• Journal of Korea Foundry Society
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• v.32 no.2
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• pp.65-74
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• 2012

In this paper, we present the results of our studies on optimal die design towards development of a vacuum die casting process to fabricate fuel cell bipolar plate with micro-channel array. Cavity and overflow shape is designed by computational filling analysis of MAGMA soft. Optimal die design consists of seven overflows at the end of cavity and three overflows at each side wall of cavity. The molten metal that passed the gate and reached the side wall flowed into the side overflow, no turbulent flow occurred, and the filling behavior and velocity distribution were uniform. In addition, partially solidified molten metal passing through the channel was perfectly eliminated by overflow without back-flow. When vacuum pressure, injection speed of low and high region was 300 mbar, 0.3 m/s and 2.5 m/s respectively with Silafont 36 die casting alloy, sound sample without casting defects was obtained. The experimental results are nearly consistent with simulation results.

• Advances in nano research
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• v.9 no.4
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• pp.221-235
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• 2020

The following composition establishes a nonlocal strain gradient plate model that is essentially related to mass sensors laying on Winkler-Pasternak medium for the vibrational analysis from graphene sheets. To achieve a seemingly accurate study of graphene sheets, the posited theorem actually accommodates two parameters of scale in relation to the gradient of the strain as well as non-local results. Model graphene sheets are known to have double variant shear deformation plate theory without factors from shear correction. By using the principle of Hamilton, to acquire the governing equations of a non-local strain gradient graphene layer on an elastic substrate, Galerkin's method is therefore used to explicate the equations that govern various partition conditions. The influence of diverse factors like the magnetic field as well as the elastic foundation on graphene sheet's vibration characteristics, the number of nanoparticles, nonlocal parameter, nanoparticle mass as well as the length scale parameter had been evaluated.

• Structural Engineering and Mechanics
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• v.67 no.3
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• pp.219-232
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• 2018

This paper deals with the static bending of various types of FGM sandwich plates resting on two-parameter elastic foundations in hygrothermal environment. The elastic foundation is modeled as Pasternak's type, which can be either isotropic or orthotropic and as a special case, it converges to Winkler's foundation if the shear layer is neglected. The present FGM sandwich plate is assumed to be made of a fully ceramic core layer sandwiched by metal/ceramic FGM coats. The governing equations are derived from principle of virtual displacements based on a shear and normal deformations plate theory. The present theory takes into account both shear and normal strains effects, thus it predicts results more accurate than the shear deformation plate theories. The results obtained by the shear and normal deformation theory are compared with those available in the literature and also with those obtained by other shear deformation theories. It is concluded that the present results are slightly deviated from other results because the normal deformation effect is taken into account. Numerical results are presented to show the effects of the different parameters, such as side-to-thickness ratio, foundation parameters, aspect ratio, temperature, moisture, power law index and core thickness on the stresses and displacements of the FG sandwich plates.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.6
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• pp.1051-1057
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• 2010

Database for the damage reference by armor piercing bullet test was established for both tube and plate specimens having a range of thickness. As the inclined angles of hit are increasing, it has been found that penetration damage diameter tends to increases accordingly in both specimen of the tube and plate, and such penetration damage diameter on the rear side becomes bigger than those on the front side. The tube specimen showed that the damage becomes bigger when central areas rather than the peripheral were hit. Through the plate test, it also has been found that the penetration ballistic limit for Al alloy is about 25.4mm and that of stainless steel about 12.7mm. From the fatigue analysis results using the database for damage reference, it has been identified whether the safety requirements of military aircraft could be met.

• Structural Engineering and Mechanics
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• v.78 no.4
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• pp.439-453
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• 2021

In this work, quasi three-dimensional (quasi-3D) shear deformation theory is presented for bending and dynamic analysis of functionally graded (FG) plates. The effect of varying material properties and volume fraction of the constituent on dynamic and bending behavior of the FG plate is discussed. The benefit of this model over other contributions is that a number of variables is diminished. The developed model considers nonlinear displacements through the thickness and ensures the free boundary conditions at top and bottom faces of the plate without using any shear correction factors. The basic equations that account for the effects of transverse and normal shear stresses are derived from Hamilton's principle. The analytical solutions are determined via the Navier procedure. The accuracy of the proposed formulation is proved by comparisons with the different 2D, 3D and quasi-3D solutions found in the literature.

• Steel and Composite Structures
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• v.38 no.1
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• pp.1-15
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• 2021

In this paper, a higher order shear deformation theory for bending analysis of functionally graded plates resting on Pasternak foundation and under various boundary conditions is exposed. The proposed theory is based on the assumption that porosities can be produced within functionally graded plate which may lead to decline in strength of materials. In this research a novel distribution of porosity according to the thickness of FG plate are supposing. Governing equations of the present theory are derived by employing the virtual work principle, and the closed-form solutions of functionally graded plates have been obtained using Navier solution. Numerical results for deflections and stresses of several types of boundary conditions are presented. The exactitude of the present study is confirmed by comparing the obtained results with those available in the literature. The effects of porosity parameter, slenderness ratio, foundation parameters, power law index and boundary condition types on the deflections and stresses are presented.

• The Journal of Engineering Research
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• v.6 no.1
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• pp.15-27
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• 2004

The first aim of mass product of glass in Automatic bottle glass industry is to decrease the cost and to increase the quality. Second, the cullet is how widely used to save the energy and reducing of ecomaterials. However the physical and chemical properties of Soda-lime glass would be come true at the lower than 2% $Al_2 O_3$. Unfortunately the $Al_2 O_3$ contents of domestic silica is greater than 4% Since small glass class than 200ml bottle is made in domestic silica the producting efficiency would be decreased due to the defect such as cord, knot, devitrite, pore etc. There are many problems such as devitrifiacation and deteriorated effect on production in glass industry became of increasing of plate glass cullet. It is tried to solve these kinds of problems using various analysing methods in this experiments.

• Journal of the Korean Ceramic Society
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• v.48 no.2
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• pp.160-167
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• 2011

Plasma sprayed ceramic coatings inherently contain pores and usually also cracks. Post-treatment of the plasma sprayed coatings is a way to close the connected pores and cracks. In this study, post-sealing treatment in plasma sprayed $Al_2O_3$ coatings was employed to overcome the reduction of coating properties. $Al_2O_3$ plasma thermal spray coating was made on aluminum alloys plate, $CrO_3$ post coating and heat treatment at $550^{\circ}C$ was carried out in order for final $Cr_2O_3$ to be saturated through phase transformation. Chromia sealing began at the fine defect in coated microstructure, while larger pores were permeated later. The increase in concentration and treatment frequency of sealing solution resulted in the decrease of porosity of coating layer, while cracks occurred partially after the third treatment. After twice treatment of 10M $CrO_3$ solution, microhardness and breakdown voltage of $Al_2O_3$ coatings were found to increase by ${\fallingdotseq}$ 50% and ${\fallingdotseq}$ 390% respectively than without post-treatment.

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.794-801
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• 1995

To connect the driver IC and Al coated glass, a method has been developed to plate electrolessly Ni on Al/PR system. It Is necessary to pretreat Al to remove oxide film before plating. In order to find pretreatment process which does not damage photoresist or glass, alkaline and fluoride zincate process have been investigated. Because photoresist and aluminum thin film can easily dissolve in alkaline solution, it is considered that the fluoride zincate process was a suitable one. After immersion in the zincate solution containing 1.5 g/$\ell$ ammonium bifluoride and 100 g/$\ell$ zinc sulfate, electroless nickel plating could be performed. The additive in the zincate solution and thiourea in the plating solution increased smoothness of the plated surface. Acld dip could improve the uniformit of the surface.

• Journal of Powder Materials
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• v.22 no.6
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• pp.408-412
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• 2015

This study attempts to manufacture a Ni-Cr-Al-Y coating layer using a kinetic spray process and investigates the microstructure and physical properties of the manufactured layer. The Ni-22Cr-10Al-1Y (wt.%) composition powder is used, and it has a spherical shape with an average diameter of $23.7{\mu}m$. Cu plate is used as the substrate. Optical microscope, X-ray diffraction, scanning electron microscope and Vickers hardness test are carried out to characterize the macroscopic properties of the coating layer. Furthermore, the coating layer underwent vacuum heat treatment at temperatures of $400^{\circ}C$ and $600^{\circ}C$ for 1 hour to check the effect of heat treatment temperature on the properties. The manufactured coating layer is 1.5 mm thick, and featured identical phases to those found in the powder. The porosity of the coating layer is measured at 2.99%, and the hardness is obtained at $490.57H_v$. The layer shows reduced porosity as heat treatment temperature increased, and hardness is reduced at $400^{\circ}C$ but shows a slight increase at $600^{\circ}C$. Based on the findings described above, this study also discusses possible manufacturing methods for a Ni-Cr-Al-Y coating layer using the kinetic spray process.