Chebyshev polynomial-based Ritz method for thermal buckling and free vibration behaviors of metal foam beams

This study presents the Chebyshev polynomials-based Ritz method to examine the thermal buckling and free vibration characteristics of metal foam beams.The analyses include three models for porosity distribution and two scenarios for thermal distribution.The material properties are assessed under two conditions,i.e.,temperature dependence and temperature independence.The theoretical framework for the beams is based on the higher-order shear deformation theory,which incorporates shear deformations with higher-order polynomials.The governing equations are established from the Lagrange equations,and the beam displacement fields are approximated by the Chebyshev polynomials.Numerical simulations are performed to evaluate the effects of thermal load,slenderness,boundary condition(BC),and porosity distribution on the buckling and vibration behaviors of metal foam beams.The findings highlight the significant influence of temperature-dependent(TD)material properties on metal foam beams'buckling and vibration responses.

Compression properties of cost-efficient porous expanded clay reinforced AA7075 syntactic foams fabricated by industrial-oriented die casting technology

In today’s manufacturing industries,hard competition between rival firms makes it compulsory for researchers to design lighter and cheaper machine components due to the megatrends of cost-effectiveness and anti-pollution.At this point,aluminum syntactic foams(ASFs)are new-generation engineering composites and come into the upfront as a problem-solver.Owing to their features like low density,sufficient elongation,and perfect energy absorption ability,these advanced foams have been considerably seductive for many industrial sectors nowadays.In this study,an industrial-oriented automatic die casting technology was used for the first time to manufacture the combination of AA7075/porous expanded clay(PEC).Micro evaluations(optical and FESEM)reveal that there is a homogenous particle distribution in the foam samples,and inspections are compatible with the other ASF studies.Additionally,T6 aging heat treatment was operated on one half of the produced foams to explore the probable impact of aging on the compressive responses.Attained results show that PEC particles can be an alternative to expensive hollow spheres used in the previous works.Besides,a favorable relationship is ascertained between the aging treatment and mechanical properties such as compression strength and plateau strength.

The effects of relative density of metal foams on the stresses and deformation of beam under bending

The exact analytic solution of the pure bending beam of metallic foams is given. The effects of relative density of the material on stresses and deformation are revealed with the Triantafillou and Gibson constitutive law （TG model） taken as the analysis basis. Several examples for individual foams are discussed, showing the importance of compressibility of the cellular materials. One of the objects of this study is to generalize Hill＇s solution for incompressible plasticity to the case of compressible plasticity, and a kinematics parameter is brought into the analysis so that the velocity field can be determined.

Elasto-plastic analysis of crack in metallic foams

To determine the solutions of the well-known problem of a finite width strip with single edge crack,some results on elasto-plastic fracture analysis for metallic foams are reported.Meanwhile,in order to discuss and put an insight into the nonlinear fracture analysis,the Dugdale model for plastic deformation of this configuration for metallic foams is recommended and solved.Combining the asymptotic solution with the Dugdale model and elastic solution,the stress field in the plastic zone and the size of the plastic zone are expressed as analytical forms.Based on Williams expansion method,the estimate of the scale factor is also completed and analyzed.In view of these analytical solutions,the results show the scale factor is a useful parameter for the fracture theory of metallic foams.

Experimental Study on Heat Storage Properties Comparison of Paraffin/Metal Foams Phase Change Material Composites

Heat storage properties of phase change materials(PCMs) are essential characteristics that perform a key role in thermal heat energy storage systems.The thermal properties of PCMs can be improved by developing metal foam/PCM composites.The addition of metal foam in PCMs has a significant effect on the thermal characteristics of PCMs.In this paper,the heat storage properties of two different metal foam/PCM composites were experimentally examined.The behavior of paraffin in metal foam(copper and iron-nickel)/paraffin composites concerning pure paraffin at a constant heat flux of 1000 W/m^(2) in three directions simultaneously(x,y,and z) was studied.Paraffin was infiltrated into copper and iron-nickel foams to develop composite materials which resulted in enhancing the thermal conductivity of the paraffin.A comparative analysis is made on the heat storage properties of paraffin in copper and iron-nickel foams/paraffin composites.Inner temperature distribution during the phase transition process is experimentally evaluated.This comparison indicates that temperature uniformity in copper foam/paraffin composite is better than in iron-nickel foam/paraffin composite and pure paraffin at the same heat flux.Experimental results show that at heat flux of 1000 W/m^(2),the heat storage time for copper foam/paraffin composite is 20.63% of that of iron-nickel foam/paraffin composite.

Mechanical characterization of the role of defects in sintered FeCrAIY foams

Open celled metal foams fabricated through metal sintering are a new class of material that offers novel mechanical and acoustic properties. Previously, polymer foams have been widely used as a means of absorbing acoustic energy. However, the structural applications of these foams are limited. The metal sintering approach offers a costeffective means for the mass-production of open-cell foams from a range of materials, including high-temperature steel alloys. In this first part of two-paper series, the mechanical properties of open-celled steel alloy （FeCrA1Y） foams were characterized under uniaxial compression and shear loading. Compared to predictions from established models, a significant knockdown in material properties was observed. This knockdown was attributed to the presence of defects throu- ghout the microstructure that result from the unique fabrication process. Further in situ tests were carried out in a SEM （scanning electronic microscope） in order to investigate the effects of defects on the properties of the foams. Typically, the onset of plastic yielding was observed to occur at defect locations within the microstructure. At lower relative densities, ligament bending dominates, with the deformation initializing at defects. At higher relative densities, an additional deformation mechanism associated with membrane elements was observed. In the follow-up of this paper, a finite element model will be constructed to quantify the effects of defects on the mechanical performance of the opencell foam.

ULTRALIGHT POROUS METALS:FROM FUNDAMENTALS TO APPLICATIONS

Over the past few years a number of low cost metallic foams have been produced and used as the core of sandwich panels and net shaped parts.The main aim is to develop lightweight structures which are stiff,strong,able to absorb large amount of energy and cheap for application in the transport and construction industries.For example,the firewall between the engine and passenger compartment of an automobile must have adequate mechanical strength,good energy and sound absorbing properties,and adequate fire retardance.Metal foams provide all of these features,and are under serious consideration for this applications by a number of au- tomobile manufacturers(e.g.,BMW and Audi).Additional specialized applications for foam-cored sandwich panels range from heat sinks for electronic devices to crash barriers for automobiles,from the construction panels in lifts on aircraft carriers to the luggage containers of aircraft,from sound proofing walls along railway tracks and highways to acoustic absorbers in lean premixed combustion chambers.But there is a problem.Before metallic foams can find a widespread application,their basic properties must be measured,and ideally modeled as a function of microstructural details,in order to be included in a design.This work aims at reviewing the recent progress and presenting some new results on fundamental research regarding the mi- cromechanical origins of the mechanical,thermal,and acoustic properties of metallic foams.

Mechanical Property of Foamed Metal

A comprehensive study on the mechanical behavior of foamed metals was demonstrated.The relationship among their mechanical properties,preparation method,porosity and the structure was briefly studied as well.

Modeling of the role of defects in sintered FeCrAlY foams

The metal sintering approach offers a costeffective means for the mass-production of open-cell foams from a range of materials, including high-temperature steel alloys, which offer novel mechanical and acoustic properties. In a separate experimental study, the mechanical properties of open-celled steel alloy （FeCrA1Y） foams have been characterized under uniaxial compression and shear loading. Compared to predictions from established models, a significant knockdown in material properties was observed. This knockdown was attributed to the presence of defects throughout the microstructure that result from the unique fabrication process. In the present paper, the microstructure of sintered FeCrA1Y foams was modeled by using a finite element （FE） model. In particular, microstructural variations were introduced to a base lattice, and the effects on the strength and stiffness calculated. A range of defects identified under scanning electronic microscope （SEM） imaging were considered including broken ligaments, thickness variations, and pore blockages, which are the three primary imperfections observed in sintered foams. The corresponding levels of defect present in the material were subsequently input into the FE model, with the resulting predictions correlating well with experimental data.

A plastic indentation model for sandwich beams with metallic foam cores

Light weight high performance sandwich composite structures have been used extensively in various load bearing applications.Experiments have shown that the indentation significantly reduces the load bearing capacity of sandwiched beams.In this paper,the indentation behavior of foam core sandwich beams without considering the globally axial and flexural deformation was analyzed using the principle of virtual velocities.A concisely theoretical solution of loading capacity and denting profile was presented.The denting load was found to be proportional to the square root of the denting depth.A finite element model was established to verify the prediction of the model.The load-indentation curves and the profiles of the dented zone predicted by theoretical model and numerical simulation are in good agreement.

Development in applications of porous metals

Applications of porous metal materials are reviewed so far. These applications deal with filtration and separation, energy absorption, electrode matrix, fluid distribution and control, heat exchangers, reaction materials, constructional materials, electromagnetic shielding, biomaterials and so on. All these are expected to promote the improvement of the property and structure for porous metals.

Properties and corrosion behavior of Al based nanocomposite foams produced by the sintering-dissolution process

The properties orAl based nanocomposite metal foams and their corrosion behaviors were investigated in this study. For this, the composite metal foams with different relative densities （porosity） reinforced with alumina nanoparticles were prepared using a powder me- tallurgy-based sintering-dissolution process （SDP） and NaC1 particles were used as space holders. Then, the effect of nanoparticle rein- forcement and different amounts of NaC1 space holders （corresponding porosity） on the microstructure, morphology, density, hardness, and electrochemical specifications of the samples were investigated. It was found that as the relative density increased from 60% to 70%, the wall thickness increased from about 200 to 300 pro, which led to a decrease in pore size. Also, the addition of nanoparticle reinforcement and the increased relative density result in increasing metal foam hardness. Moreover, electrochemical test results indicated that increasing the A1203 content reduced the corrosion rate, but increasing the porosity enhanced it.

Comparison of Metal Dusting Behavior of Several Alloys

A comprehensive study on the mechanical behavior of foamed metals was demonstrated. The relationship among their mechanical properties,preparation method,porosity and the structure was briefly studied as well.

Performance Evaluation of Electromagnetic Shield Constructed from Open-Cell Metal Foam Based on Sphere Functions

This study evaluates the performance of a model of open-cell metal foams generated by sphere functions.To this end,an electromagnetic shield constructed from the model was inserted between two horn antennas in an electromagnetic wave propagation simulation.The foam-hole diameter in the electromagnetic shield model was varied as d=2.5 and 5.0 mm,and the frequency of the electromagnetic waves was varied from 3 to 13 GHz.In the numerical experiments of shield effectiveness,the shields with foam holes of both diameters attenuated the electromagnetic waves across the studied frequency range.The shield effectiveness was enhanced at low frequencies and in the shield with smaller hole diameter.

Exact Solution of a Cylinder Tube Made of Metallic Foam Under Inner Pressure

Exact solution of the stress and velocity fields of a cylinder tube of metallic foams under inner pressure is given in which the Triantafillou and Gibson constitutive law （TG model） for the material is taken as a basis of the calculation. The nonlinear equation is turned linear equation by introducing a kinematics parameter. The differences between the full condensed materials and the effect of the relative density are also discussed.

Fabrication of Near Net Shape Metallic Foam via Plaster Mould

Fabrication characteristics are unstable in direct foaming method. Therefore, most of near net-shape metallic foams are produced, and investigated by powder metallurgy. Direct foaming method, however, has many benefits （i.e. reduce the unit cost of goods and fabrication process etc.） to fabrication of metallic foams. In this article, the fabrication characteristic of near net-shape metallic foams by direct foaming method was evaluated. Al and Plaster was used for base material and mould material respectively. Ca and TiH2 were added to molten Al as thickening and blowing agent for stable condition of bubbles. Thickening time was about 10 min with a stirring speed of 600 r/min. Foaming time was 30-120 s for evaluation of the optimum foaming condition. Amount of agent was selected by pre-experimental data. Porosity of near net-shape goods was measured by Archimedes method. On the other hand, it seems that increasing poring time and thickening agent make the poor porosity

Thermal Modeling and Analysis of Metal Foam Heat Sink with Thermal Equilibrium and Non-Equilibrium Models

In the present study,the thermal performance of metal foam heat sink was numerically investigated by adopting the local thermal non-equilibrium(LTNE)model and local thermal equilibrium(LTE)model.Temperature field distributions and temperature difference field distributions of solid and fluid phases were presented.Detailed thermal performance comparisons based on the LTE and LTNE models were evaluated by considering the effects of the relevant metal foam morphological and channel geometrical parameters.Results indicate that a distinct temperature difference exists between the solid and fluid phases when the LTNE effect is pronounced.The average Nusselt numbers predicted by both the LTE and LTNE models are approaching with the increase of porosity,pore density,Reynolds number,large thermal conductivity ratio,and large aspect ratio.This is attributed to the significant reduction of the interstitial convective thermal resistance between the solid and fluid phases,as a result,the LTE model can replace the LTNE model for thermal modeling in these conditions.In addition,the overall thermal performance assessment of metal foam heat sink is compared with the non-porous heat sink,and it shows that the thermal performance factor of metal foam heat sink is approximately two times of the non-porous heat sink.

Low-velocity impact of rectangular foam-filled fiber metal laminate tubes

Through theoretical analysis and finite element simulation,the low-velocity impact of rectangular foam-filled fiber metal laminate(FML)tubes is studied in this paper.According to the rigid-plastic material approximation with modifications,simple analytical solutions are obtained for the dynamic response of rectangular foam-filled FML tubes.The numerical calculations for low-velocity impact of rectangular foam-filled FML tubes are conducted.The accuracy of analytical solutions and numerical results is verified by each other.Finally,the effects of the metal volume fraction of FMLs,the number of the metal layers in FMLs,and the foam strength on the dynamic response of foam-filled tubes are discussed through the analytical model in details.It is shown that the force increases with the increase in the metal volume fraction in FMLs,the number of the metal layers in FML,and the foam strength for the given deflection.

Double-layered skeleton of Li alloy anchored on 3D metal foam enabling ultralong lifespan of Li anode under high rate

The high specific capacity and low negative electrochemical potential of lithium metal anodes(LMAs),may allow the energy density threshold of Li metal batteries(LMBs)to be pushed higher.However,the existing detrimental issues,such as dendritic growth and volume expansion,have hindered the practical implementation of LMBs.Introducing three-dimensional frameworks(e.g.,copper and nickel foam),have been regarded as one of the fundamental strategies to reduce the local current density,aiming to extend the Sand'time.Nevertheless,the local environment far from the skeleton is almost the same as the typical plane Li,due to macroporous space of metal foam.Herein,we built a double-layered 3D current collector of Li alloy anchored on the metal foam,with micropores interconnected macropores,via a viable thermal infiltration and cooling strategy.Due to the excellent electronic and ionic conductivity coupled with favorable lithiophilicity,the Li alloy can effectively reduce the nucleation barrier and enhance the Li^(+)transportation rate,while the metal foam can role as the primary promotor to enlarge the surface area and buffer the dimensional variation.Synergistically,the Li composite anode with hierarchical structure of primary and secondary scaffolds realized the even deposition behavior and minimum volume expansion,outputting preeminent prolonged cycling performances under high rate.

Study on the melting process of phase change materials in metal foams using lattice Boltzmann method

A thermal lattice Boltzmann model is developed for the melting process of phase change material (PCM) embedded in open-cell metal foams. Natural convection in the melt PCM is considered. Under the condition of local thermal non-equilibrium between the metal matrix and PCM, two evolution equations of temperature distribution function are pre-sented through selecting an equilibrium distribution function and a nonlinear source term properly. The enthalpy-based method is employed to copy with phase change problem. Melting process in a cavity of the metal foams is simulated using the present model. The melting front locations and the temperature distributions in the metal foams filled with PCM are obtained by the lattice Boltzmann method. The effects of the porosity and pore size on the melting are also investigated and discussed. The re-sults indicate that the effects of foam porosity play important roles in the overall heat transfer. For the lower porosity foams, the melting rate is comparatively greater than the higher porosity foams, due to greater heat conduction from metal foam with high heat conductivity. The foam pore size has a limited effect on the melting rate due to two counteracting effects between conduction and convection heat transfer.