• Journal of Advanced Marine Engineering and Technology
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• 제18권3호
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• pp.17-25
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• 1994

Fully developed turbulent flow through three concentric annuli with both the rough inner and outer walls was experimentally investigated for a Reynolds number range Re = 15, 000 - 85, 000. Measurements were carried out for the pressure drop, the positions of zero shear stress and maximum velocity, and the velocity distributions in annuli of radius ratios, ${\alpha}$=0.26, 0.4 and 0.56, respectively. The experimental results showed that the positions of zero shear stress and maximum velocity were only weakly dependent on the Reynolds number.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.663-666
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• 2002

Hard disk drived (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. The distribution of pressure disturbance on disks has relation to flow structure. To investigate the flow structure, time-resolved hot-wire measurements of the circumferential velocity component were obtained for the flow between the center pair of four disks of common radius $R_2$ coretating at angular velocity ${\Omega}$ in a fixed cylindrical enclosure. Hot-wire supporter acts as an obstruction in this case. The effects of rotating speed and size of hot-wire supporter diameter between disks on the flow driven by disks were investigated. Velocity spectra at the fixed space were measured to obtain the structure of inner and outer region in flow field.

• 대한기계학회논문집
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• 제18권4호
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• pp.1072-1080
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• 1994

The fully developed turbulent momentum and heat transfer induced by the square-ribed roughness elements on the outer wall surface in concentric annuli are studied analytically based on a modified turbulence model. The analytical results of the fluid flow are verified by experiment. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Reynolds number, Nusselt number and Prandtl number. The study demonstrates that certain artificial roughness elements may be used to enhance heat transfer rates with advantages from the overall efficiency point of view.

• 한국소음진동공학회논문집
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• 제13권10호
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• pp.751-759
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• 2003

The theoretical method is developed to investigate the vibration characteristics of the sloshing and bulging mode for the circular cylindrical storage tank with an annular plate on free surface. The cylindrical tank is filled with an inviscid and incompressible liquid. The liquid domain is limited by a rigid cylindrical surface and a rigid flat bottom. As the effect of free surface waves Is taken into account in the analysis, the bulging and sloshing modes are studied. The solution for the velocity potential of liquid movement is assumed as a suitable harmonic function that satisfies Laplace equation and the relevant boundary conditions. The Rayleigh-Ritz method is used to derive the frequency equation of the cylindrical tank. The effect of Inner-to-outer radius ratio and thickness of annular plate and liquid volume on vibration characteristics of storage tank is studied. The finite element analysis is performed to demonstrate the validity of present theoretical method.

• Structural Engineering and Mechanics
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• 제3권6호
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• pp.541-553
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• 1995

The determination of the stress intensity factors is investigated by using the surface integral defined around the crack tip of the structure. In this work, the integral method is derived naturally from the standard path integral J. But the use of the surface integral is also extended to the case where body forces act. Computer program for obtaining the stress intensity factors $K_I$ and $K_{II}$ is developed, which prepares input variables from the result of the conventional finite element analysis. This paper provides a parabolic smooth curve function. By the use of the function and conventional element meshes in which the aspect ratio (element length at the crack tip/crack length) is about 25 percent, relatively accurate $K_I$ and K_{II}$ values can be obtained for the outer integral radius ranging from 1/3 to 1 of the crack length and for inner one zero.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1995년도 춘계학술대회논문집
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• pp.62-70
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• 1995

The inner pulley is automobile component used as airconditioner clutch assembly. in cold forging of the inner pulley . the design conditions are the same between inner length and outer length, the uniform hardness and the no shape change in inner fillet radius due toa piercing. In industries, the design of forging processes is performed based on an experience-oriented technology, that is, designer's experiences and expensive trial and error. Using the rigid -plastic finite element simulation, we propose the optimal process conditons and design of preform or redesign of final product shape without defects prodicted by metal flow, distribution fo strain, forging load during forging processes form initial workpiece to final product.

• 소성∙가공
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• 제10권2호
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• pp.91-100
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• 2001

A sectional FEA program is developed lot analyzing forming processes of sandwich sheets, which are intensively used recently as a lightweight material of an automobile body. The aluminum sandwich sheet consists of two aluminum skins and a polyprophylen core in between. The aluminum sandwich sheet is dominantly effected by the bending effects in small radius of curvature, so that an appropriate description of bending effects is required to analyze the forming processes. For the evaluation of bending effects, the bending equivalent forces are calculated from the bending moment computed using the curvature of the tool and are added to the membrane stretch forces. To verify the validity of the developed program the sectional FEA results in stretch/draw forming Processes of a square cup and draw forming Processes of an outer hood panel were compared with the measurements.

• 한국생산제조학회지
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• 제19권6호
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• pp.768-775
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• 2010

Automotive industry is a major business area in this country and it becomes more and more important. In order to maintain high quality of vehicles, every parts should be inspected. Among them the inspection job of the knuckle bracket holes of the outer tube of shock-absorber has been done manually until now. So, it takes long time and every product can not be inspected. An automatized inspection system was proposed utilizing machine vision technology, which was composed of a slit beam laser, CCD camera, image processing computer, special jig and illuminating back lights. An algorithm which could process images of the laser and bracket holes, then gave the position, radius, roundness of the holes, was developed. This system was applied for the good and no good products and the performance was confirmed.

• Journal of Advanced Marine Engineering and Technology
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• 제23권1호
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• pp.54-61
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• 1999

The fully developed turbulent momentum and heat transfer induced by the roughness elements on the outer wall surfaces in concentric annuli are analytically studied on the basis of a modified turbu-lence model. The resulting momentum and heat transfer are discussed in terms of various parame-ters such as the radius ratio the roughness density Reynolds number and Prandtl number accord-ing to the heating condition. The study shows that certain artificial roughness elements may be used to enhance heat transfer rates with advantage from the overall efficiency point of view.

• 한국초전도ㆍ저온공학회논문지
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• 제4권2호
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• pp.47-51
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• 2002

In this paper, flux distribution and operating current is calculated according to the field coil change in HTS(High Temperature Superconducting) motor. In order to calculate magnetic field characteristic of the field coil. it is computed by changing the outer radius and the inner width of field coil Bio-Savart equation is used as the analysis method for the characteristic analysis of magnet. 2D and 3D FEA(Finite Element Analysis) is used for the magnetic field distribution in HTS motor The operating current is calculated by $B{\bot}$ linked With the field coil and $I_c-B curve of superconductor.