Fig 6 - uploaded by Dirk Lehmhus
Content may be subject to copyright.
Source publication
Since their re-discovery by the scientific world at the beginning of the last decade, closed cell metal foams for structural applications have found their way into series production. However, most of today's real world applications do not rely solely on the porous metal. In contrast, the components in question tend to combine the foam with various...
Similar publications
In our current work, AZ31 magnesium alloy foams with closed-cell were successfully fabricated by melt foaming method using Ca and CaCO3 as thickening and blowing agent, respectively. The influences of porosity and pore size on the quasi-static compressive properties of the foams were systematically investigated. The results showed that the yield st...
The novel structure of metallic foams is of interest in the design of next-generation debris shields as it introduces physical mechanisms that are advantageous to hypervelocity impact shielding (e.g. increased fragmentation/melt/vaporization, energy dissipation, etc.). Preliminary investigations have shown improved shielding capability over traditi...
The sound absorption ability of metallic foams is discussed with respect to the preparation method of foam, material composition, foam porosity, thickness, structure, and various treatments to make the foam structure permeable for sound. Both powder metallurgical route prepared foams and melt route prepared foams were studied. It was observed that...
The zinc foam was studied in the porosity range of 78-91 %. It was found that to foam zinc it is necessary to overheat significantly the foam above the melting temperature of metal or to use higher amount of foaming agent. Deformation behaviour of zinc foams is comparable to aluminium foams behaviour: compression strength of zinc foams is significa...
Citations
... The cellular materials offer excellent attractive combinations of mechanical properties [1][2][3][4][5]. Therefore, these materials have a potential of use in various structural applications, mainly in the automotive, aerospace and aeronautic industries [6][7][8][9][10][11]. The growing interest in the use of these materials is due to their high stiffness rigidity for a certain density and also due to their high capacity of absorbing energy under low stress values [6]. ...
Thermo-mechanical properties of cellular materials, "metallic foams" make them very attractive in a variety of engineering applications. During plastic deformation of closedcell metallic foams, part of plastic work is converted into heat. The generated heat increases may be quantified using an infrared camera measuring radiation emitted on the surface of the metallic foam. Experimental tests were carried out under quasi-static loading conditions using Zn-22Al-2Cu (zinalco) foams featuring different pore sizes, and densities between 30% to 50% maintaining constant volume. The goal of this study was to analyse the effect of heat generation during quasistatic compression of metallic foams at constant strain rate. Some conclusions on the mechanical behaviour were obtained in terms of temperature increase, the nominal stress-strain curves and relative density.
... What is surprising is that bonding between foam and skin appears to be detrimental on the performance. This is not in agreement with previous results [17]. In order to obtain a physical interpretation of these results, an FEM analysis of the tests was performed, run with Abaqus explicit. ...
The role of an anti-intrusion bar for automotive use is to absorb the kinetic energy of the colliding vehicles that is partially converted into internal work of the members involved in the crash. The aim of this paper is to investigate the performances of anti-intrusion bars, made by tubes filled with aluminium foams. The reason for using a cellular material as a filler deals with its capacity to absorb energy during plastic deformation, while being lightweight. The study is mainly conducted by evaluating some key technical issues of the manufacturing problem and by running experimental and numerical analyses. The evaluation of materials and shapes of the closed sections to be filled is made in the perspective of a car manufacturer (production costs, weight reduction, space availability in a car door, etc.). Experimentally, foams are produced starting from an industrial aluminium precursor with a TiH2 blowing agent. Empty and foam filled tubes are tested in three point bending, in order to evaluate their performances in terms of several performance parameters. Different manufacturing conditions, geometries and tube materials are investigated. The option of using hydroformed tubes, with non constant cross section, for the production of foam filled side structures id also discussed.
... The properties of metal foams depend on many morphological features, such as pore size distribution, cell wall curvature, defects, etc [6]. It has been shown that with increasing porosity, most properties including strength, stiffness and, conductivity decrease exponentially [7]. Produce Aluminum foam by an economical method has been come to attention while having good foaming behavior, posse's good mechanical properties. ...
Metal foams are among those new materials that are recently used for many industrial applications for their special properties. An economical innovation procedure has been proposed to produce metal foams. In this innovation method, It used to silicone rubber granules as spacer to make voids and cellular structure in molten Aluminum (A356). The effect of size and percent of silicone granules on mechanical behavior and density of Metal foams has been studying.
... The length of the tubes during experiments was set at 240 mm. The maximum intrusion δl max considered is 48 mm which correspond to a vertex angle θ of 132,84°, comparable with the vertex angle of a real anti-intrusion bar deformed at δl max =120 mm, that is a typical maximum prescribed value for these components [7]. ...
... What is more surprising is that bonding between foam and skin appears to be detrimental on the performance. This is not in agreement with previous results [7]. In order to obtain a physical interpretation of these results, an FEM analysis of the tests was performed, run with Abaqus explicit. ...
The role of an anti‐intrusion bar for automotive use is to absorb the kinetic energy of the colliding bodies that is partially converted into internal work of the bodies involved in the crash. The aim of this paper is to investigate the performances of a new kind of anti‐intrusion bars for automotive use, filled with metallic foams. The reason for using a cellular material as a filler deals with its capacity to absorb energy during plastic deformation, while being lightweight. The study is the evolution of a previous paper presented by the authors at Esaform 2010 and will present new results and findings. It is conducted by evaluating some key technical issues of the manufacturing problem and by conducting experimental and numerical analyses. The evaluation of materials and shapes of the closed sections to be filled is made in the perspective of a car manufacturer (production costs, weight reduction, space availability in a car door, etc.). Experimentally, foams are produced starting from an industrial aluminium precursor with a
TiH
2
blowing agent. Bars are tested in three point bending, in order to evaluate their performances in terms of force‐displacement response and other specific performance parameters. In order to understand the role of interface between the inner surface of the tube and the external surface of the foam, different kinds of interface are tested.
... However, if you provide ideal material composition together with appropriate production parameters, quite homogeneous foam structure can be obtained by powder metallurgy route. Number of methods have been developed for manufacturing metals foams including casting, powder pressing, metallic deposition and sputter deposition [8][9][10][11]. This paper will focus on foam with powder metallurgy route, called Fraunhofer process. ...
Powders metallurgy route was used to produce foams from pure Al powders and pre-alloyed Al alloy powders (Alumix 231) with or without reinforcing elements addition. Both classical Al foam and spherical Al foam were produced with various production parameters and the results obtained have been discussed. SiC particles were used as reinforcing elements and TiH2 powders were used as foaming agent. Prior to compaction process, Al powders, reinforcing element and foaming agent were mixed in a three dimensional turbula for 30 min. Mixed powders were compacted, sintered and deformed and then foamed at 690 oC for spherical foam and 710 oC for classical foam. Effect of volume fraction of reinforcing elements, foaming temperatures and foaming agent amounts on the foaming behavior, pore structure, pore distribution, linear expansion rate, density and wall thickness of the cell were investigated. Experimental studies have shown that 1% foaming agent and 4 % SiC addition was found to be the most suitable for foaming. In general foam produced from Alumix 231 powders exhibited more homogenous pore structure compared to the ones produced from pure Al powders.
... However, a recent study by Contorno et al [115] showed [119]. An example of an application given by Stöbener et al [120] is a frontal crash energy absorber for a suburban railcar. ...
Incremental sheet forming (ISF) is a flexible process where an indenter moves over the surface of a sheet of metal to form a 3D shell incrementally by a progression of localised deformation. Despite extensive research into the process, the deformation mechanics is not fully understood. This thesis presents new insights into the mechanics of ISF applied to two groups of materials: sheet metals and sandwich panels. A new system for measuring tool forces in ISF is commissioned. The system uses six loadcells to measure reaction forces on the workpiece frame. Each force signal has an uncertainty of ±15 N. This is likely to be small in comparison to tool forces measured in ISF. The mechanics of ISF of sheet metals is researched. Through-thickness deformation and strains of copper plates are measured for single-point incremental forming (SPIF) and two-point incremental forming (TPIF). It is shown that the deformation mechanisms of SPIF and TPIF are shear parallel to the tool direction, with both shear and stretching perpendicular to the tool direction. Tool forces are measured and compared throughout the two processes. Tool forces follow similar trends to strains, suggesting that shear parallel to the tool direction is a result of friction between the tool and workpiece. The mechanics of ISF of sandwich panels is investigated. The mechanical viability of applying ISF to various sandwich panel designs is evaluated by observing failure modes and damage under two simple tool paths. ISF is applicable to metal/polymer/metal sandwich panels. This is because the cores and faceplates are ductile and largely incompressible, and therefore survive local indentation during ISF without collapse. Through-thickness deformation, tool forces and applicability of the sine law for prediction of wall thickness are measured and compared for a metal/polymer/metal sandwich panel and a monolithic sheet metal. The mechanical results for ISF of sheet metals transfer closely to sandwich panels. Hence, established knowledge and process implementation procedures derived for ISF of monolithic sheet metals may be used in the future for ISF of sandwich panels.
... Bunlar arasında en yaygın olarak ergiyik içerisine gaz enjekte edilmesi, ergiyik içerisine köpürtücü madde ilavesi ve toz metalurjisi IFAM yöntemleri sayılabilir. [2,4567. Toz Metalurjisi (TM) yöntemi, metal köpüklerin üretimi için en yaygın kullanılan yöntemlerden biridir ve bu alanda yoğun çalışmalar yapılmaktadır [8]. ...
... Toz Metalurjisi (TM) yöntemi, metal köpüklerin üretimi için en yaygın kullanılan yöntemlerden biridir ve bu alanda yoğun çalışmalar yapılmaktadır [8]. Bu yöntemle, bilinen basit köpük üretiminin yanı sıra sandviç köpük, küresel köpük, içi boş kalıp veya profil içerisinde köpürtme yapılabilmektedir [7]. Bunlara ilave olarak köpük malzemenin mekanik özelliklerini artırmak amacıyla parçacık takviyeli köpük üretimi de yapılmaktadır. ...
In this study pure Al and pre-alloyed Al alloy powders (Alumix 231- Al-Cu %2.5-Mg %0.5-Si %14) with or without reinforcing elements were used to produce classical Al foam or spherical Al foam with various production parameters by using powder metallurgy route and the results obtained have been discussed. Al2O3 and SiC particles were used as reinforcing elements and TiH2 powders were used as foaming agent. Al powders, reinforcing element and foaming agent were mixed in a three dimensional turbula for 30 min. Mixed powders were compacted, sintered and deformed and then foamed at various foaming temperatures. Effect of reinforcing elements, foaming temperature and foaming agent amount on the foaming behavior, pore structure, pore distribution, linear expansion coefficient, density and wall thickness of 1. Giriş
The work presents the development of a process to produce metallic cellular materials with different pore configurations, from commercial purity Al powder associated with preremovable organic space holders (sugar grains) and/or non-removable ceramic space holders (hollow glass micro spheres). Processing parameters were optimized and the following sort of cellular products were obtained: with coarse open pores, fine open pores, closed pores, coarse open + closed pores and fine open + closed pores. Products were analysed concerning cellular architecture, metallic walls micro structure, density, porosity, acoustic absorption ability, electrical resistivity and mechanical behaviour under compression in semi-static and dynamic tests. Physical and mechanical properties were related to the material's architecture and density. Products presented relative density from 0.6 to 0.9; acoustic absorption varied from 18 to 30%, indicating their classification as reflecting materials; presence of glass spheres in the metallic walls did not affected the acoustic behaviour. Values of electrical resistivity were in the range of 22.10-4 Ω.m and 33.10-4 Ω.m with higher values for products with higher walls/pores ratio, in the open pores material. Products with two types of pores (open + closed) presented electrical resistivity 15% higher than open pores products. Results on mechanical properties showed that the simultaneous presence of closed and open cells does not significantly influence the values of compression tension, but does contribute to higher homogeneity of the plastic deformation plateau. In dynamic tests, the cellular products presented absorption ability of 51 to 65% of the impact energy. Presence of glass micro spheres in the cell walls as closed pores, promoted reduction of 25% in the compression tension and increase of 20% of absorbed impact energy, compared to the other cellular materials investigated.
Advanced porous materials are a new group of materials where the desired properties can be controlled and even tailored. These interesting materials offer a vast field of applications, thanks to their multi-functional abilities. Several types of advanced porous structures including cellular metals and ceramic porous materials are the focus of the present investigation. Corevo® foam and perlite metallic syntactic foam are investigated in this thesis and manufactured from infiltration casting. In addition, advanced pore morphology foam elements are addressed that are fabricated using thermal expansion of a thin wire-shaped precursor. Ceramic porous structures specially developed (via foam replication) for tissue engineering scaffolds are also studied within the scope of this work. Given the similarity of the geometrical structure of all these materials, the same mechanical characterisation approaches are adopted to assess their mechanical properties. The materials properties are determined for quasi-static and dynamic compression for both small and large strain deformation. Numerical simulations are performed by making use of the highly accurate models obtained from micro-computed tomography data. Where possible, numerical results are verified by the findings of experimental testing. Detailed analysis is included in each chapter elaborating the result from the numerical simulations and the compressive loading test. Versatile tools such as electron microscopy, image based geometry analyser software and IR-thermal imaging are utilised to assist the study. The results show that all cellular metals investigated in this thesis exhibit the characteristic stress-strain curve of metallic foams. This means that a linear slope is found in the beginning of the compression loading, this is followed by a long plateau region indicating energy absorption capability and ends with a steep slope at the end representing the densification. Corevo® foam exhibits a significant amount of mechanical anisotropy in casting direction under quasi-static compressive loading. The degree of mechanical anisotropy is considered mild for perlite metallic syntactic foam in the casting direction under the same loading condition. Foam materials (Corevo® and advanced pore morphology foam element) characterised under dynamic loading show a strain-rate dependence property. Last, but not least, a possible extension of the present research is proposed at the end of this thesis in the Conclusions and Outlook section.
Applications of sandwich panels as 3D shells are limited by the high costs of tooling required for conventional forming operations. This paper presents an investigation into whether incremental sheet forming (ISF) would be mechanically feasible alternative means to form sandwich panels. Process feasibility is assessed through examination of failure modes, thinning and surface quality after application of ISF to various sandwich panel designs. It is shown that ISF can be applied to sandwich panels which have ductile and largely incompressible cores. For a formable sandwich panel, the influence of ISF on the panel and a metal sheet of comparable plastic bending moment were evaluated. Similar trends in tool forces were observed, the sine law had similar accuracy in predicting thinning and the through-thickness deformation was similar for both materials. It is shown that 3D sandwich shells with aluminium foam cores can be produced by using ISF to form a precursor expandable material and that ISF can be used to form impressions on one surface of metal foam core sandwich panels. Failure mode maps are proposed as a future means to represent the boundaries of safe forming regions.
