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Experimental investigation and numerical prediction of the peripheral coarse grain (PCG) evolution during the extrusion of different AA6082 aluminum alloy profiles
No full textICEB 2017 - Benchmark settings
No full textAim of the benchmark at ICEB conference is to examine FEM codes capabilities and users’ knowledge in the simulation of extrusion trials which were carried out and monitored by conference organizers. The comparison of the “blind” simulations by the participants with the experimental results allows users to check if their simulation settings are generally adequate to replicate the problem and software house to verify the sensitivity of their solving methods. It is very important for us to remind that, due to the complexity of this matter, it would be useless to consider the benchmark as a contest: it is, instead, an opportunity to fix some points about the everyday simulation practice, each participant with his own particular interest
Extrusion Benchmark 2017: Effect of Die Design on Profile Quality and Distortions of Thin C-Shaped Hollow Profiles
No full textThe Extrusion Benchmark 2017 is focused on the evaluation of different die design strategies for the production of two AA6005A thin C-shaped hollow profiles. The process was monitored in term of press load, profiles speed, profiles exit temperature, die temperatures (with specific focus not only on the die but also on the external die ring) and die deflection. Extruded profiles were analyzed in term of geometrical tolerances, microstructure evolution and profile distortions for both air and water quench; the profiles were also be analyzed for retrieving seam welds positions and charge welds extent. (C) 2018 Elsevier Ltd. All rights reserved
Extrusion of Magnesium Hollow Profiles for Automotive Applications
No full textThe use and adoption of magne
sium extruded profiles in
structural application is
limited because magnesium extrusion technology is at its first. Once extruded hollow
sections will be available at
a reasonable cost, a tremendous in
crease of market demand is
going to be expected due to the lowest weight of the magnesium alloys in comparison with
aluminum based ones. The press productivity re
present a key factor in this scope and the
die, due to the strong incidence of strain
and temperature in the extrudability, will play a
basic role to achieve the required stem
speed. This paper present a new approach for
designing extrusion dies specifically for
magnesium alloy ZM21 by means of FEM
simulation. The goodness of the new design has
been validated extruding an hollow profile
using an industrial press with data logging
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
Finite element modelling of the charge welds evolution in a porthole die
No full textAlthough the extrusion process is regarded as a continuous process, in practice billets are
discretely loaded into the press. The joining of two consecutive billets is guaranteed by the high
hydrostatic pressure of the process. Nevertheless, mechanical proprieties of the profile in the
welded region are lower than those of the adjacent area thus leading to the discarding of the welded
segment. Extension of the segment is mainly affected by the interaction of seam and charge welding
phenomena and, nowadays, its prediction is still a tricky task involving rough empirical relations or
labour intensive analyses. Aim of this work was to identify the starting and exhausting points of the
charge welds evolution inside an industrial multi-profiles die, in order to determine the exact
position and the minimal length to be scraped. The extrusion of four AA6060 hollow profiles
through a multi-hole die were preliminary monitored in an industrial press by accurate recording of
the process loads, temperatures and speeds during the process. The four profiles were sectioned
starting from the ‘stop mark’ then grinded and etched in order to investigate the location and the
dimension of the zone to be ridded. While the experimental activity is detailed elsewhere, this paper
is focused on the finite element modelling of the process. The numerical simulation was performed
by means of the Altair HyperXtrude code and predictions compared to experimental data with a
particular focus on the computation of the charge evolution. It was found a good agreement both in
terms of general trend and prediction of the exhausting points so thus proving the code to be a
reliable tool for an accurate determination of the scraps
Modeling of recrystallization behaviour of AA6xxx aluminum alloy during extrusion process
No full textVariations 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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