1,720,972 research outputs found
Superplastic forming of Friction Stir processed magnesium alloys for aeronautical applications: a Modeling approach
No full textMagnesium alloys are attractive for lightweight structural applications in the transportation industry because of their low density and high specific strength and stiffness [1]. With an ultrafine-grained microstructure, they exhibit superplasticity at relatively low temperatures and high strain rates [2]. Friction stir processing (FSP) was used to obtain a microstructure with ultrafine grains in the magnesium alloy AZ31. In this project, microstructures obtained using different rotational speeds are studied. Free bulge forming of the FSP processed AZ31 sheets are carried out to evaluate the superplastic behaviour [3]. The model and the evolution equations have been implemented into a commercial finite element modeling (FEM) code and different simulations are conducted to correlate the experimental and numerical results for the model validation [4]. The purpose of this study is to investigate the effect of the microstructure on the superplastic forming behaviour using free bulge forming and FE simulations
Superplastic forming/diffusion bonding of a titanium alloy for the realization of an aircraft structural component in multi-sheets configuration
No full textSuperplastic forming and diffusion bonding (SPF/DB) is a near-net-shape forming and
joining process used with alloys having superplastic properties in order to make manufact which
should have light weight and high stiffness. The aerospace is one of those sectors in which such
technology is mainly used. This process allows to reduce the buy-to-fly ratio and consequently the
production costs thanks to the possibility to produce complex shape components in a single shot.
The material widely used for this application is the Ti-6Al-4V alloy for its high strength vs weight
ratio, excellent mechanical proprieties, corrosion resistance and galvanic compatibility with carbon
fiber reinforced composite materials. In this study, finite element analysis of the SPF/DB process
has been carried out in order to investigate the thickness prediction, the optimization of the tooling’s
geometry and the definition of the sheets initial thickness in the blow forming process of a multisheets
configuratio
Bending behaviour of sandwich panels with aluminium foam core
No full textThe bending behavior of hybrid sandwich panels, with aluminum foam core, and carbon fiber reinforced thermoset resin face sheets, have been investigated. The effect of core and face sheets thickness and span , on 3-point bending test, has been evaluated for the sandwich panels .
Core yielding and indentation failure modes, influenced by the core properties, have been identified and analytical models to evaluate the maximum load have been applied. The failure mode map has been constructed, which illustrates the dominant failure mode for practical beam design. In order to simulate the different failure modes, FE analysis has been pointed out
Manufacturing of Innovative Components Formed Using SPF Processes and Filled with Aluminium Metal Foams
No full textThis work is part of scientific studies that have the wider aim of producing
components for aerospace industrial applications such as the realization of complex geometry
using innovative technologies. The aim of this paper is to verify the technological feasibility of
the manufacturing of components formed using Super Plastic Forming (hereinafter called SPF)
processes and filled with aluminium foam. The component under investigation is composed by
an outer layer in thin sheet of titanium alloy, formed by SPF technology, and a core in
aluminium foam manufactured by the powder compact melting technique. Drop weight impact
tests have been carried out to the aim to estimate the improvement of the innovative component
in terms of energy absorption compared to the sum of the single constituents. The results have
showed significant improvements in the energy absorption capability, proving that the proposed
concept is technically promising
Magnesium and Aluminium alloys Dissimilar Joining by Friction Stir Welding
No full textMulti-material lightweight structures are gaining a great deal of attention in several industries, in particular where a trade-off between reduced weight, improved performances, and cost compression is required. Magnesium alloys, such as the zinc-rare earth elements ZE41A alloy, fulfill the first two requirements; however, they are susceptible to corrosion and relatively expensive. Lightweight structures hybridization, for instance combining Magnesium alloys and Aluminium alloys, is currently under consideration as a potential solution to this problem. Nevertheless, dissimilar joining of Magnesium and Aluminium alloys is challenging due to the significant differences in physical properties, as well as to the precipitation of brittle intermetallic compounds, such as Al12Mg17 and Al3Mg2. In this study, the dissimilar joining of Magnesium and Aluminium alloys by friction stir welding process is discussed. In particular, 4 mm thick plates of ZE41A Mg alloy and AA2024-T3 Al alloy were welded in the butt joint configuration. The feasibility of the process was assessed by means of microstructure and mechanical analysis. The formation of brittle intermetallic compounds was investigated as well
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
ANALISI DELLE TENSIONI RESIDUE E DELLE PROPRIETÀ MECCANICHE DI GIUNTI FSW DI TESTA IN LEGA AA 6156
No full textNel presente lavoro sono stati studiati giunti FSW di testa in lega innovativa AA 6156, di cui sono state valutate sia le proprietà meccaniche che le tensioni residue indotte dal processo di saldatura stesso. Per lo studio delle tensioni residue è stata utilizzata una tecnica innovativa denominata QNA che si basa sull’interpretazione di immagini termografiche che ritraggono l’oggetto in esame, opportunamente sollecitato, attraverso il software matlab ed in particolare l’utilizzo della trasformata Wavelet
Hot Stretch Forming of a Titanium Alloy Component for Aeronautic: Mechanical and Modeling
No full textThe development of Hot Stretch Forming (HSF) by the Cyril Bath Company was in response to airframe designers needing to use Titanium airframe components in new commercial aircraft. Many of the airframe component structures are designed to fit against the inside radius of the fuselage curvature. By combining traditional stretch forming technology with hot titanium forming techniques, the HSF guarantees a saving in material and machining time, which are two serious cost issues for today's aircraft manufacturers. In addition, the process allows for consistent quality in a productively efficient manner, assuring the sustainable attainment of delivery and build schedules. The HSF is an innovative process on the cutting edge of the technologies, so focused research is needed in order to better understand this technology and develop new applications for this process. in this paper the HSF process is investigated: The machine and the different steps that characterized the process were described and the results of a preliminary experimental campaign was discussed focusing the attention on the metallurgical aspect. Moreover a modeling of the process was executed in order to study the stresses and strains undergone by the material among the deformation
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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