Autofrettage provides the possibility for increasing the fatigue strength of internal pressurized components. This technique introduces compressive residual stresses, applying a single pressure ...overload prior to the service load. Whereas a lot of investigations for steel materials have been done so far, this report refers to the potential of the autofrettage process for the aluminum wrought alloy EN AW-6082-T5. In order for residual stresses to ensure a reliable increase of the stress amplitude, they must not be relaxed. A significant increase in lifetime at a load amplitude of Delta p = 500 bar is shown for T-shaped bore intersection specimens that are autofrettaged at a pressure of 1500 bar. The introduced residual stresses did not relax after 2.510 super(6) number of cycles. Only for a load with a maximum equivalent stress above the yield strength the components initial compressive residual stress distribution is changed and even partially transferred to the tensile section. Therefore, using autofrettage is appropriate to increase the fatigue strength of aluminum components.Original Abstract: Eine Moglichkeit, die Schwingfestigkeit von innendruckbeanspruchten Bauteilen zu erhohen, bietet die Autofrettage. Bei diesem Verfahren werden Druckeigenspannungen erzeugt, indem einmalig ein Druck aufgebracht wird, der ueber dem spaeteren Betriebsdruck liegt. Waehrend bereits zahlreiche Untersuchungen fuer den Werkstoff Stahl vorliegen, soll in diesem Beitrag auf das Potenzial der Autofrettage fuer die Aluminiumknetlegierung EN AW-6082-T5 eingegangen werden. Um mit den eingebrachten Eigenspannungen eine dauerhafte Erhohung der ertragbaren Spannungsamplitude zu gewaehrleisten, duerfen sie sich nicht abbauen. Die bei einem Druck von 1500 bar autofrettierten T-Verschneidungsproben zeigen bei einem Pruefdruck von Delta p = 500 bar eine signifikante Erhohung der Lebensdauer. Die Eigenspannungen bleiben bis zur Grenzlastschwingspielzahl von 2,510 super(6 )stabil. Erst fuer eine Beanspruchung, bei welcher die maximale Vergleichsspannung oberhalb der Streckgrenze liegt, veraendert sich die anfaengliche Druckeigenspannungsverteilung im Bauteil und geht sogar teilweise bis in den Zugbereich ueber. Die Autofrettage ist somit ein geeignetes Verfahren um die Schwingfestigkeit von Bauteilen aus Aluminium zu erhohen.
Cylindrical bonds representative diagram of alumina-coated MWCNTs.
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▶ Comparing with uncoated-MWCNTs, alumina-coated MWCNTs has higher adsorption capacity toward lead. ▶ In the fixed ...bed mode, the percentage of lead removal increases by decreasing the flow rate. ▶ The lead removal increases when the bed thickness increases.
Alumina-coated multi-wall carbon nanotubes were synthesized and characterized by scanning electron microscopy, X-ray diffraction, and FTIR. They were used as an adsorbent for the removal of lead ions from aqueous solutions in two modes, batch and fixed bed. In the batch mode, experiments were carried out to investigate the effect of contact time, agitation speed, adsorbent dosage and solution pH on the removal of lead. The coated nanotubes exhibit better removal ability over uncoated. For fixed-bed columns, thickness of the layer and flow rate were investigated. Increasing the thickness and decreasing the flow rate enhanced the removal of lead. The prepared adsorbent displayed the main advantage of separation convenience when a fixed-bed column was used compared to the batch adsorption treatment.
Feasibility of AlCl3-based acetamide and urea deep-eutectic solvents as well as EMImCl ionic liquid as electrolyte for rechargeable Aluminium/air cell was evaluated under half-cell and full-cell ...conditions under ultra-dry atmosphere. Half-cell measurements revealed satisfactory activity of all studied electrolytes for Aluminium stripping/deposition with a certain disparity in overpotential and stability. Evaluation at Pt and more especially determination of ORR onset potential was not straightforward. Nonetheless, all systems exhibited a suitable activity and cycling ability under full-cell conditions. Current and energy efficiencies of 84% and 56% were calculated during first 15 charge/discharge Al/air cycles at 100 μA cm−2 for 3 h each in acetamide electrolyte, respectively. Since theoretical reversible electrolyte capacity was evaluated to approximately 28 mAh, only 2.5% of theoretical capacity was able to be cycled.
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•Activities of different AlCl3-based ILs and deep eutectic solvents for Al deposition/stripping and OER/ORR are compared.•Pyrolytic graphite was used as substrate for Al deposition.•Current and energy efficiency of 84 and 56% for Al/air full-cell with acetamide+ACl3 during the first 15 cycles.•First electrically rechargeable Al/air cell with acetamide.
Aluminium in brain tissue in autism Mold, Matthew; Umar, Dorcas; King, Andrew ...
Journal of trace elements in medicine and biology,
03/2018, Volume:
46
Journal Article
Peer reviewed
Open access
Autism spectrum disorder is a neurodevelopmental disorder of unknown aetiology. It is suggested to involve both genetic susceptibility and environmental factors including in the latter environmental ...toxins. Human exposure to the environmental toxin aluminium has been linked, if tentatively, to autism spectrum disorder. Herein we have used transversely heated graphite furnace atomic absorption spectrometry to measure, for the first time, the aluminium content of brain tissue from donors with a diagnosis of autism. We have also used an aluminium-selective fluor to identify aluminium in brain tissue using fluorescence microscopy. The aluminium content of brain tissue in autism was consistently high. The mean (standard deviation) aluminium content across all 5 individuals for each lobe were 3.82(5.42), 2.30(2.00), 2.79(4.05) and 3.82(5.17) μg/g dry wt. for the occipital, frontal, temporal and parietal lobes respectively. These are some of the highest values for aluminium in human brain tissue yet recorded and one has to question why, for example, the aluminium content of the occipital lobe of a 15year old boy would be 8.74 (11.59) μg/g dry wt.? Aluminium-selective fluorescence microscopy was used to identify aluminium in brain tissue in 10 donors. While aluminium was imaged associated with neurones it appeared to be present intracellularly in microglia-like cells and other inflammatory non-neuronal cells in the meninges, vasculature, grey and white matter. The pre-eminence of intracellular aluminium associated with non-neuronal cells was a standout observation in autism brain tissue and may offer clues as to both the origin of the brain aluminium as well as a putative role in autism spectrum disorder.
Disks of an Al-6061 metal matrix composite, reinforced with 10vol.% Al2O3 particles, were processed by high-pressure torsion (HPT) at room temperature for 1/4, 1/2, 1, 5 and 10 turns under an applied ...pressure of 6.0GPa. The evolution of microstructure was investigated using optical microscopy and scanning electron microscopy. During HPT processing the average grain size within the aluminum matrix decreased from ∼35μm in the unprocessed condition to ∼170nm after processing through 10 turns but there was no significant effect on the size and distribution of the alumina particulate clusters. The values of the Vickers microhardness were recorded across the surface of each disk and then plotted as two-dimensional and three-dimensional color-coded contour maps. The results show the hardness increases from ∼56Hv in the initial condition to ∼165Hv after HPT for 10 turns. The results demonstrate that, as in many unreinforced metallic alloys, the evolution of hardness with strain exhibits strain hardening without any significant recovery.
•The average grain size of the Al matrix was ~170nm after processing for 10 turns.•No significant effect of HPT on the size and distribution of the Al2O3 particles.•The evolution of microhardness demonstrates strain hardening without recovery.•The microhardness at low strains increases linearly from the center to the edge.•The microhardness at high strains becomes homogeneous with a saturation of ~170Hv.
The preparation and properties of reduced graphene oxide (rGO) and graphene nanosheets (GNSs) reinforcement of aluminium matrix nanocomposites (AMCs) are reported. For the rGO-AMCs, commercial ...colloidal GO was coated onto aluminium powder particles and then reduced via thermal annealing. For the GNS-AMCs, graphene exfoliated from graphite through ultrasonication and centrifugation was coated onto aluminium particle surfaces via dispersion mixing, filtering and drying. Pure aluminium and aluminium composites with various reinforcement concentrations of rGO and GNS were cold compacted into disc-shaped specimens and sintered in inert atmosphere. The mechanical properties and microstructure were studied and characterised via Vickers hardness, X-ray diffraction, density measurement, and scanning electron microscopy. The reinforcements were uniformly distributed onto the aluminium particle surfaces before and after consolidation within the composites. The relevant factors for the powder metallurgy process (compaction pressure, density, and sintering conditions) were optimised. Increased levels of increased hardness were recorded, over baseline compacted and sintered pure aluminium samples, prepared under identical experimental conditions, of 32% and 43% respectively for the 0.3wt.% rGO-Al and 0.15wt.% GNSs-Al composites. The process developed and presented herein provides encouraging results for realising rGO-AMC and GNS–AMC nanocomposites via low cost cold powder compaction and sintering metallurgy techniques.
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•Developed powder metallurgy method for rGO and GNS-aluminium matrix composites•Mechanical and chemical property determination of for graphene–aluminium composites•Significant increase in composite compact hardness over pure metal baseline•Correlation of composite density with compaction pressure and reinforcement levels•Elaboration of areas of focus on method for further improvements in graphene-AMCs
The paper communicates the flow, heat and mass transfer of a hybrid nanofluid (AA7072–AA7075/water) between the parallel plates, by incorporating chemical reactions, activation energy and heat ...source/sink effects. The governing partial differential equations are upgraded to ordinary differential equations by selecting relevant dimensionless variables and then are numerically resolved. Validation of the problem is confirmed between the present and existing work for the limiting cases and is found to be excellent concord. Moreover, the graphs are displayed to discuss the flow, heat and mass transport, friction drag, rate of heat and mass coefficient behaviour for different implanted parameters. It is noted that larger chemical reaction values minimize the concentration curve, while activation energy has the opposite pattern. Furthermore, upsurge values of heat source/sink parameter improve the rate of heat transport, but solid volume fraction reduces the drag friction. Also it has been discovered that AA7072–AA7075/water is a more efficient liquid than AA7072/water. Moving pistons, chocolate fillers, power transfer and compression are all examples of areas where the current research may be useful.
Recent innovations in geopolymer technology have led to the development of various different types of geopolymeric products, including highly porous geopolymer-based foams, which are formed by the ...addition of foaming agents to a geopolymer fly-ash based matrix. These agents decompose, or react with the liquid matrix or oxygen in the matrix, resulting in the release of gases which form pores prior to the hardening of the gel. The hardened structure has good mechanical and thermal properties, and can therefore be used for applications in acoustic panels and in lightweight pre-fabricated components for thermal insulation purposes.
This study presents the results of the pore-forming process in the case when two different foaming agents, i.e. aluminium powder amounting to 0.07, 0.13 and 0.20 mass. % and H2O2 amounting to 0.5, 1.0, 1.5 and 2.0 mass. %, were added to a fly-ash geopolymer matrix. The physical, mechanical, and microstructural properties of the thus obtained foams, and the effects of the type and amount of the added foaming agent, are presented and discussed. Highly porous structures were obtained in the case of both of the investigated foaming agents, with overall porosities up to 59% when aluminium powder was added, and of up 48% when H2O2 was added. In the latter case, when 2% of the H2O2 foaming agent was added, finer pores (with diameters up to 500μm) occurred in the structure, whereas somewhat larger pores (some had diameters greater than 1mm) occurred when the same amount of aluminium powder was added. The mechanical properties of the investigated foams depended on their porosity. In the case of highly porous structures a compressive strength of 3.3MPa was nevertheless achieved for the samples containing 0.2% of aluminium powder, and 3.7MPa for those containing 2.0% of H2O2.
•Preparation of geopolymer foams based on fly ash with the addition of Al powder or H2O2 as foaming agents•Determination of density, porosity and mechanical properties of such foams•Characterization of foaming process by means of X-ray micro-tomography (μcT)
This research experimented with different aluminum can casting compositions from recycled materials. The objective was to analyze the casting yield and the resulting chemical compositions of the ...process. In the first process, 20 kg of aluminum cans was melted, resulting in a 10.2 kg ingot, which presented a 51% yield. In the second process, 10 kg of 6063 T6 aluminum was used and 10.2 kg of the first casting was added. This mixture produced an ingot of 50% recycled aluminum and 50% 6063 aluminum that weighed 18.23 kg. Similarly, a second ingot was produced, but with the addition of 4 wt% of rice husk ash and 2 wt% of magnesium. From each ingot, the samples were removed for chemical analyses, which consisted of tests of the samples that had the incorporation of rice husk ash in the molten aluminum. These analyses included scanning by electron microscopy, density analysis, Brinell hardness, and Charpy impact force tests. The results of the second ingot analysis showed superior characteristics in Si and Mg levels due to the addition of rice husk ash and magnesium. Also, the second ingot presented increased hardness as well as a reduction fragility and density.
Aluminium (Al) is the most abundant metal in the earth’s crust. Al exposure can cause a variety of adverse physiological effects in humans and animals. Our aim was to demonstrate that specific ...probiotic bacteria can play a special physiologically functional role in protection against Al toxicity in mice. Thirty strains of lactic acid bacteria (LAB) were tested for their aluminium-binding ability, aluminium tolerance, their antioxidative capacity, and their ability to survive the exposure to artificial gastrointestinal (GI) juices.
Lactobacillus plantarum
CCFM639 was selected for animal experiments because of its excellent performance in vitro. Forty mice were divided into four groups: control, Al only, Al plus CCFM639, and Al plus deferiprone (DFP). CCFM639 was administered at 10
9
CFU once daily for 10 days, followed by a single oral dose of aluminium chloride hexahydrate at 5.14 mg aluminium (LD
50
) for each mouse. The results showed that CCFM639 treatment led to a significant reduction in the mortality rates with corresponding decrease in intestinal aluminium absorption and in accumulation of aluminium in the tissues and amelioration of hepatic histopathological damage. This probiotic treatment also resulted in alleviation of hepatic, renal, and cerebral oxidative stress. The treatment of
L. plantarum
CCFM639 has potential as a therapeutic dietary strategy against acute aluminium toxicity.
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