Taking into account fire-protection requirements it is advantageous for aluminum foam, after melting at a temperature considerably exceeding the melting point, to have a structure of discontinuous suspension of solid inclusions to liquid metal instead of liquid consistency. Continuity of the suspension depends on the solid phase content. The boundary value of the phase determined by J. Śleziona, above which the suspension becomes discontinuous, is provided by the formula (1). Figure 1 presents the relationship graphically. Boundary values of the v_s content resulting from the above relationship is too low, taking into account the data obtained from the technology of suspension composites [4]. Therefore, based on the structure assumed for the suspension shown in Figure 2 these authors proposed another way of determining the contents, the value of which is determined by the relationship (3) [5]. For purposes of the experimental study presented in the paper two foams have been molten: a commercially available one, made by aluminum foaming with titanium hydride, and a foam manufactured in the Marine Materials Plant of the Maritime University of Szczecin by blowing the AlSi7 +20% SiC composite with argon. Macrophotographs of foam cross-sections are shown in Figure 3. The foams have been molten in the atmosphere of air at a temperature of 750°C. The products of melting are presented in Figure 4. It appears that molten aluminum foam may have no liquid consistency, being unable to flow, which is a desired property from the point of view of fire-protection. The above feature of the molten foam results from the fact that it may be a discontinuous suspension of solid particles in a liquid metal. The suspended particles may be solid particles of the composite that served for making the foam or oxide membranes formed on extended metal surface of the bubbles included in the foam. The desired foam ability to form a discontinuous suspension after melting may be intensified by insertion of solid particles into the metal serving for foam formation.
Przedmiotem badań eksperymentalnych i modelowania numerycznego jest piana ze stopu aluminium, o porach zamkniętych (nazwa handlowa Alporas), o gęstości 0.22 g/cm3 i kompozycji Al + 1,5 procent Ca + 1,5 procent Ti. Na podstawie danych literaturowych przyjęto, że piana jest izotropowa po homogenizacji. Przeprowadzono próby wytrzymałościowe ściskania jednokierunkowego, rozciągania jednokierunkowego oraz ścinania w płaszczyźnie prostopadłej do arkusza piany. Pianę po homogenizacji opisano modelem materiałowym MAT 026 w systemie LS-Dyna. Do walidacji eksperymentalnej modelowania numerycznego procesów quasi-statycznych w elementach z piany Alporas zaproponowano próbę ściskania jednokierunkowego statycznego pod kątem 20 ° do osi próbki sześciennej (jednoczesne ściskanie, ścinanie i zginanie). Wyznaczono wartość współczynnika proporcjonalności (wymaganego w przypadku modelu MAT 026) krzywej ścinania w funkcji odkształcenia objętościowego do krzywej ściskania również w funkcji odkształcenia objętościowego, przy której uzyskano zgodność symulacji z eksperymentem.
EN
The study presents the experimental investigations and numerical modelling of closed-cell aluminium alloy foam (trade name Alporas), with 0.22 g/cm3 density and structural composition Al + 1,5 per cent Ca + 1,5per cent Ti. The considerations are under assumption of homogenization and isotropy of the foam material. Three basic strength tests have been conducted, i.e. the unidirectional compressive test, the unidirectional tensile test, the shear test in the piane perpendicular to the foam sheet. The homogenized foam has been described with MAT 26 material model implemented in FE code LS-Dyna. In order to validate experimentally numerical modelling of quasi-static processes in elements made of Alporas foam the unidirectional compressive static test at 20 ° angle with respect to the specimen axis (simultaneous compression, shear and bending) is proposed. The coefficient expressing proportionality of the shear curve vs. volumetric strain to the compression curve vs. volumetric strain has been determined, at which the simulation and the experiment are in good conformity.
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