• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.12
• /
• pp.86-92
• /
• 2002

This paper presents a new model of NC verification in NC milling using z-map. The model can describe the motion of machine tool like a real machine effectively. The model uses x, y, and z directional feed rate as well as cutting data for modeling Z-map of workpiece. The model verifies the over-cut, the under-cut and the surface topography using NC codes and cutting conditions. To investigate the performance of the model, simulation study was carried out. As the results, the model gave the geometry accuracy of workpiece, the surface topography, and the chip loads.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.10 no.1
• /
• pp.78-87
• /
• 2001

This paper deals with the study on the cutting characteristics in ball-end milling process. First of all, the effects of the geometric cutting conditions such as the cutting speed, feedrates and the path interval on the surface integrity were evaluat-ed by the analytical and the experimental approaches. Secondly, the cutting mechanism model was developed to predict the cutting force accurately. It is possible for the proposed model to predict the shape error, estimate system stability and build the reliable adaptive control system. A large amount of experimental set are performed to show the validities of the proposed theories and to investigate the effect of cutting geometry such as rubbing effects, burr effects and etc.

• Transactions of Materials Processing
• /
• v.14 no.2 s.74
• /
• pp.153-159
• /
• 2005

Design modification of the stamping die for the upper member of a front end module carrier is carried out in order to improve the surface quality of the final product. The small inferiority induced by wrinkling near the wall of the upper member has been inspected after the draw-forming process. The finite element analysis is pursued with the whole geometry in order to consider the complicated shape. The simulation shows that the excess metal is developed by the irregular contact of the blank the tool and it remains after the final stroke. This paper proposes two guidelines for the modification. One is to add the draw-bead near the critical region in order to increase the draw-in force. The other is to modify the tool shape such as the forming shape at the wall in order to absorb the excess metal before the final stroke. Simulation results show that the proposed guidelines both guarantee the improved surface quality.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2000.04a
• /
• pp.129-133
• /
• 2000

It is reasonable to use the stereo vision and image processing technique to digitize 3D coordinates of grid points and to evaluate surface strains on a sheet metal parts. However this method has its intrinsic problems such as the difficulty in enhancement of bad images inevitable error due to digital image resolution of camera and frame grabber unreliability of strains and thickness evaluated from coarse grid on the corner area with large curvature and the limitation of the area that can be measured at a time. Therefore it is still hard to measure strain distribution over the entire surface of a medium,- or large-sized stamped part at a time even by using an automated strain measurement system. In this study the curvature correction algorithm based on the grid refinement and the geometry assembling algorithm based on the global error minimization (GEM) scheme are suggested. Several applications are presented to show the reliability and efficiency of these algorithms.

• Journal of Ocean Engineering and Technology
• /
• v.18 no.3
• /
• pp.32-39
• /
• 2004

A design procedure for a ship with minimum total resistance has been developed using a numerical optimization method called SQP(sequential quadratic programming) to search for different optimal hull forms. The frictional resistance has been estimated using the ITTC 1957 model-ship correlation line formula, and the wave resistance has been evaluated using a potential-flow panel method that is based on Rankine sources with nonlinear free surface boundary conditions. The geometry of a hull surface has been modified using B-spline surface patches, during the whole optimization process. The numerical analyses have been carried out for the modified Wilgey hull at three different speeds (Fn=0.25, 0.316, 0.408), and the calculation results were compared.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03b
• /
• pp.565-567
• /
• 2008

In the present study, a least square/level set based two-phase flow code has been developed using finite element discretization, which can be utilized for the analysis of a free surface flow problem in a complex geometry. Since the finite element method is employed for the spatial discretization of governing equations, an unstructured mesh can be naturally adopted for the level set simulation of a bubble-in-liquid flow without an additional load for the code development except that solution methods of the hyperbolic type redistancing and advection equations of the level set function should be devised in order to give a bounded solution on the unstructured mesh. For the discretization of hyperbolic type redistancing and advection equations, least square method is adopted. From the numerical experiments of the present study, it is shown that the proposed method is both robust and accurate.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1995.10a
• /
• pp.68-75
• /
• 1995

The milling process is one of the most important metal removal processes in industry. Due to the complexities inherent to the cutter insert geometry and the milling cutter kinematics, these processes leave an analytically difficult to predict texture on the machined surface's hills and valleys. The instantaneous uncut chip cross sectional area may be estimated by the relative position between the workpiece and the cutter inserts. furthermore, since the cutting forces are proportional to the instantaneous uncut chip cross sectional area, the cutting forces in face milling operations can not be estimated easily. A new simulation program which is based upon the numerical method has been proposed to estimate the cutting force components, with the ability to predict the machined surface texture left by the face milling operation.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1004-1009
• /
• 2003

Electroosmotic flow induced by an applied electrostatic potential field in microchannel is analyzed in this study. The electroosmotic flow is an alternative to pressure driven flow in microchannels, but the usage has been limited to the simple cases. In this study, We analyze electroosmotic flow driven by inhomogeneous surface charge on the channel wall. The surface charge varies along a direction perpendicular to the electric field in order to generate the electroosmotic flow. A numerical results substantiate the highly efficient mixing performance. It is highly the beneficial to fabrication process since only straight microchannel rather than complex geometry is enough to yield efficient mixing.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2002.05a
• /
• pp.54-57
• /
• 2002

In order to find the effect of lubricant viscosity, sheet surface roughness, tool geometry, and forming speed on the frictional characteristics in sheet metal forming, a sheet metal friction tester was designed and manufactured and friction tests of various sheets were performed. Friction test results showed that as the lubricant viscosity becomes lower, the friction coefficient is higher. When surface roughness is extreme1y low or high, the friction coefficient is high. As punch comer radius and punch speed are bigger, the value of friction coefficient is smaller. The sensitivity of friction coefficient is mainly governed by lubricant viscosity and sheet surface roughness.

• Transactions of Materials Processing
• /
• v.5 no.4
• /
• pp.343-352
• /
• 1996

One of the preferred methods that can be used to verify the results of finite element analysis is to measure surface strains of the deformed part for purpose of direct comparison with simulation results. Instead of using the usual manual method the vision-based measurement method is capable of determining surface geometry and strain from the deformed grid pattern automatically with the help of a computer. To obtain strain distribution over an area, the coordinates of such a surface grid are determined from the multiple video images by applying the photogrammetry principle. Methods to improve the overall accuracy of the vision-based strain measurement system are explored and the possible accuracies that can be attained by such a measurement method are discussed. A major emphasis is placed on the initial grid application method its accuracy and ease of subsequent image processing. Finite element analyses of limiting dome height(LDH) test are carried out and the results of them are compared with exsperimen-tal data.