Foam Cylinder Research Articles

Deformation Field in Diametrically Loaded Soft Cylinders

Deformation fields at the surface of diametrically squeezed shallow cylinders in the large deformation regime are measured experimentally and numerically for different material behaviour in the large deformation regime. By means of a digital image correlation method optimized for large displacements, strain fields are measured and compared with finite element simulations. Assuming a neo-Hookean behaviour for cylinders made of rubber silicone, the strain field is found to be in quantitative agreement with non-linear finite element simulations up to the highest deformations reached in our experiments (15%). For materials that follow an elastoplastic constitutive law, agreement is lost after few percents of deformation and location of the strain field differences are identified up to strains as high as 30%. Strain field evolution is also measured for solid foam cylinders up to 60% of global deformation strain. This method that can be applied to a broad variety of materials, even in the occurrence of large deformations, provides a way to study quantitatively local features of the mechanical contact.

Impacts of porous material fluid bulk properties on noise attenuation performance of cylinder shell structure based on finite element model

SummaryThe noise control method of laying acoustic blanket is adopted to construct a cylinder cell noise experimental device; a typical porous material, melamine foam (MF), is used for noise attenuation experiments in aluminum (Al) and aluminum/melamine foam (Al/MF) cylinder shells and to achieve corresponding in‐shell noise response spectrograms. Based on the Virtual Lab acoustics software, a finite element model has established for the analysis of noise in the Al/MF cylinder shell and numerical simulation computation has been conducted for the acoustic mode and in‐shell acoustic response; the correctness of the finite element model is verified via comparison with theoretical and measured data. On this basis, the impacts of porous material fluid bulk properties on the noise attenuation effect of the Al/MF cylinder shell are further studied within the frequency range of 0 ∼ 1000 Hz. It is suggested that fluid bulk properties changes pose relatively high impacts on internal noise response of a cylindrical cavity. Within low‐frequency and high‐frequency ranges, the response value of sound pressure increases with flow resistivity, while the response value of sound pressure decreases with the increases of tortuosity, porosity, flow resistivity (only for the medium frequency range), and viscous characteristic length in the medium and high frequencies ranges.

Modeling of Supersonic Radiative Marshak Waves Using Simple Models and Advanced Simulations

We study the problem of radiative heat (Marshak) waves using advanced approximate approaches. Supersonic radiative Marshak waves that are propagating into a material are radiation dominated (i.e., hydrodynamic motion is negligible), and can be described by the Boltzmann equation. However, the exact thermal radiative transfer problem is a non-trivial one, and there still exists a need for approximations that are simple to solve. The discontinuous asymptotic P1 approximation, which is a combination of the asymptotic P1 and the discontinuous asymptotic diffusion approximations, was tested in previous work via theoretical benchmarks. Here, we analyze a fundamental and typical experiment of a supersonic Marshak wave propagation in a low-density SiO2 foam cylinder, embedded in gold walls. First, we offer a simple analytic model that grasps the main effects dominating the physical system. We find the physics governing the system to be dominated by a simple, one-dimensional effect, based on the careful observation of the different radiation temperatures that are involved in the problem. The model is completed with the main two-dimensional effect which is caused by the loss of energy to the gold walls. Second, we examine the validity of the discontinuous asymptotic P1 approximation, comparing to exact simulations with good accuracy. Specifically, the heat front position, as a function of the time, is reproduced perfectly in comparison to exact Boltzmann solutions.

Enhanced Aluminium Foam Based Cylindrical Sandwiches: Bending Behaviour and Numerical Modeling

Closed-cell aluminium foams are a relatively new class of structural and functional materials that have attracted increasing attention, for which they are candidate materials in many applications of several industrial fields. One of the aims of the research can be the improvement of the mechanical behaviour of foam-based structures by means of reinforcements that preserve their peculiar property of lightness. In view of this challenge, the present paper describes the production, the mechanical characterization and the numerical modelling of enhanced aluminium foam samples. More specifically, cylindrical sandwiches, characterized by a closed-cell aluminium foam core reinforced with a skin of lightweight aluminium alloy wire mesh embedded into a matrix of low porosity foam, were produced in a one step process; therefore, mechanical three point bending tests were carried out, in order to compare the properties of these innovative sandwiches with plain foam cylinders. The results of the experimental campaign highlight a significant improvement of the mechanical properties of the samples, when so reinforced. Moreover, a FEM numerical model of the cylindrical sandwiches was developed and validated, by comparing the simulations with the results of the experimental tests.

Prevention of clogging in a polyurethane foam packed biotrickling filter treating emissions of 2-butoxyethanol

Biotrickling filter (BTF) tend to accumulate biomass leading to clogging and a subsequent increase in pressure losses and energy demands at high volatile organic compound (VOC) loadings under long-term conditions. Besides higher pressure losses and energy demands, the treatment performance gradually declines due to inhomogeneous gas distribution within the biofilm. Clogging prevention techniques are highly interesting regarding the design of BTFs, high performance levels, energy efficiency and corresponding costs.Squeezing out and backflushing as clogging prevention techniques with optional addition of auxiliary gas injections and chemicals were tested under various conditions. Five BTFs equipped with 17.6 L of different Poret® PPI10 PU foam structures were used to analyze removal efficiencies of both biomass and 2-butoxyethanol as VOC, testing different clogging prevention techniques in comparison to two reference systems without prevention steps. Up to 109.5 g organic dry matter were removed (270 s of gas injection, 0.2 w% sodium hydroxide). With removal efficiencies of 91.7% and 72.8% and corresponding elimination capacities of 36.6 and 56.2 g C·m−3·h−1 the highest performance levels were achieved at specific loadings of 39.9 and 77.1 g C·m−3·h−1 at 12.6 s of empty bed residence time (EBRT), using a PU foam cylinder as package material. Removal efficiencies were evaluated in a pilot system with 2.1 m³ of package volume and 8.9 s of EBRT for treatment of air containing 95% 2-butoxyethanol and 5% styrene according to a waste gas problem in aviation industries. Even though additional installations like a compressor and different valves were necessary, total construction costs, total operational costs and energy costs for the BTF with clogging prevention techniques were reduced by nearly 10%, 20%, and 40% compared to conventional BTFs. Variations in microbial community over time were also tested.

Large-scale drop test on perlite–metal syntactic foam

Perlite–metal syntactic foam is a low-cost cellular metal intended for use in automotive impact protection. To test the viability of the material a 2.5 ton drop test was conducted. Impact mass and energy were selected to replicate the conditions of a frontal impact between a large passenger vehicle and a crash cushion. A hollow syntactic foam cylinder was manufactured to decelerate the drop weight in a controlled manner. Accelerometers and high-speed imaging were utilized to evaluate the performance of the energy absorbing element.

Performance of tubular aluminum foam heat exchangers in multiple row bundles

Two sets of aluminum foam cylinders, 5 and 15 mm thick, are being tested in two-row and three-row bundles for their thermo-hydraulic performance. The bundles are formed using fixed transversal and longitudinal pitch distances and subject to airflow between 0.5 and 5.0 at 0.5 m s−1 interval under cross-flow. The effects of foam layer thickness and the number of row under staggered configuration are investigated. Thermo-hydraulic results are benchmarking against those of a conventional finned tube bundle of similar dimensions with pre-determined number of fins and assembled using the same pitch distances.

The effects of microstructure on propagation of laser-driven radiative heat waves in under-dense high-Z plasma

This work was motivated by previous findings that the measured laser-driven heat front propagation velocity in under-dense TiO2/SiO2 foams is slower than the simulated one [Pérez et al., Phys. Plasmas 21, 023102 (2014)]. In attempting to test the hypothesis that these differences result from effects of the foam microstructure, we designed and conducted an experiment on the GEKKO laser using an x-ray streak camera to compare the heat front propagation velocity in “equivalent” gas and foam targets, that is, targets that have the same initial density, atomic weight, and average ionization state. We first discuss the design and the results of this comparison experiment. To supplement the x-ray streak camera data, we designed and conducted an experiment on the Trident laser using a new high-resolution, time-integrated, spatially resolved crystal spectrometer to image the Ti K-shell spectrum along the laser-propagation axis in an under-dense TiO2/SiO2 foam cylinder. We discuss the details of the design of this experiment, and present the measured Ti K-shell spectra compared to the spectra simulated with a detailed superconfiguration non-LTE atomic model for Ti incorporated into a 2D radiation hydrodynamic code. We show that there is indeed a microstructure effect on heat front propagation in under-dense foams, and that the measured heat front velocities in the TiO2/SiO2 foams are consistent with the analytical model of Gus'kov et al. [Phys. Plasmas 18, 103114 (2011)].

Numerical analysis of forced convection of high-temperature exhaust gas around a metal-foam wrapped cylinder

Due to its high volumetric porosity and large specific surface area, open-cell metal foam has considerable advantages in compact heat exchangers for waste heat recovery system of internal combustion engines (ICEs). In order to simulate the forced convection around a metal foam-wrapped tube, a precise macroscopic model using the Darcy-Forchheimer-Brinkman momentum equation and the local thermal non-equilibrium energy equation has been established, and the heat transfer and pressure drop performance are investigated. Effects of key parameters, including porosity, pore density, foam thickness and Reynolds number are numerically studied and analyzed. It is found that the presence of a foam layer around the cylinder changes the flow structure, especially in the rear of the cylinder, and then influences the heat transfer and pressure field. A comparative study has been conducted between foam cylinders and a bare tube for various Reynolds number. The results indicate that, compared to a bare cylinder, the average Nusselt number of metal-foam wrapped cylinders can improve as much as 10 times at Re=1000 and 18 times approximately at Re=6000, which shows significant improvement in heat transfer performance.

Mechanical Characterization and FEM Modeling of Hybrid Metal Foam/Bio-Composite Samples

This study investigates the mechanical properties of a hybrid metal foam/bio-composite component useful for industrial applications like, e.g., security systems in the automotive field. Cylindrical samples were fabricated by manually wrapping fabrics of hemp fibers, impregnated with epoxy resin, around aluminum foam cylinders. Successively, the mechanical properties of the hybrid structures and of the single constituents (foam cylinders and bio-composite tubes) were determined by means of quasi-static compression and bending tests. The experimental campaign highlights that the hybrid samples show a very significant improvement of the properties, compared to the sum of the single constituents, due to the synergistic interaction between the core and the skin. Finally, a FEM model of the samples was validated by means of a numerical/experimental comparison of the results of the mechanical tests.

Origins of rolling friction

When a hard object rolls on a soft surface, or vice versa, rolling friction arises from deformation of the soft object or the soft surface. The friction force can be described in terms of an offset in the normal reaction force or in terms of energy loss arising from the deformation. The origin of the friction force itself is not entirely clear. It is investigated qualitatively in this paper by rolling a steel ball on soft foam and by rolling a foam cylinder on a hard surface. The deformation of the foam was observed visually, providing simple insights into the origin of the friction force.

New Proximal Femoral Compaction Blade Provides Strong Antirotation Stability of the Femoral Head.

This study investigated the mechanical properties of a new rectangular compaction blade and compared this blade with other types of nail. Three types of nail were tested: the Magnum lag screw (Robert Reid Inc, Tokyo, Japan), proximal femoral nail, and Magnum Fid blade (Robert Reid Inc). The nails were inserted into solid rigid polyurethane foam, and the torsional moments were loaded with an Instron testing machine (Instron, Kanagawa, Japan). The force curve was recorded, and the average maximum torque was calculated from this curve. A simulation study was performed with finite element models to determine the mechanism underlying differences in rotational stability. Mechanical testing showed that the new compaction blade had stronger resistance against rotational force than the helical blade and lag screw implants. Finite element analysis also showed that the new compaction blade had stronger resistance to migration of the polyurethane foam cylinder than the other implant types. In addition, the new compaction blade had strong rotational stability. This implant should be useful for the treatment of unstable trochanteric fracture in patients with osteoporosis. [Orthopedics. 2017; 40(3):e491-e494.].

Shell-Based Numerical Modelling and Experimental Validation of Closed-Cell Aluminum Foams

This work proposes the creation and the validation of shell-based numerical models of closed-cell aluminum foams, useful for FEM analyses. Foam cylinders were produced and specimens extracted by them were morphologically characterized and mechanically tested. Successively, commercial software packages were used for, firstly, creating and modifying geometrical models and, successively, generating FEM models based on shell elements. The results of FEM fit well with the mechanical tests, in terms of stress-strain response. Moreover, they highlight a results variability, reflecting the original variability associated to random generation of the geometrical models.

Implosion dynamics of a megampere wire-array Z-pinch with an inner low-density foam shell at the Angara-5-1 facility

The implosion dynamics of a pinch with a highly inhomogeneous initial axial distribution of the load mass was studied experimentally. A cascade array consisting of a double nested tungsten wire array and a coaxial inner cylindrical shell located symmetrically with respect to the high-voltage electrodes was used as a load of the Angara-5-1 high-current generator. The cylindrical foam shell was half as long as the cathode− anode gap, and its diameter was equal to the diameter of the inner wire array. It is shown experimentally that two stages are typical of the implosion dynamics of such a load: the formation of two separate pinches formed as a result of implosion of the wire array near the cathode and anode and the subsequent implosion of the central part of the load containing the cylindrical foam shell. The conditions are determined at which the implosion of the central part of the pinch with the foam cylinder is preceded by intense irradiation of the foam with the soft X-ray (SXR) emission generated by the near-electrode pinches and converting it into the plasma state. Using such a load, which models the main elements of the scheme of a dynamic hohlraum for inertial confinement fusion, it is possible to increase the efficiency of interaction between the outer accelerated plasma sheath and the inner foam shell by preionizing the foam with the SXR emission of the near-electrode pinches.

Direct sputtering- and electro-deposition of gold coating onto the closed surface of ultralow-density carbon-hydrogen foam cylinder

This work aimed to fabricate a gold coating on the surface of ultralow-density carbon-hydrogen foam cylinder without electroless plating. Poly (divinylbenzene/styrene) foam cylinder was synthetized by high internal phase emulsion, and chemical vapor deposition polymerization approach was used to form a compact poly-p-xylylene film on the foam cylinder. Conducting gold thin films were directly deposited onto the poly-p-xylylene-modified foam cylinder by magnetron sputtering, and electrochemical deposition was adopted to thicken the gold coatings. The micro-structures and morphologies of poly (divinylbenzene/styrene) foam cylinder and gold coating were observed by field-emission scanning electron microscopy. The gold coating content was investigated by energy-dispersive X-ray. The thicknesses of poly-p-xylylene coating and sputtered gold thin-film were approximately 500 and 100nm, respectively. After electrochemical deposition, the thickness of gold coating increased to 522nm, and the gold coating achieved a compact and uniform structure.

Decolorization of Reactive Orange 16 in Rotating Drum Biological Contactor

A laboratory scale Rotating Drum Biological Contactor (RDBC; drum length×diameter: 255×130mm) filled by randomly arranged particulate carriers with mycelium of the white rot fungus Irpex lacteus was tested for Reactive Orange 16 (RO16) decolorization. Five mycelium carriers were pre-screened for fungus immobilization and the dye degradation in static cultures. The best mycelium growth was observed with the straw, wooden shavings and polyether foam cylinders. Considerable dye adsorption (up to 30%) was observed with natural carriers; very low adsorption was observed with carrier particles made of plastics. Natural mycelium carriers with attached I. lacteus yielded the highest RO16 decolorization efficiency (50–90%). The straw, wooden shavings and polyether foam particles were tested in the RDBC in batch dye degradation experiments and the straw was also tested in continuous experiments. The straw yielded the fastest and stable dye decolorization in the subsequent batches. With the straw, wooden shavings and polyether foam particles RO16 decolorization higher than 90% was achieved within 48h in batch experiments and better than 80% decolorization was attained at liquid mean residence time of 33.3h in continuous experiments. Dye degradation rate of 3.5–4.0gm−3h−1 was achieved in the batch RDBC and the rate of 1.1–1.5gm−3h−1 in the continuously operated reactor.

Hybrid design and energy absorption of luffa-sponge-like hierarchical cellular structures

Luffa sponge has hierarchical cellular structure with macro-pores and micro-pores. Its strength is greatly enhanced by the stiff inner-surface layer around the macro-pores. This hierarchical bio-cellular structure was mimicked to construct a hierarchical aluminum foam cylinder reinforced by stiff thin-walled carbon fiber reinforced plastic (CFRP) tubes. Compression behaviors of the luffa-sponge-like hierarchical foam cylindrical structures were revealed and it is found that the specific energy absorption (SEA) of the hierarchical structure is greatly improved compared with the pure aluminum foam cylinder. Interaction between the CFRP tube and the aluminum foam lets the SEA of the hierarchical cylinder is greater than the linear summation of the SEA of each component in the hierarchical foam. Through hybrid and hierarchical design, an ultra-light composite cellular structure with excellent energy absorption was developed.

Thermal development in open-cell metal foam: An experiment with constant wall heat flux

Experimental heat transfer results for a commercial open-cell aluminum foam cylinder heated at the wall by a constant heat flux and cooled by water flow, are presented. The results cover thermal-entry and fully-developed regions. Measurements include wall temperature along flow direction as well as average inlet and outlet temperatures of the water. Flow rates are in the Darcy and non-Darcy (transitional and Forchheimer) regimes. The wall temperature along the foam clearly shows two distinct behaviors related to thermally-developing and fully-developed conditions, which is confirmed by the behavior of local Nusselt number. The thermal entry length is determined and discussed in detail; it is also compared to its analytical counterpart for Darcy flow. The thermal entry region in metal foam is found to be significant and much longer than its analytically-predicted value. A method for estimating the bulk fluid temperature is envisioned for calculating the local Nusselt number. Previously undiscussed phenomenon is captured in the behavior of Nusselt number for non-Darcy regimes, which suggests periodic thermal development along the foam. The fully-developed data for the Darcy flow cases is compared to its analytical counterpart, and a correlation for the Nusselt number as a function of Reynolds number is proposed for non-Darcy flows.

Air–soil exchange of organochlorine pesticides in a sealed chamber

So far little is known about air–soil exchange under any sealed circumstances (e.g., in plastic and glass sheds), which however has huge implications for the soil–air–plant pathways of persistent organic pollutants including organochlorine pesticides (OCPs). A newly designed passive air sampler was tested in a sealed chamber for measuring the vertical concentration profiles of gaseous phase OCPs (hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs)). Air was sampled at 5, 15, and 30cm above ground level every 10th day during a 60-day period by deploying polyurethane foam cylinders housed in acrylonitrile butadiene styrene-covered cartridges. Concentrations and compositions of OCPs along the vertical sections indicated a clear relationship with proximity to the mixture of HCHs and DDTs which escapes from the soils. In addition, significant positive correlations were found between air temperatures and concentrations of HCHs and DDTs. These results indicated revolatilization and re-deposition being at or close to dynamic pseudo-equilibrium with the overlying air. The sampler used for addressing air–soil exchange of persistent organic pollutants in any sealed conditions is discussed.

Improvement in the coating homogeneity in electrosynthesized Rh structured catalysts for the partial oxidation of methane

The precipitation of Rh/Mg/Al and Rh/Al hydroxides on the surface of FeCrAlloy foams by a base electrogeneration method was investigated to improve the properties of the deposited film (homogeneity and composition) and therefore the performances of the structured catalysts, obtained by calcination, in the Catalytic Partial Oxidation of CH4 to syngas. The work focussed on decreasing current gradients within open-cell foam cylinders by increasing the number of electrical contacts from 1 to 3 points to promote a more homogeneous precipitation of the hydroxides. Electrochemical and catalytic tests as well as SEM/EDS and μ-XRF/XRD analyses allowed to correlate the effect of the number of electrical contact points with materials properties. Lastly, syntheses were performed on Pt plates to study the effect of the electrical behaviour and shape of the support on the composition of the film.A more homogeneous coating of the foam surface was achieved by adopting a configuration with 3 contact points since the reduction of nitrates and water molecules that generates the basic media in the vicinity of the support was enhanced. Layer thicknesses up to 5–15μm were deposited; however, the sequential precipitation of a film with composition closer to the expected one and a layer enriched in Al and Rh (outer layer) was not avoided. The improvement in the coating gave rise to enhanced performances for a sample prepared at −1.1V for 3000s. Contrarily, the low adherence of the outer layer in a sample prepared at −1.2V for 2000s during both calcination and catalytic tests may be responsible of the unexpected decrease in catalytic performances. The same sequential precipitation was observed by performing the syntheses on Pt plates, showing that the electrical nature the support did not play a key role on this phenomenon.