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Due to their nanoscale features, nanometric multilayers can have a large variation in properties for varying bilayer heights. While the hardening at small feature sizes and the consequent softening at even smaller feature sizes have been observed for decades, the underlying mechanisms are still under debate. In this study, molecular dynamics uniaxial compression simulations are employed to study the mechanical properties of Al/Ni multilayers for bilayer heights h from 100 nm down to 5 nm. The effect of the microstructure on Young's modulus and the yield strength was investigated. Furthermore, the mechanical properties of equiatomic and equivolumetric multilayers were compared. A comparison with experimental results from the literature showed good agreement. Both the hardening at intermediate bilayer heights as well as the softening at very small bilayer heights were observed. The results are discussed in the context of possible hardening and softening mechanisms. While the Hall–Petch effect with a h − 1 / 2 scaling is not contradicted, it is shown that, although the underlying mechanisms are different, both the hardening as well as the softening are based on a general size effect with a scaling of ln (h) / h. [ABSTRACT FROM AUTHOR]

Ferroelectric (Al, Sc)N thin films have the potential for use in low-power memory applications. This study demonstrates the thickness scalability of ferroelectricity down to an approximately 20 nm-thick (Al0.8Sc0.2)N film sandwiched between microfabricable TiN electrodes. The impact of the deposition gas atmosphere during the sputtering process and the top electrode materials on the crystal structures and ferroelectric properties was investigated for 20–30 nm-thick (Al0.8Sc0.2)N thin films deposited on Si substrates covered with a TiN layer by radio frequency magnetron sputtering. The deposition atmosphere did not strongly affect the crystal structures of the 30 nm-thick (Al0.8Sc0.2)N films but significantly affected their ferroelectric properties. The leakage current density decreased for films deposited under pure N2 gas compared to the films deposited under a gas mixture of 0.67Ar + 0.33N2. The ferroelectric properties of 20 nm-thick (Al0.8Sc0.2)N films were changed by the top electrode materials; both the switching electric field and its maximum applicable electric field increased for the TiN top electrodes compared with the Pt top electrodes, improving the saturation characteristics of the remnant polarization (Pr) against the applied electric field. Consequently, the 20 nm-thick (Al0.8Sc0.2)N film sandwiched between the microfabricable TiN top and bottom electrodes showed ferroelectricity without noticeable degradation with decreasing film thickness; the film maintained large Pr values of over 100 μC/cm2 in the temperature range from room temperature to 150 °C. The present data open the door to scalable ferroelectric random-access memories using almost thickness-degradation-free thin (Al, Sc)N films with microfabricable TiN electrodes. [ABSTRACT FROM AUTHOR]

This work focuses on investigation of the internal blast resistance of metal sandwich tubes with continuously radial density-graded aluminum foam cores. Based on the 3D-Voronoi technology in polar coordinates, unidirectionally and bidirectionally continuously density-graded aluminum foam were developed for the cores of sandwich tubes in Finite Element (FE) model. And the correctness of core gradient was verified by comparing theoretical design with the actual value generated by FE model. Effects of core density distribution and core density gradient on blast resistance of sandwich tubes were explored and identified. The results indicate that, when the core density gradient is constant, the sandwich tube with negative-gradient core exhibits the smallest maximum deformation of the outer tube, while the negative-middle-low-gradient core tube shows the highest specific energy absorption (SEA). For negative-gradient core tube, as the core density gradient increases, the maximum deformation of the outer tube decreases significantly, with only slight reduction of the structural SEA. For negative-middle-low-gradient core tube, as the core density gradient increases, the maximum deformation of the outer tube decreases, while the SEA increases. [ABSTRACT FROM AUTHOR]

In the impact application, the impactor doesn't have to be perpendicular to the structure. This study mainly focuses on numerical low velocity oblique impact analysis performed on silicon aluminum composite foam using ABAQUS®. In this paper, the shear failure model is used to estimate damages in silicon aluminum composite foam model for different angles of the impactor. Here, dissipation energies, impact load histories and load displacement curves for damages under different angles of impactor have been characterized. From the study, it is found that the contact force intensity and penetration time decrease as the angle of the impactor increases. In the study of energy time histories, it is seen that energy increases and penetration time decreases as the angle of the impactor increases. From the contact force study, it is found that the contact force decreases, and contact time increases as the angle of the impactor decreases. The studies for displacement show that oblique impactor displacement increases as the angle of the impactor increases. [ABSTRACT FROM AUTHOR]

Metal foams are highly useful in industries because of their lightweight, energy and vibration absorption properties. This study investigated the propagation of torsional waves in an elastic layer over a fluid-saturated fractured poroelastic half-space with a metal foam coated layer. It is assumed that the interfaces are in sliding contact with two different sliding parameters. The coated layer is closed-cell aluminium foam. We use the separation variable technique and the Bessel function to solve the equation of motion in different layers. The displacement components are written in terms of the second kind Whittaker functions. Using an asymptotic formulation of the Whittaker function and appropriate boundary conditions, the dispersion equation is derived in terms of the determinant. The control of the vibration due to the metal foam-coated layer is one of the important goals of this study. Also, numerical and graphical analyses have been done with the help of Mathematica software to see the effect of different parameters on torsional wave propagation. It is found that the presence of coated metal foam layer decreases the phase velocity of the torsional wave propagation. The work may be helpful in the seismology, automobile, and aerospace industries. [ABSTRACT FROM AUTHOR]

The porous structure, in which many pores are intentionally placed inside the material, has excellent impact energy absorption properties. Recent studies have attempted to fabricate multi-layered porous structures with different mechanical properties within a single porous structure sample, and the mechanical properties of these structures are being elucidated. However, these studies mainly attempted to vary the densities, pore structures, and alloy compositions within a single material, such as aluminum, for the entire sample. Since multi-materials are now being promoted to utilize the most suitable material type in the right place, porous structures made of different materials, such as a combination of aluminum and resin, are expected to be required in the future. In this study, we attempted to fabricate two-layered porous structure samples of different materials by printing a resin porous structure using a 3D printer on an aluminum foam fabricated by a precursor foaming process. Static compression tests were performed on the resulting two-layered porous structure samples to investigate their mechanical properties. The resin porous structure printed by the 3D printer and the aluminum foam were both designed to expose the porous structure on the surface of the specimen so that the deformation behavior can be easily observed. The density of the resin porous structure was varied by systematically varying the filling rate of the resin porous structure to be printed, and the effect on the compression properties was investigated. The fabricated two-layered porous structure was effectively bonded between the two layers by the anchor effect, which is a mechanical bonding caused by the resin penetrating into the pores. The layers exhibited robust bonding with no evidence of separation. It was possible to fabricate a two-layered porous structure that exhibited both properties of aluminum foam and those of resin porous structure. It was found that the plateau stress in the resin porous structure layer can be controlled between about 0.5 MPa and 40 MPa, and the deformation behavior and energy absorption properties of the two-layered porous structure can be controlled by varying the resin filling rate of the resin porous structure layer. That is, it was indicated that multi-layered porous structures with various densities and consisting of various types of materials allow for the optimal design of porous structures used in structural materials. [ABSTRACT FROM AUTHOR]

In this work, we focused on the characterization of closed-cell Al foams and aluminum honeycomb panels, in particular their energy absorption capacity under conditions of static compressive stress. Through experimental tests, the specific energy absorbed by different samples was evaluated: in the honeycomb panels the mechanical behavior was analyzed both for large assemblies and for structures with a reduced number of cells, and the effect of the number of cells was studied too. Furthermore, for larger structures, the specific energy absorbed was calculated from stress–strain compressive graphs. For the closed-cell Al foams, manufactured in the laboratory using the powder compaction method with different percentages of SiC and TiH2 and characterized by different relative densities, the specific energy absorbed was evaluated too. The experimental results showed that the specific energy absorbed by the Al honeycomb was always higher than that of the different types of closed-cell foams. However, when selecting the material for each specific application, it is necessary to take into account numerous parameters such as the relative density, absorbed energy, peak stress, plateau stress, plateau extension, densification strain and so on. Consequently, the overall performance must be evaluated from time to time based on the type of application in which the best compromise between strength, stiffness and lightness can be achieved. [ABSTRACT FROM AUTHOR]

The squeezing deformation of surrounding rock is an important factor restricting the safe construction and long-term operation of tunnels when a tunnel passes through soft strata with high ground stress. Under such soft rock geological conditions, the large deformation of the surrounding rock can easily lead to the failure of supporting structures, including shotcrete cracks, spalling, and steel arch distortion. To improve the lining support performance during the large deformation of squeezed surrounding rock, this work selects aluminum foam with densities of 0.25 g/cm3, 0.42 g/cm3 and 0.61 g/cm3 as the buffer layer material and carries out uniaxial confined compression tests. Through the evaluation and analysis of energy absorption and the comparison of the yield pressure of aluminum foam with those of other cushioning materials and yield pressure support systems, the strength, deformation and energy absorption of aluminum foam with a density of 0.25 g/cm3 meet the yield pressure performance requirements. The numerical model of the buffer layer yielding support system is then established via the finite element analysis software ABAQUS, and the influence of the buffer layer setting on the lining support is analyzed. Compared with the conventional support scheme, the addition of an aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining. The maximum and minimum principal stresses of the primary support are reduced by 13% and 15%, respectively. The maximum and minimum principal stresses of the secondary lining are reduced by 15% and 12%, respectively, and the displacement deformation of the secondary lining position is reduced by 15%. In summary, the application of aluminum foam buffer layer can reduce the stress and deformation of the primary support and secondary lining, improve the stress safety of the support and reduce the deformation of the support. [ABSTRACT FROM AUTHOR]

Three-dimensional Voronoi models are built to analyze the buffering and energy absorption performance of stepwise density-graded aluminum foams during quasi-static and dynamic compression. The validity of the aluminum foam model with selected mesostructure and simulation parameters is verified by the correlation between the experimental and numerical results. Strain-stress responses, deformation propagation, and energy absorption capabilities are compared and analyzed to probe the deformation mechanisms and stress transmission. The results show that there are three deformation modes: quasi-static mode, transitional mode, and dynamic mode, which are formed successively with increasing compression velocity. The method of obtaining the first critical velocity of the deformation mode transformation in two-dimensional stepwise density-graded aluminum foams is extended to the three-dimensional cases. Meanwhile, a new method based on the deformation concentration is developed to determine the second critical velocity. The different stepwise density graded aluminum foams exhibit similar performances under quasi-static mode, but exhibited significant differences under dynamic mode. However, a negative gradient of aluminum foam is advantageous for reducing the stress on the support end and optimizing the energy absorption under dynamic mode. [ABSTRACT FROM AUTHOR]

To accurately predict the trajectory and attitude of the projectile obliquely penetrating the laminated aluminum foam target, the penetration resistance function which conclude normal stress, shear stress and friction is established in this paper. Then, we establish the differential equation of the projectile motion combined with the momentum theorem and the momentum moment theorem. Finally, we use finite element software Ansys/Ls-Dyna to simulate the oblique penetration, and the attitude deflection under different initial velocity or different initial attitude angle is emphatically analyzed. The results show that there is a peak of attitude deflection at the beginning of oblique penetration, and the peak is little correlated with initial velocity, but is positively correlated with initial attitude angle. The projectile will deflect three times during oblique penetration, and the variation is "increase-decrease-increase". When the projectile finally through the target, the value of attitude deflection is negatively correlated with initial velocity and positively correlated with initial attitude angle. [ABSTRACT FROM AUTHOR]

This study investigates the axial compression mechanics and energy absorption characteristics of aluminum foam-filled carbon fiber-reinforced polymer (CFRP) tubes from both experimental and simulation perspectives. Quasi-static compression experiments of aluminum foam specimens, single CFRP tubes and aluminum foam-filled CFRP tubes are carried out. Based on the experimental results, compression simulations are conducted to investigate the structural deformation and the energy absorption characteristics of aluminum foam-filled CFRP tubes at the mesoscale. The effects of structural parameters on the compression mechanics and energy absorption characteristics of aluminum foam-filled CFRP tubes are explored. [ABSTRACT FROM AUTHOR]

Abstract\nHIGHLIGHTSPolycarbonate (PC) is a polymer material widely utilized in various engineering applications, characterized by its transparency and impact strength. The analysis of the mechanical behavior of PC presents challenges due to its nonlinear mechanical properties. This study employs a modified model to examine the mechanical behavior of PC through a combination of experimental and numerical approaches. Numerical simulation provides data regarding the deformation pattern and energy absorption efficiency for PC. The results affirm the model’s reliability in assessing the mechanical properties of PC across different temperatures and strain rates. This establishes a benchmark for mechanical analysis across various scenarios.By combining quasi-static and dynamic tensile experiments, the basic tensile properties of polycarbonate at different temperatures and strain rates were investigated, and the true stress-strain curves were obtained by interpolation using the DIC technique, based on which the parameters of the Liu-Subhash model were fitted, and applied to the extreme loading conditions.The modified Liu-Subhash model used in the field of aluminium foam is improved and combined with the Hart tensile deformation criterion to make it suitable for describing the mechanical behaviours of polymer materials and applied to the tensile simulation of PC. The numerical simulation results are well fitted in terms of both deformation patterns and load values.After considering the thermal effect and strain rate effect, the subroutine based on the improved Liu-Subhash model was written in this paper and applied in the simulation of high-velocity impacts, and the numerical values and trends of the deflection results were basically consistent with the experimental images, which verified the feasibility of its application in the analysis of extreme loading conditions.By combining quasi-static and dynamic tensile experiments, the basic tensile properties of polycarbonate at different temperatures and strain rates were investigated, and the true stress-strain curves were obtained by interpolation using the DIC technique, based on which the parameters of the Liu-Subhash model were fitted, and applied to the extreme loading conditions.The modified Liu-Subhash model used in the field of aluminium foam is improved and combined with the Hart tensile deformation criterion to make it suitable for describing the mechanical behaviours of polymer materials and applied to the tensile simulation of PC. The numerical simulation results are well fitted in terms of both deformation patterns and load values.After considering the thermal effect and strain rate effect, the subroutine based on the improved Liu-Subhash model was written in this paper and applied in the simulation of high-velocity impacts, and the numerical values and trends of the deflection results were basically consistent with the experimental images, which verified the feasibility of its application in the analysis of extreme loading conditions. [ABSTRACT FROM AUTHOR]

In this paper, a sinusoidal corrugated filled tube (SCFT) is proposed by filling aluminum foam into a sinusoidal corrugated tube, the finite element model is established using the finite element software Pro/Engineer and Abaqus/Explicit, and the accuracy of the finite element model is verified. Crashworthiness studies under axial impact show that SCFT has better energy absorption (EA) performance than a circular filled tube (CFT) under the same outer tube wall thickness conditions, and the EA and specific EA of SCFT are 1.16 times and 1.12 times that of CFT, respectively; in addition, SCFT has a better interaction effect than CFT under the same outer tube wall thickness. Subsequently, a parametric study of SCFT by amplitude, wavenumber, outer tube wall thickness and aluminum foam density was systematically carried out. The structure studied in this paper can provide a reference for the innovative structural design of filled tubes. [ABSTRACT FROM AUTHOR]

Percolation casting technology is used to produce alumina ceramic hollow spheres of different sizes that are neatly and tightly arranged according to certain rules. Then, aluminum metal melt infiltrates the gap of adjacent ceramic hollow spheres, forming a sphere-reinforced aluminum metal matrix syntactic foam (MMSF). To compare the mechanical properties between aluminum foam and MMSF, the same base material and pore size were used. Based on quasi-static testing, split Hopkinson pressure bar experiments were conducted on the MMSF and aluminum foam at different strain rates using pulse-shaping and high-speed photography techniques. The influence of alumina ceramic hollow spheres on the MMSF (including compressive strength, failure process, and energy absorption performance) was analyzed. Results indicate that the addition of alumina ceramic hollow spheres significantly enhances the compressive strength and energy absorption capacity of MMSFs. It also improves the strain rate sensitivity to some extent, rendering the composite formed by aluminum foam and ceramic hollow sphere to be strain rate-sensitive. Furthermore, the energy utilization efficiency and absorbed energy per unit volume of the MMSF were higher than those of the aluminum foam. The MMSF exhibited better strain rate sensitivity in terms of impact resistance than the aluminum foam; the higher the strain rate, the higher the absorbed impact energy. The MMSF has significant application prospects to aerospace engineering and explosion protection in the military. [ABSTRACT FROM AUTHOR]

Introduction: This paper investigates the free vibration problem of variable thickness graphene-reinforced porous cylindrical curved plates, which is limited by simply supported boundary conditions. The cylindrical curved plate consists of graphene platelets (GPL) and porous aluminum foam. To improve its performance, the graphene-reinforced porous cylindrically curved plate is approximated as a functional gradient layered structure. The cylindrically curved plate structure has a varying thickness in the radial direction, which can affect its stiffness. Methods: The nonlinear dynamic equations of the cylindrically curved plate structures with variable thickness are obtained by employing the improved Halpin–Tsai model, mixing rule, first-order shear deformation theory (FSDT), and Hamilton's principle. Finally, the natural frequencies of the system are obtained by Navier's method. Results: Several factors, including the distribution pattern of GPL, the pore's distribution mode, the mass fraction of graphene, the subtended angle, the thickness function's exponent, the radius-to-thickness ratio and length-to-thickness ratio, are considered for determining their impacts on the natural frequencies and modal shapes of variable-thickness graphene-reinforced porous cylindrically curved plates. [ABSTRACT FROM AUTHOR]

The effect of the metal foam thickness on the conduction and convection heat transfer for a metal foam flat plate impinged by a circular air jet is investigated. The IR thermography and thin-metal foil technique are used for the measurement of local heat transfer. An open-cell aluminum metal foam is used for the metal foam flat plate. A 3D-printed resin foam and detached metal foam flat plate are used for the appreciation of the conduction and convection heat transfer. The varying parameters are the thickness of the foam, Reynolds number, and the nozzle exit to plate distance. The presence of the metal foam offers a conduction effect. This predominates over the attenuation in the convective heat transfer by foam due to additional hydraulic resistance. The additional hydraulic resistance offered by the porous foam increases with the increase in the foam thickness. The heat transfer of a porous foamed flat plate decreases with the increase in the foam thickness. The local Nusselt number of the resin foam and detached foam flat plate is almost the same. The conduction effect and attenuation in the convection heat transfer of a metal foam flat plate are quantified by attenuation and enhancement factors. The overall augmentation offered by 4, 8, and 12 mm thick metal foam flat plates is 1.71, 1.42, and 1.43 times compared to the smooth flat plate case, respectively. Hence, it is advisable to use a metal foam flat plate with 4-mm-thick metal foam under circular air jet impingement. [ABSTRACT FROM AUTHOR]

The main objective of this study is to analyze the impact resistance of aluminum foam composites containing fillers and coatings and to investigate the effect of different thickness ratios of the composites on this capability. We prepared composites using aluminum foam and polyurea and performed impact tests and numerical simulations. A comparison of the results shows that the Abaqus simulation results are in general agreement with the test results. The results show that the polyurea filler material and polyurea coating can significantly improve the impact resistance of the aluminum foam, and the best impact resistance of the aluminum foam composite with polyurea coating on the back. An extended study of the composites was carried out using a numerical model validated by the test results. For the energy absorption effect of the aluminum foam composites in the impact resistance process, there is an optimum value for the thickness ratio of the aluminum foam/polyurea composite, which is 3:1. The remaining kinetic energy of cylindrical fragments in the 3-1-1-2 composite material decreased by 13.26%, in the 4-1-1-2 composite material decreased by 11.91%, in the 2-1-1-2 composite material decreased by 11.78%, and in the 1-1-1-2 composite material increased by 2.7% when compared to the remaining kinetic energy of cylindrical fragments in the control group. The energy absorption efficiency of the aluminum foam composite increases as the residual kinetic energy of the cylindrical fragments decreases. The 3-1-1-2 composite can significantly improve the energy absorption effect, which can be used as a reference for the design of impact-resistant composites in the future. [ABSTRACT FROM AUTHOR]

A shaking table model test of the tunnel was carried out to compare the damping effects of polyurethane foam aluminum(AF/PU) and sponge rubber. The test shows that the damping effect of polyurethane foam aluminum is better, and the dynamic earth pressure and strain values of each measuring point of the tunnel lining are relatively smaller. The ANSYS software was used for the ground motion simulation. The first principal stress and first principal strain of the lining were compared and analysed between the two types of damping layers. It was found that the damping effect of AF/PU was better, which is consistent with the test results. The damping effects of AF/PU with thicknesses of 10, 20, and 30 cm were 22.3%, 29.03%, and 31.41%, respectively. The damping effect increases with an increase in thickness, but the growth rate slows. [ABSTRACT FROM AUTHOR]

Azo dyes like methyl orange (MO) are very toxic components due to their recalcitrant properties which makes their removal from wastewater of textile industries a significant issue. The present study aimed to study their removal by utilizing aluminum and Ni foam (NiF) as anodes besides Fe foam electrodes as cathodes in an electrocoagulation (EC) system. Primary experiments were conducted using two Al anodes, two NiF anodes, or Al-NiF anodes to predict their advantages and drawbacks. It was concluded that the Al-NiF anodes were very effective in removing MO dye without long time of treatment or Ni leaching at in the case of adopting the Al-Al or NiF-NiF anodes, respectively. The structure and surface morphology of the NiF electrode were investigated by energy dispersive X-ray (EDX), and field emission scanning electron microscopy (FESEM). Response surface methodology was utilized to predict the optimum conditions by considering current density with 4-8 mA/cm² range, NaCl concentration in the range of 0.5-1 g/L, and electrolysis time of 10-30 min as controlling parameters. A very high MO dye removal percentage was achieved (97.74%) at 8 mA/cm², 1 g/L of NaCl within 30 min of electrolysis and consumed energy was 36.299 kWh/kg. This cost-effective EC system with the Al-NiF anodes besides Fe foam as cathode approved its high efficiency in removing MO dye with moderate amounts of NaCl due to the excellent 3D structure of these foam electrodes which highlight foam electrodes as an excellent choice for EC system in an environmentally friendly pathway. [ABSTRACT FROM AUTHOR]

The design and multi-objective optimization of auxetic sandwich panels (ASPs) are performed to enhance the blastworthiness of armored fighting vehicles (AFVs). Various metastructures in the form of four auxetic geometries are proposed as the sandwich core: re-entrant honeycomb (REH), double-arrow honeycomb (DAH), star honeycomb (SH), and tetra-chiral honeycomb (CH). This paper employs a combination of finite element and machine learning methodologies to evaluate blastworthiness performance. Optimization is carried out using the nondominated sorting genetic algorithm II (NSGA-II) method. The optimization results show significant improvements in blastworthiness performance, with notable reductions in permanent displacement and enhancements in specific energy absorption (SEA). Global sensitivity analysis using SHapley Additive exPlanations (SHAP) reveals that cell thickness is the most critical factor affecting blastworthiness performance, followed by the number of cells and corner angle or radius for CH. The application of optimized ASP on AFVs shows promising results, with no failure occurring in the occupant floor. Furthermore, AFVs equipped with the optimized ASP DAH significantly reduce maximum displacement and acceleration by 39.00% and 43.56%, respectively, and enhance SEA by 48.30% compared to optimized aluminum foam sandwich panels. This study concludes that ASPs have potential applications in broader engineering fields. [ABSTRACT FROM AUTHOR]

Design and testing of real materials is a costly process and usually requires some specific equipment. To alleviate this task numerical methods can be leveraged. In this work we show possible modelling technique for closed-cell material structure using Weaire–Phelan unit cells. As an example existing aluminum structures were used and modelled parametrically, allowing to establish different geometrical models for different applications. Numerical simulations for compression was also done on the developed models to reveal the material response. The influence on the cell wall thickness and the friction between the material and the compression plate was investigated. It was found that the friction coefficient has no significant effect on the material response, except in the case where bonded connection was assumed. It was also demonstrated that material response and the porosity controlled by cell wall thickness have an approximately linear relationship with each other. This method proved to be a flexible and alternative solution of real laboratory tests and targeted to reduce costs of material design. [ABSTRACT FROM AUTHOR]

In order to improve the energy absorption performance of hydraulic support and solve the problems such as cylinder explosion of support column when roadway rock burst occurs, a kind of multi-cell tube energy absorption component with square tube and round tube nested with each other is proposed and applied in series to the hydraulic support. Based on the simplified super folding element theory, the energy dissipation path of multi-cell tubes is analyzed, and the equivalent axial load prediction formula of multi-cell tubes with different section shapes is derived. The energy absorption performance and buckling deformation morphology of multi-cell tubes with different section shapes under axial crushing were obtained by numerical simulation. It was found that multi-cell square tubes (SS type) had relative energy absorption advantages, and the reliability of numerical simulation was verified by experiments. Meanwhile, the average load obtained by numerical simulation and experiment was compared with the equivalent axial load predicted by theory. It is proved that the equivalent axial load prediction formula has high prediction accuracy. Based on the research foundation of aluminum foam filling method in multi-cell square tube, the filling method with 25% filling rate with relative energy absorption advantage was selected to carry out axial quasi-static compression test of aluminum foam filling multi-cell square tube with different porosity. The results show that the aluminum foam filling can improve the deformation resistance of the multicellular square tube. Among them, the load fluctuation of the multi-cell square tube with 71.18% porosity is the smallest, the effective deformation length and energy absorption are the largest, and the energy absorption effect is the best, which can make the energy absorption and displacement process more stable. When the impact velocity remains unchanged, under different impact energy conditions, compared with the with the traditional hydraulic support without adding energy absorbing components, the plastic energy of the support part is reduced by about 87%, the impact time is extended by about 307%, and the yield distance is increased by about 282%. The plastic deformation of the support is effectively reduced through the buckling deformation of the energy absorption component. Sufficient time is provided for the opening of the support column safety valve. The application of aluminum foam filled multi-cell square tube reduces the risk of cylinder explosion of the support column and improves the impact resistance of the column.

Reactive multilayers store large amounts of chemical energy, which can be released through a self-sustaining reaction. One way of triggering the self-sustaining reaction is mechanical ignition, which is a prerequisite for designing a self-healing system. For potential integration into various devices, it is important to understand how Al/Ni reactive multilayers behave under shock compression. In this study, molecular dynamics (MD) simulations are employed to investigate Al/Ni reactive multilayers under shock compression. MD simulations allow for the understanding of what is happening at the atomistic level. Furthermore, they give access to bilayer heights that are difficult to study otherwise. This allows studying the shock wave propagation from bilayer heights of 100 down to 5 nm, while at the same time observing what is happening atomistically. Shock compression is studied both, for interfaces parallel and normal to the shock wave. It is shown that when the shock wave is parallel to the Al–Ni interfaces, there is a clear relationship between bilayer height and effective elastic modulus, which is not true when the interfaces are normal to the shock wave. Furthermore, intermixing of Al and Ni, as a prerequisite for ignition, strongly depends on the bilayer height as well as the impact velocity. Behind the shock wave, a phase transformation occurs, which strongly depends on the impact velocity, with a weak dependence on the bilayer height. Furthermore, void nucleation and fracture are observed, where the voids start nucleating in the Al layers. [ABSTRACT FROM AUTHOR]

The stability and accuracy of atomic devices can be degraded by the evolution of their cell inner atmosphere. Hence, the undesired entrance or leakage of background or buffer gas, respectively, that can permeate through the cell walls, should be slowed down. In this work, we investigate helium permeation in microfabricated alkali vapor cells filled with He and whose windows are made of borosilicate glass (BSG) or aluminosilicate glass (ASG). The permeation is then derived from routine measurements of the pressure-shifted hyperfine transition frequency of an atomic clock. We first confirm that ASG reduces the He permeation rate by more than two orders of magnitude, in comparison to BSG. In addition, we demonstrate that Al 2 O 3 thin-film coatings, known to avoid alkali consumption in vapor cells, can also significantly reduce He permeation. The permeation through BSG is thereby reduced by a factor up to 130, whereas the one through ASG is decreased by a factor up to 5.0 compared to uncoated substrates. These results may contribute to the development of miniaturized atomic clocks and sensors with improved long-term stability or sensitivity. [ABSTRACT FROM AUTHOR]

The present work investigates factors which control the stress generated at the back face of end wall-mounted shock-loaded aluminum foam. When the applied shock pressure is higher than the plastic strength of the foam, the foam deforms plastically generating a compaction wave traveling below shock velocity. Wave reflection and momentum transfer at the end wall result in shock amplification. With increasing foam length, the stress at the end wall decreases, finally leading to shock mitigation. A relation between compaction wave characteristics, foam densification, and stress generated at the end wall is established. [ABSTRACT FROM AUTHOR]

The development of sustainable cooling technologies and increased concern for recycled materials will affect the reduction of greenhouse gas emissions, which primarily originate from the production industry. In this research paper, a twofold contribution to sustainability is made through the efficient application of a workpiece, obtained by recycling waste in the form of metal chips, and the machining of the obtained workpiece by using alternative cooling techniques comparing them to cutting fluids. Minimum quantity lubrication and cold compressed air cooling were selected as two sustainable, alternative cutting environments. Using Taguchi's L9 orthogonal array, the influence of cutting speed, feed rate and cutting environment on drilling thrust force, built-up edge formation and hole deviation was observed. Using the analysis of variance method, feed rate was identified to have the highest influence on the output parameters (31%), followed by cooling and lubrication techniques (18%) and lastly by cutting speed (5%). Based on the grey relation analysis, optimal controllable factors were identified. This analysis indicated that low cutting speeds and feed rates, coupled with the MQL cutting environment, produced the lowest thrust force, deviation of hole and built-up edge formation. [ABSTRACT FROM AUTHOR]

The hybrid sandwich structures possessing composite faces and an aluminum foam (ALF) core exhibit lightweight and superior impact resistance. However, limited studies pay attention to the mechanical behavior of hybrid sandwich beams with various ALF densities. The present article has focused on the influence of foam densities on the quasi‐static and low‐velocity impact (LVI) behaviors of hybrid sandwich beams with aramid‐fiber‐reinforced polymer (AFRP) faces and ALF core. The failure mode, loading response, and energy absorption of sandwich beams have been obtained experimentally and the failure map with a wide range of dimensional configurations has been established theoretically. Increasing core density significantly enhances the load‐carrying capacity of the sandwich beam, and the enhanced effect becomes more obvious for a thicker core. The medium‐density ALFs provide the maximum specific energy absorption, while the high‐density ALFs offer the highest energy absorption for hybrid sandwich beams. The applicability of core densities in hybrid sandwich structures is provided. Highlights: Normal strain distribution under quasi‐static loading is analyzed using DIC.AFRP face microbuckling provides higher impact resistance than core failure.The applicability of core density in hybrid sandwich structures is given. [ABSTRACT FROM AUTHOR]

Aluminium foam sandwich panels (AFSPs) have a high impact resistance and are suitable for a wide range of engineering applications. To improve corrosion resistance, this paper proposes an anti-corrosion sandwich panel with stainless steel as the upper sheet. Drop hammer impact tests were performed on a total of ten AFSPs to investigate their dynamic response and failure patterns. To assess the deformation performance of AFSPs, a laser displacement meter was used to obtain the bottom centre displacement. The effects of the impact energy and the thickness of each component of AFSPs on the peak impact force and deformation performance were studied. Test results showed that the thickness of each component had notable effects on the impactor and bottom displacements. In addition, the effect of the unit mass of the components in AFSPs on decreasing the bottom displacement was discussed. Compared to increasing the aluminium foam and lower sheet thicknesses, increasing the upper sheet thickness was more effective in decreasing the bottom displacement. A finite element model of AFSPs was developed to conduct parameter analysis, indicating that impactors with larger diameters resulted in higher peak forces and reduced deformation of AFSPs. [ABSTRACT FROM AUTHOR]

This study introduced a novel numerical modeling for the evaluation of a hybrid heat sink design by replacing the solid fins with aluminum foam fins (AFF) for the same thickness of 2 mm within a phase change material (PCM). This innovation is designed to enhance thermal performance in electronic cooling applications. Heat fluxes of 2, 3, and 4 kW/m2 were applied to the base. The performance has been verified at set point temperatures (SPT) of 60°C, 70°C, and 80°C, encompassing a range relevant to various applications. Different AFF thicknesses (4 and 6 mm) and foam porosities (0.85, 0.90, and 0.95) were investigated. The study demonstrated that AFFs improve heat transfer by increasing fin surface area and by effectively raising the thermal conductivity of the PCM. Compared to the SF heat sink, the results show that the AFF design extended the operational time by 5%–8% for the range of heat fluxes. Notably, AFFs with a thickness of 6 mm achieved a significant 41% improvement in the operation time at a lower SPT (60°C). The metal foam porosity of ε = 0.85 exhibited superior thermal performance within the investigated temperature range. This research paves the way for optimizing hybrid heat sink designs using metal foam for efficient thermal management and reduction of weight. [ABSTRACT FROM AUTHOR]

This paper presents a study on heat transfer in two-phase mixtures (air–water and air–oil) flowing through heated horizontal channels filled with open-cell aluminum foams characterized by porosities of 92.9–94.3% and pore densities of 20, 30, and 40 PPI. The research included mass flux densities ranging from 2.82 to 284.7 kg/(m2·s) and heat flux densities from 5.3 to 35.7 kW/m2. The analysis examined the effects of flow conditions, fluid properties, and foam geometry on the intensity of heat transfer from the heated walls of the channel to the fluid. Results indicate that the heat transfer coefficient in two-component non-boiling flow exceeds that of single-phase flow, primarily due to fluid properties and velocities, with minimal impact from flow structures or foam geometry. An assessment of existing methods for predicting heat transfer coefficients in gas–liquid and boiling flows revealed significant discrepancies—up to several hundred percent—between measured and predicted values. To address these issues, a novel computational method was developed to accurately predict heat transfer coefficients for two-component non-boiling flow through metal foams. [ABSTRACT FROM AUTHOR]

The objective of this research paper is to examine the shock-absorption capabilities of sandwich structures that utilize polyurethane foam and aluminum as energy-absorbing materials. A series of drop weight impact tests were conducted on sandwich structures comprising polyurethane foam, aluminum, and concrete. The investigation encompasses variations in the thickness of the polyurethane foam-aluminum absorption layer, the impact height, and different structural combinations, coupled with numerical simulations. Results indicate that as the thickness of the polyurethane foam-aluminum energy absorption layer increases, the energy absorbed by the composite structure also increases. However, the rate of this increase tapers off as the layer thickness continues to grow. The impact height influences energy absorption within a defined range, enabling optimal utilization of the deformation and energy absorption capacities of the polyurethane foam-aluminum layer. Notably, the double-sandwich structure outperforms the single-sandwich structure in terms of impact resistance. The incorporation of the polyurethane foam-aluminum sandwich structure significantly enhances the impact resilience of concrete. Among the tested configurations, the double-sandwich structure composed of polyurethane foam, aluminum, and concrete exhibits the optimal absorption performance. Nevertheless, the layered nature of the structure significantly increases its construction complexity, potentially impacting the practical feasibility of utilizing the polyurethane foam-aluminum-concrete composite structure in real-world applications. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) and their composites are gaining popularity due to their exceptional strength qualities. It is well known that adding CNTs to metal foam composites boosts compressive strength. On the other hand CNT addition is still a costly process due to high cost of the CNTs. This study presents a novel and cost-effective solution by selectively adding CNTs to the structurally weakest regions of aluminum foam materials produced via powder metallurgy, employing a newly developed focused multi-step additive method. The cell borders of aluminum foam are strengthened with multiple spherical layers of CNTs, using a transfer method by initially coating the space holders used at the foaming process. The strength increase effect of this CNT addition method was compared with the widely known aluminum foam production parameters via a 4-parameter design of experiment (DOE) study. Compressive strength values of the samples were evaluated using a constant speed compression test acc. to ISO13314. The compacting pressure, CNT concentration, sintering temperature, and sintering period were chosen as DOE parameters, and 78% of the interactions effecting on final compressive strength could be explained with the model. As a result, it was established that, compared to the other parameters, sintering duration had the highest influence on compressive strength. But besides It has also been shown that adding 0.53% CNT by weight only to the cell border regions increases overall strength by 9%. This weight-strength increase ratio is compared with similar studies in the literature and found to be providing a production cost advantage due to the lower amount of CNT addition requirement for the comparable weight relative strength increase. Focused strength increase method has potential to enable controlled failure of foam materials by selectively strengthening strength critical areas of a component. [ABSTRACT FROM AUTHOR]

In recent years, high-performance lightweight and multifunctional aluminum foam sandwiches (AFSs) can be successfully applied to spacecraft, automobiles, and high-speed trains. Friction stir welding (FSW) has been proposed as a new method for the preparation of AFS precursors in order to improve the cost-effectiveness and productivity of the preparation of AFS. In this study, the AFS precursors were prepared using the FSW process. The distribution of foaming agents in the AFS precursors and the structure and morphology of AFS were observed using optical microscopy (OM), scanning electron microscopy (SEM), and X-ray energy dispersive spectroscopy (EDS). The effects of the temperature and material flow on the distribution of the foaming agent during the FSW process were analyzed through experimental study and numerical simulation using ANSYS Fluent 19.0 software. The results show that the uniform distribution of the foaming agent in the matrix and excellent densification of AFS precursor can be prepared when the rotation speed is 1500 r/min, the travel speed is 25 mm/min, the tool plunge depth is 0.2 mm, and the tool moves along the retreating side (RS). In addition, the experimental and numerical simulations show that increasing the welding temperature improves the uniformity of foaming agent distribution and the area of AFS precursor prepared by single welding, shortening the thread length inhibits the foaming agent from reaching the upper sandwich plate and moving along the RS leads to a more uniform distribution of the foaming agent. Finally, the AFS with porosity of 74.55%, roundness of 0.97, and average pore diameter of 1.192 mm is prepared. [ABSTRACT FROM AUTHOR]

An improved melt foaming method is employed to fabricate composite aluminum foam tubes (CAFTs) with varying diameter ratios, achieving metallurgical bonding between the aluminum foam and aluminum tubes. Based on the structural characteristics of aluminum foam‐filled tubes and traditional numerical formula for calculating the energy absorption properties of metal foams, a new calculation formula is proposed to accurately evaluate energy absorption performance of CAFTs under axial load, enabling more precise numerical calculation of total energy absorption. Furthermore, drop weight impact tests and finite element simulations are conducted to investigate the axial impact performance and deformation mechanism of CAFTs. The influence of diameter ratio on crashworthiness and energy absorption performance is also analyzed. As the diameter ratios decrease, both the impact resistance and total energy absorption of CAFTs increase, while the degree of tube damage gradually decreases. Moreover, finite element simulation results demonstrate that metallurgical combination between aluminum foam and aluminum tubes effectively transfers stress to thin‐walled tubes with better load‐bearing performance, preventing concentrated collapse of aluminum foam core. Additionally, the presence of aluminum foam provides robust restraint against deformation or rupture in thin‐walled tubes. [ABSTRACT FROM AUTHOR]

This study explores the simulation and analysis of the infiltration process for manufacturing A356 aluminum alloy foams using vacuum pressure. The infiltration technique, known for its versatility in liquid-state metal processing, is widely employed for metal foam production due to its ease of application. The study investigates the relationship between the geometric parameters of the preform, system pressure, and filling times, revealing a correlation. The simulation using the Flow 3D software determines the pressure and vacuum time required to achieve successful aluminum foam without filling failures. Experimental validation through infiltration casting using NaCl as a removable preform aligns with the simulated results, yielding high-quality aluminum foam samples with diverse pore sizes (0.5 mm, 1.0 mm, and 2.0 mm), uniform and interconnected pore distribution, average porosity percentages of 65%, and a relative density of 0.35. The research contributes insights into optimizing the infiltration process for aluminum foam fabrication, bridging the gap in limited literature on cellular metals. [ABSTRACT FROM AUTHOR]

An experimental investigation was carried out on high porosity metal foams subjected to array jet impingement with an objective to develop enhanced heat transfer configurations. In this study, we propose an integrated thermal management system (TMS) aimed toward leveraging the conjugate heat transfer capabilities of target plate, metal foam, and the jet plate--all made from aluminum and assembled such that a proper contact between them can be established. Steady-state heat transfer experiments were carried out for 10 and 20 pores per inch (PPI) aluminum foams of 0.93 porosity. Both metal foams were 12.7-mm thick. The normalized jet-to-jet spacing was varied from 2 to 12 times the jet diameter, while the jet diameter was fixed. The ratio of the jet plate thickness and jet diameter (nozzle aspect ratio) was 6.35, which ensured proper development of jets inside the nozzles. Experiments were conducted over a wide range of Reynolds number (based on jet diameter) varied from 100 to 5000. The obtained convective heat transfer coefficient for different configuration was evaluated in context with pressure drop. The analysis of experimental results reveal that large open area ratio jets combined with high porosity metal foams provide highly efficient and high-performance cooling for the investigated range of Reynolds numbers. [ABSTRACT FROM AUTHOR]

To investigate the effect of different thickness ratios of the upper and lower panels on the foam aluminum sandwich panels, this paper conducts three-point bending tests. And use micro-CT technology to perform phased scans of the bending process in the experiment. The results show that, the collapse, splitting, and lateral extrusion of each cell are simultaneously present in three different forms of damage. At a span of 100mm, cell collapse dominates the damage deformation. At spans of 80mm and 60mm, splitting becomes the dominant factor. When the intrusion depth of the loading roller significantly increases, lateral extrusion damage becomes dominant. [ABSTRACT FROM AUTHOR]

Capillary pressure and permeability of porous media are important for heat transfer devices, including loop heat pipes. In general, smaller pore sizes enhance capillary pressure but decrease permeability. Introducing a bi-porous structure is promising for solving this trade-off relation. In this study, the bi-porous aluminum was fabricated by the space holder method using two different-sized NaCl particles (approximately 400 and 40 μm). The capillary pressure and permeability of the bi-porous Al were evaluated and compared with those of mono-porous Al fabricated by the space holder method. Increasing the porosity of the mono-porous Al improved the permeability but reduced the capillary pressure because of better-connected pores and increased effective pore size. The fraction of large and small pores in the bi-porous Al was successfully controlled under a constant porosity of 70%. The capillary pressure of the bi-porous Al with 40% large and 30% small pores was higher than the mono-porous Al with 70% porosity without sacrificing the permeability. However, the bi-porous Al with other fractions of large and small pores did not exhibit properties superior to the mono-porous Al. Thus, accurately controlling the fractions of large and small pores is required to enhance the capillary performance by introducing the bi-porous structure. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of High Pressure Physics is the property of Chinese Journal of High Pressure Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights Interpenetrating phase composites (IPCs) can combine the advantages of each component and have a good application prospect. IPCs were prepared by combining open‐cell aluminum foam (AF) and epoxy resin (EP) in three‐dimensional space in this study. Different contents of silica powder (SP, 80, 100, 120, and 140 wt%) were added to EP to improve the compressive and three‐point bending properties of IPCs. In the bending test, acoustic emission (AE) was applied to track the bending deformation of the samples, and k‐means clustering algorithm was applied to identify the damage modes. The compressive and bending properties of IPCs increased first and then decreased with the increase of SP content, and reached the maximum when the SP content was 100 wt%, with a compressive yield strength of 74.6 MPa and a bending peak load of 1.96 kN. The performance degradation was mainly attributed to the AF/EP debonding due to SP distribution at the interface. The X‐type shear band and EP/AF debonding appeared in compression failures of AF and IPCs, respectively. The AE clustering results showed that under bending load, plastic deformation of matrix (60–200 kHz) and fracture failure (230–340 kHz) modes appeared in AF, while EP/AF debonding (60–120 kHz), EP failure (120–230 kHz) and plastic deformation of foam matrix (230–250 kHz) modes appeared in IPCs. Silica powder was added to improve compressive and bending properties of IPCs. Acoustic emission was used to monitor bending of foam and IPCs firstly. k‐means clustering was used to identify and classify bending damage patterns. [ABSTRACT FROM AUTHOR]

In this paper, we numerically investigate the dynamic response and explosion resistance of gradient aluminum foam sandwich tubes subjected to external blast loads. Based on 3D-Voronoi technology, we construct density-graded aluminum foam cores to systematically explore the influence of core density distribution, density gradient, and average relative density on the protective performance of these structures. Our primary objective is to identify optimal design parameters that maximize explosion mitigation capabilities while balancing energy absorption and specific energy absorption capacities. The research results show that a positive gradient core configuration exhibits superior anti-explosion performance, significantly outperforming its uniform and negatively graded counterparts, particularly when the gradient value is substantial. For the positive gradient cores, an increase in the gradient value leads to a corresponding enhancement in explosion resistance. Conversely, in negatively graded cores, a higher gradient value diminishes the anti-explosion performance. Furthermore, while augmenting the relative density of the core layer does improve the overall explosion resistance of the sandwich tube, it comes at the cost of reduced energy absorption and specific energy absorption capabilities, highlighting the need for a delicate balance among these competing factors. [ABSTRACT FROM AUTHOR]

In this paper, three‐phase composites were made by combining N220 carbon black rubber powder with open‐cell aluminum foam and epoxy resin with mass fractions of 3 %, 5 %, and 7 %, respectively. The mechanical and energy absorption properties of three groups of epoxy resin/rubber powder/aluminum foam three‐phase composites with added aluminum foam and different mass fractions of N220 carbon black rubber powder were analyzed during quasi‐static compression at a compression rate of 2 mm/minute. The mechanical parameters in the quasi‐static compression experiments were compared with those of the two‐phase composites of epoxy resin/rubber powder with no added aluminum foam. Finally, the micro‐morphology of the composites after quasi‐static compression damage was observed by scanning electron microscopy. The results show that the collapse deformation of aluminum foam during compression affects the stability of the epoxy resin/rubber powder composite matrix and reduces the toughness of the epoxy resin/rubber powder composite matrix. [ABSTRACT FROM AUTHOR]