• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.1
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• pp.43-53
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• 2008

Surface edge crack in transversely isotropic piezoelectric material is analyzed. The concentrated antiplane mechanical and inplane electrical loadings are applied to an arbitrary point of the surface, where the impermeable crack boundary condition is imposed. Using Mellin transform the problem is formulated, from which Wiener-Hopf equations are derived. By solving the equations the solution is obtained in a closed form. Mechanical and electric intensity factors and energy release rate are obtained and discussed. This problem could be used as a Green's function to generate the solutions of other problems with the same geometry but of different loading conditions.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.367-372
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• 2000

Accuracy of a machined component is determined by the relative motion between the cutting tool and the workpiece. One of the important factors which affects the accuracy of this relative motion is the geometric error of machine tools. In this study, geometric error is modeled using form shaping motion of machine tool, where a form shaping function is derived from the homogeneous transformation matrix. Geometric errors are measured by laser interferometer. After that, the local positioning error can be estimated from the form shaping model and geometric error data base. From this information, we can remodel the part by shifting the design surface to the amount of positional error. By generating tool path to the redesigned surface, we can reduce the machining error.

• Korean Journal of Mathematics
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• v.23 no.1
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• pp.115-128
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• 2015

Plumbing surfaces of links were introduced to study the geometry of the complement of the links. A basket surface is one of these plumbing surfaces and it can be presented by two sequential presentations, the first sequence is the flat plumbing basket code found by Furihata, Hirasawa and Kobayashi and the second sequence presents the number of the full twists for each of annuli. The minimum number of plumbings to obtain a basket surface of a knot is defined to be the basket number of the given knot. In present article, we first find a classification theorem about the basket number of knots. We use these sequential presentations and the classification theorem to find the basket number of all prime knots whose crossing number is 7 or less except two knots $7_1$ and $7_5$.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.2
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• pp.171-176
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• 2012

So far, carbide insert production technology was carried out using a diamond grinding wheel. This production technology has problem that raise production costs and decrease in productivity. The SIDE PRESS method to solve this problem have been developed. In this paper, the machining characteristics of lateral chip breaker turning inserts produced by the SIDE PRESS method was studied. The cutting force and the resulting surface roughness were measured at various cutting conditions. The experimental results indicate that the chip breaker inserts of three-dimensional geometry is the best cutting performance.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.515-518
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• 1994

Holographic interferometry is a useful whole-field nondestructive testing for measuring deformations and vibrations of engineering structure. A diverging beam is used as a light source int the most of holographic interferometer practically. For a relatively small object the optical arrangement using a collimated light source has no difficulty in use technically, but for a large object it is difficult to use a collimated beam. In this study we calculate the error of measured displacement from the sensitivity vector dominated by the geometry of optical arrangement for holographic interferometer and show the result obtained with 2-D plots. A Plane surface and a cylindrical surface were chosen as objects to be calculated and computer analysis was carried out for the cases of a diverging beam and a collimated one.

• Journal of electromagnetic engineering and science
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• v.9 no.1
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• pp.46-52
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• 2009

This paper conducts a study on the frequency-dependent filtering and blocking effects of a variety of periodic structures, dubbed frequency selective surface(FSS). The periodic structures of interest are 1D and 2D repeated patterns of metal patches or slots sitting on the interface between the two different regions in the layered media which will show the capacitive or inductive behaviors and incorporated with the electromagnetic bandgap(EBG) geometry as another stratified media. Besides the normal substances so called double positive(DPS)-type in the layered media, metamaterials of double negative(DNG) are considered as layering components on the purpose of investigating the unusual electromagnetic phenomena. Frequency responses of transmission(absorption in terms of scattering) and reflection will be calculated by a numerical analysis which can be validated by the comparison with the open literature and demonstrated for the periodic structures embedding metamaterials or not. Most importantly, numerous examples of FSS will present the useful guidelines to have absorption or reflection properties in the frequency domain.

• The KSFM Journal of Fluid Machinery
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• v.10 no.5
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• pp.34-40
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• 2007

An optimization approach is investigated for the design of new nozzle system in a automatic car wash machine. Three-dimensional computational fluid dynamics and design of experiment methods have been employed to know the mutual interaction between the nozzle shape in the automatic car wash machine and the airflow velocity distribution on the vehicle surface. The performances of air nozzle system were defined as the velocity magnitude and the uniformity of the velocity on the surface of the car. Predicted jet velocity distributions for the optimized geometry were compared with experimental data and the comparisons showed generally good agreements. Also, the performance of the dryer was improved with the optimized results.

• Laser Solutions
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• v.3 no.3
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• pp.31-37
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• 2000

In this paper, the possibilities of the laser overlap spot welding were studied to utilize the advantageous properties of amorphous metal foils. In order to estimate the usage of amorphous metals foils as structural members, the tensile shear strength and the fracture features were investigated. Although the crystalline zone on the surface was formed, it was not the direct cause of the fracture of the weld. The fracture of the weld resulted from the geometry discontinuity between the workpiece and the protrusion zone, which was formed during the weld process. The vein pattern - the typical feature of the fracture of the amorphous metal - was formed on the fracture surface. The tensile shear stress was reached to 1200 N/㎟ (2-foils overlap welding) and 900 N/㎟ (10-foils overlap welding), whereas the tensile strength of the workpiece was 1500-2000 N/㎟.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.5
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• pp.395-401
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• 2014

Development of five axis tool grinding machine and CAD/CAM systems increase tool design flexibility. In this research, investigated are cutting characteristics of ball-end mill with different helix angle. Special WC ball-end mills with $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$ helix angles are designed and used in various cutting tests. Machining performance according to helix angle variation is evaluated from cutting forces, surface roughness, tool wear, produced chip shape, and vibration characteristics. The ball-end mill with $10^{\circ}$ helix angle shows the best cutting performance due to appropriate chip load distribution and smooth chip flow. This research can be used for cutting edge geometry optimization and novel design of ball-end mill.

• Proceedings of the KWS Conference
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• 1996.10a
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• pp.148-152
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• 1996

A transient two-dimensional (2D) model was developed for investigating the heat and fluid flow in old pools and determining velocity profile and temperature distribution for the Gas Metal Arc (GMA) welding process. The mathematical formulation deals with the driving farces (electromagnetic, buoyancy, surface tension and plasma drag forces) as well as energy exchange between the molten filler metal droplet and weld pools. A general thermofluid-mechanics computer program, PHOENICS, was employed to numerically solve the governing equation with the associated source terms. The results of computation have shown that the electromagnetic and surface tension farces as will as the molten filler metal droplet have major influence in shaping the weld pool geometry.