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Manuale della difettologia nei getti pressocolatiHandbook of defects in high pressure diecastings
No full textManuale della difettologia nei getti pressocolati II Edizione- Handbook of defects in high pressure diecastings
No full textNUMERICAL SIMULATION OF SEMI-SOLID CASTING OF AN AUTOMOTIVE COMPONENT
No full textFor setting up innovative processing technologies, such as semi-solid casting, a fundamental contribution can be offered by numerical simulation, which, once correctly elaborated, allows the prediction of fluid-dynamics and thermal fields induced by the process.
This paper is focussed on the study, by means of the MAGMAthixo module of the MAGMASOFT code, of the semi-solid casting process of an automotive component (engine bracket). The requirements for a proper development of the numerical model are described and the results of simulation are presented as mass and temperature distributions and compared with the output of experimental processing tests and with microstructural investigations.
The good correspondence between experimental data and numerical simulation results confirms the reliability of this approach in developing processes and products
Classification and Survey of Defects and Imperfections in Al-alloy castings
No full textDefects and imperfections are intrinsically generated by casting processes, due to several reasons. The final properties and in-service behaviour of castings are always related to microstructural features and to defects and imperfections: both microstructure and defects/imperfections are the results of process stages, alloys properties and dies & tools design. As an example, it should be considered that in HPDC filling stage extreme conditions are established: complexity of components leads to complex dies, and the high production rates required (up to 120 shots/h) lead to very high filling velocities for the molten alloy (up to 40 m/s) with strong generation of turbulence in the flow. Solidification takes place in few seconds, and the die is first in contact with a molten alloy at more than 700 °C and, after 30-40 seconds, with a sprayed lubricant at room temperature. For these reasons HPDC (as well as other Aluminium alloys casting processes, such as permanent mould casting process) can be considered a “defect generating process”. Not only an average 5-10% scrap is typically produced, but the type, size and severity of defects and imperfections are varying.
From these considerations, it seems that the potential of high-pressure die-casting and permanent mould casting processes will be completely exploited only when the quality level will be perfectly optimised. In this regard, the analysis of defects and imperfections allows the foundry to monitor the products quality respect to a quality standard. Further, the analysis of defects and imperfections provide to the foundry useful correlations between their type/distribution and their origin, so that it could be possible to define process modification for improving the quality. One of the current targets of the StaCast project is the compilation and dissemination of common tools to allow foundries to define a proper, comparable, quality standard. The first tool to be proposed is a common basis of language, i.e. a terminology and classification of defects and imperfections in order to help die-casting foundries to face with increased confidence and ability the defect-related issues, to assure quality and reliability of their products
Public survey on European foundries producing Aluminium alloy castings
No full textStaCast Project has been aimed at individuating by means of properly elaborated questionnaires and of dedicated surveys the specific standardization needs for what concerns Al alloys castings.
This activity is the direct consequence of the StaCast Project motivation, which is based on four key-issues.
1. The vast potential of Aluminium Alloys EU Foundry Industry strongly needs a coordinated set of Support Actions, in which a central role MUST be played by the elaboration of new and advanced Standards, particularly in the fields of Defects classification and Mechanical Design, which are mutually inter-related.
2. The use of a new EU Standard for the Classification of Casting Defects, which will help EU Aluminium alloys foundries at promptly performing corrective actions to reduce/eliminate defects, is becoming strategic. Such Standard will be also a useful “communication tool” among all the actors of the design and manufacturing chain.
3. The development of a new Standard on mechanical properties is strongly needed too, in order to correctly evaluate the effective mechanical potential of Al foundry alloys.
4. The design and manufacturing of Al alloys cast components NEED the availability of dedicated rules and guidelines, in order to correctly make use of the two new standards deriving from issues 2) and 3).
The four issues above need, first of all, to be confirmed by a dedicated survey to be carried out on an EU basis. This is the background which led to the set up of the Questionnaire, and to the answers elaboration which are described in the present Chapter
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
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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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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