Papers by Keyword: Metal Foam

Abstract: This paper presents a numerical study on the passive cooling of an electronic component inside a rectangular enclosure filled with phase change material (PCM). The electronic component is centrally located on a substrate and generates volumetric heat. The study utilizes the enthalpy-porosity approach and the thermal equilibrium model. Its goal is to enhance the performance of the PCM by incorporating metal foam and nanoparticles. The investigation examines the impact of varying metal foam porosity while keeping the nanoparticle volume fraction constant. The results indicate that a lower porosity (0.85) significantly improves the thermal conductivity of the PCM by 3 times, which increases the cooling efficiency of the PCM-based heat sink. Meanwhile, nanoparticles have a negligible effect when metal foam is present.

Abstract: Copper (Cu) foam is a promising material that owns a high surface area that can be utilized in a thermal application. In this research, the brazing of Cu substrate to Cu foam in the sandwich configuration using Cu alloy filler foil was carried out. The foam at different pore per inch (PPI) of 15, 25 and 50 are brazed at different brazing temperatures. Mechanical and microstructure analysis were conducted to investigate a suitable brazing temperature and the best pore density of foam. The compressive strength of brazed 50 PPI foam has yielded the highest due to the highly dense interconnected branches. While the highest shear strength of brazed interface using 15 PPI foam has been recorded. The large branch size of 15 PPI foam has contributed to the sound joint between the brazed joint interface of Cu substrate and foam. Both mechanicals analysis above exhibits a highest strength at 660 °C as a brazing temperature The shear stress-strain curve of Cu substrate and foam brazed joint interface shows a brittle behaviour which accordance with the discoverable brittle phases of Cu₃P and Ni₃P using X-ray diffraction (XRD). Scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDX) have presented the formation of Cu₃P and Ni₃P at the brazed joint interface of Cu substrate and foam.

Abstract: In this paper, a case study is performed for the possibility of using water ethanol mixture in predicting the bubble behavior in multiphase flow. The study compares the concept of formation of foam at the surface of the mixture with the procedure of producing aluminum foam by direct gas injection. Material properties such as kinematic viscosity, density and surface tension on the foaming process will be studied experimentally, while the foam bubble size will be studied by means of digital image processing. Finally the path of the bubble from the nozzle to the liquid surface shall be simulated by means of computational fluid dynamics software and verified experimentally by the usage of a speed camera. Acquirement of this practical knowledge can improve the effectiveness of the real foaming process of the aluminum and aluminum alloys. Simultaneously, it helps to understand main basic features of the formed metal foams. The study is meant to define the best parameters for the foaming process for water-ethanol mixture. Such results are to be compared to their corresponding parameters for the direct injection foaming method for aluminum. The main aim to be able to correlate the 2 processes, in means to decreasing time and cost required to produce aluminum metal foam through test trials, usually causing the waste of material, fuel and energy. Furthermore, the quality and quantity evaluation of the created foam is presented. The effect of the flow rate of the quality of foams can be observed experimentally. The theoretical calculation can reproduce the bubble dynamics observed experimentally.

Abstract: In this research developed the technique for the metal foam based on the Al-carbon nanotubes composite material. The optimal regimes for the samples foaming are proposed. The pilot samples were received. The behavior of the pores distribution in the samples volume is presented.

Abstract: The self-similar isotropic hardening model developed by Deshpande and Fleck has been widely used. An important issue in this model is to determine the value of ellipticity. The ellipticity was treated as a constant in the subsequent yield, but different values were suggested in the literature. In this paper a cell-based finite element model based on the 3D Voronoi technique is used to verify the Deshpande-Fleck foam model. It is found that the ellipticity determined from uniaxial and hydrostatic compressions varies with the equivalent plastic strain.

Abstract: As an initial step of this research, open cell magnesium foams were obtained by infiltration casting using a preform of salt particles with irregular morphology. Despite this metallic foam was a successful approach to bone replacement scaffold, the properties of a metal foam need to be improved to meet the requirements by accurately adjusting the porous geometry. The tissue scaffold structure should be submissive biologically as well as mechanically and should at best mimic the natural properties of bone to act as an accurate bone substitute. The architectural and mechanical bone scaffold parameters determine the biological outcome.This work aims to design and manufacture an ordered foam with mechanical and architectural properties similar to those of the bone using an Mg alloy as a base material. Accordingly, representative features were identified to generate computer-aided designed (CAD) unit cells. Then, a set of the selected cells was assembled to obtain a specified architecture for bone replacement. Finite element method analysis was applied to calculate the mechanical response. The architectural parameters were varied to match the elastic properties of human bone concerning suitable exposed area, volume, and pore size. The best architecture was determined by compression loading acting on the assembly. Finally, polymeric stamps with sets of truncated octahedrons will be printed from the CAD model and were replicated in a clay made with a combination of salt and flour. Infiltration casting will obtain last of all, open cell magnesium foams.

Abstract: The impact toughness of closed-cell aluminum foam with various densities was investigated. The impact load history revealed an elastic region followed by a rapid load drop region. The peak load and impact toughness of aluminum foam increases exponentially with density. The power exponents for impact toughness test are greater than that for compressive test. Fracture analysis indicated a mixed-rupture mode of quasi-cleavage and small shallow dimples. It can be attributed to the complex state of stress of notched specimens and elevated impact velocity under impact loading.

Abstract: The third octave sound absorption coefficient testing is conducted to compare the sound absorption properties metal foam and flexible cellular materials, by using sound absorption tester with the method of trasfer function sound absorption tester with the method of trasfer function. The sound absorption mechanisms are discussed by changing the parameters of sound absorption structure, such as the thickness of matrix materials and the thickness of cavity. The results show that pearl wool and glass wool exhibited excellent sound absorption properties. The peak value of sound absorption coefficient for pearl wool reaches to 0.991, and for glass wool, 0.985. The average sound absorption coefficient for pearl wool is 0.729, and for glass wool, 0.679. Among of three metal foams, the foamed aluminum material exhibited optimum sound absorption properties, and is superior to flexible sound absorption materials. The peak value of sound absorption coefficient reaches to 0.993, and the average value reaches to 0.781. This can be attributed to the flow resistance, porosity, thickness, cavity and structure factor, which influence the sound absorption of open cell materials.

Abstract: Bipolar plates in Proton Exchange Membrane fuel cells (PEMFC) distribute fuel and oxidant over the reactive sites of the membrane electrode assembly. In a stack, bipolar plates collect current, remove reaction products and manage water. They also separate neighboring cells and keep the oxidant and the fuel from mixing; they provide structural support to the stack. The plates are typically graphite with parallel or serpentine channels. The efficiency of a stack depends on the performance of the bipolar plates, which depends on the material and flow field design. The drawbacks of graphite include weight, fabrication inaccuracy, cost, porosity, and brittleness. Open-cell metal foam is investigated as a flow field/bipolar plate and compared to conventional graphite bipolar plates. The complex internal structure of the foam was modeled using an idealized unit cell based on a body center cube. This cell maintained the actual structural features of the foam. Clones of the idealized cell were virtually connected to each other to form the new bipolar plate. SolidWorks, and Auto-CAD were used to generate the unit cell and the computational domain, which was imported into ANSYS. Meshing of the domain produced than 350,000 elements, and 70,000 nodes. Appropriate boundary and operating conditions for PEMFC were applied, and the PEMFC module within ANSYS was used to obtain the temperature and flow distribution as well as the fuel cell performance. In comparison to conventional bipolar plates, results show that the cell current and voltage densities were improved, and temperature distribution on the membrane was even, and within the allowable limit. As importantly, there was a weight reduction of about 40% as a result of using metal foam as a bipolar plate.

Abstract: In this study, the dynamic energy absorption behavior of metal foam is investigated. A 3D Voronoi numerical model is established. Uniaxial compression under quasi-static and impact with velocities in the range of 10m/s to 200m/s are implemented, respectively, to investigate the energy behavior. During the impact process, the impact energy is transferred into kinetic energy and the internal energy. The kinetic energy varies with fluctuation due to the propagation and reflection of plastic shock wave. When the plastic shock wave arrives at the impact side or support side, the rate of internal energy absorption increases, and the kinetic energy possesses a local maximum/minimum value. The dynamic internal energy is obvious higher than quasi-static internal energy, due to the region behind the wave front is compacted tightly resulted from the plastic shock wave.