• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.1
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• pp.67-75
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• 2002

In this Paper, we discuss the PEEC method and construct the PEEC equivalent circuit of the test structure and construct the system matrix, which was simulated by numerical analysis. And we got node voltages and currents. Constructing the equivalent circuit, we extracted the parasitic parameter(R, L, C)using the simulator, which is based on finite element method, hence we could simulate the transient analysis.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.4 no.2
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• pp.193-198
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• 2004

This paper describes an automatic finite element (FE) mesh generation for three-dimensional structures consisting of tree-form surfaces. This mesh generation process consists of three subprocesses: (a) definition of geometric model, (b) generation of nodes, and (c) generation of elements. One of commercial solid modelers is employed for three-dimensional solid structures. Node is generated if its distance from existing node points is similar to the node spacing function at the point. The node spacing function is well controlled by the fuzzy knowledge processing. The Voronoi diagram method is introduced as a basic tool for element generation. Automatic generation of FE meshes for three-dimensional solid structures holds great benefits for analyses. Practical performances of the present system are demonstrated through several mesh generations for three-dimensional complex geometry.

• Transactions of Materials Processing
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• v.17 no.8
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• pp.607-612
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• 2008

The groove rolling is a process that transforms the bloom or billet into a shape with circular section through a series of rolling. Inhibition of surface defect generation in groove rolling is a matter of great importance and therefore many research groups proposed a lot of models to find the location of surface defect initiation. In this study, we propose a model for maximum shear stress ratio over equivalent strain to catch the location of surface defect onset. This model is coupled with element removing method and applied to box groove rolling of POSCO No.3 Rod Mill. Results show that proposed model in this study can find the location of surface defect initiation during groove rolling when finite element analysis results is compared with experiments. The proposed criterion has been applied successfully to design roll grooves which inhibit the generation of surface defect.

• Smart Structures and Systems
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• v.9 no.5
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• pp.411-426
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• 2012

Thin-walled adaptive structures render a large and important group of adaptive structures. Typical material system used for them is a composite laminate that includes piezoelectric material based sensors and actuators. The piezoelectric active elements are in the form of thin patches bonded onto or embedded into the structure. Among different types of patches, the paper considers those polarized in the thickness direction. The finite element method (FEM) imposed itself as an essential technical support for the needs of structural design. This paper gives a brief description of a developed shell type finite element for active/adaptive thin-walled structures and the element is, furthermore, used as a tool to consider the aspect of mesh distortion over the surface of actuators and sensors. The aspect is of significance for simulation of behavior of adaptive structures and implementation of control algorithms.

• Journal of the Korean Institute of Intelligent Systems
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• v.15 no.3
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• pp.343-348
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• 2005

This paper describes an automatic finite element (FE) mesh generation for three-dimensional structures consisting of free-form surfaces. This mesh generation process consists of three subprocesses: (a) definition of geometric model, i.e. analysis model, (b) generation of nodes, and (c) generation of elements. One of commercial solid modelers is employed for three-dimensional solid structures. Node is generated if its distance from existing node points is similar to the node spacing function at the point. The node spacing function is well controlled by the fuzzy knowledge processing. The Delaunay method is introduced as a basic tool for element generation. Automatic generation of FE meshes for three-dimensional solid structures holds great benefits for analyses. Practical performances of the present system are demonstrated through several mesh generations for three-dimensional complex geometry.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.7
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• pp.152-157
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• 2014

Pro-program function of Pro/E has been utilized to expedite the design process of bellows. Design parameters selected for bellows design are manipulated to obtain the shapes user specified. User-oriented function may automate the bellows design process and this function may enable to reduce the design time remarkably. Generated bellows solid model has been applied to study of design sensitivity and optimum design. Among the selected design parameters, thickness of bellows affects system response most. Control-ring installed bellows may reduce the stress and prove to be an effective element for heavy load. The finite element analysis results combined with 3D model generated by pro-program may provide the feasible design directions to the bellows designer.

• Journal of KSNVE
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• v.9 no.2
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• pp.310-316
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• 1999

4-Pole parameter method based on an acoustic theory is very popular for the analysis of the acoustic behavior of the car exhaust system. However, this method is applicable only for the simple shape of acoustic elements of the muffler. Numerical methods such as FEM(Finite Element Method) or BEM(Boundary Element Method) can also provide acceptable results for the acoustic analysis of the car exhaust system. Even though these numerical methods have benefits for the analysis of complicated shape of acoustic elements of the muffler, time consuming is another problem during modeling and numerical calculation. Combining benefits of both methods, the new code called the hybrid method for car exhaust system is introduced. And the developed code is utilized for calculation of the transmission loss of a main muffler of an automobile comparing with the experimental results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.402-407
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• 1997

For cylindrical shells, the closed-form solutions are limited only to the cases with special boundary and/or loading conditions. Though the finite element method is certainly a powerful solution approach for the general structural dynamics problems, it is known to provide reliable solutions only in the low frequency region due to the inherent high sensitivities of structural and numerical modeling errors. Instead, the spectral element method has been proved to provide extremely accurate dynamic responses even in the high frequency region. Since the wave characteristics of a cylindrical shell becomes identical to that of a flat plate as the frequency increases, an equivalent plate model (EPM) representing the high-frequency dynamic characteristics of a cylindrical shell is introduced herein. The EPM-based spectral element analysis solutions are compared with the known analytical solutions for the corresponding cylindrical shell to confirm the validity of the present modeling approach.

• Geophysics and Geophysical Exploration
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• v.19 no.3
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• pp.136-144
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• 2016

Since seismic inversion is based on the wave equation, it is important to calculate the solution of wave equation exactly. In particular, full waveform inversion would produce reliable results only when the forward modeling is accurately performed because it uses full waveform. When we use finite-difference or finite-element method to solve the wave equation, the convergence of numerical scheme should be guaranteed. Although the general proof of convergence is provided theoretically, the consistency and stability of numerical schemes should be verified for practical applications. The implementation of source function is the most crucial factor for the consistency of modeling schemes. While we have to use the sinc function normalized by grid spacing to correctly describe the Dirac delta function in the finite-difference method, we can simply use the value of basis function, regardless of grid spacing, to implement the Dirac delta function in the finite-element method. If we use frequency-domain wave equation, we need to use a conservative criterion to determine both sampling interval and maximum frequency for the source wavelet generation. In addition, the source wavelet should be attenuated before applying it for modeling in order to make it obey damped wave equation in case of using complex angular frequency. With these conditions satisfied, we can develop reliable inversion algorithms.

• Journal of Powder Materials
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• v.31 no.3
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• pp.213-219
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• 2024

Additive Manufacturing (AM) is a process that fabricates products by manufacturing materials according to a three-dimensional model. It has recently gained attention due to its environmental advantages, including reduced energy consumption and high material utilization rates. However, controlling defects such as melting issues and residual stress, which can occur during metal additive manufacturing, poses a challenge. The trial-and-error verification of these defects is both time-consuming and costly. Consequently, efforts have been made to develop phenomenological models that understand the influence of process variables on defects, and mechanical/ electrical/thermal properties of geometrically complex products. This paper introduces modeling techniques that can simulate the powder additive manufacturing process. The focus is on representative metal additive manufacturing processes such as Powder Bed Fusion (PBF), Direct Energy Deposition (DED), and Binder Jetting (BJ) method. To calculate thermal-stress history and the resulting deformations, modeling techniques based on Finite Element Method (FEM) are generally utilized. For simulating the movements and packing behavior of powders during powder classification, modeling techniques based on Discrete Element Method (DEM) are employed. Additionally, to simulate sintering and microstructural changes, techniques such as Monte Carlo (MC), Molecular Dynamics (MD), and Phase Field Modeling (PFM) are predominantly used.