• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.84-87
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• 2009

This paper describes a novel method for fabricating large area metallic stamp with high aspect ratio micro intaglio features. Micro machined brass master with pillar and larger width groove patterns were electroformed to form inverse structures on the large area metallic stamp. This enabled large area metallic stamp with fine micro high aspect ratio micro intaglio features which were small width groove patterns and quadrilateral hole patterns that cannot be fabricated by direct micro machining process. Fabricated large area metallic stamp with high aspect ratio micro intaglio features was measured and analyzed.

• Structural Engineering and Mechanics
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• v.37 no.6
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• pp.633-648
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• 2011

This paper investigates the aspect-ratio locking of the isoparametric 8-node quadrilateral (QUAD8) element. An important finding is that, if finite element solution is carried out with in exact arithmetic (i.e., with no truncation and round off errors), the locking tendency of the element is completely avoided even for aspect-ratios as high as 100000. The current finite element codes mostly use floating point arithmetic. Thus, they can only avoid this locking for aspect-ratios up to 100 or 1000. A novel method is proposed in the paper to avoid aspect-ratio locking in floating point computations. In this method, the offending terms of the strain-displacement matrix (i.e., $\mathbf{B}$-matrix) are multiplied by suitable scaling factors to avoid ill-conditioning of stiffness matrix. Numerical examples are presented to demonstrate the efficacy of the method. The examples reveal that aspect-ratio locking is avoided even for aspect-ratios as high as 100000.

• International Journal of Aeronautical and Space Sciences
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• v.9 no.2
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• pp.41-47
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• 2008

The nonlinear structural analyses of high-aspect-ratio structures were performed. For the high-aspect-ratio structures, it is important to understand geometric nonlinearity due to large deflections. To consider geometric nonlinearity, finite element analyses based on the large deflection beam theory were introduced. Comparing experimental data and the present nonlinear analysis results, the current results were proved to be very accurate for the static and dynamic behaviors for both isotropic and anisotropic beams.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.7
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• pp.385-389
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• 2017

Generally, refrigerant temperature out of the receiver is assumed to be saturated. This may be true for horizontal or vertical receivers having small aspect ratio. However, this assumption needs verification for vertical receiver having large aspect ratio. No study has reported information on this issue. The objective of this study was to determine the effect of liquid level and mass flow rate on liquid subcooling of a long vertical receiver using R-410A. During the test, inlet subcooling was maintained at $5^{\circ}C$ while saturation temperature was maintained at $10^{\circ}C$. Results showed that subcooling was maintained for the long vertical receiver. Subcooling preservation ratio (ratio of exit to inlet subcooling) was increased as mass flow rate or liquid level was increased. As a whole, 50 to 70% subcooling preservation was possible for the present receiver. Further investigations are needed to enhance information on this issue using receivers having different aspect ratios.

• Journal of Ship and Ocean Technology
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• v.12 no.3
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• pp.14-25
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• 2008

Recently, there has been a serious effort to design a wing in ground effect (WIG) craft. Vehicles of this type might use low aspect ratio wings defined as those with smaller than 3. Design and prediction techniques for fixed wings of relatively large aspect ratio are reasonably well developed. However, Aerodynamic problems related to vortex lift on wings of low aspect ratio have made it difficult to use existing techniques. In this work, we firstly focus on understanding aerodynamic characteristics of low aspect ratio wings and comparing the results from experimental measurements and currently available numerical predictions for both inviscid and viscous flows. Second, we apply an improved numerical method, "B-spline based high panel method with wake roll-up modeling", to the same problem.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.1
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• pp.99-105
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• 2006

In this study, nonlinear static and dynamic aeroelastic analyses for a high-aspect-ratio wing have been performed. To achieve these aims, the transonic small disturbance (TSD) theory for the aerodynamic analysis and the large deflection beam theory considering a geometrical nonlinearity for the structural analysis are applied, respectively. For the coupling between fluid and structure, the transformation of a displacement from the structural mesh to the aerodynamic grid is performed by a shape function which is used for the finite element and the inverse transformation of force by work equivalent load method. To validate the current method, the present analysis results of a high-aspect-ratio wing are compared with the experimental results. Static deformations in the vertical and torsional directions caused by an angle of attack and gravity loading are compared with experimental results. Also, static and dynamic aeroelastic characteristics are investigated. The comparisons of the flutter speed and frequency between a linear and nonlinear analysis are presented.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.671-672
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• 2009

• Journal of the Korean Society for Advanced Composite Structures
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• v.5 no.4
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• pp.18-23
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• 2014

In this paper. the effects of the aspect ratio on the natural frequency of the advanced composite road structures is studied. The advanced composite structures are too difficult for such design engineers for construction and some simple but accurate enough methods are necessary. Some laminate orientations have decreasing values of $D_{16}$, $B_{16}$, $D_{26}$ and $B_{26}$ stiffnesses as the ply number increases. The plate aspect ratio considered is from 1 to 5. Most of the road structures have large aspect ratios, for such cases further simplification is possible by neglecting the effect of the longitudinal moment terms.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.731-732
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• 2008

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.274-277
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• 2012

Large eddy simulation is applied to the turbulent flow and heat transfer in straight cooling passages with varying aspect ratio. The turbulent statistics of the flow and thermal quantities are calculated and the characteristics of Nusselt number are investigated. To scrutinize near-wall streamwise vortices, a conditional sampling technique is adopted. Clockwise and counter-clockwise rotating streamwise vortices are sampled and the probability density function of the vortex circulation Reynolds number and wall Nusselt number are calculated.