• Journal of the Korean Society for Precision Engineering
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• v.23 no.10
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• pp.44-51
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• 2006

According to global trend of the expanding need of high-quality automobiles, the usage of small precise worm consisting of gearing part for motors to actuate convenience modules has increased rapidly. Precision of those worms has very sensitive characteristic to motor performance and noise. Forming process has been generally used to manufacture worms because of its mass productivity. However, it has problems such as deformation due to residual stress and wear of dies. Planetary milling and side milling are among alternatives using cutting tools. To overcome those problems the two machining methods have some contrast features in the sense of tool numbers and cutting mechanism. In this paper, machinability of both methods was compared in terms of cutting force, precision and cycle time.

• Transactions of the Korean Society of Automotive Engineers
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• v.2 no.1
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• pp.96-105
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• 1994

Cup drawing tests were performed to evaluate the friction characteristics of sheet metals. The linear relationship between drawing force and blank holding force obtained from the cup drawing test was used to calculate the coefficient of friction of the sheet metal. The friction coefficient was compared to that from conventional draw bead friction test. It was clarified that the cup drawing test can be used as a simple and convenient method for evaluating the friction characteristic of the sheet metal and also lubricity of the lubricant used.

• Proceedings of the Korean Institute of Interior Design Conference
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• 2007.05a
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• pp.275-280
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• 2007

The modern society of the 21century is becoming a discussion as spaces appearing as ambiguous boundaries caused by complexed cultural phenomenon. As for the spacial factors we recognize, which appears as phenomenon in which is emphasizing the existing system of cognizance and thinking through drawing inviable parts of the effort within escaping the limits of gravity. This Merleau-Ponty and Gilles Deleuze refines it as theories called "Perception" and "Sense", and through the 'visible and invisible' of Merleau-Ponty and the 'Nonsense and paradox' of Gilles Deleuze, this study object is forming these inviable representations into space. Using the similarities of these two theories as a tool, we will analyze the examples of space with drawing the force that forms invisibility into embodiment, building a possibility of improvement in future spaces.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.162-167
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• 2000

The warm deep drawability in square cup drawing is investigated about a newly developed high-strength steel sheet with retained austenite which is transformed into martensite during forming. For this investigation, six steps of temperature ranges, from room temperature to $250^{\circ}C$, and five kinds of drawing ratio, from 2.2 to 2.6 were adopted. As a result the maximum drawing force and the maximum drawing depth were affected by the elevated temperatures, and the more stable thickness strain distribution was observed to the elevated temperatures. But blue shortness happened over $200^{\circ}C$. The FEM analysis using the LS-DYNA code is adopted to compare the experimental results with the analytical results for thickness strain distribution.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.203-206
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• 2006

The drawbeads, which is used for controlling the flow of the sheet by imposing the tension and for preventing the springback in the sheet metal forming process, affects a lot the formability because of the differences in the restraint and opening forces according to the drawbead shapes and dimensions. In this study, the experimental device enabling to measure the drawbead restraining forces and the drawbead opening forces associated with various drawbead shapes and dimensions and their theoretical evaluation are introduced and verified through the experimental measurement of those of a circular drawbead.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.747-752
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• 2000

Rotary shearing using of rotating and locally shear force has been studied. It is possible to be obtained in any case for requested blank diameters. In this paper, different local forming zones, that are clearances between upper roller and vertically taped low roller, were investigated. Required shearing force is calculated by undecided coefficient method for clearances and strokes of upper roller. Rotary shearing is completed undergoing some processes composed of pressing steps and standing steps. The reason for using these processes is to avoid jamming or tearing of blank by means of upper roller during shearing.

• 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.

• Transactions of Materials Processing
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• v.19 no.5
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• pp.273-276
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• 2010

In this paper, back pressure forging processes of which back pressures are exerted by mechanical forces including spring reaction are simulated by three-dimensional finite element method. The basic three-dimensional approach extended from two-dimensional approach is accounted for. An axisymmetric backward and forward extrusion process having a back pressing die, which is exposed to oscillation of forming load due to variation of reduction ratios with stroke and its related frequent variation of major deforming region, is simulated by both two and three dimensional approaches to justify the presented approach by their comparison. A three-dimensional forging process having a back pressing die attached to the punch by a mechanical spring is simulated and the results are investigated to reveal accuracy of the presented approach.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.389-392
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• 2009

The application of an equivalent drawbead model(EDM) for sheet metal forming analysis, which adopts the forces instead of complex geometries in modeling the drawbead, to the numerical simulation of auto-panel stamping process is introduced in this study. In terms of the thinning and draw-in, better agreement with experimental measurements was found in EDM than in commercial code models so that the excellence of EDM in the accuracy of drawbead forces for the simulation of auto-body stampings was revealed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.145-151
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• 2012

In this study, finite element analysis is carried out to estimate horizontal forces needed for the required power calculation and vertical forces applied on the structural analysis model for the development of automatic serrated surface at metal gasket core machining system. By considering of elasto-plastic material characteristics, nonlinear contact analysis was conducted to compute these loads according to the change of roll reduction, frictional coefficient and core thickness. As the result, horizontal and vertical reaction force variations are found according to parameters and maximum reaction force is also confirmed to be most affected by roll reduction.