• Tribology and Lubricants
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• v.19 no.4
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• pp.230-236
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• 2003

In applications such as MEMS and NEMS devices, the adhesion force and contact load may be of the same order of magnitude and the static friction coefficient can be very large. Such large coefficient may result in unacceptable and possibly catastrophic adhesion, stiction, friction and wear. To obtain the static friction coefficient of contacting real surfaces without the assumption of an empirical coefficient value, numerical simulations of the contact load, tangential force, and adhesion force are preformed. The surfaces in dry contact are statistically modeled by a collection of spherical asperities with Gaussian height distribution. The asperity micro-contact model utilized in calculation (the ZMC model), considers the transition from elastic deformation to fully plastic flow of the contacting asperity. The force approach of the modified DMT model using the Lennard-Jones attractive potential is applied to characterize the intermolecular forces. The effect of the surface topography on the static friction coefficient is investigated for cases rough, intermediate, smooth, and very smooth, respectively. Results of the static friction coefficient versus the external force are presented for a wide range of plasticity index and surface energy, respectively. Compared with those obtained by the GW and CEB models, the ZMC model is more complete in calculating the static friction coefficient of rough surfaces.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1988.10a
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• pp.24-29
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• 1988

In this paper, it is proposed hew the rigid element method suggested in the first paper can be applied to the elastic and elasto-plastic analysis of spherical shell with the open stiff ring. In the analytical model, the solution domain is divided into rectangular-shaped spherical bending elements. Each contact surface of two adjacent elements is interconnected with four elastic springs, and it is assumed that the internal forces are distritributed into springs. The 6 degrees of freedom of the element are placed in the center of elements, and the 6 cen-teroidal rigid displacements affect other elements through springs around elements. And then the solution domain is estimated by the behavior of elements and springs. In this study, these concepts are applied to the elastic and elasto-plastic analysis for the eight cases of the spherical shell according to the condition of stiff ring, the condion of loading and the size of opening. And then some numerical results such as the distribution of stresses, the force-displacement curves and the mode of fractures will he shown.

• Transactions of Materials Processing
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• v.26 no.4
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• pp.228-233
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• 2017

In flat rolling mills, demands for precise process set-up and control are increasing than ever before. Consequently, it is imperative to establish a novel approach, which would provide valuable information regarding the detailed aspects of deformation behavior of the strip, and rolls during rolling. In this paper, we present a finite element (FE) approach for 3-D coupled analysis of the elastic-plastic deformation of the strip and the elastic deformation of rolls in the roll-stack of a mill stand.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1078-1084
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• 2005

The relationship between fatigue crack opening behavior and the reversed plastic zone sizes is studied. An elastic-plastic finite element analysis (FEA) is performed to examine the opening behavior of fatigue crack, where the contact elements are used in the mesh of the track tip area. The smaller element size than reversed plastic zone size is used fer evaluating the distribution of reversed plastic zone. In the author's previous results the FEA could predict the crack opening level, which crack tip elements were in proportion to the theoretical reversed plastic zone size. It is found that the calculated reversed plastic zone size is related to the theoretical reversed plastic zone size and crack opening level. The calculated reversed plastic zone sizes are almost equal to the reversed plastic zone considering crack opening level obtained by experimental results. It can be possible to predict the crack opening level from the reversed plastic zone size calculated by finite element method. We find that the experimental crack opening levels correspond with the opening values of contact nodes on the calculated reversed plastic zone of finite element simulation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.10a
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• pp.28-31
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• 1997

Buckling analysis of thin compressed beam has been carried out. Pre-buckling and post-buckling are simulated by finite element method incorporating with the incremental nonlinear theory and the Newton-Raphson solution technique. In order to find the bifurcation point, the determinent of the stiffness matrix is calculated at every iteration procedure. For post-buckling analysis, a small perturbed initial guess is given along the eigenvector direction at the bifurcation point. Nonlinear elastic buckling and elastic-plastic buckling of cantilever beam are analyzed. The buckling load and buckled shape of the two models are compared.

• Journal of Advanced Marine Engineering and Technology
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• v.32 no.6
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• pp.931-937
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• 2008

The rail/wheel rolling contact affects the microstructure in the surface layer of rail. Recently. continuum damage mechanics allows us to describe the microprocesses involved during the straining of materials and structures at the macroscale. Elastic and plastic strains. the corresponding hardening effects are generally accepted to be represented by global continuum variables. The purpose of continuum damage mechanics is to introduce the possibility of describing the coupling effects between damage processes and the stress-strain behavior of materials. In this study. the continuum damage mechanics caused by elastic deformation was briefly introduced and applied to the fatigue damage of the rails under the condition of cyclic loading. The material parameter for damage analysis was first determined so that it could reproduce the life span under the compressive loading in the vicinity of fatigue limit. Some numerical studies have been conducted to show the validity of the present computational mechanics analysis.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.319-322
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• 2003

For the analysis of leveling process by the 3-dimensional elastic-plastic finite element method, a finite element analysis program modeling large deformation of shell has been developed. This program fur analyzing large deformation of sheet during leveling includes spring-back analysis as well as efficient contact treatment between sheet and rolls of leveler. This is verified by the simple leveling experiment with 5 rolls at laboratory. Besides the leveling examples, problems within the category of large strain and rotation, such as 3-dimensional roll-up and gutter occurrence at continuous bending-unbending process are also tested for verification of the program. The residual curvatures of strip predicted by finite element analysis are within 20% error range of the experiment. The formation and direction of anticlastic curvature or gutter during bending-unbending under tension is predicted and this agrees with the experimental results.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.4
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• pp.19-30
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• 2002

The stability of slope using root-pile like to the reinforcements is affected by the interaction behavior mechanism of soil-reinforcements. Through the studying on the interaction in joint of its, therefore, the control roles can be find out in installed slope. In study, the stress level ratio based on the insert angle of installed reinforcements in soil used to numerical analysis, which was results from the duty direct shear test in Lab. The maximum shear strain variation on the reinforcements was observed at insert angle, which was approximately similar to the calculated angle based on the equation proposed by the Jewell. The elasto-plastic joint model on the contact area of soil-reinforcements was presumed, the reinforced soil assumed non-linear elastic model and the reinforcements supposed elastic model, respectively. The finite element analysis of assumed models was performed. The shear strain variation of non-reinforced state obtained by the FEM analysis including elasto-plastic joint elements were shown the rationality of general limit equilibrium analysis for the slope failure mode on driving zone and resistance zone, which based on the stress level step according to failure ratio. Through the variation of shear strain for the variation of inserting angle of reinforcements, the different mechanism on the bending and the shear resistance of reinforcements was shown fair possibility.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.77-79
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• 2006

To achieve high productivity of assembly hull blocks, it is important to predict welding deformations accurately and to apply these data to the production planning. In the deformation analysis of hull block, simplified methods (elastic analysis) such as inherent method, equivalent loading method and local & global approach are usually used instead of thermal-elastic-plastic analysis because of calculating time and cost. To be much more practical, these simplified methods should consider gravity effect of plate and contact condition between the plate and the positioning jig. In this research, using finite element method, practical predicting method for the welding deformation of the curved hull blocks with considering welding sequence, gravity effect and contact condition is proposed.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2214-2219
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• 2008

The thermal contact resistance(TCR) of nanosized contact spots has been investigated through a multiscale analysis which considers the resolution of surface topography. A numerical simulation is performed on the finite element model of rough surfaces. Especially, as the contact size decreases below the phonon mean free path, the size dependent thermal conductivity is considered to calculate the TCR. In our earlier model which follows an elastic material, the TCR increases without limits as the number of nanosized contact spots increases in the process of scale variation. However, the elastoplastic contact induces a finite limit of TCR as the scale varies. The results are explained through the plastic behavior of the two contacting models. Furthermore, the effect of air conduction in nanoscale is also investigated.