• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.06a
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• pp.9-16
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• 1998

New program for springback analysis has been developed to predict the deformation of springback more accurately. Static implicit FEM is used to find out the static equilibrium after springback. The shell element with 6 dogrees of freedom and 4 nodes is carefully implemented to improve the accuracy and the compatibility between forming analysis and springback analysis. Co-rotational approach and Newton-Raphson nonlinear iteration are used to resolve the nonlinearity of large deformation. The benchmark results show that the developed program gives good predictions in comparison with experimental and other commercial S/W's results. As practical examples, U draw bending and S-rail problems are carried out by the developed program.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.217-219
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• 2008

A new experimental model for determining drawbead forces, which modifies the dieface of Nine's experimental model, is introduced and the better validity of the drawbead opening and restraining forces of new model than those of Nine's is demonstrated. While Nine's model considers a blank holding force as one of forming variables, new model excludes it by removing blank holder in the dieface. The comparison of the strains found by FEM simulation of automotive fender draw forming process with those measured in a formed panel recommends the new model for accurate drawbead forces.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.281-284
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• 2008

Film insert melding is one of the surface processes that enhances functional or aesthetic qualities of an existing product's surface. In general, film insert molding consists of three processes including thermoforming, trimming and injection molding. Thermoforming, which is the first process of film insert molding, is the most important process because the variation of film thickness has an effect on the mold design and process conditions for the subsequent processes, that are, trimming and injection molding. This study is focused on predicting the film thickness distribution through film insert thermoforming process using commercial FEM code. In order to describe rheological behavior of thermoplastic film (ABS), G'Sell's viscoelastic constitutive law was adopted. The numerical model of film insert thermoforming was established, and the simulation to predict film thickness distribution was performed. Comparison between the results of simulation and experiment was made to validate the proposed finite element analysis.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.9
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• pp.149-158
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• 1999

The modern trends of optical storage devices can be characterized by high density in information recording, and high bandwidth in data input/output processing rate. These make servo engineers to face with a new barrier on control system design in much more difficult way. The first step to attack this barrier will be through a systematic modeling for the dynamic characteristics of optical storage drive. in this paper, an analytical dynamic model for an optical storage drive based on FEM is drived, and compared with experimental results. Through this comparison, a practical dynamic model on the focusing and tracking motion of optical storage drive is proposed for the initiation of real control system design problem.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.139-146
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• 2004

In this study, to achieve the optimal conditions for mechanical hyper-fine pattern fabrication process, deformation behavior of the materials during indentation scratch test was studied with numerical method by ABAQUS S/W. Brittle materials (Si, Pyrex glass 7740) were used as specimens, and forming conditions to reduce the elastic recovery and pile-up were proposed. The indenter was modeled as a rigid surface. Minimum mesh sizes of specimens are 1-l0nm. Variables of the nanoindentation scratch test analysis are scratching speed, scratching load, tip radius and tip geometry. The nano-indentation scratch tests were performed by using the Berkovich pyramidal diamond indenter. Comparison between the experimental data and numerical result demonstrated that the FEM approach can be a good model of the nanoindentation scratch test. The result of the investigation will be applied to the fabrication of the hyper-fine pattern.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.147-150
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• 2005

The torsion beam axle type is widely used in the rear suspension for small passenger car because of low cost, good performance and etc. The FE and dynamic analysis using the computer are very helpful for the efficiency of the torsion beam design. First of all, the reliability on the computational model must be verified for the analysis. In this study, The FE model of the torsion beam was verified according to comparison with he test data. And after making the flexible body using the FE model, the dynamic characteristic of the tubular type torsion beam axles was compared with that of the V-beam type.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.217-218
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• 2015

Two axial flux permanent magnet (AFPM) machines using soft magnetic composite (SMC) and lamination steel are studied. Generally stator cores of AFPM machines are manufactured using SMC because AFPM machines need 3 dimensional core structures. However, SMC cores have very disadvantages in magnetic properties. Especially permeability value is much lower than that of lamination steel, so magnetic field density is also lower. In terms of core losses, SMC cores have much larger loss values than lamination steel cores because SMC core can't be laminated. In this study, AFPM machine was designed using laminated steel, and iron losses in two machines using SMC and laminated steel were studied. Simulations were carried out by a commercial 3-D FEM tool.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.165-173
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• 2003

In this study, the applicability of currently used pipeline.soil interaction force and previously proposed analytical relationship for the response analysis of buried pipeline subjected to transverse permanent ground deformation (PGD) due to liquefaction is evaluated. Based on meaningful contemplation, the improvement of interaction force and proposition of analytical relationship is made. Improved interaction force includes various patterns of PGD or spatial distributions of interaction force caused by the decrease of soil stiffness, and proposed relationship based on improved formula is applicable without regard to the width of PGD. Through the comparison of numerical results by use of commercial FEM program, the rational applicability of proposed relationship is objectively confirmed.

• Advances in materials Research
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• v.6 no.4
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• pp.349-361
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• 2017

The nonlinear thermal buckling load parameter of the laminated composite panel structure is investigated numerically using the higher-order theory including the stretching effect through the thickness and presented in this research article. The large geometrical distortion of the curved panel structure due to the elevated thermal loading is modeled via Green-Lagrange strain field including all of the higher-order terms to achieve the required generality. The desired solutions are obtained numerically using the finite element steps in conjunction with the direct iterative method. The concurrence of the present nonlinear panel model has been established via adequate comparison study with available published data. Finally, the effect of different influential parameters which affect the nonlinear buckling strength of laminated composite structure are examined through numerous numerical examples and discussed in details.

• Computers and Concrete
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• v.7 no.6
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• pp.533-547
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• 2010

Recent developments in concrete mixing made possible the production of concretes with high compressive strength showing, simultaneously, high workability. These concretes also present high strengths at young ages, allowing the application of loads sooner. It is of fundamental importance to verify if creep models developed for current concrete still apply to these new concretes. First, a FEM-based software was adopted to test available creep models, most used for normal strength concrete, considering examples with known analytical results. Several limitations were registered, resulting in an incorrect simulation of three-dimensional creep. Afterwards, it was implemented a Kelvin-chain algorithm allowing the use of a chosen number of elements, which adequately simulated the adopted examples. From the comparison between numerical and experimental results, it was concluded that the adopted algorithm can be used to model creep of high strength concrete, if the material properties are previously experimentally assessed.