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1
McKown, Simon Thomas. "The progressive collapse of novel aluminium foam structures." Thesis, University of Liverpool, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414813.
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Ainsworth, Mark J. "Metal-foam interface stability during the filling of lost foam moulds with aluminium alloys." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/1481/.
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Aluminium Lost Foam castings were made using gravity and counter-gravity filling techniques. Tensile strength was found to be most uniform in those castings which had been filled slowly from the bottom and where the metal front had remained stable throughout filling sequence. Pores containing carbon deposits were found on the fracture surfaces of all the castings made and this suggested that the defect was caused by polymer entrapment. A Saffman-Taylor instability was observed at the interface between Hg and a viscous glucose syrup which were contained in an analogue, that was used simulate the casting of Lost Foam moulds at room temperature. The liquid degradation products of the polystyrene patterns were also found to be viscous, although this was reduced by treatment with Br. Under the same conditions of temperature and velocity, the interface observed during the filling of a Br-treated pattern was planar whereas that of an untreated pattern was unstable. This demonstrated not only that the interfacial instability entrapped polymer degradation products, which adversely affected casting quality, but was probably of the Saffman-Taylor type.
3
Idris, Maizlinda Izwana Materials Science & Engineering Faculty of Science UNSW. "Structural integrity of carbon fibre/aluminium foam sandwich composites." Awarded By:University of New South Wales. Materials Science & Engineering, 2010. http://handle.unsw.edu.au/1959.4/44722.
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This thesis focuses on closed-cell aluminium foams (ALPORAS and ALULIGHT) and on sandwich panels comprising these foams laminated with 2/2 twill carbon fibre (MTM56/0300) skins. The thesis experimentally and analytically investigates the response of foam-only panels (ALPORAS) to indentation with various indenter sizes and shapes; and also studies the behaviour of sandwich panels to contact damage caused quasi-statically or by impact. Quasi??static uniaxial compression testing is used to determine the mechanical properties of the foams (ALPORAS and ALULIGHT). It is revealed that the plastic collapse strength (σ* pl) obtained from the stress??strain curves is lower than the values predicted by the Gibson-Ashby theoretical model. This phenomenon is explained by the fact that the aluminium foams tested are imperfect, non-homogeneous and non-isotropic, and show a distinct cell elongation. Whereas, the Gibson-Ashby theoretical model was based on the finite element method applied to the response of a unit tetrakaidecahedral closed cell having flat faces. The experimental work shows that the deformation of the foam-only panels to indentation is caused by progressive crushing of the cell bands and by shearing and tearing of the cell walls. This thesis presents new analytical models for the response of the foam-only panels and estimates the applied deformation load in all types of indentation. By fitting the experimental load-displacement curves, the shear strength (τ* pl) and the tear energy (γ) are deduced. Compared to the literature, more consistent results are obtained for the shear strength (τ * pl) and the tear energy (γ) from all types of indentation. It is also suggested to determine (τ * pl) and (γ) through indentations with long punches (FEP and LCP), instead of hemi-spherical or cylindrical indenters, because indentation on enclosed areas shows some indenter size dependence. It is concluded that thinner panels are not suitable for the determination of the tear energy (γ) since the densification of the foam is achieved before the tear resistance is fully engaged. Another objective of this thesis is to study the response of sandwich panels comprising a closed??cell aluminium foam core and laminated with carbon fibre skin to quasi-static and impact local damage. Special attention is paid to the residual (remnant) strength in bending of the already indented sandwich panels (quasi-statically or by impact) up to the failure point. The remnant strength in bending is determined by carrying out four point bending strength tests. The local damage is located on either the compressive or on the tensile side of the sandwich panels. Thus, the capacity of the panels to resist transverse loads after they have been locally damaged at contact is investigated. The contact damage on the sandwich panels is experimentally simulated using spherical indenters. The quasi-static indentation is carried out at a low constant velocity (0.5mm/min) ?? the induced contact damage is found to be independent on the sample thickness but dependent on the indenter diameter. On the contrary, the impact test indicates velocity-dependence of the failure mode of the sandwich panel (i.e. skin breakage or punch through) which is found from the load-displacement curves. The results reveal that there is a correlation between the area of the contact damage and the remnant strength, and that the use of metal foam cores leads to high contact damage resilience of composite structures.
4
Curran, David Charles. "Aluminium foam production using calcium carbonate as a foaming agent." Thesis, University of Cambridge, 2004. https://www.repository.cam.ac.uk/handle/1810/252945.
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The current state of the art with regards to the production of metallic foams is reviewed, with melt-based processes identified as the most promising for cost-effective large-scale production. The potential for metal carbonates as an alternative to currently-used titanium hydride foaming agents is explored, with calcium carbonate identified as the most suitable. The influence of a range of material and processing parameters on the stability of metallic foams in the molten state is discussed, and current methods of controlling melt viscosity and surface tension are reviewed. Characteristic features of the compressive deformation of metallic foams are described in the context of use as an impact-absorbing material, with a review of work in the literature linking the bulk mechanical properties to details of the cell structure. Calcium carbonate is found to be a highly effective foaming agent for aluminium. The foams obtained have notably finer cell structures than can be achieved in foams produced with titanium hydride, coupled with enhanced stability in the molten state. This is attributed to the presence of a thin continuous surface film of metallic oxide that counteracts the effect of surface tension. This film, combined with the finer cell structure of the calcium carbonate-based foams, is found to significantly reduce the rate of gravity drainage of the melt. The formation of the thin oxide film during foaming gives rise to a number of artefacts on the cell surface, including stretch marks and tear bands. A range of chemical and surface analysis techniques are used to identify the chemical composition and thickness of the oxide film. The distribution of refractory particles in the cell faces, which are commonly employed to stabilise molten foam structures, is found to be highly non-uniform in foams which undergo significant gravity drainage of liquid metal during the foaming process. Experiments in which the concentration of particles is varied demonstrate the importance of their effect on the melt viscosity in addition to their known role as a surface stabilising phase. The effect of alloy content and foaming gas on the stability of standing molten foams is also investigated in the context of other foaming processes. The formation of an oxide film on the surface of the cells is shown thermodynamically to be a necessary step in the production of low-density aluminium foams with a calcium carbonate foaming agent. A temperature-dependent upper limit on porosity is observed. It is established that this is the result of inhibition of the calcium carbonate decomposition reaction by its products as the thickness of the surface oxide film increases. The effect of varying cell size, porosity and chemical composition on the thickness of the surface oxide film is derived. The rate of thermal decomposition of calcium carbonate is found to be dominated by the partial pressure of carbon dioxide, with particle size and small impurity contents having only a small effect. Compressive mechanical properties of the foams produced are compared with those of foams produced with a titanium hydride foaming agent and theoretical predictions. A reduced cell size apparently minimises the influence of point defects on the properties of specimens of finite dimensions. A significant difference in the shape of the stress-strain curves of calcium carbonate- and titanium hydride-based foams is noted, with the latter marked by extensive serrations. This difference is demonstrated to be independent of differences in cell size. Microstructural analysis of foams in various stages of failure suggests that this is due to differences in the distribution of refractory particles in the two foams, which is in turn a consequence of the reduced extent of gravity drainage of liquid metal in the calcium carbonate-based foams.
5
Styles, Millicent, and milli styles@anu edu au. "Characterisation of the flexural behaviour of Aluminium Foam Sandwich Structures." The Australian National University. Faculty of Engineering and Information Technology, 2008. http://thesis.anu.edu.au./public/adt-ANU20080813.170807.
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Aluminium foam has a range of properties that are desirable in many applications. These properties include good stiffness and strength to weight ratios, impact energy absorption, sound damping, thermal insulation and non combustibility. Many of these characteristics are particularly attractive for core materials within sandwich structures. The combination of aluminium foam cores with thermoplastic composite skins is easily manufactured and has good potential as a multifunctional sandwich structure useful in a range of applications. This thesis has investigated the flexural behaviour of such structures using a combination of experimental and modelling techniques. The development of these structures towards commercial use requires a thorough understanding of the deformation and strain mechanisms of the structure, and this will, in turn, allow predictions of their structural behaviour in a variety of loading conditions.
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The experimental research involved the use of an advanced 3D optical measuring technique that produces realtime, full-field strain evolution during loading. This experimental characterisation of strain evolution in this class of sandwich structure under flexural loading is the first of its kind in the world. The experimental work studied the sandwich structure undergoing four-point bend testing. Initial studies compared the behaviour of the aluminium foam structure with a more traditional polymer foam sandwich structure. The aluminium foam structure was found to have equivalent or improved mechanical properties including more ductile deformation and an enhanced energy absorption. An investigation was conducted on the effect of core and skin thickness on the metal structure and a range of flexural behaviours were observed. Analysis of the strain distribution showed a complex development including localised effects from the non-uniform cellular structure of the material. An understanding of the variation with size is important in establishing design methods for utilising these structures. In particular, it is desirable that finite element simulations can be used to predict behaviour of these structures in a diverse range of loading conditions. This aspect was considered in the second half of this study. An existing constitutive model for aluminium foam, developed for use in compression energy absorption studies, was used to investigate finite element simulations of the flexural behaviour of the sandwich structure. The FE model was able to predict the general deformation behaviour of the thinner skinned structures although the magnitude of the load-displacement response was underestimated. It is suggested this may be related to the size effect on the input parameter characterisation. The strain distribution corresponded well with the experimental strain measurements. It was found a simple increase in the material model input parameters was able to more closely match the magnitude of the load-displacement response while maintaining the appropriate strain distribution. The general deformation shape of the model with the thicker skin corresponded reasonably well with the experimental observations. However, further work is necessary on the element failure criterion to capture the shear cracking observed. The strain distributions of the model predicted this failure with high strain concentrations matching those of the experimental contours. The last part of the thesis describes a parametric study on the effect of the foam material model input parameters on the flexural behaviour of the sandwich structure model. An important conclusion of this work is that this material model for aluminium foam can, with some development, be utilized to provide a viable method for simulating aluminium foam composite sandwich structures in flexural loading situations.
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Tan, Serdar. "Optimization Of Macrostructure In Aluminium Foams." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/2/1011196/index.pdf.
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Pure aluminium and aluminium-5wt % TiO2 aluminium foams were produced by powder metallurgy technique with the use of TiH2 as foaming agent. Two sizes of TiH2 were used: 20µm and 3µ
m. It has been confirmed that high level of compaction is the primary requirement in foaming. It was shown that hot swaging could be used as a method of compaction for foaming as it leads to values close to full density. Pure aluminium foamed at 675°
C and 725°
C leads to a volume expansion between 90-180 %. A model was developed for pure aluminium to explain the pore initiation and the resultant pore size. The model predicts a critical particle size for TiH2 below which bubbles could not form. The size appears to be in the neighborhood of 30µ
m for 675°
C and 6µ
m for 725°
C and is temperature dependent. Equilibrium pore size appears to be a function of TiH2 particle size and not affected significantly by the temperature of foaming. It has also been shown that depth effect, i.e. hydrostatic pressure of liquid metal, is unimportant in foaming process and can be neglected. According to the model, to produce pores of fine sizes, two requirements must be met: use of fine foaming agent and the use of high foaming temperature. Al-5 wt % TiO2 was foamed at 750°
C and 800°
C, i.e. at temperatures that yield viscosities similar to pure aluminium. The structure of foamed metal and level of foaming, 120-160%, was similar to pure aluminium. Unlike pure aluminium, internal reactions are dominant feature of TiO2 stabilized systems. Solid content of the system increases as a result of internal reactions between Al-Ti and Al- TiO2. When this change occurs, however, is not known. It is possible that the viscosity of the system may be four times of its original value.
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Styles, Millicent. "Characterisation of the flexural behaviour of aluminium foam composite sandwich structures /." View thesis entry in Australian Digital Theses Program, 2008. http://thesis.anu.edu.au/public/adt-ANU20080813.170807/index.html.
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8
Mustaffar, Ahmad Fadhlan Bin. "Irregular aluminium foam and phase change material composite in transient thermal management." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3338.
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Traction systems generate high loads of waste heat, which need to be removed for efficient operations. A new transient heat sink is proposed, which is based on salt hydrate phase change material (PCM). The heat sink would absorb heat during the short stationary phase i.e. at stations in which the PCM melts, a process accelerated by aluminium foam as it increases the rate of heat transfer within the PCM. When the train moves, the PCM is solidified via a forced convection stack. This creates a passive and efficient thermal solution, especially once heat pipe is employed as heat conduit. At the outset, the characteristics of the foam needed to be accurately determined. The foam was uncommon as its pore morphology was irregular, therefore it was scanned in a medical computed tomography (CT) scanner, which allowed for the construction of a three dimensional (3D) model. The model accuracy was enhanced by software, resulting in an extremely useful analytical tool. The model enabled important structural parameters to be measured e.g. porosity and specific surface area, which were crucial for the subsequent thermal and fluid flow analyses. A defect dense region was also detected, the effect of which was further investigated. Interestingly in the volume devoid of this defect, the porosity and specific surface area were uniform. A test rig was constructed that mimicked liquid cooling (or in the planned application, heat pipe cooling) in power electronics. At the core was a heat sink of salt hydrate PCM, impregnated within the foam. The sink with its current specifications (with liquid cooling) was able to absorb a thermal load consistent from a group of 4-5 IGBTs, which dissipated a low power of 20W per module during stops. The heating period of 1600-3500s per cycle meant the sink could be fitted to intercity locomotives. The foam increased the effective thermal conductivity by a factor of 24, from 0.45 to 10.83 W/m.K. 3D volume averaged numerical simulation was validated by experiment, which could be used to facilitate scale up or redesign for further optimization. As well as a support structure for the storage component of the system, the foam could replace conventional fins in forced convection, adding value to the potential manufacturer of the system. Heat transfer coefficient calculation incorporated the actual surface area that was derived from the 3D model, a first for metal foam studies. Results have shown a good Nu/Re correlation, comparable with other metal foam works.
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Betts, Charles. "Structural integrity of open-cell aluminium foam sandwich panels for lightweight wing structures." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/17995.
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The overarching aim of this work was to concentrate on the mechanical modelling and experimental characterisation of novel open-cell aluminium foam core sandwich panels for prospective use as an airplane wing skin material. A repeating unit cell 2D FE model was created to assess the mechanical behaviour of infinitely long, regularly tessellated honeycomb core sandwich panels. An analytical model using Timoshenko beam theory was developed to predict the Young’s modulus of a hexagonal honeycomb core; there is good agreement between the two models. A microtensile test procedure was developed to determine the mechanical properties of individual foam struts. A FE model of the as-tested struts was created, using XMT scans of the undeformed struts to define the geometry, to establish a method that compensates for grip slippage inherent in the testing of the struts. Strut deformation was described by a calibrated continuum viscoplastic damage model. The damage model was implemented into 3D FE models of an open-cell aluminium alloy foam core sandwich panel subjected to uniform compression to study the effect of varying the strut aspect ratio on the mechanical properties of the core. FE models of the panel subjected to three and four point bending were created to provide a virtual standardised test to assess the core elastic properties. The extent of structural damage in the panels was simulated for indentation loading indicative of a tool strike; an optimal strut aspect ratio was identified providing the best energy absorption per unit mass whilst ensuring core damage is detectable. The effect of morphological imperfections on the mechanical properties and extent of detectable damage of the core was studied. The shear modulus of the core was greatly reduced under the presence of both fractured cell walls and missing cells. The extent of visible damage was largely unaffected by either type of defect.
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Kubilay, Ceylan. "Effect Of Tih2 Particle Size On Foaming Of Aluminium." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/2/12606897/index.pdf.
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ABSTRACT
A study is carried out on the production of aluminum foams via powder processing. The study deals mainly with the effect of TiH2 particle size on the process of foaming. Mainly two TiH2 particle sizes were usednamely 27,5 &
#61549
m and 8,5 &
#61549
m. Foaming experiments were carried out at temperatures between 675oC &ndash
840oC. The viscosity of the system is adjusted by controlled addition of Al2O3. The study shows that choice of foaming agent size is influential in the foaming process. With the use of fine foaming agent, temperatures in excess of 800oC would be required for successful foaming. The study further showed that the relation between foaming and viscosity was also dependent on the particle size. Viscosity of 2.3 mPa.s was found to be a limiting value for successful foaming with fine foaming agent. This value appears to increase with increasing particle size. An analysis is presented with regard to temperature dependence of foaming which takes into account the effect of particle size.
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Ribeiro, Daniel Tadeu de Carvalho. "Estudo da viabilidade técnica do processo de fabricação de espumas metálicas por reciclagem de cavacos da liga AA356." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263567.
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Orientador: Maria Helena RobertDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este trabalho tem como objetivo desenvolver um método alternativo para a fabricação de espumas metálicas pela reciclagem de cavacos de Al e a caracterização mecânico-metalúrgica do produto obtido. O processo investigado envolve a espumagem de compactados de misturas de cavacos e pó de agente espumante, com a espumagem ocorrendo na liga em estado semi-sólido tixotrópico. Foram fabricados precursores espumáveis pela mistura de cavacos da liga de Al AA356, com duas distintas granulometrias, a 1,5wt% do agente espumante TiH2 e posterior compressão também em duas distintas condições: compressão simples a frio e compressão dupla, a frio e a quente. Os elementos precursores foram aquecidos, sofrendo espumagem em estado semi-sólido, pela dissociação do agente espumante formando gás H2 no interior do metal. As espumas metálicas produzidas foram analisadas quanto à sua qualidade interna, arquitetura celular (dimensões, geometria de poros, espessura de paredes metálicas), propriedades físicas (densidade, teor de porosidade, condutividade e difusividade térmicas) e mecânicas em compressão semi-estática. O comportamento mecânico em compressão e o comportamento térmico das espumas produzidas foram também estimados teoricamente utilizando modelos da literatura. Os resultados obtidos mostraram que o processo proposto é eficaz para a produção de espumas de boa qualidade. Os melhores resultados são obtidos com o emprego de compactação dupla e espumagem direcional do precursor. Não foi possível observar influência das dimensões dos cavacos utilizados, na faixa de tamanhos empregada, nas características e propriedades das espumas produzidas. O comportamento das espumas metálicas sob compressão semi-estática demonstrou a formação de um platô de deformação plástica ascendente, o que indica uma grande capacidade de absorção de energia mecânica; todas as amostras apresentaram condutividade térmica bastante inferior e difusividade superior à do metal maciço, representando boas propriedades isolantes térmicas. Os valores de propriedades mecânicas estimadas teoricamente diferem dos obtidos experimentalmente, indicando necessidade de cuidado no emprego destes modelos
Abstract: This work aims to develop an alternative method for manufacturing metal foams by Al alloy machined chips recycling and mechanical and metallurgical characterization of the product. The process investigated involves foaming a compressed mixture of Al chips and foaming agent powder, with foaming occurring with the alloy in semi-solid thixotropic state. Foamable precursors were manufactured by mixing Al alloy A356 machined chips in two different particle sizes, to 1.5 wt% of the foaming agent TiH2 and its posterior compression also in two distinct conditions: simple cold compression and double compression, cold and hot. The precursors were heated, being foamed in semisolid state, by dissociation of the foaming agent generationg H2 into the bath. The internal quality, cellular architecture (pore size and geometry, cell wall thickness), physical properties (density, porosity level, thermal conductivity and thermal diffusivity) and mechanical behaviour under semi-static compression were analyzed for the metal foams produced. The mechanical behavior under compression and thermal behavior of the foams produced were also calculated using theorical models from literature. The results showed that the procedure proposed is effective for the production of foams of good quality. The best results are obtained foaming directionaly precursors manufactured by double compression. It was not possible to observe the influence of the dimensions of the machined chips, considering the size range adopted, on the characteristics and properties of the foams produced. The mechanical behavior of metallic foams under semi-static compression showed the formation of a ascendent plateau of plastic deformation, which indicates a great capacity of absorbing mechanical energy; all samples showed significantly lower thermal conductivity and diffusivity compared to the solid metal, what represents good thermal insulation properties. The theorical estimative of the sample's mechanical properties differ from those obtained experimentally, indicating that the matematical models proposed has to be used carefully
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
12
Barbakadze, Archil. "Untersuchung des Einflusses der Gießparameter auf die Porosität bei Aluminium-Vollformgussteilen." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2009. http://nbn-resolving.de/urn:nbn:de:swb:105-1725160.
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Beim fallenden Vollformguss mit Aluminiumlegierungen existiert wegen der vergleichsweise zu Gusseisen niedrigen Gießtemperatur, nahezu kein Gasspalt zwischen der Schmelze und dem Schaumstoffmodell. Durch die Variierung der Schmelzezufuhr konnten Vorteile des fallenden Vollformgießens gegenüber dem steigenden Vollformgießen verdeutlicht werden. Außer wirtschaftlichen Vorteilen erfordert das fallende Gießen deutlich geringere Formfüllzeiten, die sehr wichtig bei der Herstellung von Seriengussteilen sind. Eine Abhängigkeit der Porosität von der Schichtdicke der Schlichte wurde nachgewiesen. Bei der Versuchsreihe mit Entgasung, kombiniert mit dem Unterdruck, konnten sehr niedrige Porositätswerte erzielt werden. Die Argonspülung unmittelbar vor dem Gießen beeinflusst auch die Formfüllgeschwindigkeit positiv. Durch die mikroskopischen Untersuchungen konnten die Poren visualisiert und die zweidimensionalen Größen, wie Fläche, Durchmesser sowie minimale und maximale Querschnitte gemessen werden.
13
Siavashi, Kiavash. "The effect of casting parameters on the fluidity and porosity of aluminium alloys in the aost foam casting process." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3525/.
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The Lost Foam Casting process has been firmly established for Aluminium and ferrous alloys. This process offers many advantages over conventional casting processes but its full potential has yet to be reached due to the many defects introduced to the casting associated with decomposition of the foam pattern during mould filling. The foam pattern commonly used in this process is Expanded Polystyrene (EPS) which degrades to liquid and vapour byproducts. The liquid decomposition byproducts travel to the metal/mould interface, where the globules of liquid foam can become trapped against the coating and their molecular weight is reduced due to the heat from the molten metal. At the same time, they release bubbles of gas into the castings. These globules can wick into the refractory coating only if their molecular weight is sufficiently reduced to below a critical molecular weight. In this study, to improve the quality of Aluminium alloys made by Lost Foam Casting, easier removal of the decomposition byproducts was obtained by using low molecular weight foam patterns. The molecular weight of expanded Polystyrene was not reduced when it was exposed to γ-rays because of cross-linking while the molecular weight of Poly Methyl Methacrylate (PMMA) was significantly due to chain session. Therefore, plates of Probead-70™ (a copolymer of Polystyrene 30 wt %-Poly Methyl Methacrylate 70 wt %) were exposed to γ-rays and reduced their molecular weight by up to about 85% below the critical molecular weight value. With low molecular weight foam patterns the decomposition byproducts require less reduction to reach the critical molecular weight to become absorbed by the coating, and consequently less defects are introduced into the casting. γ-radiation was employed to reduce the molecular weight of the foam. The porosity content of the castings was significantly reduced leading to an improvement of their mechanical properties such as their fatigue life which was increased by 100%. Lost Foam Casting has also been reported to experience complexities with fluidity. Misrun is likely to occur in Lost Foam Casting due to the formation of a large amount of gas at the metal/foam interface, increasing the back pressure, compared to the conventional castings. This reduces the velocity of the molten metal which might lead to solidification of the molten metal before filling the mould entirely. In the current work, a reproducible fluidity test was designed and the effects of different casting parameters on fluidity were examined. In some of the castings inserted thermocouples were employed to study the filling behaviour to determine the velocity of molten metal, thickness of the metal/foam interface and the time of freezing. It was concluded that it is not recommended to alter the coating thickness in order to improve fluidity, because the effect of coating thickness depends on the pouring temperature of the castings and permeability of the coating. The metallostatic pressure was found to affect the fluidity insignificantly (within the values in the current work, 2600-2700 Pa). Instead, increasing coating permeability, decreasing the density of the foam pattern and increasing the pouring temperature were found to increase the fluidity in Lost Foam Casting. However the effect of increasing pouring temperature and decreasing foam density may be detrimental to the quality of castings. The molecular weight of the foam pattern and the use of brominated foam patterns did not have a considerable effect on fluidity in Lost Foam Casting. It was also found that solidification in the Lost Foam Casting occurs at the metal/foam interface. A heat balance between the molten metal and the mould, and the foam pattern, was developed to give a fluidity equation to aid interpretation of the fluidity results. In summary, this research has provided a better understanding of the effect of casting parameters on the fluidity of Lost Foam Casting and the heat transfer from the molten metal to the foam pattern and to the mould. In addition, the quality of AL alloys castings was improved by reducing the molecular weight of the foam pattern used in the Lost Foam Casting process.
14
GUGLIELMOTTI, ALESSANDRO. "Tecnologia delle strutture cellulari." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2010. http://hdl.handle.net/2108/1203.
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La porosità nei materiali utilizzati a scopi ingegneristici è spesso indesiderata per applicazioni strutturali. Tuttavia, la porosità offre notevoli vantaggi in termini di leggerezza, riduzione dei costi di produzione, smorzamento, isolamento termico e energia specifica. Inoltre, i materiali porosi sono ampiamente utilizzati in molteplici applicazioni industriali in diversi settori quali: automotive, aeronautico e navale. Negli ultimi anni, l’attenzione è stata rivolta a questa particolare classe di materiali in quanto combinano alte performance e basso peso. I materiali cellulari, generalmente, sono prodotti attraverso la combinazione di materiali organici. Tuttavia, recentemente, sono state introdotte anche tecnologie per la produzione di materiali cellulari a base metallica.
Nel presente lavoro è stata descritta una nuova tecnologia di schiumatura per resine termoindurenti. Una resina non curata sotto forma di polvere viene compattata a freddo in uno stampo di acciaio e usata come precursore. La pasticca, quindi, viene scaldata in un forno a muffola ad alta temperatura per ottenere la schiuma. Nessun agente schiumante è stato introdotto in quanto il meccanismo di formazione della schiuma dipende solamente dal punto di ebollizione della resina non curata. La temperatura di schiumatura viene impostata per essere alta a sufficienza da raggiungere velocemente la temperatura di ebollizione della resina ma non così alta da provocare fenomeni di degrado. Durante l’ebollizione, la resina polimerizza e le bolle rimangono intrappolate nella forma finale. Attraverso questa tecnologia, possono essere prodotti sia compositi che nano-compositi. Infatti, prima della compattazione, la resina in polvere può essere miscelata con diversi tipi di rinforzo ceramici o metalli micro o nano-particellari.
Per quanto riguarda le schiume di alluminio, è stata proposta una nuova tecnologia di schiumatura per produrre schiume a celle aperte di alluminio attraverso la “replicazione”. Il processo consiste in quattro step fondamentali: la preparazione della preforma di cloruro di sodio (NaCl); l’infiltrazione dell’alluminio fuso nella preforma di sale; la solidificazione del metallo; la dissoluzione del sale in acqua. Per la produzione della preforma è stato utilizzato un sale grosso e successivamente sono state studiate le caratteristiche meccaniche della schiuma di alluminio ottenuta.
In conclusione, è stato proposto, inoltre, un metodo alternativo per piegare le schiume di alluminio reperibili in commercio utilizzando un laser a diodi. Pannelli a celle aperte e chiuse sono stati piegati al laser ed è stata studiata l’influenza dei principali parametri di processo (potenza laser e velocità di scansione) sull’efficienza di piegatura. Attraverso le prove condotte si è potuto constatare come il laser sia capace di formare agevolmente i pannelli senza provocare danneggiamenti al campione.Porosity in dense engineering materials is often undesirable for load-bearing applications. However, porosity is highly beneficial for weight and cost reduction, damping, thermal insulation and specific strength. Moreover, porous materials are extensively used in several industrial applications: automotive, aeronautics, and naval. In the last years, the attention has been focused on new materials because of the combination of high performances and low weight. Cellular materials were initially produced by means of organic compounds: recently, technologies for the processing of metallic cellular materials have been introduced as well. In the present work, a new foaming process is described for thermosetting resins. Uncured resin tablets are fabricated by pressing commercial powders in a steel mould at room temperature, and used as foam precursors. The tablets foam when heated in a muffle at high temperature. No blowing agent is added as the foaming mechanism depends on the uncured resin boiling point. The foaming temperature is set to be high enough to rapidly produce the resin boiling but not excessive to avoid the thermal degradation. During boiling, the resin polymerizes and the bubbles froze in the final structure. By means of this technology, composite and nano-composite foams may be produced as well. In fact, before compaction, the resin powder may be easily mixed with several fillers such as ceramic or metallic micro and nano-particles. As regards the aluminium foams, a new foaming technology was also proposed to produce open-cell aluminium foams by “replication”. Particularly, the process consisted of four main steps: the preparation of a pre-form of sodium chloride (NaCl); the infiltration of the pre-form with molten aluminium; the metal solidification; the water dissolution of the salt. Coarse NaCl grains were used to produce the pre-forms and the mechanical properties of the solidified foams were evaluated. In conclusion, a different method to shape commercial metallic foam panels was proposed by using a diode laser. Open- and closed-cell panels were laser bent and the effect of the main process parameters (laser power and scan velocity) on the bending efficiency was investigated. As a result, a very good formability was observed for the laser processed panels.
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Delbin, Daniel. "Estudo da viabilidade de produção de esponjas da liga A2011 a partir do estado semi-solido." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263622.
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Orientador: Maria Helena RobertDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Neste trabalho é estudada a viabilidade de produção de esponjas metálicas pela conformação de pasta tixotrópica da liga A2011, sobre camada de agente bloqueador (NaCl) posteriormente removido para formação da porosidade. Investiga-se a influência da temperatura de tratamento térmico, para obtenção da pasta semi-sólida, e da granulometria do agente bloqueador, na estrutura formada do material celular (aspecto geral, caracterização qualitativa e quantitativa dos poros, microestrutura da parede celular e densidade) e nas características de processo (forças de tixoforjamento e capacidade de penetração da pasta). São produzidos cilindros de material poroso metálico tipo sanduíche, compostos de camada porosa entre camadas maciças da liga, com três diferentes classes de porosidade: fina, média e grosseira. As esponjas foram submetidas à tomografia computadorizada e à análise metalográfica para sua caracterização estrutural. Os resultados obtidos mostram a viabilidade de obtenção de esponjas metálicas utilizando a tecnologia de semi-sólidos e o tipo de bloqueador utilizado. O sucesso do processo depende da fração líquida presente na pasta metálica tixotrópica, reduzida fração líquida pode resultar em incompleta infiltração e compressão das partículas do agente bloqueador. Nas condições analisadas a granulometria do agente bloqueador não teve influência sensível na qualidade do produto. A densidade do material poroso aumenta com o aumento da temperatura de processo, devido ao aumento da espessura de paredes metálicas na estrutura porosa
Abstract: The work analyses the possibility of the production of cellular material by pressing the A2011 alloy in the thixotropic semi-solid state, into a space holder pre-form. Space holder particles used are NaCl, which are removed from the product after the forming operation, resulting the porous material. It is investigated the influence of the thixoforming temperature and the size of space holder particles, in the structure of the obtained porous material (general aspect, quantitative and qualitative characterization of porosity, microstructure of cell walls and density of the product), as well as in the processing characteristics (required forces for infiltration, penetration ability of the slurry in the salt pre-form). Cylindrical samples, sandwich type, with a porous layer inserted between layers of compact alloy are produced, presenting three different ranges of porosity. The cellular material obtained contains opened porosity, being characterized as sponge. Products were analyzed by tomography and metallographic techniques. Results show that the proposed process is able to produce acceptable porous material, with a simple and low cost technique. The quality of the product depends rather on the processing temperature than on the size of space holder particles. Low liquid fraction in the thixotropic slurry can lead to incomplete infiltration and deformation of the pre-form. In the analyzed conditions, influence of the size of space holder particles could be observed neither in the processing ability nor in the quality of the product. Density of produced porous material increases as processing temperature increases, due to the increase of thickness of cell walls
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
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Bilík, Michal. "Návrh předního deformačního členu vozidla Formule Student." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230252.
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This diploma thesis deals with Formula Student Impact Attenuator design. The aim of the thesis is to select suitable material and put it to the test of deformation. From results to suggest dimensions of Impact Attenuator and then perform its test. Next aim of the thesis is to perform FEM analysis of Anti-Intrusion plate and supporting rack.
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Rodrigues, Tiago Alexandre Morais. "Tubes reinforced with foams with density gradients." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17994.
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Mestrado em Engenharia MecânicaEstudos na área dos materiais têm desempenhado um importante papel na indústria automóvel. Com o tempo, a utilização de materiais pesados tem vindo a ser substítuido por materiais mais leves como ligas de aço avançados, ligas de alumínio e compósitos. Quanto mais leves forem as estruturas, melhor o seu desempenho em termos de consumo de combustível e emissão de gases. No entanto, as estruturas necessitam de manter a sua integridade, assegurando a segurança activa e passiva dos ocupantes. Sendo assim, este estudo concentra-se em estudar o comportamento mecânico à compressão de tubos de alumínio preenchidos com espumas de alumínio. As espumas fechadas são produzidas através do método de pulverotecnologia ao passo que as espumas abertas são fabricadas com recurso à técnica de fundição de precisão. Este estudo passa também pela análise de espumas abertas preenchidas com polímeros, neste caso silicone e epóxido, comummente chamadas espumas híbridas. Os testes de compressão foram realizados em condições quasi-estáticas e dinâmicas, sendo analisados com recurso a uma técnica não destrutiva (Termografia Infravermelha), na qual se obtêm imagens térmicas (termogramas), utilizados no estudo dos modos de deformação. A análise dos resultados passa não só pelo estudo dos modos de deformação mas também da sua influência na capacidade de absorção de energia, mas também na ocurrência de fendas e fracturas. Os resultados demonstram que os tubos preenchidos com espumas de alumínio de porosidade fechada durante a etapa de formação da própria espuma, designados in-situ, são aqueles que garantem melhor resposta mecânica, tendo um comportamento mais estável e prevísivel.
Research in materials has been playing and important role in automotive industry. With time, the use of heavier material is being replaced by lighter materials such as advanced steel alloys, aluminium alloys and composites. The lighter the structures the better in terms of fuel consumptions and gas emission’s reduction. However, these structures have to maintain their reliability, ensuring active and passive security to vehicles passengers. Therefore, this study concentrates on studying the mechanical behaviour of aluminium tubes filled with aluminium foams under compression. The closed foams are produced through a powder metallurgical method, while the open-cell foams are produced through investment casting. This study also focuses on the study of open-cell foams embedded with polymers, silicone and epoxy, commonly called ’Hybrid Foams’. Compression tests are made under quasi-static and dynamic conditions, and analysed with non-destructive technique (Infrared Thermography), which allows to obtain thermal images (thermogrames), used to study the deformation modes. The analyses of the results passes not only through the study of the deformation modes but also focuses on its influence in energy absorption capability, as well as in the occurrence of cracks and fractures. The results show that foam filled tubes with closed-cell, expanded inside the tube itself ( designated as in-situ), ensures a better mechanical response, due to its more stable and predictable behaviour.
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Yüksel, Sinan Güden Mustafa. "Crushing behaviour of aluminum foam-filled composite tubes/." s.l.]: [s.n.], 2005. http://library.iyte.edu.tr/tezler/master/makinamuh/T000380.pdf.
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Thesis (Master)--İzmir Institute of Technology, İzmir, 2005.Keywords:crushing, aluminum foam, foam filling, energy absorber, composite tubes. Includes bibliographical references (leaves. 93-96).
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Keltner, Noelle Joy. "Study of PocoFoam (TM) as a heat exchanger element in cryogenic applications." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51774.
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Superconductors present great potential for weight reduction and increased power delivery when compared to traditional copper power delivery systems, but current systems require cryogenic cooling systems. Traditional superconductor cooling systems consist of helium cooled by helical heat exchangers made of Oxygen Free High thermal Conductivity (OFHC) copper tube. The helium is cooled by bulky heat exchangers consisting of OFHC copper coils wrapped around a cryogenic cooler heat sink for heat transfer into the working fluid. Metal foams have recently been studied in a variety of heat transfer applications, and could greatly reduce the weight of heat exchanger modules in superconductor cooling systems while simultaneously providing increased heat transfer effectiveness. Aluminum and Copper foams have been available for several years, but more recently, graphite foams, such as PocoFoam™, have been developed which have particularly good heat transfer characteristics. Using Computational Fluid Dynamics (CFD) to model a cryogenic heat exchanger application, this study examines the effectiveness and pressure drop of several metal foam heat exchangers, and compares their performance with the traditional helical coil design for superconductor cooling applications. The CFD simulation results show that a heat exchanger with the same heat sink contact area as existing helical heat exchangers weighs up to 95 percent less and can be up to 25 percent more effective, depending on system conditions such as pressure, cryogenic cooler temperature and helium inlet temperature. Aluminum and copper foam heat exchangers had comparable weight to the PocoFoam heat exchanger, but were significantly less effective than the helical or PocoFoam heat exchanger models.
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Merrett, Richard Peter. "Dynamic response of aluminium foams." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10739.
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This thesis presents the results of an investigation into the response of two types of aluminium foam (ALPORAS and Cymat) to quasi-static, impact, and blast loading. The design of experiments and experimental results are reported.
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Akseli, Ilgaz Güden Mustafa. "The application of aliminum foam for the heat and noise reduction in automobiles/." [s.l.]: [s.n.], 2005. http://library.iyte.edu.tr/tezler/master/makinamuh/T000343.pdf.
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Thesis (Master)--İzmir Institute Of Technology, İzmir, 2005.Keywords: Aluminum matrix composites, thermal conductivity, sound insulation, foam, metal matrix composites, aluminum foam. Includes bibliographical references (leaves. 77-81).
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Zaragoza, Gael. "Aluminium foams for heat transfer applications." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/3882/.
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Open cell metal foams show great potential as a heat exchangers, due to their permeability to fluids and the high conductivity of the metallic network. In this study, aluminium foams were produced using the replication technique with NaCl, flour and water used to create the preform. The samples produced included both uniform pore sizes and examples where different pore sizes were created in different parts of the sample as well as these, samples made commercially by a similar technique (Corevo foams) and by an investment casting process (Duocel foams) were examined. A bespoke rig was designed, built and used to measure the thermal and fluid flow performance of all foams being investigated under forced convection conditions. Results for heat transfer coefficient and pressure drop across the sample with the comparison between each type of sample are presented. It was found that all the foams tested can have favourable heat transfer behaviour under certain conditions asymmetric behaviour can be obtained when non-uniform pore sizes are present; a factor that could be exploited in heat exchanger design.
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Joesbury, Adam Michael. "New approaches to composite metal joining." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/10009.
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This thesis explores new methods for achieving load-carrying joints between the dissimilar materials of continuous fibre reinforced polymer matrix composites and structural metals. The new composite-to-metal joining methods investigated in this work exploit the metal-to-metal joining techniques of arc micro-welding, resistance spot welding, and metal filler brazing, to form novel micro-architectured metal adherends that can be used for enhanced composite-to-metal joining. Through a combination of equipment instrumentation and metallographic inspection of fabricated prototype joints, understanding is gained of how materials respond when processed by manufacturing techniques that have not previously been exploited for dissimilar material joining. Mechanical testing of prototype joints; both to ultimate loading strength and partial failure states, with subsequent inspection of specimens and comparative performances evaluation enabled joining performance characterisation of the new joining methods. Key results include: the identification of micropin reinforced adhesive joints to exhibit pseudo-ductile failure characteristics, resistance spot weld reinforcement of adhesive joints to boost bonding performance, and the use of a polymer infused metal foam to overcome difficulties of thermoplastic to metal adhesion. Through this work knowledge of how novel micro-architectures reacted under mechanical loading enabled insights to be gained into how perceived manufacturing defects can benefit joining performance. Such examples include, localised material weakness that lead to global pseudo-ductile failure behaviour, and low-strength secondary joining mechanisms boosting primary load transfer systems. By comparison of the diverse joining methods investigated in this work, trends were identified that suggest joining performance between the two dissimilar materials is improved by increasing the direct interaction between the composite reinforcement fibres and the metal structure. It is demonstrated that joining improvements are gained by forming mechanical connections between metals and composite precursory material before the final manufacturing process of the composite.
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Kavi, Halit Güden Mustafa. "Investigation of compression mechanical behaviour of aluminum foam filled metal tubes/." [s.l.]: [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/makinamuh/T000488.pdf.
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Nammi, Sathish Kiran. "Finite element analysis of aluminium foams under compressive loading." Thesis, University of Bolton, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.573674.
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This thesis is concerned with developing numerical models to predict the mechanical behaviour of closed-cell aluminium (AI) foams under uniaxial loading. Many of the existing models produce responses which are very stiff initially and fall sharply after an initial peak (Type-II response). In contrast, the real Al foams exhibit a reduced stiffness and give a flat-topped curve in the neighbourhood of peak-load (Type-l response). Thus, the weakness of the existing unit-cell models in relation to the two qualitatively different load displacement responses was identified. A link has been established between the stretching dominated mode of deformation to the Type-II response and the bending dominated to the Type-l response respectively. The absence of Type-l response in the current unit-cell models in the literature moved the present research in a direction to identify an improved new 3D unit-cell, which can be used by future researchers to represent closed-cell Al foam in loading scenarios with large deformations. The unit-cell identified has a right polyhedra structure. Furthermore, the deformation for this model is bending dominated thus giving Type-l response in three principal loading directions. Two sets of polyhedra unit-cell based finite element (FE) models for the crushing of closed-cell Al foam were presented. The first set was constructed by stacking up to 6-cells along principal material loading directions. Perpendicular to the loading direction, the mechanical behaviour for an infinite system was simulated by using periodic boundary conditions (PBC). In the second set, a finite domain sample containing up to 64 unit-cells was used to capture the compressive response behaviour. The crush features of this system were obtained using 3D array of many cells (MC). Additionally, the application of the second type of FE models was extended further to study the performance of Al foam containing imperfections under low-velocity impact by a rigid indenter. A simple imperfection in the form of reduced cell-wall thickness was introduced into the unit-cell Al foam and a set of two different populations of imperfections were considered. All these aforementioned FE foam model predictions were compared with experimental results. Finally, the new 3D unit-cell model results were compared with the contemporary stretching dominated (Type-II response giving) models in literature namely, the truncated-cube and cubic-spherical. A parametric study was conducted to quantify the mechanical properties of aforementioned unit-cell models alongside the model developed in this thesis. It was demonstrated that the plateau phase stress-strain response of the developed 3D unit-cell model was more representative of real closed-cell Al foams. Further, it was shown that the crushing resistance and energy absorption features of this new 3D unit-cell model were higher, compared to the truncated-cube and cubic-spherical models.
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Senior, Faye. "The development of aluminium foams for enhanced heat transfer." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/18317/.
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A novel replication technique for the production of open-celled aluminium foam has recently been devised and is undergoing commercial development by the company Constellium. The technique allows close control over the pore size and shape; a feature that is uncharacteristic of metal foam production methods in general and control to such an extent is unprecedented. The method provides an excellent pathway for the exploration of pore geometry/heat transfer behaviour relations, which is the objective of this study. This also aligns with the commercial goals of Constellium as heat transfer applications have been identified as a key market for their foams. Based on the technique; the focus of this work was the development of a laboratory protocol to allow the production of aluminium foam samples with a range of different mesostructures. The heat transfer behaviour, including permeability, of foams with differing matrix metal, pore size, pore aspect ratio and pore shape were examined under forced convection conditions. Decreasing pore size was found to provide enhanced heat transfer, although for pores < 3mm the benefit was outweighed by a large decrease in permeability. Small changes in pore shape as a result of preform compaction during processing may be exploited to provide improved heat transfer without reducing permeability. Elongation of pores provided no enhancement of heat transfer or permeability.
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Santosa, Sigit P. "Crash behavior of box columns filled with aluminum honeycomb or foam." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10484.
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Bartolucci, Stefano 1976. "Commercial application of aluminum honeycomb and foam in load bearing tubular structures." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28868.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.Includes bibliographical references.
Small dimension engineering tubular structures subjected to a complex load system are designed like hollow circular shells. For minimum weight design, the ratio between the shell radius and the thickness has to be as large as possible, but its maximum value is limited by the onset of local buckling. Tubular natural structures subjected to a complex load system have often an outer shell of solid material supported by a low density, compliant core, which makes them more resistant to local buckling. Biomimicking of natural constructions offer the potential to improve the design of small diameter tubular engineering structures. Here, the fabrication technology of biomimicked engineering tubular structures integrating aluminum foam or honeycomb as core material is discussed. A viability analysis is presented including technical performance, cost, utility, and risk assessments. Aluminum compliant core shells have potential for substituting CFRP and aluminum tubular structures in aerospace and high-level sport applications. The case of sailboat masts was considered in detail. Results of our analysis proved that use of honeycomb as core material can lead to a significant reduction of the mast weight. Business opportunities based on this application are discussed.
by Stefano Bartolucci.
M.Eng.
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Mutsakatira, Innocent. "The effect of the surface condition of Aluminium ingot (AA3003) during roll bonding with clad Aluminium alloy (AA4045) to form an Aluminium brazing material." Master's thesis, Faculty of Engineering and the Built Environment, 2021. http://hdl.handle.net/11427/32875.
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Hulamin is the leading producer of aluminium products in South Africa. One of the products made at Hulamin is the aluminium brazing sheet. The aluminium brazing sheet is made from two aluminium alloys, AA3003 and AA4045. The main alloying element in the 3XXX series alloy is manganese and the main alloying element in the 4XXX series alloy is silicon. An aluminium brazing sheet is manufactured during an industrial process called “accumulative roll bonding”, where AA4045 is termed “the clad” and AA3003 “the core”. The two materials are stacked together with the core sandwiched between two clad layers. Before the materials are stacked together, they undergo surface preparation. At Hulamin, the surface roughness of the core is kept at 10 µm and the surface roughness of the clad at 1 µm. After surface preparation, the stacked material is put into a hot rolling mill, where it undergoes reduction through several passes until it reaches the desired gauge. The aim of this project is to determine the effect of the surface roughness of both the clad and the core on the quality of the bond after roll bonding. While the relevant literature specifies that an increase in surface roughness increases bond strength, the current set surface finishes being implemented at Hulamin have been obtained through trial and error, with no validated experimental work to support them. This research aims to find the optimum surface finish in order to streamline the process of surface preparation. A design matrix was constructed based on the surface finish being used at Hulamin, where the core was at 10 µm and the clad at 1 µm. Fourteen surface conditions were formulated and three tests were performed on each surface condition. The samples were manually ground on different grit papers to an average surface roughness of 0.5 µm, 1 µm and 3 µm for the clad and 7 µm, 10 µm, 15 µm and 25 µm for the core. Simulation of the hot rolling at the University of Cape Town's (UCT's) Centre for Materials Engineering (CME) laboratory was achieved using plane strain compression testing (PSC) on the Gleeble 3800. The PSC sample geometry of 30 mm x 50 mm x 10 mm was achieved by stacking a 5 mm sample from the clad liner plate and a 5 mm thick sample from the as-cast core material. To simulate the hot roll bonding the tests were run at 450 ºC at a strain rate of 1.5 s-1 . The test parameters were obtained from the Hulamin mill log data. In order to assess the strength of the bond, post PSC test, tensile shear testing was performed on specimens wire-cut from the gauge of the deformed PSC sample. The tensile shear specimens were designed according to ASTM D3165. The tensile shear tests were performed on a Zwick Universal Testing machine, in conjuction with single-camera Digital Image Correllation (DIC). The purpose of the DIC was to monitor the strain localisation at the interface. The tensile test was run at 0.0012 mm/min at room temperature. The shear test results confirmed that surface roughness played a major role in the bond strength formed between these two dissimilar materials. It was found that the Hulamin benchmark surface preparation, set at 10 µm and 1µm, could be improved by increasing the surface roughness of the core to 15µm while keeping the clad surface finish constant. The rolling direction (RD) of the specimen was cut, mounted and polished for microstructural feature characterisation, using light microscopy and scanning electron microscopy (SEM) with backscattered electron (BE) imaging. In order to characterise the bond further, energydispersive X-ray spectroscopy (EDS) was performed across the interface of the samples to show the diffusion of Si. Microstructural analysis revealed that a poor bond resulted in the presence of large voids, while a high integrity metalurgical bond contained very small voids. Also, a good metallurgical bond allowed for the diffusion of Si across the bond, although these results were qualitative because diffusion of Si across the interface is largely time- and temperature-dependent. Combined strain and microstructural results showed that finer surface roughnesses yielded poorer bonds because of minimal frictional force and that rougher surface finishes also yielded poorer bonds, owing to larger troughs on the surface of the material that led to void formation at the interfaces, which in turn caused sites of delamination. There had to be an optimum surface finish that existed between the two alloys where the finish would obtain a metallurgical bond that was of optimum strength. Should this optimum finish be exceeded, the strain level would inevitably increase during tensile shear testing, with the induced voids increasing in size and Si diffusion across the interface decreasing, thereby indicating a compromise in the quality of the bond. It was found that the Hulamin benchmark surface preparation, set at 10 µm and 1µm, could be improved by increasing the surface roughness of the core to 15µm while keeping the clad surface finish constant. The findings of this research could be of significant value to Hulamin in the improvement of the quality and cost of the end product under consideration.
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Martinec, Pavel. "Návrh bezpečnostních prvků vozidla Formule Student." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229847.
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The subject of this thesis is to design safety components for the Formula Student car. The aim is to handle the driver’s safety proposals regarding the competition rules. The main point of interest is focused on the impact attenuator issue, which is designed and tested by appropriate method. In addition are designed other security features such as seat belts, seat belts installation and driver equipment are.
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Velay, Xavier. "Analysis of the conform process : a specific form of aluminium extrusion." Thesis, Bournemouth University, 2004. http://eprints.bournemouth.ac.uk/432/.
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Since the Conform process was patented 30 years ago, there have only been approximately 200 machines sold worldwide. Given that Conform competes economically with conventional extrusion and is also reported to be a more energy efficient process, it is surprising that the use of Conform is not more widespread in today's increasingly environmentally conscious and high-production focussed world. One explanation for this is likely to be due to the fact that there is still limited knowledge of the thermo-mechanical behaviour of the workpiece during extrusion. Furthermore, for the aluminium industry, there are still issues remaining regarding the production of flash and the quality of the extrudate in terms of mechanical properties. This study provides the reader with the findings of the research and experimental work undertaken by the author, his co-workers and fellow specialists, in the field of aluminium extrusion including Conform. The experimental work includes both laboratory experiments performed with a direct extrusion press and an experimental machine set up to replicate the Conform process. The experimental work is also simulated using finite element modelling techniques. The results from these analyses are then validated by comparing industrial and experimental data. The finite element analyses are enhanced by using parallel processing technology and user sub-routines. The author proposes new models to allow for the study of the different sub-processes in Conform. These include the coining of the feedstock, formation of the upset zone, extrusion of the flash, the filling-up of the expansion chamber / feeder plate and the extrusion of the extrudate. The author also investigates methods which predict microstructure and surface cracks in the extrudate. The author suggests innovative techniques to improve the efficiency of finite element analysis in metal forming. Finally the author recommends procedures for the study of structural integrity and the optimisation of the tooling used in Conform.
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Al, Tenaiji Mohamed. "Characterisation of aluminium matrix syntactic foams under static and dynamic loading." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/18857/.
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In this study, aluminium matrix syntactic foams reinforced with several types of ceramic micro-sphere were produced by pressure infiltration. The mechanical properties of a range of aluminium matrix syntactic foams were investigated in order to optimise the composition and structure to find the best configuration in terms of high energy absorption capability, and to validate the finite element predictions against the corresponding experimental results. Initially, the compressive behaviour of six different types of aluminium matrix syntactic foam was evaluated. It was shown that the size of the ceramic micro-spheres, the grade of the aluminium matrix and the volume fraction of the aluminium matrix all have a significant influence on the compressive strength and energy absorption capability of the material. Then, the three-point bending and shear fracture properties of aluminium syntactic foams were evaluated. These tests indicated that density plays an important role in determining the stiffness, specific energy absorption and ultimate flexural strain. Here, it was found that the specific energy absorption related to shear was lower than that corresponding to flexure. Following this, the behaviour of the syntactic foams under low velocity impact was characterised and the underlying failure mechanisms were identified to evaluate their effective mechanical performance. It was found that the aluminium syntactic foams subjected to drop-weight impact have 20–30% higher plateau values than samples subjected to the equivalent level of quasi-static compression. Subsequently, the Split Hopkinson Pressure Bar technique was used to investigate the behaviour of the material at high strain-rates, which highlighted the material sensitivity of aluminium syntactic foams under high strain-rate loading. Following this, terminal ballistic tests were conducted to determine the perforation resistance of the aluminium syntactic foams. The results showed that the syntactic foams have the ability to prevent the perforation of projectile velocities up to 120 m/s. Finally, blast tests were performed to investigate the influence of the charge mass and sample thickness on the dynamic response of the syntactic foams. The results showed that syntactic foams with a thickness of 14 mm have the capability to sustain a blast load of 4.82 Ns. Finite element models were developed to simulate the structural behaviour of aluminium syntactic foams subjected to various quasi-static and dynamic loads. Here, an elasto-plastic model with both ductile and shear failure criteria was employed to predict the material performance. The rate-dependent response of the foam was considered by a stress-ratio based model to take strain-rate effects into account. The numerical simulations were compared with their corresponding experimental results with reasonably good correlation. In general, the essential features of the aluminium syntactic foams tested under different loading regimes were captured by the FE models, including load-displacement traces, deformation and failure modes.
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Mariani, Laura Leana. "Electroless coatings on titanium hydride for use in the production of aluminum foam." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99525.
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Aluminum foam is a porous form of solid aluminum. One method of producing aluminum foam is the powder metallurgy process. Aluminum powder is mixed with a foaming agent, generally titanium hydride (TiH2), and pressed to form a compact. In the foaming process, the compact is heated and hydrogen gas is released from the agent to form bubbles within the surrounding aluminum. However, there is a significant gap between the onset of the decomposition temperature of the TiH2 (400°C) and the melting point of aluminum (660°C). The hydrogen gas evolution begins while the aluminum is still solid, creating an accumulation of gas pressure which eventually causes microfissures inside the matrix. As a result, the final structure has interconnected pores and inferior properties.This problem may be overcome by delaying the temperature of hydrogen evolution so that it coincides with the melting point of aluminum. Coating the titanium hydride with copper or nickel can create a kinetic barrier that retards the flow of hydrogen into the surrounding matrix.
Electroless plating is a process that can be used to deposit metallic coatings on non-conductive materials. Metallic ions in solution are reduced by a suitable agent, creating a metal deposit on the substrate. The process is autocatalytic and continues until all the metallic ions are consumed.
The objective of this work was to investigate the effect of the copper and nickel coatings on the hydrogen evolution of titanium hydride powders. It was found that the metal coatings do tend to delay the temperature of gas release and that this could potentially be used to improve the foaming process.
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Toksoy, Ahmet Kaan Güden Mustafa. "Quasi-static axial compression behavior of empty and polystyrene foam filled aluminum tubes/." [s.l.]: [s.n.], 2003. http://library.iyte.edu.tr/tezler/master/makinamuh/T000246.rar.
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Vendra, Lakshmi Jyotshna. "Processing and Characterization of Aluminum-Steel Composite Metal Foams." NCSU, 2008. http://www.lib.ncsu.edu/theses/available/etd-05282008-163908/.
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Composite Metal Foam (CMF), a new material belonging to the class of advanced cellular and porous materials, has been successfully processed using Gravity Casting technique for the first time at NC State University. This material comprises of steel hollow spheres and a solid Aluminum alloy matrix. The complete characterization of the material included mechanical testing such as monotonic compression, compression-compression fatigue, micro hardness, nano hardness and higher strain rate compression. The energy absorption behavior of the material under static compression has been studied extensively. Experimental results show that Al-steel CMF not only has a higher energy absorption capability than that of other commercially available metal foams produced from similar materials, but also possess a higher strength to density ratio. The microstructural analysis of the material was used to study and explain the formation of different phases at the Aluminum-Steel interface and their effect on the deformation behavior of the composite foam under compression. The effect of processing temperature on the microstructure of the composite metal foam and specifically on the sphere-matrix interface was studied by experimental means. The mechanical properties of the ternary phases formed in the microstructure of the composite foam were characterized using micro and nano-hardness tests. The phases were chemically characterized and formulated using Energy Dispersive Spectroscopy analysis and Al-Fe-Si alloy ternary phase diagrams. The fatigue behavior of the composite metal foams was studied under compression-compression fatigue loading and the results were compared with those of other closed cell metal foams. The elastic modulus of the foams was evaluated using experimental and analytical techniques and the results were found to be in good agreement. Composite metal foams were also processed using a higher solidification rate with water cooling. The effect of alterations in microstructure on the mechanical properties of the composite metal foams was studied and results presented. As the result of high strength, the increase in energy absorption of the composite metal foam samples ranges over thirty times compared to that of 100% Al foams and over six times compared to that of 100% steel foams.
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Elbir, Semih Güden Mustafa. "Preparation and characterization of aluminum composite closed-cell foams/." [s.l.]: [s.n.], 2001. http://library.iyte.edu.tr/tezler/master/kimyamuh/T000022.pdf.
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Zhang, Chuan. "Aluminum foams composite : elaboration and thermal properties for energy storage." Thesis, Troyes, 2017. http://www.theses.fr/2017TROY0015/document.
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L'objectif de cette thèse est d'étudier et d'optimiser le processus de fabrication des mousses métalliques et le comportement thermique du matériau de la mousse d'aluminium/matériau de changement de phase (MCP) par des méthodes expérimentales et numériques. Le processus d’élaboration de la mousse d’aluminium à pore ouvert est développé et optimisé pour contrôler précisément les paramètres de fabrication. Deux modèles de mousse d'aluminium à haute porosité (MAHP)/MCP composite et à faible porosité (MALP)/MCP composite sont établis pour la simulation numérique. En simulant le processus de fusion d'un système de stockage d'énergie, les composites MAHP/MCP et MALP/MCP sont comparés numériquement afin d'évaluer la performance de stockage d'énergie thermique. Les résultats montrent que la mousse d'aluminium améliore nettement le processus de transfert de chaleur dans MCP en raison de sa haute conductivité thermique. La porosité des mousses d'aluminium influence non seulement le processus de fusion du composite mais aussi la performance de stockage d'énergie thermique. Grâce à la collaboration avec EPF, une nouvelle méthode d’élaboration des mousses périodiques d'aluminium à pore ouvert est développée dans cette thèse sur la base d’impression 3D. Le comportement thermique des mousses d'aluminium périodiques à pore ouvert/MCP est analysé expérimentalement et numériquementThe objective of this thesis is to study and optimize the manufacturing process of metal foams and the thermal behavior of the aluminum foam/phase change material (PCM) composite by experimental and numerical methods. The manufacturing process of open-cell aluminum foam is developed and optimized to precisely control the parameters of mufacturing. Two pore-scale models of high porosity aluminum foams (HPAF)/PCM composite and low porosity aluminum foams (LPAF)/PCM composite are established for numerical simulation. By simulating the melting process of a layer energy storage system, the HPAF/PCM and LPAFS/PCM composite are compared numerically in order to evaluate the energy storage performance. The results show that aluminum foam improves greatly the heat transfer process in PCM due to its high thermal conductivity. The porosity of aluminum foams could not only influence the melting process of composite but also the energy storage performance. Thanks to the collaboration with EPF, a new manufacturing method of periodic open-cell aluminum foams is developed based on 3D rapid tooling. The thermal behavior of the periodic open-cell aluminum foams/PCM composite is experimentally and numerically analyzed
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Klinter, Andreas. "Wetting behaviour of aluminum alloys on ceramic substrates and its effect on the stability of aluminum foams." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92344.
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Bernardo, Franco. "Sviluppo di procedimenti di saldatura LASER e LASER arco per pannelli AFS (Aluminum Foam Sandwich)." Doctoral thesis, Universita degli studi di Salerno, 2010. http://hdl.handle.net/10556/207.
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2008 - 2009La tesi presenta l’attività di ricerca condotta presso il laboratorio LASER del centro di ricerca ENEA - Trisaia (MT) per lo sviluppo di un procedimento di saldatura, ancora poco diffuso a livello industriale, che è la saldatura ibrida LASER-arco. Inoltre, la novità del lavoro riguarda anche i materiali oggetto di indagine consistenti in estrusi di lega di alluminio, saldati a formare una struttura portante, a cui sono stati collegati pannelli sandwich di schiuma di alluminio (AFS), con una giunzione continua tale da garantire un collegamento strutturale. Considerate alcune problematiche, rilevate dal lavoro di ottimizzazione dei parametri della saldatura LASER-MIG, è stata verificata la possibilità di superare questi problemi (ad esempio la mutua influenza di parametri LASER e di quelli MIG) con l’impiego di un altro tipo di tecnologia LASER-arco basata su generatori a caratteristica cadente di tipo TIG e materiale d’apporto sotto forma di filo freddo. Per questa parte, il lavoro è stato mirato fondamentalmente alla progettazione del nuovo sistema e alla realizzazione di un primo prototipo che ha permesso di evidenziare alcuni importanti risultati. Nella prima parte del lavoro si sono analizzate le prove di saldatura ibrida LASER-MIG tra AFS e profilati di lega di alluminio. Dall’analisi delle prove è emerso che la saldatura ibrida, applicata a materiali altamente riflettenti alla radiazione LASER CO2 come la lega AA6060 T6, permette la saldatura con adeguati fili d’apporto, al contrario della saldatura LASER stand alone. Infatti, questo tipo di lega, di cui sono costituite anche le pelle dei pannelli AFS, riflette fortemente la radiazione LASER CO2 inibendo l’innesco del processo di saldatura keyhole anche con potenze specifiche di 4 x 106 W/cm2. Tale problematica è influenzata molto dall’impostazione dei parametri geometrici LASER-MIG, in particolare il posizionamento relativo delle sorgenti e, più in generale, permette una variabilità molto limitata nell’impostazione dei parametri geometrici, elettrici, delle velocità di saldatura e la quantità di filo d’apporto. Per limitare il problema della mutua interazione fra LASER ed arco, poiché il processo MIG non permette una regolazione della quantità di filo indipendente dalla erogazione della potenza, nella parte finale delle attività si è descritta l’analisi dei componenti necessari, le scelte progettuali, la progettazione di componenti specifici per l’implementazione di una stazione di saldatura ibrida LASER –TIG. Si è realizzato un prototipo con il quale si sono fatti dei test preliminari. Con il prototipo, se pur limitante per quanto riguarda le regolazioni possibili rispetto alle attrezzature definitive progettate, si sono eseguite alcune prove di penetrazione su acciaio inossidabile e leghe di nichel, per le quali erano già noti i benchmark, in termini di velocità massima di processo, alla massima potenza del LASER per ottenere la piena penetrazione, sulla stazione di lavorazione ND:YAG del C.R. ENEA - Trisaia. Da queste prove è emerso chiaramente che la saldatura ibrida, in termini di produttività, è molto più vantaggiosa della saldatura con il solo LASER poiché si sono riscontrati, su tali materiali, aumenti di velocità variabili tra il 60% e il 70% (a parità di potenza LASER). Chiaramente trattandosi di prove esplorative i valori devono intendersi solo indicativi, ma comunque superiori al 20%-30% che normalmente la letteratura riporta come dato. [a cura dell'autore]
VIII n.s.
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Hardwicke, Canan Uslu. "Processing and properties of Ti-6A1-4V hollow sphere foams from hydride powder." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/19650.
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Grönvall, Sarah. "Jugendornamentik feat. Vectorestetik : Utemöbler för Berga Form AB." Thesis, Linköping University, Carl Malmsten - Centre for Wood Technology & Design, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-6998.
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Denna rapport presenterar det examensarbete på 10 poäng jag gjorde på möbeldesignprogrammet vid Carl Malmsten CTD våren 2006. Syftet med denna rapport är att beskriva och klargöra processen av detta examensarbete samt formgivningen av produkterna som styrts av mitt koncept. Rapporten grundar sig på dokumentation från processens gång och jag har valt att redovisa mitt arbete i denna rapport i fyra kapitel. Den första inledande delen beskriver bakgrunden till projektet, den andra redovisar insamlingsetappen i form av bild, skissmaterial och konceptbeskrivning, den tredje handlar om skissetappen och själva designprocessen och den sista visar dokumentationen av gestaltningsarbetet av prototyperna. Avslutningsvis kommer en resultatanalys och kommentarer till arbetet och produkterna. Bakgrunden till valet av mitt examensarbete var att jag var nyfiken på hur möbler för utemiljö kan se ut och vilka funktioner de eventuellt kan ha.Jag ville tillföra något som utstrålade något nytt, men som inte förlorat sina kvalitativa egenskaper i fråga om hållbarhet och problemfritt underhåll. Med dessa ideér kontaktade jag Berga Form AB eftersom min uppfattning var att de, liksom jag, värderar kvalité och omsorg för detaljer högt, dessutom har de sin huvudsakliga produktion på Java, Indonesien. Och det var just i denna miljö jag vistades i när jag kontaktade Berga Form första gången. Jag gjorde tre månaders praktik i Singapore/Java höstterminen 2005 när jag fick idén för mitt examensarbete. Resultatet är ett bord och en sittbänk för utemiljö i gjuten aluminium och massiv ask. Produkternas funktion underlättar transport, lagerhållning och vinterförvaring hos kund. Estetiken är exlusiv och stilfull för att passa i Berga Forms nuvarande sortiment. Formspråket som sammanfattar stämmningen för mitt kandidatarbete är; “svart & vitt, prunkande ornamentik, inspirerat av jugend & vectorestetik, samt massivt trä i strama former.”
This report presents the graduation project worth 10 points that I completed in the Furniture Design Program at Carl Malmsten CTD, spring 2006. The purpose of this report is to describe and explain the process of this graduation project and the design of the products that has
shaped the form of my concept.
The report is based on the documentation from the process. I have choosen to present my
work for this report in four chapters. The first and opening chapter describes the background of the project, the second one shows the research, using pictures, and the concept for the
project. The third, is about the design and sketching process, while the last one presents the prototyping. The final part is an analysis of the result and some comments on the work and the
products.
The reason I chose this as my graduation project was beacuse I was curious about outdoor furniture and the possible functions they can have. These types of furniture will not go out of date, as long as the weather permits, as we will always spend time outdoors and will always have a need for products in this environment. I was looking to provide something new in this area, without losing the inherent properties to outdoor furniture.
I presented these ideas for Berga Form AB, because my understanding was that they, just like me, value quality and care for details. Furthermore, they produce the majority of their
products in Java, Indonesia. I was in this area when I contacted Berga Form the first time. I did a 3 months internship in Singapore/Java the autum semester of 2006, when I thought up the idea for my graduation project.
The result if this project is a table and a bench for outdoor environments. The material is cast aluminum and solid Ash tree. This product has a function that will ease transport for Berga Form and winter storage for the customer. The furniture posesses an aesthetic that is exclusive and stylish to match Berga Form´s present collection.
The design concept for this graduation project is;
“black & white, dazzling patterning, inspired by Jugend and Vector aesthetically and solid wood reserved shapes”.
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Simpson, Ronald James. "The use of chills as a means of influencing solidification in lost foam cast aluminum alloy A356." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ28662.pdf.
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Bonaldi, Patrik Oliveira. "Obtenção de espuma de alumínio através do processo de Metalurgia do Pó e propriedades mecânicas de estruturas sanduíche." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/75763.
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Espumas de alumínio são materiais de estrutura porosa que combinam as propriedades de materiais celulares com as dos materiais metálicos. A espuma metálica, com porosidade acima de 70%, pode ser obtida principalmente pela via “metal líquido” e via “metalurgia do pó”. Este trabalho visa uma contribuição para o desenvolvimento da produção de espumas de alumínio via Metalurgia do Pó (MP), inédita no Brasil. Busca-se estudar e definir os parâmetros para produzir a espuma de alumínio e estruturas sanduíche através do processo de MP e por fim conhecer o seu comportamento mecânico. É proposta, também, uma otimização do processo, pois, atualmente, a etapa de compactação do pó ocorre através do processo de extrusão, ou compactação a quente ou laminação, ou ainda a combinação desses. Para definir os parâmetros do processo foi estudada a condição de mistura, além da proporção do pó de alumínio e o agente expansor (TiH2). Foram estudadas as condições do processo de espumagem variando temperatura e tempo. A partir desses resultados foram obtidas as estruturas sanduíche, sendo que o foco foi tubos metálicos de aço preenchidos por espuma de alumínio. Posteriormente, foi estudado o comportamento mecânico da espuma e dos tubos preenchidos com espuma através dos ensaios de compressão e flexão. Os resultados das propriedades das espuma foram comparados com as propriedades previstas através de equações propostas por Ashby et. al.. Os resultados indicam a real possibilidade de realizar apenas a compactação axial a frio do pó metálico, atingindo densidade superior a 95% do material denso com 450 MPa de pressão de compactação. O processo de mistura dos pós mais adequado foi o realizado em misturador convencional do tipo “duplo V” por 2 horas, obtendo uma boa homogeneidade. A condição mais adequada de obtenção de espuma foi com a proporção de mistura de 1,0% de TiH2, com espumagem em 710oC por 10 minutos. Os ensaios mecânicos mostraram que os tubos preenchidos com espuma de alumínio apresentam um aumento considerável nas propriedades.Aluminum foams are materials of porous structure that combine the properties of cell material with those of metallic materials. The metal foam, with porosity above 70%, can be achieved mainly by the "liquid metal route" and by "powder metallurgy". This study aims to contribute to the development of aluminum foam production by powder metallurgy process (PM), unprecedented in Brazil. The objective is to study and define the parameters for producing aluminum foam and sandwich structures by the process of PM, and understand its mechanical behavior. It is proposed also a process optimization, since nowadays the powder compaction phase takes place by the process of extrusion, hot compression or rolling, or even a combination of these. To establish the process parameters, the condition of mixing was studied, as well as the amount of aluminum and blowing agent (TiH2) powder. Were also studied the foaming process conditions by varying the temperature and time. From these results were obtained the sandwich structures, being the focus on steel metal tubes filled with aluminum foam. Subsequently, it was studied the mechanical behavior of the foam and the tubes filled with foam through bending and compression tests. The results of the properties of the foam were compared with the properties predicted by equations proposed by Ashby et. al .. The results showed real possibility to perform only cold axial compression of the metal powder, reaching a density greater than 95% with 450 MPa of compaction pressure. The most adequate mixing of the powders process was carried out in a conventional mixer such as "double V" for 2 hours to give a good homogeneity. The best condition for obtaining foam was with the mixing amount of 1.0% TiH2, with foaming at 710oC for 10 minutes. The mechanical tests showed that the tubes filled with aluminum foam present a considerable increase in the properties.
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Proa, Flores Paula Mercedes. "Aluminium foams fabricated by the PM route using nickel- coated titanium hydride powders of controlled particle size." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=92343.
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Ibrahim, Ahmed Hamed. "Effect of material and processing parameters on the morphology of aluminium foams produced by the PM route." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976253623.
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Gaytan, Guillen Sara Marisela. "Additive layer manufacturing of TI-6AL-4V by electron beam melting from powder particles solid, mesh and foam components study /." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Jinnapat, Apichart. "The manufacture and characterisation of aluminium foams made by investment casting using dissolvable spherical sodium chloride bead preforms." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.588085.
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This project sought to design, implement and evaluate a process for the manufacture of porous, spherical salt beads, in order to enhance the reproducibility in mechanical properties of open cell aluminium foams made by a replication-based manufacturing technique. Porous beads were favoured in order to increase the dissolution rate of the salt from the preform, thereby making the manufacture of large foam parts practical. Salt beads were made by a novel method using fine NaCI powder, flour and water to make a paste that was subsequently disintegrated into large beads by mechanical stirring in oil. The NaCI paste viscosity was found to be important to the production of spherical beads and by varying the intensity of mechanical disintegration of the paste, control of the bead size was possible. The salt beads with sizes from 0.5 to 3 mm diameter were compacted into preforms and made into moulds for infiltration with molten pure aluminium by pressure- assisted investment casting. The heat treatment used to "cure" the plaster mould containing the preform was sufficient to remove the flour from the beads, sinter the preform and increase its strength. The effect of preform compaction conditions on the size, shape and volume fraction of porosity was quantified using a number of techniques, including mercury porosimetry, which was used to model the infiltration process. At the highest infiltration pressure 0.25 MPa (2.5 bar) the resulting foam densities were higher, but led to extensive penetration of molten aluminium into the porous beads, slowing down salt removal. In general, the compression strength increased with increasing foam density, and was highly reproducible, but where metal infiltration into the beads was extensive, the foam density increased but with little improvement in the compressive strength.
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Abdulla, Taha. "The effect of pulsed bipolar plasma electrolytic oxidation coatings on the mechanical properties of open cell aluminium foams." Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/3806/.
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Metal foams have attracted wide range of interest from researchers and industries because of their unique combinations of properties. Of particular interest, open cell metallic foams have good weight-specific mechanical properties, and improvements could make these materials highly desirable for lightweight structural and energy absorption applications. These properties could potentially be increased for open cell foams by treatments affecting their large surface areas. The effect could be very significant, especially when the dominant deformation mode is bending of the foam struts, as the coating will be located away from the neutral bending axis of these struts maximizing its effect. This has been previously found after the application of surface treatments, such as electroplating. The technique of Plasma Electrolytic Oxidation (PEO) is another process that shows an even greater effect on foam specific mechanical properties. In this work, Plasma Electrolytic Oxidation (PEO) coating treatment is applied to open celled aluminium foams with different structures, aiming to improve the mechanical and weight-specific properties of the hybrid material. Open cell aluminium foams of different types, both investment cast (Duocel foam) and replicated (produced in the laboratory) have been produced and PEO coated using a range of different processing parameters. Two pore sizes of Duocel aluminium foam (measured as 2.2 mm and 2.5 mm average pore diameter) with porosity of 90–91%, and a single pore size (1.6 mm diameter) of the pure aluminium replicated foam with porosity around 60–64% have been examined. The PEO treatment of foams was carried out in the pulsed bipolar current mode, with a range of processing times (20, 40, 60 and 80 minutes), pulse frequencies (50 to 6250 Hz) and duty cycles (different ON/OFF waveform ratios). These processing parameters were explored in the present work in four different stages of investigation, as will be explained in detail later. The mechanical properties (yield stress, specific strength, Young’s modulus and energy absorption) of the coated foams produced are assessed experimentally, both in tension and compression, and simple models developed to describe the elastic behaviour, based on either the Gibson-Ashby model of foams as a regular cellular array, or the Markaki-Clyne model of randomly intersecting fibres are used to make predictions to compare to these results. Complimentary characterisation was carried out using SEM, EDX, XRD and nanoindentation techniques to understand the nature of PEO coatings on foams (including coating thickness, growth rate, mechanical properties, porosity, elemental and phase compositions), and the effect this has on mechanical properties. Thereby, the process can be optimised to improve the mechanical performance of the foams. It was demonstrated that PEO coatings can be successfully applied to open cell foams (of low and high level of porosity) and the coating penetrates completely into the structure up to several millimetres depth, with thickness diminishing with depth. The presence of this coating is of benefit for uniaxial mechanical properties as well as specific foam properties. PEO pulse frequency influences coating thickness, porosity and the measured mechanical properties. The major effect on coating hardness and elastic modulus as well as on the strength and stiffness of the coated foams is associated with the volume fraction of porosity within the coating. The effect of using different duty cycles (associated with the ON and OFF times in each cycle in the current pulse frequency used) results in different coating morphology, thickness, distribution and deposition rate. Very fast coating growth rate has been shown to be not always beneficial, whereas low coating growth rate may be useful for the formation of good quality coatings (containing fewer microcracks and possibly lower intrinsic stresses), with potential for a very even distribution into the foam internal structure. An assessment based on strength increase (∆σ) and density increase (∆ρ) of the coated foams shows that the benefits of the application of PEO coatings to metal foams are greater than those shown in other metal foams coated by different techniques. The primary reason for this is that the oxide ceramic coatings formed on foams have low density, excellent mechanical properties and good adhesion to the substrate. These properties have been improved for foams by the PEO optimization process carried out in the present work.
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Comeau, Christian R. "Critical Erosion/Corrosion Piping Wall Thicknesses Under Static and Fatigue Stress Conditions According to ASME Guidelines." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/34057.
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The purpose of this project was to show the updated procedures and to make additions to the computer program called Tmin designed by E. I. DuPont De Nemours and Company. This program is used as a screening tool for determining the largest of the minimum pipe-wall thicknesses in a piping system.
This project involved several additions that will be released in the next version of the Tmin computer program. The first major additions to be implemented are four alternating Stress-to-Number of cycles curves: Aluminum 1100, Aluminum 3003-0, Aluminum 6061-T6, and Nickel 200. In addition, procedures of the ASME for fatigue curve analysis and implementation of fatigue data were investigated. These four stress-to-number of cycles (S-N) fatigue curves were added to Tmin's internal Microsoft Access® database. Next, a 2-D vertical piping span configuration was incorporated. Finally, DuPont required a Microsoft Word® document output of the pipe-wall thickness data including the piping span model information. Other user-friendly additions were included.
Since this computer program was to be American Society of Mechanical Engineers (ASME) compliant, a study of the ASME Pressure Vessel and Piping standards and codes was made to determine how pipe-wall thickness calculations were to be processed. The 2-D vertical piping span calculation procedures were investigated. Once the 2-D vertical piping span analysis was complete, the largest pipe-wall thickness value calculated were passed to a Microsoft Word® document. The last implementation is the inclusion of help files. Help file button additions in all input boxes allowed for the user to know exactly what was needed before a data entry was made.Master of Science
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ROCHA, ROSA M. da. "Obtencao e caracterizacao de ceramicas no sistema Si-Al-O-N-C empregando pirolise de misturas de polissiloxano e cargas." reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11187.
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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP