• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.348-353
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• 2008

A vibration analysis for a rotating cantilever beam with the tapered cross section is presented in this study. The stiffness changes due to the stretching caused by centrifugal inertia forces when a tapered cantilever beam rotates about the axis perpendicular to its longitudinal axis. When the cross section of cantilever beam are assumed to decrease constantly, the mass and stiffness also change according to the variation of the thickness and width ratio of a tapered cantilever beam. Such phenomena result in variations of natural frequencies and mode shapes. Therefore it is important to the equations of motion in order to be obtained accurate predictions of these variations. The equations of motion of a rotating tapered cantilever beam are derived by using hybrid deformation variable modeling method and numerical results are obtained along with the angular velocity and the thickness and width ratio.

• Korea-Australia Rheology Journal
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• v.11 no.3
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• pp.225-232
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• 1999

This study presents 1-dimensional simple model for sheet casting or rectangular fiber spinning process. In order to achieve this goal, we introduce the concept of force flux balance at the die exit, which assigns for the extensional flow outside the die the initial condition containing the information of shear flow history inside the die. With the Leonov constitutive equation that predicts non-vanishing second normal stress difference in shear flow, we are able to describe the anisotropic swelling behavior of the extrudate at least qualitatively. In other words, the negative value of the second normal stress difference causes thickness swelling much higher than width of extrudate. This result implies the importance of choosing the rheological model in the analysis of polymer processing operations, since the constitutive equation with the vanishing second normal stress difference is shown to exhibit the characteristic of isotropic swelling, that is, the thickness swell ratio always equal to the ratio in width direction.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.4
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• pp.363-369
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• 2009

A vibration analysis for a rotating cantilever beam with the tapered cross section is presented in this study. The stiffness changes due to the stretching caused by centrifugal inertia forces when a tapered cantilever beam rotates about the axis perpendicular to its longitudinal axis. When the cross section of cantilever beam are assumed to decrease constantly, the mass and stiffness also change according to the variation of the thickness and width ratio of a tapered cantilever beam. Such phenomena result in variations of natural frequencies and mode shapes. Therefore it is important to the equations of motion in order to be obtained accurate predictions of these variations. The equations of motion of a rotating tapered cantilever beam are derived by using hybrid deformation variable modeling method and numerical results are obtained along with the angular velocity and the thickness and width ratio.

• Journal of Welding and Joining
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• v.18 no.6
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• pp.83-88
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• 2000

Variation of welded-joint hardness and tensile strength of a accelerated-cooled fine-grained ferritic-pearlitic steel with heat input was investigated. In a weld heat-affected zone, a softened zone was formed and it had lower hardness than that of a base metal. While the width of a softened zone increased continuously with an increase of heat input up to 100kJ/cm. the minimum hardness in a softned zone was almost constant after a continuos decrease up to 60KJ/cm. Because of a softened zone, the welded-joint was fractured in the HAZ and its maximum reduction of tensile strength was about 20%. Measured welded-joint tensile strength and calculated minimum tensile strength in a welded-joint was almost same, which means that the plastic restraint of a softened zone did not occur in this experiment. It is believed that as a softened zone width-to-specimen thickness ratio is as high as 2~6 in this experiment, the plastic restraint effect does not occur. Theoretical analysis shows that the plastic restraint effect occurs only when the ratio is below 0.5.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2544-2547
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• 2008

A micro channel heat sink has been studied and optimized for mixed pressure driven and electroosmotic flows through three-dimensional numerical analysis. The effects of ionic concentration represented by zeta potential and Debye thickness are studied with the various steps of externally applied electric potential. Optimization of the micro channel heat sink has been performed considering two design variables related to the micro channel width, depth and fin width. The surrogate-based optimization is performed using a search algorithm taking overall thermal resistance as objective function. The thermal resistance is found to be more sensitive to channel width-to-depth ratio than fin width-to-depth of channel ratio.

• Journal of the Korea Fashion and Costume Design Association
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• v.7 no.1
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• pp.33-40
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• 2005

Gathering is method used to control fullness along a seam line. The purpose of this study was to investigate the relationship between the quantitative research and qualitative method; the effect of gather and the types of gather drape. The experimental design consists of four factors: (l) three kinds of different weight and thickness of fabrics (2) three kinds of stitch densities (3) five kinds of ratio of gathers (4) three kinds of grain directions. Therefore one hundred thirty five (135) samples were made. And utilized SPSS WIN 10.0 Package in data analysis. The results of this study were as follows; First, after frequency analysis, side height, hem line width, node depth, node count, node width accorded with these result data recording. Second, after correlation analysis, side height related with front statements. Side height and entire visual was negative correlation. Hem line width, node depth, node count with section statements was negative correlation but node width at section statements was positive correlation. Third, after $k^2$ analysis, front picture parts getting excellent evaluation were 1st side height, 3rd hem line width, 4th node depth, 3rd node count, 3rd node width. And section illustration parts getting excellent evaluation were 4th side height, 1st hem line width, 2nd node depth, 3rd node count, 4th node width.

• Journal of Korean Society of Steel Construction
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• v.8 no.4 s.29
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• pp.3-17
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• 1996

The purpose of this paper is to investigate experimentally and theoretically the strength and deformation of K-joints in welded Warren-type square hollow structural section truss. There are 2 types in K-joints in K-joints having one compression bracing member and one tension bracing member. One type is KP-series that brae members are rotated to $45^{\circ}$, another type is KS-series that are not rotated. Principal parameters are the ratio of the chord width to thickness (D/T=33.3, 25, 16.7), the ratio of brace width to chord width(d/D=0.4, 0.5, 0.67, 0.83, 1.0) and the ratio of eccenticity to chord height (e/D=0.25, 0.125, 0, -0.125, -0.25, -0.375, -0.5). The important results obtained from the experiments are as follow ; The strength of K-joints increase proportionally as the D/T ratio decreases, and the d/D ratio increases. But the e/D ratio has no correlation with the strength of K-joints. Generally the strength and ductility ratio of KP-series increase more than a current type(KS-series) in full ${\beta}$range.

• Structural Engineering and Mechanics
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• v.21 no.4
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• pp.407-422
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• 2005

Plate elements in fully profiled sandwich panels are generally subjected to local buckling failure modes and this behaviour is treated in design by using the conventional effective width method for plates with a width to thickness (b/t) ratio less than 100. If the plate elements are very slender (b/t > 1000), the panel failure is governed by wrinkling instead of local buckling and the strength is determined by the flexural wrinkling formula. The plate elements in fully profiled sandwich panels do not fail by wrinkling as their b/t ratio is generally in the range of 100 to 600. For this plate slenderness region, it was found that the current effective width formula overestimates the strength of the fully profiled sandwich panels whereas the wrinkling formula underestimates it. Hence a new effective width design equation has been developed for practical plate slenderness values. However, no guidelines exist to identify the plate slenderness (b/t) limits defining the local buckling, wrinkling and the intermediate regions so that appropriate design rules can be used based on plate slenderness ratios. A research study was therefore conducted using experimental and numerical studies to investigate the effect of plate slenderness ratio on the ultimate strength behaviour of foam supported steel plate elements. This paper presents the details of the study and the results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1338-1346
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• 2003

Three-dimensional formability of the thermoplastic laminar composite was studied according to manufacturing conditions. Five different types of the plain weave fabric were used as reinforcement with PET matrix. The square blank was made by press consolidation technique and formed in the type hemisphere. B-factor defined as the ratio of width of yarn and distance between yarns was used as the factor of formability in the type of plain weave fabric. The formability of PET/Glass fabric laminar composite was estimated in terms of forming rate and B-factor with the thickness distribution, area ratio of blank, and intra-ply shear angle. The thickness distribution across hemisphere was strongly affected by the B-factor, forming rate and blank thickness. The area ratio of blank was increased with B-factor, forming rate and blank thickness. Also, it was found that the intra-ply shear angle depends on the B-factor and forming rate.

• Journal of Korean Society of Steel Construction
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• v.17 no.3 s.76
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• pp.357-363
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• 2005

There is a great need for high-strength steel especially for the high-rise steel building structure. High-strength steels, however, may have mechanical properties that are significantly different from those of the conventional steels. The application of high-strength steels to building structures should be reviewed as to whether the inelastic behavior equivalent to that of conventional steels can be attained or not. In this study, SM570TMC steel was tested to evaluate buckling strength under axial compressive force. The comparison tests for local buckling strength evaluation of box-type and H-shaped welded columns were performed with variable width-thickness ratios. As for the experimental check, the maximum strength of stub column was determined by local buckling as far as the limit of width-to-thickness ratio was satisfied with current design codes. Also, the strength of the stub column did not decrease suddenly by local buckling before maximum strength even when the ratio is not satisfied. The buckling strength of SM570TMC steel was higher than both ASD (Allowable Stress Design) and LRFD (Load and Resistance Factor Design) specifications.