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1

Investment Casting of AZ91 Magnesium Open-Cell Foams

Kapłon Honorata, Dmitruk Anna, Naplocha Krzysztof

Archives of Foundry Engineering

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2023

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Vol. 23, iss. 1

11--16

EN

The process of investment casting of AZ91 magnesium alloy open-cell porosity foams was analysed. A basic investment casting technique was modified to enable the manufacturing of magnesium foams of chosen porosities in a safe and effective way. Various casting parameters (mould temperature, metal pouring temperature, pressure during metal pouring and solidifying) were calculated and analysed to assure complete mould filling and to minimize surface reactions with mould material. The foams manufactured with this method have been tested for their mechanical strength and collapsing behaviour. The AZ91 foams acquired in this research turned out to have very high open porosity level (>80%) and performed with Young’s modulus of ~30 MPa on average. Their collapsing mechanism has turned out to be mostly brittle. Magnesium alloy foams of such morphology may find their application in fields requiring lightweight materials of high strength to density ratio or of high energy absorption properties, as well as in biomedical implants due to magnesium’s high biocompatibility and its mechanical properties similar to bone tissue.

2

Mechanical and Thermal Properties of Aluminum Foams Manufactured by Investment Casting Method

Dmitruk Anna, Kapłon H., Naplocha K.

Archives of Foundry Engineering

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2022

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Vol. 22, iss. 1

37--42

EN

A method for the open-cell aluminum foams manufacturing by investment casting was presented. Among mechanical properties, compressive behaviour was investigated. The thermal performance of the fabricated foams used as heat transfer enhancers in the heat accumulator based on phase change material (paraffin) was studied during charging-discharging working cycles in terms of temperature distribution. The influence of the foam on the thermal conductivity of the system was examined, revealing a two-fold increase in comparison to the pure PCM. The proposed castings were subjected to cyclic stresses during PCM’s subsequent contraction and expansion, while any casting defects present in the structure may deteriorate their durability. The manufactured heat transfers enhancers were found suitable for up to several dozen of cycles. The applied solution helped to facilitate the heat transfer resulting in more homogeneous temperature distribution and reduction of the charging period’s duration.

3

Evaluation of Properties of Cast Metal Foams with Irregular Inner Structure

Kroupová I., Lichý P., Ličev L., Hendrych J., Souček K.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 4

1847--1851

EN

Internal structure of metal foams is one of the most important factors that determine its mechanical properties. There exists a number of methods for studying the nature of the inner porous structure. Unfortunately most of these processes is destructive and therefore it is not possible to reuse the sample. From this point of view, as a suitable method seems to be the ability of using the so-called X-ray microtomography (also micro-CT). This is a non-destructive methodology used in a number of fields (industry, science, archaeology, medicine) for a description of the material distribution in the space (e.g. pores, fillers, defects, etc.). In principle, this technology works on different absorption of X-ray radiation by materials with changing proton number. The contribution was worked out in collaboration with experts from the Faculty of Electrical Engineering and Computer Science of the VŠB-Technical University of Ostrava and it is focused on the analysis of internal structure of the metal foam casting with irregular arrangement of internal pores by using micro-CT. The obtained data were evaluated in the commercial software VGStudio MAX 2.2 and in the FOTOMNG system. For the evaluation of these data a new specialized module was introduced in this system. Several methods of pre-processing the image was prepared for the measurement. This preliminary processing consists, for example, from a binary image thresholding for better diversity between the internal porosity and the material itself or functions for colour inversion.

4

Geometrical and mechanical properties of polyamide PA 12 bonds in composite advanced pore morphology (APM) foam structures

Kovačič A., Novak N., Vesenjak M., Dubrovski P. D., Ren Z.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 4

1198--1206

EN

Adhesive bonds have very strong influence on mechanical properties of composite particulate metal foams. This study experimentally investigates for the first time the geometrical and mechanical properties of PA 12 adhesive bonds between spherical advanced pore morphology (APM) elements made of AlSi10 foam. A new experimentation setup for mechanical testing of bonds in APM structures is based on APM element puncturing. The results show that mechanical behaviour of adhesive bonds differs much from the basic mechanical behaviour of adhesive. Two different bond failure modes are identified, depending on the bond geometry. The geometrical and mechanical results are statistically interpreted for simpler representation, applicability, and modelling of bonds in APM composites in the future.

5

Udział objętościowy powietrza w przepływie dwufazowym gaz-ciecz przez kanał wypełniony pianą aluminiową

Płaczek M., Dyga R.

Inżynieria i Aparatura Chemiczna

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2013

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Nr 4

364--365

PL

Przedstawiono wyniki badań doświadczalnych udziału objętościowego gazu w przepływie dwufazowym powietrze-woda przez poziomy kanał wypełniony pianami aluminiowymi o różnej gęstości upakowania porów. Stwierdzono, że udział objętościowy gazu zwiększa się wraz ze wzrostem prędkości pozornej gazu. Jednocześnie wzrost prędkości fazy ciekłej przyczynia się do redukcji udziału objętościowego gazu. Zaobserwowano występowanie zjawiska poślizgu międzyfazowego. Stwierdzono brak wpływu parametrów strukturalnych piany metalowej na wartość udziału objętościowego faz.

EN

Experimental results dealing with gas volume fraction in air - water two phase flow through a horizontal pipe filled with aluminum foams of different pore density are presented in the paper. It was stated that gas volume fraction increased when the superficial gas velocity increased. The increase of liquid phase velocity causes the reduction of gas volume fraction. It was observed that the interfacial slip phenomenon occurred. Test results indicated no effect of metal foam structural parameters on both gas and liquid volume fractions.

6

2-/3-D Digital Material Representation and Evaluation of Metal Foams

Yang C, An Y., Greenfield R., Hodgson P.

Computer Methods in Materials Science

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2013

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Vol. 13, No. 4

425--435

EN

Recently metal foams are becoming popular in engineering application due to their high energy absorption ability and low density, which are being utilised in automotive engineering and aerospace engineering as well as biomedical engineering. As a typical porous or cellular material, from the material design’s point of view, metal foams have typical heterogeneous structures cross length scales, which can be defined by only two phases: matrix material and voids, which is termed as cells or pores . Their structures can be characterised by several main geometric parameters related to the cells, such as size, shape, spatial distribution and arrangement and so on. The digital material representation of metal foams has been employed to represent metal foams accounting for their complex structures. However random distributions of the size and shape of cells in most foam materials make the digital material representation and modelling of such materials very complicated. Furthermore, effects of size and shape of cells on mechanical behaviours of metal foams have been found and investigated numerically and experimentally in authors' previous studies in which the authors have developed a digital framework for the representation, modelling and evaluation of multi-phase materials including metal foams. In this study, the developed digital framework for the representation, modelling and evaluation of microstructured or multi-phase materials has been further developed with a multi-scale sense including both two-/three-dimensional (2-/3-D) finite element modelling to represent metal foams with a certain distribution on cell size and shape, which can be used for digital or virtual testing to determine mechanical properties and behaviours of such foams. A linkage between 2-D and 3-D finite element models has been build up through a comparativeness analysis between them. For validation and verification purpose, the results obtained from these models have been compared with those from experimental work and good agreement has been found which demonstrated the effectiveness of the digital framework developed for metal foams.

PL

Ze względu na ich dużą zdolność do absorpcji energii i niską gęstość pianki metaliczne znajdują ostatnio szerokie zastosowanie w przemysłach samochodowym i lotniczym, a także w bioinżynierii. Jako typowy materiał porowaty lub komórkowy pianki metaliczne mają strukturę niejednorodną, która może być zdefiniowana przez dwie fazy: materiał osnowy i pustki nazywane komórkami lub porami. Struktury komórek są charakteryzowane przez ich główne parametry geometryczne, takie jak rozmiar, kształt, rozkład w przestrzeni i aranżacja. Cyfrowa reprezentacja materiału została wykorzystana do reprezentowania pianek metalicznych z uwzględnieniem ich złożonej struktury. Z drugiej strony nierównomierność rozkładu rozmiaru i kształtu komórek w większości pianek powoduje, że taka cyfrowa reprezentacja i modelowanie stają się bardzo trudne. Wpływ rozmiaru i kształtu komórek na własności mechaniczne pianek metalicznych był badany numerycznie i doświadczalnie we wcześniejszych pracach autorów. W tych pracach opracowana została numeryczna platforma dla reprezentacji, modelowania i oceny wielofazowych materiałów, w tym pianek metalicznych. W niniejszej pracy przedstawiono dalszy rozwój tej platformy. Stworzono wieloskalowe modele 2D i 3D połączone z metodą elementów skończonych (MES) do opisu pianek metalicznych z zadanym rozkładem rozmiaru i kształtu komórek. Ten program może być dalej stosowany do wyznaczania własności mechanicznych oraz do opisu zachowania się pianek metalicznych pod obciążeniem. Połączenie między modelami 2D i 3D MES zostało zbudowane na podstawie analizy podobieństwa między tymi rozwiązaniami. Dla walidacji i weryfikacji modelu porównano otrzymane wyniki z badaniami doświadczalnymi i otrzymano dobrą zgodność, co potwierdziło efektywność cyfrowej platformy dla pianek metalicznych.

7

Methodology for experimental investigations of metal foams and their mechanical properties

Stręk A. M.

Mechanics and Control

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2012

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Vol. 31, no. 2

90-96

EN

This paper presents a comprehensive, systematic approach on experimental investigations of structure and mechanical properties of metal foams. Based on a thorough state of the art study, the existing solutions have been synthesised with recent developments in the discussed field to become a proposition of a possibly complete methodology for observation and testing of cellular metals. Material properties acquired in the described manners can constitute reliable reference result base e.g. for identification and verification of failure criteria. This paper describes sample preparation procedures and next discusses techniques which enable one to characterise foam structure. There are also presented procedures for determining strength limits in different load cases: uniaxial tension or compression, shear and torsion as well as multiaxial states. The tests are discussed in terms of their specific application to study cellular metallic materials.

PL

Przedstawiono kompleksowe, systematyczne podejście do badań doświadczalnych struktury i właściwości mechanicznych pian metalowych. Na podstawie dogłębnej analizy stanu rzeczy rozwiązania istniejące zsyntetyzowano, uwzględniając najnowsze zmiany w omawianym zakresie tak, aby przedstawić propozycje możliwie pełnej metodologii obserwacji i badań metali komórkowych. Właściwości materiału uzyskane w czasie zaproponowanych testów mogą stanowić wiarygodną bazę odnośnych wyników, np. do identyfikacji i weryfikacji kryteriów wytężenia. Opisano procedury przygotowania próbek, a następnie omówiono techniki umożliwiające scharakteryzowanie struktury piany. Przedstawiono również procedury określania granic wytrzymałości w różnych przypadkach obciążenia: jednoosiowego rozciągania lub ściskania, ścinania i skręcania oraz wieloosiowych stanach obciążenia. Badania zostały omówione w odniesieniu do szczególnego zastosowania ich do zbadania komórkowych materiałów metalicznych.

8

Casting routes for porous metals production

Lichý P., Bednarova V., Elbel T.

Archives of Foundry Engineering

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2012

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Vol. 12, iss. 1

71-74

EN

The last decade has seen growing interest in professional public about applications of porous metallic materials. Porous metals represent a new type of materials with low densities, large specific surface, and novel physical and mechanical properties, characterized by low density and large specific surface. They are very suitable for specific applications due to good combination of physical and mechanical properties such as high specific strength and high energy absorption capability. Since the discovery of metal foams have been developed many methods and techniques of production in liquid, solid and gas phases. Condition for the use of metal foams - advanced materials with unique usability features, are inexpensive ways to manage their production. Mastering of production of metallic foams with defined structure and properties using gravity casting into sand or metallic foundry moulds will contribute to an expansion of the assortment produced in foundries by completely new type of material, which has unique service properties thanks to its structure, and which fulfils the current demanding ecological requirements. The aim of research conducted at the department of metallurgy and foundry of VSB-Technical University Ostrava is to verify the possibilities of production of metallic foams by conventional foundry processes, to study the process conditions and physical and mechanical properties of metal foam produced. Two procedures are used to create porous metal structures: Infiltration of liquid metal into the mold cavity filled with precursors or preforms and two stage investment casting.

9

Determination of metal foam flow conditions at a temperature higher than the liquidus temperature

Grabian J.

Archives of Foundry Engineering

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2011

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Vol. 11, iss. 1

27-30

EN

As it is known a foam made of composite with aluminium alloy matrix and SiC particles reinforcement does not reach the liquid state even at a temperature over 1000oC. The causes of such behaviour of foam have been examined. It has been found that it is due to two phenomena. One is connected with the creation of continuous layer of oxides at the boundary of gaseous pores and liquid metallic phase. The other is an increase of the apparent viscosity of solids suspended in liquid metal along with an increased content of these inclusions to the point where the suspension loses its continuity.

10

Simulation and modelling of metal foams

Pieczonka Ł., Uhl T.

Archives of Transport

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2009

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Vol. 21, iss. 3-4

115-124

EN

The paper describes an approach to geometrical modeling and Finite Element simulations of the dynamics of metal foams. Metal foams are a new class of materials with novel mechanical properties. With an excellent stiffness-to-weight ratio they are an interesting new material for contemporary structural engineering applications. Despite the growing interest in metal foams as an engineering material there are no modeling and simulation guidelines that can be folIowed. Different authors propose modeling methods that are based on simple continuous geometry and constitutive relations with estimates of mechanical properties extracted from experiments, methods based on periodic geometrical features or methods based on imaging techniques to obtain an exact geometrical model. In the presented approach it was decided to build an exact geometrical model in order to study dynamical features of sandwich panels. Therefore, a software package that allows automated generation of randomised geometrical models of sandwich paneIs with metal foam core has been prepared. Model generation is based on random sampling procedure with Latin Hypercube approach and Voronoi tessellation of the three dimensional domain. Generated geometrical models can be directly passed to a Finite Element pre-processor where can be meshed without additional processing. The paper contains the description of software tools that were created for the purpose of this study and the analysis of the dynamical properties of sandwich panels with the Alporas aluminum foam core. The paper is concluded with remarks about modeling problems and uncertainty issues in metal foams.

PL

W artykule przedstawiono podejście do modelowania i symulacji pian metali z użyciem Metody Elementów Skończonych (MES) oraz autorskich narzędzi do modelowania geometrii. Piany metali są stosunkowo nową klasą materiałów o interesujących własnościach mechanicznych. Jednak pomimo rosnącego zainteresowania tą klasą materiałów nie istnieją modele i wytyczne, które mogłyby być użyte w symulacjach takich struktur. W literaturze znaleźć można różne podejścia do modelowania struktur piankowych. Niektóre z nich bazują na modelach geometrycznych złożonych z prostych struktur periodycznych, inne na pozyskiwaniu dokładnej geometrii pian metalu z technik obrazowania trójwymiarowego np. tomografii komputerowej, jeszcze inne na modelach konstytutywnych. W prezentowanym podejściu zdecydowano się na zbudowanie dokładnego modelu geometrycznego piany metalu, który pozwalał będzie na uwzględnienie losowości jej struktury. W tym celu przygotowano oprogramowanie umożliwiające automatyczne generowanie modeli elementów skończonych (MES) paneli typu sandwich z rdzeniem wykonanym z piany metalu typu Alporas. Model geometryczny bazuje na losowym próbkowaniu w przestrzeni trójwymiarowej z użyciem schematu hipersześcianów łacińskich (z ang. Latin Hypercube Sampling) oraz na teselacji Voronoia tak wygenerowanych punktów. Tak uzyskany model geometryczny przekazywany jest do pre-procesora MES gdzie automatycznie tworzona jest siatka elementów skończonych i przypisywane są parametry mechaniczne. Na wygenerowanych modelach przeprowadzono analizę wpływu losowości geometrii piany metalu na częstości drgań własnych paneli typu sandwich. Artykuł zawiera opis przygotowanego oprogramowania oraz wstępne wyniki analizy niepewności.

11

Recent powder metallurgy research in Institute of Nonferrous Metals.

Missol W.

Rudy i Metale Nieżelazne

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2002

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R. 47, nr 12

627-632

EN

The paper is related to Institute's research activity over the last few years concerning powder metallurgy (P/M) in the fields of: electric contact tips manufactured by P/M techniques (excluding tips and rivets obtained by mechanical working), modern fine-grained hard metals for instruments, metal foams, self-lubricating bearings for high load rating conditions and soft and hard magnetic materials prepared by metallic powder consolidation.