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1

Neural Networks in Crashworthiness Analysis of Thin-Walled Profile with Foam Filling

Rogala Michał

Advances in Science and Technology. Research Journal

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2020

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Vol. 14, no 3

93--99

EN

This article presents the numerical tests of thin-walled compressed columns with a square cross-section. The crush efficiency indicators were determined using the finite element method (Abaqus) and neural networks of MLP. The models had a constant circular trigger, with a diameter of 32 mm. During dynamic analysis, the samples were loaded with 1700 J. The numerical models were filled with aluminum foam from 40 mm to 180 mm every 20 mm. The study presents the conclusions for the thin-walled models with crushable foam.

2

Optimizing glue joint of aluminium metallic foams

Nowacki J., Sajek A.

Journal of Achievements in Materials and Manufacturing Engineering

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2016

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Vol. 75, nr 1

14--23

EN

Purpose: Characteristics of aluminium foams as construction material were given, along with some exemplary applications. The purposefulness of lowering the mass of constructions comprising aluminium foams was discussed, and bonding techniques as well as prospects of reducing the mass of a joint were analysed. A computer simulation was performed for a representative fragment of a glue joint in aluminium foam with the purpose of analyzing existing stresses for three variants of thickness of a layer of epoxy glue. Design/methodology/approach: Preliminary tests on the complete test specimen were conducted, and then a new model of a joint was made, based on a small part of the geometry of the joint. The methodology employed allowed for a precise investigation of the working conditions of a glue joint in a statics hear test depending on the thickness of a layer of glue. Findings: A high interdependence between stresses in a metallic foam and the thickness of a glue joint was observed – the thicker the layer of glue, the stiffer the joint. The thickness of the glue layer inspected in the simulation does not influence the strength of the joint. Research limitations/implications: The tests were conducted with the use of an improved yet simplified model of a joint that allowed to determine stresses present both in metallic foam and in the weld. Further course of action in the modelling of glue joints was set with the aim of establishing a more detailed definition of weld work conditions. Practical implications: Basic factors affecting the efficiency of joining aluminium foams by means of gluing were defined, and guidelines concerning the technology for producing a proper joint were given. Originality/value: A problem concerning gluing aluminium foams with regard to mass optimization was highlighted. A mechanism for minimizing stresses in the structure of a weld through the regulation of weld thickness was presented.

3

Experimental Study On Fracture Property Of Double Cantilever Beam Specimen With Aluminum Foam

Kim Y. C., Choi H. K., Cho J. U.

Archives of Metallurgy and Materials

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2015

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Vol. 60, iss. 2B

1151--1154

EN

This study aims to investigate double cantilever beam specimen with aluminum foam bonded by spray adhesive to investigate the fracture strength of the adhesive joint experimentally. The fracture energy at opening mode is calculated by the formulae of British Engineering Standard (BS 7991) and International Standard (ISO 11343). For the static experiment, four types of specimens with the heights (h) of 25 mm, 30 mm, 35 mm and 40 mm are manufactured and the experimental results are compared with each other. As the height becomes greater, the fracture energy becomes higher. After the length of crack reaches 150 mm, the fracture energy of the specimen (h=35 mm) is greater than that of the specimen (h=40 mm). Fatigue test is also performed with DCB test specimen. As the height decreases, the fracture energy becomes higher. By the result obtained from this study, aluminum foam with adhesive joint can be applied to actual composite structure and its fracture property can possibly be anticipated.

4

Analiza numeryczna dynamicznego oddziaływania fali ciśnienia na złożoną strukturę panelu energochłonnego

Panowicz R., Kołodziejczyk D., Sybilski K., Barnat W., Niezgoda T.

Przegląd Mechaniczny

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2012

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nr 11

40--45

PL

W artykule przedstawiono wyniki weryfikacji oddziaływania fali ciśnienia pochodzącej z detonacji ładunku wybuchowego TNT na wielowarstwowy panel energochłonny zawierający warstwę piany aluminiowej. Na podstawie tych wyników określono obszar zmian, które powstały w panelu na skutek wymuszenia. W badaniach rozważono przypadki oddziaływania fali ciśnienia o różnej intensywności. Na początku przeprowadzono badania doświadczalne, a następnie, na ich podstawie, dokonano walidacji modelu numerycznego opisującego zjawisko oddziaływania fali. Do analiz zjawisk szybkozmiennych użyto nieliniowej metody elementów skończonych zawartej w programie LS-Dyna.

EN

The comparison between numerical and experimental results of a blast wave originating from detonation of a TNT explosive charge on the multilayered energy absorbing panel containing a layer of aluminum foam were presented in the paper. Deformation of the panel forced by the pressure wave was determined based on these results. The influence of pressure intensity on the investigation results was considered. At the beginning, experimental studies were performed, and then, on this basis, validation of the numerical model describing the phenomenon of fluid structure interaction was carried out. A nonlinear finite element method implemented in LS-Dyna software was used in dynamic phenomena analysis.

5

Badania eksperymentalne i modelowanie piany aluminiowej alporas

Klasztorny M., Małachowski J., Dziewulski P., Nycz D., Gotowicki P.

Modelowanie Inżynierskie

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2012

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T. 12, nr 43

97-112

PL

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.

6

Numerical and experimental study of real foam microstructure models

Miedzińska A., Szymczyk W.

Journal of KONES

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2010

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Vol. 17, No. 2

309-314

EN

Metal foams are new, as yet imperfectly characterized, class of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. They offer a potential for lightweight structures, for energy absorption, and for thermal management; and at least some of them are cheap. Such characteristics have been appreciated by the automotive industry in the aspect of crash and impact phenomenon. Energy absorption capacity of foams under dynamic load was analytically confirmed based on a rigid-perfectly plastic-locking foam model. In this paper the development process of a real closed cell foam microstructure based on finite element model with the use of SD scanning is shown. Computed tomography (CT) is a medical imaging method employing tomography created by computer processing. Digital geometry processing is used to generale a three-dimensional image of the inside of an object from a large series of two-dimensional X-ray images taken around a single axis of rotation. The numerical analyses carried out with the usage of LS Dyna computer code of the quasi static and dynamic compression tests are presented. The most important mechanisms and phenomena that appeared in the microstructural sample are described. In the final part of these investigations the comparison process between numerical and experimental test was performed. The results confirmed the good correspondence between both tests.

7

Blast loading on aluminum foam microstructure

Miedzińska D., Panowicz R.

Journal of KONES

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2010

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Vol. 17, No. 3

287-292

EN

One of the possible options as a material for protective layers is aluminum foams which become also very popular due to their lightweight and excellent plastic energy absorbing properties. Such characteristics have been appreciated by the automotive industry with continued research to further understand foam properties. Compressed foaming materials exhibit extensive plastic response, while the initial elastic region is limited in tension by a tensile brittle-failure stress. Aluminum foams have become also an attractive material as blast protective layers due to their desirable compressive properties. With different material engineering techniques (as, for example double-layer foam cladding) they can be customized to achieve the most desirable properties. Energy absorption capacity of foams microstructures under blast load was analytically confirmed based on a rigid-perfectly plastic-locking foam model Initial research indicates that energy absorbed by the cladding is much larger than that under quasi-static conditions due to strain rate effect. In this paper a numerical model of a closed cell aluminum foam idealistic microstructure was presented. The quasi static compression tests were carried out with the use of LS Dyna computer code. Then the sample was numerically loaded with the blast wavefrom detonation of explosives and its behavior was analyzed. The results ofboth analyses were compared.

8

Aluminium foam testing for impact energy absorption aims

Niezgoda T., Miedzińska D.

Journal of KONES

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2009

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Vol. 16, No. 3

283-289

EN

Aluminium foams are a new group of materials used for impact energy absorbing elements. They are light (typically 10-25% of the density of the metal they are made of) and stiff, and are frequently proposed as a light weight structural material. That is why they often are applied in automotive and transport industry solutions, for example as parts of bumpers. The methods of numerical modelling for open and closed cell aluminium foams are presented in the paper as well as closed and open cellfoam microstructure model. The numerical models of foam ideal microstructures created with shell finite elements are shown. The models were developed on the basis of Kefain tetrakaidecahedrons - structures consisting of six squares and eight hexagons. In the case of closed cell foams, the polyhedron with full walls was adopted. In the case of open cell foams the circle wholes were removed from polyhedron surfaces. Then the numerical analysis of a created models compressive test was carried out with the usage of LS Dyna computer code. The nonlinear procedures were applied. The results were analyzed in the scope of energy absorbing properties of aluminium foams.

9

Behaviour of aluminum foam under fire conditions

Grabian J., Gawdzińska K., Szweycer M.

Archives of Foundry Engineering

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2008

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Vol. 8, iss. 2

41-44

EN

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.

10

Absorpcja energii przy odkształceniach ściskających pian aluminiowych

Koza E., Leonowicz M., Wojciechowski S., Pakieła Z.

Inżynieria Materiałowa

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2003

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R. XXIV, nr 6

322-324

PL

Piany aluminiowe wytworzono metodą metalurgii proszków ze stopu AlSi10 z dodatkiem środka spieniającego w ilości 0,9 % wag. TiH2. Otrzymane piany poddano pomiarom gęstości i jednoosiowej próbie ściskania, z różną szybkością odkształcania w zakresie 3,3x10 do potęgi -3 /s - 1,66x10 do potęgi -1 /s i 5/s - 55/s. Oceniono wpływ szybkości odkształcenia na zaabsorbowaną energię i wytrzymałość na ściskanie. Przeprowadzone badania wykazały, że zwiększanie szybkości odkształcania w badanym zakresie powoduje wzrost zaabsorbowanej przez piany energii, a także nieznaczne zmniejszenie wytrzymałości na ściskanie sigma c. Zaabsorbowaną energię obliczono przy zastosowaniu dwóch różnych metod wyznaczania odkształcenia, przy którym rozpoczyna się zagęszczanie piany (epsilon D). Zmierzona wartość epsilon D maleje ze wzrostem gęstości pian i szybkości ich odkształcania.

EN

Aluminium foams were produced by powder metallurgy method from AlSi10 alloy with addition of 0,9 wt. % of foaming agent (TiH2). The foams were subjected to density measurements and uniaxial compressive tests with different strain rates in the ranges of 3,3x10 to the -3 /s - 1,66x10 to the -1 /s and 5/s - 55/s. The influence of strain rate on the absorbed energy and compressive strength were investigated. The results showed that increase of strain rate, in the investigated range, leads to increase of the absorbed energy, as well as to slight decrease of compressive strength, sigma c. Absorbed energy was calculated using two different methods for determination of the strain values at which foam densification starts (epsilon D). The epsilon D values measured from the stress-strain curves decrease with increase of the foam density and strain rate.

11

Analiza strukturalna pian aluminiowych

Koza E., Leonowicz M., Wojciechowski S.

Kompozyty

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2002

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R. 2, nr 4

229-232

PL

Uzyskano piany aluminiowe ze stopu AISi12Mg1-1%TiH2 wykonane metodą metalurgii proszków. Otrzymane w różnych temperaturach piany poddano pomiarom gęstości, analizie strukturalnej i jednoosiowej próbie ściskania. Przeprowadzone badania wykazały, że wraz z malejącą gęstością (będącą wynikiem wzrostu temperatury spieniania) maleją liczba porów na jednostkę powierzchni NA i powierzchnia względna w objętości jednostkowej SV, a objętość porów VV rośnie. Nieco inną charakterystykę przedstawia piana o gęstości względnej 0,2, która ma najbardziej jednorodną strukturę pod względem wielkości i kształtu porów. Piana ta charakteryzuje się również najwyższą względną wytrzymałością na ściskanie (bc/d = 37 MPa; bc - wytrzymałość na ściskanie, d = plps - gęstość względna). Tylko piany o gęstości względnej mniejszej od 0,3 wykazują charakterystyczne dla pian tzw. plateau.

EN

The precursor material, in a form of a rectangular rod 20x5 mm, was prepared by extrusion of a mixture of powders: AISi12Mg1-1%TiH2. The samples of the precursor rod (20x20x5 mm) were foamed at temperatures in the range of 600:800°C, in times 3:30 min. The density of the foams was measured after removing their surface metallic skin, which for small samples had a substantial influence on the mechanical properties. The foam structure was studied using computer image analysis method. The foams, which were foamed at various temperatures, exhibited different structure (Fig. 1). Even without special analysis one can see that the foam, which had relative density 0.2, exhibited most regular and homogeneous pore structure. In Figure 2a the parameters such as relative number of pore sections Na, relative pore area within a unit volume Sv and relative pore volume Vv are plotted versus relative density. With decreasing density the volume parameter Vv increased and the parameters SV and na decreased. However, when the pores in the walls were neglected the parameters, na and Sv showed a maximum for the foam, which had relative density 0.2. The dependence for Vv did not change (Fig. 2b). The calculated values of average pore size and shape of pores were substantially influenced by the small pores in the walls. The best structural homogeneity, represented by the narrow distribution of equivalent diameter - d2, was found again for the foam having relative density 0.2 (fig. 4). The foams processed at temperatures lower and higher than 700°C exhibited much broader distribution of the pore size. The lowest density foams showed large pores with the equivalent diameter up to 7:8 mm. The appearance of very large pores for the foams, which had been processed at high temperature, was supposed to be caused by a fast growth of small pores and their interconnections. Another significant parameter in structural analysis of metallic foams is the pore shape. For the characterisation of the pore shape such parameters as the elongation and convexity were calculated. The most circular pore structure showed the foam with relative density 0.2. The foams were subjected to the compressive tests. The deformation was parallel to the foaming direction. The specimens having densities between 0.1 and 0.26 exhibited curves typical of foam materials with characteristic, extended plateau, ranging up to 60% strain (Fig. 5). The sample with density 0.49 did not show plateau. The highest relative compressive strength (37 MPa) attained the foam having relative density 0.2. The best mechanical properties exhibited foam, which had the maximum value of stereological parameters Sy and NA and the most regular and homogeneous pore structure. The experiments proved that the mechanical properties of aluminium foam depend not only on their density, but also on the pore structure.