• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.1
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• pp.22-33
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• 1998

A continuum analysis of the evolution of plasticity and Bauschinger effect in a short fiber reinforced metal matrix composite, based on the FEM solution for a single fiber model has been performed to investigate the strengthening behavior. The evolution of matrix field quantities during one cycle of fully reversed loading have been examined in detail. The results indicate that the role of constrained matrix flow in generating different levels of matrix triaxiality during forward and reversed loading provides an important contribution to the developement of the Bauschinger effect in the metal matrix composite. Therefore, even when the plastic flow of the matrix material follows on isotropic hardening behavior, the Bauschinger effect is predicted for the composite material.

• Journal of Mechanical Science and Technology
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• v.20 no.5
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• pp.621-633
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• 2006

To reflect the size effect of material $(1\sim15{\mu}m)$ during plastic deformation of polycrystalline copper, a constitutive equation which includes the strain gradient plasticity theory and intrinsic material length model is coupled with the finite element analysis and applied to plane strain deformation problem. The method of least square has been used to calculate the strain gradient at each element during deformation and the effect of distributed force on the strain gradient is investigated as well. It shows when material size is less than the intrinsic material length $(1.54{\mu}m)$, its deformation behavior is quite different compared with that computed from the conventional plasticity. The generation of strain gradient is greatly suppressed, but it appears again as the material size increases. Results also reveal that the strain gradient leads to deformation hardening. The distributed force plays a role to amplify the strain gradient distribution.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.177-184
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• 2000

In this work, some inaccuracies and limitation of prior indentation theory, which is based on the deformation theory of plasticity and experimental observations, are first investigated. Then effects of major material properties on the configuration of indentation load-deflection curve are examined via incremental plasticity theory based finite element analyses. It is confirmed that subindenter deformation and stress-strain distribution from the deformation theory of plasticity are quite dissimilar to those from incremental theory of plasticity. We finally suggest the optimal data acquisition location, where the strain gradient is the least and the effect of friction is negligible. This data acquisition point increases the strain range by a factor of five.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.281-284
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• 2004

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.298-302
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• 1997

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.365-365
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• 2008

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.167-170
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• 2005

This paper briefly reviews various existing methods to account for the effect of particle size on mechanical properties of particulate metal matrix composites. A simple and easy method is to use a size-dependent constitutive equation for the matrix. The suggested method does not require the development of a new computational algorithm and is compatible with any standard finite element software. Finite element analyses have been carried out to show how the deformation behavior of a metal matrix composite changes as the particle size and volume fraction are varied.

• PNF and Movement
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• v.6 no.2
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• pp.39-50
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• 2008

Purpose : This article reviewed the advances in the understanding of the effect of motor rehabilitation and brain plasticity on functional recovery after CNS damage. Methods : This is literature study with Pubmed, Medline and Science journal. Results : The inability of CNS neurons to regenerate is largely associated with nonneuronal aspects of the CNS environment. Especially, this neuronal growth inhibition is mediated by myelin associated glycoprotein, olygodendrocyte-myelin glycoprotein, and NOGO. Enriched environment, motor learning, forced limb use have been utilized in scientific studies to promote functional reorganization and brain plasticity. Especially, enriched environment and motor enrichment may prime the brain to respond more adaptively to injury, in part by expressed neurotrophic factors. Conclusions : These reviews suggest that activity-induced neural plasticity occur in damaged brain areas in order to functional reorganization, where it could contribute to motor recovery, and represent a target for stroke rehabilitation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.714-724
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• 2001

In this work, some inaccuracies and limitation of prior indentation theory, which is based on the deformation theory of plasticity and experimental observations, are first investigated. Then effects of major material properties on the configuration of indentation load-deflection curve are examined via incremental plasticity theory based finite element analyses. It is confirmed that subindenter deformation and stress-strain distribution from the deformation theory of plasticity are quite dissimilar to those from incremental theory of plasticity. We finally suggest the optimal data acquisition location, where the strain gradient is the least and the effect of friction is negligible. This data acquisition point increases the strain range by a factor of five.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.914-922
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• 2003

In this paper, the strain localization of voided ductile material has been analyzed by nonlocal plasticity formulation in which the yield strength not only depends on an equivalent plastic strain measure (hardening parameter), but also on the Laplacian thereof. The gradient terms in yield criterion show an important role on modeling strain-softening phenomena of material. The influence of the mesh size on the elastic -plastic deformation behavior and the effect of the characteristic length parameter for localization prediction are also investigated. The proposed nonlocal plasticity shows that the load -strain curves converge to one curve. Results using nonlocal plasticity also exhibit the dependence of mesh size is much less sensitivity than that for a corresponding local plasticity formulation.