• Title, Summary, Keyword: Aluminum Foam

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Evaluation of Close-Range Blast Pressure Mitigation using a Sacrificial Member (희생부재를 이용한 근거리 폭파압력 저감 효과)

  • Shim, Chang-Su;Yun, Nu-Ri
    • Journal of the Earthquake Engineering Society of Korea
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    • v.14 no.1
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    • pp.11-23
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    • 2010
  • A sacrificial member with aluminum foam of excellent energy absorption capacity was proposed for the protection of significant structures. Parametric studies of explicit finite element analyses were performed to investigate the pressure mitigation of close-range air-blasts. The scaled distance of the blast had a range of Z=0.48~0.95 and an empirical blast load function was utilized. The analytical parameters of the aluminum foam were density, thickness and the existence of a cover sheet. Analytical results showed that the transmitted pressure can be controlled to have a similar level of yield values of the foam by using a foam with low density and higher thickness. As the blast load increased, the sacrificial member needed to have higher density and thickness. A cover sheet of the foam clearly showed its effect on the wider distribution of blast pressure. It is necessary to determine the design parameters of sacrificial foams considering different energy dissipation capacities according to the scaled distance.

Physical Modeling of Process Parameters for Aluminum-Foam Generation (물리적 모델링을 이용한 알루미늄 발포공정 영향 인자 해석)

  • 옥성민;문영훈
    • Transactions of Materials Processing
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    • v.10 no.7
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    • pp.558-564
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    • 2001
  • An experimental modeling is applied to investigate the formation of forms in molten aluminum By using a specially designed equipment, the effect of process variables, such as the shape of stirrer, stirring velocity and fluid viscosity, on the formation of foams were studied in the glycerine added water. Bubbles formed in water had various diameter from 1 to 10 mm and the number of bubbles was 0 to 20/$cm^2$. It turned out that among various variables the stirring velocity and fluid viscosity played important roles on the formation of bubbles. The results obtained from the model experiment were preyed to be convincible also in the real aluminum foam.

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Properties of Plaster Mold for Open Cell Aluminum Foam (발포금속 제조를 위한 석고주형의 특성)

  • Kim, Ki-Young;Paik, Nam-Ik
    • Journal of Korea Foundry Society
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    • v.21 no.4
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    • pp.253-259
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    • 2001
  • There are many methods to produce metal foams, which can be classified into three groups according to the state of the starting metal i.e. liquid or powder or solid. Three types of defects such as cell closing, cell deformation or breakdown and cell misrun are thought to be occurred when we make the open cell aluminum foams by precision casting. Filling ability of the mold slurry between preform is related with cell closing, mold collapsibility is related with cell deformation or breakdown, mold temperature and pouring pressure are related with cell misrun. These factors can be evaluated by measuring slurry fluidity, burnout strength and permeability of the mold. Properties of the plaster mold were evaluated to find optimum mold conditions for high quality open cell aluminum foam in this study. Permeability was almost zero independent of burnout conditions, however, crack initiation was found on the surface of all specimens one or two minutes after taking out from the furnace. Crack has grown and disappeared with time. This crack may facilitate the mold filling when molten metal is poured, because of the improved mold permeability. It was considered that crack initiation and disappearance was closely related with temperature difference between the surface and inner part. Knocking-out the mold is a difficult problem due to the small cell size, because continuous mesh structure of the metal foam is not strong. It is not easy to remove molding material after pouring. We can expect that water quenching can facilitate the knocking-out the mold after solidification without damaging cell structures. Collapsed particles after water quenching became bigger with the increase in time.

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Fabrication and Evaluations of Hydrogenation Properties of TiH2/TiH2-Al agents on Aluminum Foam Alloy (알루미늄 발포용 TiH2/TiH2-Al의 제조와 수소화 특성 평가)

  • Hong, T.-W.;Cho, G.-W.;Kweon, S.-Y.;Kim, I.-H.;Lee, J.-I.;Ur, S.-C.;Lee, Y.-G.;Ryu, S.-L.
    • Transactions of the Korean hydrogen and new energy society
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    • v.15 no.3
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    • pp.235-243
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    • 2004
  • A number of potential applications of aluminum foams are being identified and renewed interest in these engineering materials is also reflected by several current research projects. One of the key issues for industrial exploitation of aluminum foams is the development of cost-effective manufacturing strategies facilitating, preferably, net shape production of foams with controlled porosity and cell size, and minimized structural imperfection. Especially, melt route to aluminum foam production based on the foaming agents offer attraction of low cost and the potential for good microstructure. The present paper is focused mainly on foaming agents of melt-foam aluminum such as $TiH_2$ or $TiH_2-Al$ mixture. For the purpose of economical manufacturing, we are proposed to hydrogen induced mechanical alloying (HIMA) process. Thermo-physical properties of particles synthesized are compared with conventional methods. Specimens synthesized are characterized by scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), thermo- gravimetry-differential scanning calorymetry (TG-DSC), pressure-composition-isotherm. (PCI).

The Performance Characteristics of the Open Celled Aluminum Foam Applied for Heat Dissipation (다공성 알루미늄 방열핀의 성능특성 연구)

  • Kim, Jong-Soo;Lee, Hyo-Jin
    • Journal of the Korean Solar Energy Society
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    • v.23 no.2
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    • pp.91-98
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    • 2003
  • Experimental study for a porous aluminum heat dissipator/or heat sink made by casting method is conducted to evaluate the performance of the porous aluminum heat sinks. The parameters applied for the present study are the manufacturing method. various bonding materials for the bottom plate of heat sink, and their different material, pore size, etc.. The casting method for porous aluminum heat sink is suggested for the best performance of heat dissipation in this experiment. The bottom plate applied by melting aluminum is introduced and proved their excellent characteristics compared with brazing, soldering, and bonding methods. In the present experiment, aluminum with different conductivities, such as AC8A and pure aluminum, are tested and the pure aluminums with the higher conductivity than AC8A shows their improvement of the performance. And the proper dimensions related to the pore size and the height of porous aluminum heat sinks are proposed in the present study.

Investigation on Characteristics of Various Mold Packing Materials in Lost Foam Casting of Aluminum Alloy (알루미늄 합금 소실모형주조 시의 주형충전재에 따른 특성변화)

  • Kim, Ki-Young;Lee, Kyung-Whoan;Rim, Kyung-Hwa
    • Journal of Korea Foundry Society
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    • v.22 no.3
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    • pp.137-143
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    • 2002
  • Silica sand, zircon sand, and steel shots were used as mold packing materials in lost foam casting of the aluminum alloy bar. Vibration acceleration in three directions and temperatures in the casting and mold were measured, and packing and cooling characteristics of these materials were investigated. Packing densities increased with increase in vibration magnitude and time, and were $1.41{\sim}1.49g/cm^2$ for silica sand, $2.54{\sim}2.86g/cm^2$ for zircon sand, and $3.92{\sim}4.52g/cm^2$ for steel shots. Sound castings were obtained only without evacuation of the flask during pouring. Solidification time became faster in order of silica sand, zircon sand and steel shot packing because steel shot has the highest cooling capacity of them. Solidification time of steel shot packing was shortened to about 1/2 of silica sand packing. Cooling capacity of sand mold was generally evaluated by heat diffusivity of the mold, however could be simply evaluated with specific heat per unit volume of the packing material in lost foam casting.

A Study on Light Weight Hood Design for Pedestrian Safety (보행자 충돌안전 경량후드 형상설계에 관한 연구)

  • Lee, Won-Bae;Kang, Sung-Jong
    • Transactions of the Korean Society of Automotive Engineers
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    • v.15 no.1
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    • pp.106-115
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    • 2007
  • In this study, first, child headform model was built up, satisfying requirement in the headform validation test. Also, for decreasing both acceleration peak and deformation, a new hood with dome shaped forming in inner panel was investigated. Next, headform impact, complying with draft of EEVC W/G 17, on the central portion of the newly proposed hood were simulated for a steel hood and three aluminum hoods with different thickness for examining the material and thickness effect on HIC value and inner panel deformation. The analysis results explained that aluminum hoods with dome shaped forming in inner panel were highly promising not only for meeting headform safety regulations but also for leading to weight savings. Finally, hood edge design technology in order to reduce pedestrian injury due to the high stiffness of beam type edge and the rigid support, was discussed. Various types of the foam filled edge were designed and their headform safety performance were evaluated. The edge structure with foam filled in upper one third of section exhibited excellent results.

Effect of Mold Materials on the Microstructure and Tensile Properties of Al-Si based Lost Foam Casting Alloy (Al-Si계 소실모형주조합금의 미세조직 및 인장성질에 미치는 주형재료의 영향)

  • Kim, Jeong-Min;Lee, Gang-Rae;Choe, Kyeong-Hwan
    • Journal of Korea Foundry Society
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    • v.39 no.5
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    • pp.87-93
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    • 2019
  • The effects of mold materials on the microstructure and tensile properties were investigated to develop a mass production technique of aluminum alloy parts with excellent mechanical properties using a lost foam casting method. The microstructures of the plate-shaped cast alloy showed a tendency to be finer in proportion to the thickness of the plate, and a remarkably fine structure was obtained by applying a steel chill or a ball as a mold material compared to general sand. When a steel ball was used, it was observed that the larger the ball, the finer the cast structure and the better the tensile properties. The microstructure and tensile properties of the cast parts with complex shapes were greatly affected by the gating system, but the positive effects of the steel chill and the steel ball as a mold material were clear.

A Study on the Application of 3-D Sandwich Composite Structures to the Double-deck Light Train Carbody (3-D 복합재료 샌드위치 구조물의 2층 경전철 철도차량 구조체 적용성에 관한 연구)

  • 이영신;김재훈;이호철;길기남;박병준
    • Journal of the Korean Society for Railway
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    • v.3 no.2
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    • pp.92-99
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    • 2000
  • Composites are very useful material for light train carbody due to its high specific strength and lightweight characteristics. The composites, called 3-D board, are developed with a special stitching method. In this process, the glass fiber fabrics of skin material and foam core material are stitched together with glass fiber thread. The glass thread in Z-axis turns into FRP form. The conventional delamination problem can be solved with 3-D sandwich structure. In addition, with the lower density of foam, the weight of the panel and the operation expenses can be highly reduced. To evaluate the usefulness of the 3-D board, the double-deck light train carbody is studied. The stress analyses are carried out under various loads and boundary conditions with FEM Code, ANSYS. On comparing with the aluminum carbody, 3-D board carbody can be reduced by about 2 ton for the total weight of carbody.

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