• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2007.11a
• /
• pp.559-560
• /
• 2007

• Korean Journal of Materials Research
• /
• v.22 no.6
• /
• pp.309-315
• /
• 2012

Metal foam has many excellent properties, such as light weight, incombustibility, good thermal insulation, sound absorption, energy absorption, and environmental friendliness. It has two types of macrostructure, a closed-cell foam with sealed pores and an open-cell foam with open pores. The open-cell foam has a complex macrostructure consisting of an interconnected network. It can be exploited as a degradable biomaterial and a heat exchanger material. In this paper, open cell Mg alloy foams have been produced by infiltrating molten Mg alloy into porous pre-forms, where granules facilitate porous material. The granules have suitable strength and excellent thermal stability. They are also inexpensive and easily move out from open-cell foamed Mg-Al alloy materials. When the melt casting process used an inert gas, the molten magnesium igniting is resolved easily. The effects of the preheating temperature of the filler particle mould, negative pressure, and granule size on the fluidity of the open cell Mg alloy foam were investigated. With the increased infiltration pressure, preheat temperature and granule sizes during casting process, the molten AZ31 alloy was high fluidity. The optimum casting temperature, preheating temperature of the filler particle mould, and negative pressure were $750^{\circ}C$, $400-500^{\circ}C$, and 5000-6000 Pa, respectively, At these conditions the AZ31 alloy had good fluidity and castability with the longest infiltration length, fewer defects, and a uniform pore structure.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.29 no.5
• /
• pp.437-445
• /
• 2016

Recently, polyurethane foam has been used in various industry fields to preserve temperature environment of structures, and a wide range of loads from the static to the dynamic are imposed on the material during a life period. The biggest characteristic of polyurethane foam is porosity as being polymeric material, and it is generally known that insulation performance of the material strongly depends on internal void size. In addition, polyurethane foam's mechanical behavior has high dependence on strain rate and temperature as well as being highly non-linear ductile for compression. In the non-linear compressive behavior, volume fraction of voids and elastic modulus decrease as strain increases. Therefore, in this study, temperature-dependent viscoplastic-damage constitutive model was developed to describe the non-linear compressive behavior with the aforementioned features of polyurethane foam.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.11a
• /
• pp.1145-1148
• /
• 2007

Resilient materials are generally used for the floating floors to reduce the floor impact sound. Dynamic stiffness of resilient material, which has the most to do with the floor impact sound reduction. The resilient materials available in Korea include EPS (Styrofoam), recycled urethane types, EVA (Ethylene Vinylacetate) foam rubber, foam PE (Polyethylene), glass fiber & rock wool, recycled tire, foam polypropylene, compressed polyester, and other synthetic materials. In this study, we tested floor impact sound reduction characteristic to a lot of kinds of resilient material. The result of test showed that the amount of the heavy-weight impact sound reduction appeared by being influenced from this dynamic stiffness of resilient material. The dynamic stiffness looked like between other resilient materials, a similar to the amount of the heavy-weight impact sound reduction was shown.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.163-166
• /
• 1997

Aluminium foam material is a highly porous material having complicated cellular structure defined by randomly distributed air pores in metallic matrix. this structure gives the aluminium a set of properties which cannot be achieved by any of conventional treatments. The properties of aluminium foam material significantly depend on its porosity, so that a desired profile of properties can be tailored by changing the foam density. Melting method is the one of foaming processes, which the production has long been considered difficult to realize becaues of such problems as the low foamability of molten metal, the varying size of. cellular structures, solidification shrinkage and so on. These problems, however, have gradually been solved by researchers and some manufacturers are now producing foamed aluminum by their own methods. Most of all, the parameters of solving problem in electric furnace were stirring temperature, stirring velocity, foaming temper:iture, and so on. But it has not considered about those in induction heating, foaming velocity and foaming temperature in semi-solid state yet. Therefore, this paper presents the effects on these parameter to control cell size, quantity and distribution.

• Korean Journal of Materials Research
• /
• v.27 no.12
• /
• pp.688-694
• /
• 2017

Porous materials such as polymeric foam are widely adopted in engineering and biomedical fields. Porous materials often exhibit complex nonlinear behaviors and are sensitive to material and environmental factors including cell size and shape, amount of porosity, and temperature, which are influenced by the type of base materials, reinforcements, method of fabrication, etc. Hence, the material characteristics of porous materials such as compressive stress-strain behavior and void volume fraction according to aforementioned factors should be precisely identified. In this study, unconfined uniaxial compressive test for two types of closed-cell structure polyurethane foam, namely, 0.16 and $0.32g/cm^3$ of densities were carried out. In addition, the void volume fraction of three different domains, namely, center, surface and buckling regions under various compressive strains (10 %, 30 %, 50 % and 70 %) were quantitatively observed using Micro 3D Computed Tomography(micro-CT) scanning system. Based on the experimental results, the relationship between compressive strain and void volume fraction with respect to cell size, density and boundary condition were investigated.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.18 no.12
• /
• pp.1262-1269
• /
• 2008

Though multilayered foam-panel structures have been widely used to reduce sound transmission in various fields, most of the previous works to design them were conducted by repeated analyses or experiments based on initially given configurations or sequences. Therefore, it was difficult to obtain an optimal sequence of multilayered foam-panel structure yielding superior sound isolation capability. In this work, we propose a new design method to sequence a multi-panel structure lined with a poroelastic material having maximized sound transmission loss. Being formulated as a one-dimensional topology optimization problem fur a given target frequency, the optimal sequencing of panel-poroelastic layers is systematically carried out in an iterative manner. In this method, a panel layer is expressed as a limiting case of a poroelastic layer to facilitate the optimization process. This means that main material properties of a poroelastic material are treated as interpolated functions of design variable. The designed sequences of panel-poroelastic multilayer were shown to be significantly affected by the target frequencies; more panels were obtained at higher target frequency. The sound transmission loss of the system was calculated by the transfer matrix derived from Biot's theory.

• Elastomers and Composites
• /
• v.50 no.2
• /
• pp.81-86
• /
• 2015

In this study, natural rubber latex foam was prepared in order to replace commercialized polyurethane foams as a car seat material. Physical properties of the latex foam were investigated and the light stability was improved. The latex foam was mixed in an aqueous solution state, and the degree of foaming and the accelerator ratios were appropriately controlled. Tensile properties, hysteresis and dynamic mechanical properties of the latex foam were measured to compare with those of polyurethane foams. UV light absorbers and radical scavengers were added for improving light stability of the latex foam. Xenon lamp test was conducted to investigate the effects of the reagents on light stability. Our results revealed that the prepared latex foam including a light absorber with an antioxidant showed excellent light stable performances.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.47 no.1
• /
• pp.110-122
• /
• 2023

The COVID-19 pandemic increased people's time at home and caused an 80% increase in noise disputes between floors. The purpose of this study is to propose suitable materials for making indoor shoes (insoles) to minimize noise between floors. Subjects without back pain and leg-related disease (e.g. arthritis, etc.) from three different age groups (childhood, adolescence, and adulthood) were recruited for the study. Five polymer insole materials were considered: Chloroprene Rubber (CR foam), Ethylene Propylene Diene Monomer (EPDM foam), Natural Latex foam, Ethylene Vinyl Acetate (EVA foam), and Polyurethane (PU foam). From these materials, 20 combinations were prepared and randomly tested for noise and vibration. The results revealed a significant difference in noise and vibration levels based on the type of material used and the age of the subject. Nevertheless, all materials under consideration successfully reduced noise and vibration; in particular, type A-C greatly decreased. The CR foam material was especially effective at noise and vibration reduction (p<.01). This study suggests that adding insoles into socks that children wear at home could reduce noise vibration and disputes between floors.

• Journal of the Korean Ceramic Society
• /
• v.51 no.5
• /
• pp.511-515
• /
• 2014

The thermodynamic instability of bubbles in wet-foam colloidal suspension is due to the substantial area of their gas/liquid interface. Several physical processes lead to gas diffusion from smaller to larger bubbles, resulting in a coarsening and Ostwald ripening of wet foam. This includes a narrowing of the bubble size distribution. The distribution and microstructure of porous ceramics, the adsorption free energy and Laplace pressure of $Al_2O_3$ particle-stabilized colloidal suspension, and $SiO_2$ content were investigated for tailoring the bubble size. Wet-foam stability of more than 80% is related to the degree of hydrophobicity with contact angles of $62-70^{\circ}$ achieved from the surfactant. The contact angle replaces part of the highly energetic interface and lowers the free energy of the system. This leads to an apparent increase in the surface tension (26-33 mN/m) of the colloidal suspension.