• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.1059-1061
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• 2002

A FE model is to develop a personalized biomechanical model of the scoliotic spine that will allow the design of clinical test providing optimal estimation of the post-operation results. A flexible multi-body model of the spine including rib cage, clavicle, and scapular was developed to simulate several mobility simulations. Vertebrae, clavicle and scapular were represented using rigid bodies and ribs and sternum were modeled as flexible bodies. Kinematical Joints and spring elements were used to represent the intervertebral disc and ligaments respectively. Postero-anterior and lateral radiographics of a scoliotic spine were used to represent a 3D reconstruction. CT data for same patient were also used to verify vertebrae rotation driven from postero-anterior and lateral radiographic images. Simulated results showed good reducibility almost uniformly distributed along the spinal segments. It was also found that boundary and loading conditions, required to mimic the operation procedures, were proven to be very sensitive parameters to its results rather than its mechanical properties

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.329-332
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• 2002

The upper bound analysis by stream function is used to study the torsional forward extrusion. The torsional forward extrusion process not only reduces forming load but also increase optimal die angle. Optimal die angle is determined by the optimization technique. The advantages of this process are that the low capacity of pressing machine can be used and the process with a large die angle can be applied. To verify the theoretical result, we have carried out experiments using model material (plasticine) and FE simulations using DEFORM3D.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.49-55
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• 2005

The objective of this study was presented with a prediction on the alignment of cementite in pearlite lamella structure of high carbon steel by means of finite-element method(FEM) simulation. Pearlite strcuture was characterized by its nano-sized microstructure feature of alternation ferrite and cementite. FEM simulations were performed based on a suitable FE model describing the boundary conditions and the material behavior. With the alignment of lamella structure in high carbon pearlite steel wire, material plastic behavior was taken into account on plastic deformation and alignment of cementite. The effects of many important parameters(reduction in area, semi-die angle, initial angle of cementite ) on wire drawing process were predicted by DEFORM-2D. As the results, the possibility of wire fracture could be considerably reduced and the productivity of final product could be more increased than before.

• Journal of the Optical Society of Korea
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• v.17 no.5
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• pp.399-404
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• 2013

This article proposes a digital image correlation (DIC) strain measurement method based on a finite element (FE) algorithm. A two-step digital image correlation is presented. In the first step, the gradient-based subpixels technique is used to search the displacements of a region of interest of the specimen, and then the strain fields are obtained by utilizing the finite element method in the second step. Both simulation and experiment processing, including tensile strain deformation, show that the proposed method can achieve nearly the same accuracy as the cubic spline interpolation method in most cases and higher accuracy in some cases, such as the simulations of uniaxial tension with and without noise. The results show that it also has a good noise-robustness. Finally, this method is used in the uniaxial tensile testing for Dahurian Larch wood specimens with or without a hole, and the obtained strain values are close to the results which were obtained from the strain gauge and the cubic spline interpolation method.

• Structural Engineering and Mechanics
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• v.5 no.6
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• pp.755-765
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• 1997

Within the framework of anisotropic combined viscoplastic hardening formulation, accounting macroscopically for residual stress as well as texture development at finite deformations of metals, simple shear analyses for the simulation of fixed-end torsion experiments for ${\alpha}$-Fe, Al and Cu at different strain rates are reviewed with an emphasis on the role of constitutive spins. Complicated responses of the axial stresses with monotonically increasing shear deformations can be successfully described by the capacity of orthotropic hardening part, featuring tensile axial stresses either smooth or oscillatory. Temperature effect on the responses of axial stresses for Cu is investigated in relation to the distortion and orientation of yield surface. The flexibility of this combined hardening model in the simulation of finite inelastic strains is discussed with reference to the variations of constitutive spins depending upon strain rates and temperatures.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.942-949
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• 2014

We studied about the rotor design change using a Ferrite ring magnet to reduce material cost in the condition of the same stator core design. However, this design direction has many weak points such as the decrease of BEMF, the low maximum output, the irreversible demagnetization characteristics of a permanent magnet and so on. In order to mitigate such disadvantages, an optimization design of the BLDC motor has been developed by changing each design parameter and by improving the electromagnetic structure. In the proposed water pump SPM BLDC motor using Ferrite magnet, the outer and inner diameter of stator is fixed to the value of the conventional IPM BLDC motor using Nd-Fe-B magnet. The design specification requirements should be satisfied with the same output power and efficiency characteristics in the same dimension. As a result of this study, the design comparison results considering driving performances and material cost are represented. Through the actual experiment with the prototype of the designed motor, the simulations results are verified.

• Transactions of Materials Processing
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• v.23 no.3
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• pp.139-144
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• 2014

In the current study, we present a new model for predicting width spread of a slab with a dog-bone shaped cross section during rolling in the roughing train of a hot strip mill. The approach is based on the extremum principle for a rigid plastic material and a three dimensional admissible velocity field. The upper bound theorem is used for calculating the width spread of the slab. The prediction accuracy of the proposed model is examined through comparison with the predictions from 3-D finite element (FE) process simulations.

• Transactions of Materials Processing
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• v.23 no.3
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• pp.145-150
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• 2014

Precision control of the slab is crucial for product quality and production economy in hot strip mills. The current study presents a new model for predicting width spread of a slab with a rectangular cross section during roughing. The model is developed on the basis of the extremum principle for a rigid plastic material and a three dimensional admissible velocity field. This model incorporates the effect of process variables such as the shape factor and the ratio of width to thickness. We compare the results of this model to 3-D finite element (FE) process simulations and also to results from a previous study.

• Tunnel and Underground Space
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• v.20 no.2
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• pp.73-81
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• 2010

The paper presents the application of FE simulations of NATM tunnel using different constitutive models. The results from a series of two dimensional plane strain finite element analyses of medium-liner interaction for NATM are presented. Four types of constitutive models are considered, namely, linear elastic, elasto-plastic Mohr-Coulomb, Hardening-Soil, Soft-Soil model. The design for tunnels requires a proper estimate of surface settlement and lining forces. It is shown that the advanced constitutive model gives better predictions for both ground movement and structural forces.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.11
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• pp.145-151
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• 1998

Unlike the drawing of round section from round bar, the shaped drawing like polygonal section is known to have influence not only drawing stress but also corner filling. Therefore. this study analyze the drawing process of suqare rod from round bar using nonsteady state rigid-plastic FEM. To investigate effects of process variables of the drawing process of square rod from round bar, FE-simulations with variety of reduction in area and semi-die angle for a given frictional condition have been conducted. By this results, it has to suggest optimal process condition on the drawing stress and the corner filling. In addition, it has determined forming limit considering necking and bulging.