• Journal of the Korean institute of surface engineering
• /
• v.35 no.3
• /
• pp.113-120
• /
• 2002

Injection molded plastic parts have many surface defects. These include a weld line, sink mark, flow mark, gloss, shading, scratching etc. Because these surface faults are not aesthetically acceptable, plastic parts are produced through painting or texturing. The purpose of this paper is to develop paintless molded parts using a flow control method. Computer aided injection mold filling simulations were used in order to minimize the number of defects from injection molding. Based on the numerical results, FR(Flame Retardant) HIPS was developed and the guidelines for part design, mold design, and the processing conditions were established. The effects of cost savings, improvements in productivity, and recycling were considered by reducing the number of surface faults and eliminating the painting process.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1992.03a
• /
• pp.159-176
• /
• 1992

Limit analysis has been rendered versatile in many problems such as structural problems and metal forming problems. In metal forming analysis, a slip-line method and an upper bound method approach to limit solutions is considered as the most challenging areas. In the present work, a general algorithm for limit solutions of plastic flow is developed with the use of finite element limit analysis. The algorithm deals with a generalized Holder inequality, a duality theorem, and a combined smoothing and successive approximation in addition to a general procedure for finite element analysis. The algorithm is robust such that from any initial trial solution, the first iteration falls into a convex set which contains the exact solution(s) of the problem. The idea of the algorithm for limit solution is extended from rigid/perfectly-plastic materials to work-hardening materials by the nature of the limit formulation, which is also robust with numerically stable convergence and highly efficient computing time.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.5
• /
• pp.43-50
• /
• 2002

Friction welding has many merits such as energy efficiency, simple processing, etc butt difficult to obtain good weld at the welded interface and heat affected zone. To date, the continuum mechanics and fracture mechanics are utilized to analyse stresses at the interface and propagation of cracks. In this study. STS304 and SM15C are selected because they can be differentiated distinctively from metallic point of view and crack can be observed easily. It is ovserved during friction welding that STS304, rotary part is hatter than SH15C, fixed part. The last fracture occurs around the center because the surface of fatigue fracture has smooth regions, due to the separation phenomenon in plastic flows layers and striation dimple pattern.

• Journal of Ocean Engineering and Technology
• /
• v.15 no.4
• /
• pp.86-91
• /
• 2001

In lateral ground flow, slope stability, and land slide problems, H-piles have been often used for a horizontally deforming ground to prevent the failure of mass of soil in a downward and outward movement of a slope. Here, Theoretical equations are derived to estimate the lateral force, assuming that the Mohr-coulomb's Plastic states occures in the ground just around H-piles. In this study, the mechanism of lateral force acting on passive pile that is in a row, situated in the ground undergoing plastic deformation was discussed, and its theoretical analysis was carried out considering the interval between H-piles. The solution of the theoretical equation derived from here showed resonable characteristic for constants of soil as well as for the interval, widths, and heights of H-pile.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.784-787
• /
• 2003

The present work covers three-dimensional flow simulation and deformation analysis of injection molded plastic lenses using solid elements. A numerical scheme to evaluate part deformation has been proposed from the results of injection molding analysis. Proposed scheme has been applied to the injection molding processes of optical plastic lenses: a spherical lens and an aspheric lens for a photo pick-up device. Through the simulation processes. residual stress is estimated and the final deformed patters are obtained for both products. The reliability of the proposed approach has also been verified in comparison with the results of real experiments.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.8 s.173
• /
• pp.100-107
• /
• 2005

The objective of the study is to improve the quality of wheel bearing hub by the rigid-plastic finite element analysis and the response surface methodology. The rigid-plastic finite element codes, AFDEX-2D and DEFORM-3D, were used to analyze the two-dimensional and three-dimensional forging processes, respectively. The response surface analysis is used to find the minimum underfill by the variation of design variables such as the height of billet after upsetting and punch angles of blocker dies. The metal flow of forged product shows good agreement with the results from 2D and 3D analysis. Also, the quality of the wheel bearing hub has been improved by the optimization of design variables and the machining time has been reduced by the machining allowance.

• Geotechnical Engineering
• /
• v.13 no.5
• /
• pp.133-144
• /
• 1997

It was proved from the viscosity test for deposits of debris flows(Kim and Seo, 1997) that the property of debris flows could be represented as Bingham plastic model. Based on this bahavior, numerical analysis for the movement of debris flows is carried out by using a computer progran Polyflow which huts been developed for the analysis of the behavior of non-Newtonian fluid. The numerical results obtained from two sites agree well with the movement predicted by an empirical formula. It can be concluded, therefore. that this scheme can be used for the analysis of the movement of debris flow.

• Transactions of Materials Processing
• /
• v.10 no.5
• /
• pp.396-401
• /
• 2001

The concept of the mixtures can be used not only in the composites but also in the materials with precipitates and matrix. In this investigation, the finite element method of axisymmetric unit cell models and the rule of mixtures of the Voigt and the Reuss models are used to analyze the overall mechanical response of composites with homogeneously distributed particles. The calculations have been cameo out by taking the materials as i) hardening and ii) perfect plastic materials. The Plastic properties are predicted for various volume fractions of the soft and hard particles. The computational results are compared with the results of the rule of mixtures. It is found that the plastic flow curves agree well with the Voigt model when the volume fraction of the particles is high. On the other hand, the calculated flow curves exist between the Voigt model and the Reuss model when the volume fraction of the particles is low.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.05a
• /
• pp.263-265
• /
• 2009

In this study, ultrafine grained (UFG) oxygen free high conductivity copper (OFHC Cu) having two different grain morphologies, one the severely elongated and the other the equiaxed, was prepared by equal channel angular pressing (ECAP) with routes A and $B_c$, respectively. The results of quasi-static tensile tests at $10^{-1}\;s^{-1}$ and $1\;s^{-1}$ and dynamic compression tests at $10^3\;s^{-1}$ order revealed that the equiaxed UFG Cu exhibited higher strength and less ductility compared to the elongated one. The difference of the plastic flow characteristics between the two were rationalized by considering their dislocation mean free length based on the orientation relationship between the possible slip planes and the loading direction.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• v.16 no.3
• /
• pp.181-192
• /
• 2012

Here in this paper, the steady paint film flow on a vertical wall of a non-Newtonian pseudo plastic fluid for drainage problem has been investigated. The exact solution of the nonlinear problem is obtained for the velocity profile. Also the average velocity, volume flux, shear stress on the wall, force to hold the wall in position and normal stress difference have been derived. We retrieve Newtonian case, when material constant ${\mu}_1$ and relaxation time ${\lambda}_1$ equal zero. The results for co-rotational Maxwell fluid is also obtained by taking material constant ${\mu}_1$ = 0. The effect of the zero shear viscosity ${\eta}_0$, the material constant ${\mu}_1$, the relaxation time ${\lambda}_1$ and gravitational force on the velocity profile for drainage problem are discussed and plotted.