• 대한기계학회논문집B
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• 제29권5호
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• pp.568-576
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• 2005

A 3-D finite element model combined with a volume tracking method is presented in this work to simulate the mold filling for casting processes. Especially, the analysis involves an adaptive grid method that is created under a criterion of element categorization of filling states and locations in the total region at each time step. By using an adaptive grid wherein the elements, finer than those in internal and external regions, are distributed at the surface region through refinement and coarsening procedures, a more efficient analysis of transient fluid flow with free surface is achieved. Adaptive grid based on VOF method is developed in tetrahedral element system. Through a 3-D analysis of the benchmark test of the casting process, the efficiency of the proposed adaptive grid method is verified. Developed FE code is applied to a typical industrial part of the casting process such as aluminum road wheel.

• 대한기계학회논문집A
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• 제22권1호
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• pp.121-131
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• 1998

This paper applies the FE analysis procedure, developed in the Part I of the companion article, to the three-dimensional rubber pad deformation during rubber-pad forming process. Effects of different algorithms corresponding to incompressibility constraint and time integration methods on numerical solution responses are investigated. Laboratory scale experiments support the validity of the developed FE procedure an demonstrate the accuracy of the numerical models. Full scale model responses are also predicted using the reasonable method and parameters obtained in laboratory modeling.

• Structural Engineering and Mechanics
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• 제53권6호
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• pp.1067-1081
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• 2015

This study investigates structural and mechanical behaviors of RC (Reinforced concrete) beams strengthened with tapered CFRP (Carbon fiber reinforced polymer) sheets having various configurations. Toward this goal, experiments are performed on RC beams strengthened with four layers of CFRP sheets and each layer of the CFRP is prepared to have different length. Experimental results show that tapered CFRPs have better strengthening effect than non-tapered CFRP sheets and maximum loads of the beams with tapered CFRPs are governed by the length of first CFRP layer rather than total length of CFRP layers. In addition, analyses are performed using FE (Finite Element) models including cohesive elements to predict debonding behaviors between FRP and concrete elements. The predicted results from the FE models show good agreement with the experimental results.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권2호
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• pp.1-8
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• 2001

This paper deals with magnetic field analysis and computation of cogging torque using an analytical method in Interior Permanent Magnet Motor (IPMM). The magnetic field is analyzed by solving space harmonics field analysis due to magnetizing and the cogging torque is analyzed by combining field analysis with relative permeance. In reducing cogging torque, the inferences of various design variable and magnetizing distribution are investigated. It is shown that the slot and pole ratio (the pole-arc / pole-pitch ratio) combination has a significant effect on the cogging torque and presents a optimal flux barrier shape to reduce the cogging torque. The validity of the proposed technique is confirmed with 2-D Finite Element(FE) analysis.

• Journal of Magnetics
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• 제21권4호
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• pp.503-508
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• 2016

The roll- and pitch-induced eddy currents create a magnetic field that contributes to the total magnetic signature of naval vessels. The magnetic signature is of concern, as it exposes the ship to the threat of modern influence mines. It is estimated that the eddy current is the second most important source contributing to a ship's underwater magnetic field following the ferromagnetic effect. In the present paper, the finite element (FE) method is used to predict the eddy current signature of a real ship. The FE model is validated using the measurements of the Canadian research vessel CFAV QUEST at the Earth's Field Simulator (EFS) in Schirnau, Germany. Modeling and validation of the eddy current magnetic signature for a real ship represents a novelty in the field. It is shown that the characteristics of this signature depend on frequency. Based on these results, a ship's degaussing system could be improved to cancel both the ferromagnetic and the eddy current contribution to the magnetic signature simultaneously, reducing the susceptibility to sea mines.

• Structural Engineering and Mechanics
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• 제32권5호
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• pp.667-683
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• 2009

FE model-based dynamic analysis has been widely used to predict the dynamic characteristics of civil structures. In a physical point of view, an FE model is unavoidably different from the actual structure as being formulated based on extremely idealized engineering drawings and design data. The conventional model updating methods such as direct method and sensitivity-based parameter estimation are not flexible for model updating of complex and large structures. Thus, it is needed to develop a model updating method applicable to complex structures without restriction. The main objective of this paper is to present the model updating method based on the hybrid genetic algorithm (HGA) by combining the genetic algorithm as global optimization method and modified Nelder-Mead's Simplex method as local optimization method. This FE model updating method using HGA does not need the derivation of derivative function related to parameters and without application of complicated inverse analysis methods. In order to allow its application on diversified and complex structures, a commercial FEA tool is adopted to exploit previously developed element library and analysis algorithms. Moreover, an output-level objective function making use of measurement and analytical results is also presented to update simultaneously the stiffness and mass of the analysis model. The numerical examples demonstrated that the proposed method based on HGA is effective for the updating of the FE model of bridge structures.

• 센서학회지
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• 제8권4호
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• pp.298-307
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• 1999

This paper describes the application of the coupled FE-BEM (finite element-boundary element method) for the numerical harmonic analysis of the linear dynamic behaviour of a magnetostrictive Terfenol-D rod in water. The magnetostrictive rod is three-dimensionally simulated to transduce applied electric current in a helical coil around the rod to mechanical displacement. The theoretical derivation of the magnetostrictive matrix equation is described in detail. The steady-state resonance response of the displacement is shown. In addition, the directivity pattern and the radiation impedance are also shown.

• 한국해양공학회지
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• 제25권1호
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• pp.61-66
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• 2011

According to recent figures, 35% of the world's blades are made using prepreg blades, by Vestas and Gamesa. They are the most advanced in the market today. In this study, we investigated the validity of the finite element method (FEM) applied to an FE analysis of a hybrid composite wind-turbine blade. Two methods were suggested for a composite FE analysis: using the equivalent properties of the composite or using stacking properties. FE analysis results using the stacking properties of the composite were in good agreement with results of using the equivalent properties. The difference between FE results was approximately 0.6~13.3%.

• Structural Engineering and Mechanics
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• 제19권1호
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• pp.97-106
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• 2005

The standard practice is to seismically qualify the safety related equipment and structural components used in the nuclear power plants. Among several qualification approaches the qualification by the analysis using finite element (FE) method is the most common approach used in practice. However the predictions by the FE model for a structure is known to show significant deviations from the dynamic behaviour of 'as installed' structure in many cases. Considering such limitation, few researchers have advocated re-qualification of such structures after installation at site to enhance the confidence in qualification vis-$\grave{a}$-vis plant safety. For such an exercise the validation of FE model with experimental modal data is important. A validated FE model can be obtained by the Model Updating methods in conjugation with the in-situ experimental modal data. Such a model can then be used for qualification. Seismic analysis using the updated FE model and its advantage has been presented through an example of an in-core component - a perforated horizontal tube of a nuclear reactor.

• 한국정밀공학회지
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• 제29권10호
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• pp.1050-1055
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• 2012

The bearing coupling section of machine tools is the most important factor to determine their static/dynamic stiffness. To ensure the proper performance of machine tools, the static/dynamic stiffness of the rotating system has to be predicted on the design stage. Various parameters of the bearing coupling section, such as the spring element, node number and preload influence the characteristics of rotating systems. This study focuses on the prediction of the static and dynamic stiffness of the rotating system with the bearing coupling section using the finite element (FE) model. MATRIX 27 in ANSYS has been adopted to describe the bearing coupling section of machine tools because the MATRIX 27 can describe the bearing coupling section close to the real object and is applicable to various machine tools. The FE model of the bearing couple section which has the sixteen node using MATRIX 27 was constructed. Comparisons between finite element method (FEM) predictions and experimental results were performed in terms of the static and dynamic stiffness.