1,720,958 research outputs found
Fatigue assesment of AA8090 friction stir butt welds after surface finishing treatment
No full textCombining great performances with high standards of safety and efficiency is the challenge for most aircraft manufacturers. Aircraft are subjected to extraordinary loads, repeated for millions of cycles also in extreme environmental conditions, hence every component must be designed and manufactured to maximize its fatigue resistance.
Friction Stir Welding of aluminium alloys and surface finishing process es might be a good solution to reach this goal.
The high performances reached in this field with the use of this technique could be further increased reducing the welded surface irregularity, which might promote the development of a dangerous fatigue failure mechanism.
In this work, the effect of the welded surface finishing treatment on the fatigue behaviour of AA8090 FSW butt joints was assessed. The results obtained from the dynamic tests highlighted the higher fatigue resistance of finished specimens, with respect to the as-welded joints
Environmental effects on methacrylate adhesive
No full textIn recent years, bonding techniques have been widely used to assist or even replace traditional joining techniques, such as welding and riveting. This study investigates how environmental conditions affect the mechanical behaviour of bonded joints. Analyses were carried out on single lap shear joints bonded by a two-component methacrylate-based flexible structural adhesive, extensively used in marine applications. The degradation of bonded joints in marine environment is mainly due to humidity and seawater-induced corrosion. Thus, the bonded samples were prepared for test by ageing in a climatic chamber with no applied stress (at controlled temperature and humidity) and immersion-drying cycles in a saline solution (seawater-like effect). Afterwards, tensile stress tests were performed. In order to evaluate the environment-induced degradation of the tested joints, the tensile strength of aged samples was compared with that of similar un-aged joints
Friction stir welding between extrusions and laminates
No full textCurrent market demands drive companies to innovate their production techniques to improve products and simultaneously hold down costs. In the search for solutions aimed at an optimization of production processes, semi-finished products in aluminium alloys very definitely play a significant role. Moreover, the assembly of extruded parts with laminates may result in considerable difficulties, especially in relation to distortions or generated residual stress and process productivity. A solution to these issues may be found in the application of friction stir welding (FSW), characterized by low thermal input and high productivity. The asymmetry of the FSW process determines a different thermal input to the edges of the pieces to be joined. This aspect can be exploited when it is necessary to join pieces characterized by a very different thermal lag, as occurs in the case of joining extruded products and sheeting. This study aims to identify optimal FW parameters, placing particular attention on heat transferred to materials so as to provide an adequate thermal input that will allow for compensation of the different thermal capacity of the pieces in question
Caratterizzazione meccanica di un pannello sandwich
No full textConoscere la risposta del materiale a determinati carichi è fondamentale per valutarne l’applicabilità
a specifici impieghi. Nel caso di un composito il discorso si complica, in quanto per definire le proprietà
della struttura occorre prima indagare quelle dei singoli componenti. I risultati di tale approccio
su un pannello sandwich sono riassunti in questo studio
Il processo di giunzione ibrido RSW-incollaggio: Caratterizzazione della morfologia dei giunti e del loro comportamento a fatica
No full textThis article presents the results of a comparison between the microstructural characterization of RSW welds in micro-alloyed steel for automotive application and hybrid RSW-bonded joints. The objective is to verify, by microstructural analysis and destructive testing, the effect of the adhesive on the mechanical properties and fatigue behaviour of the joint. The results obtained were compared with the FEM simulations, aimed at analyzing the influence of external stresses on RSW and RSW-bonded joints behaviour
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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