutions through numerical tests for standard benchmark problems. It is also noted that the element is applicable to transient dynamic analysis of Mindlin plates.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.65-72
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• 1997

This study is the bending analysis of rectangular plates with 4-sides simply supported by Finite Element Method using substructuring technique. In finite element method, as the more number of finite element, the more dimension of matrix, it is difficult to obtain accuracy solution. In this paper substructuring technique is applied to finite element method in order to reduce the dimension of matrix according to the number of finite element mesh. To validate finite element method using substructuring technique, deflections and moments of rectangular plates by that method is compared with those of references. Considering the symmetry of the plate and load, one fourth of plate is analyzed. Operating time and the error of solutions according to the number of finite element mesh and substructure are compared with each other.

• The KSFM Journal of Fluid Machinery
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• v.20 no.2
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• pp.11-16
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• 2017

The accurate prediction of leakage flow through the brush element of brush seal at the steam turbine is important to find optimum design parameters for increasing an efficiency. In this study, CFD analysis method using commercial software FLUENT is proposed to predict leakage through the brush element. Since the brush element has a complex three-dimensional shape with many bristle assemblies, it is difficult to analyze the flow field. Therefore, if the brush element is assumed to be porous medium region, the analysis time can be shortened. Two determination methods of resistance coefficients of the Darcian porous medium equation are suggested. By comparing the 2D and 3D CFD analysis results for the leakage of the brush element using the two resistance coefficient determination methods, the effectiveness of the analysis for the porous medium assumption is proved.