1,721,050 research outputs found
Numerical simulation of an U-channel component tailored tempering process considering the effect of stress on the shift of TTT curves
No full textA numerical model of the tailored hot stamping process was developed in the framework of the commercial FE code ForgeTM and accurately calibrated in order to take into account the influence of applied stress and strain on the phase transformation kinetics. The calibration was carried out by introducing in the numerical model data on the shift of the TTT curves due to applied stress and the transformation plasticity coefficients, which were obtained through an extensive dilatometric analysis. The numerical model was validated through a laboratory-scale hot-formed U-channel produced using a segmented die with local heating and cooling zones. The predicted distribution of Vickers hardness and evolution of microstructure given by the numerical model was compared with the experimental results to show the significant predictive improvements introduced by considering the influence of the transformation plasticity and deformation history on the phase transformation kinetics
Anisotropy influence on the mechanical and microstructural characteristics of AZ31B sheets deformed at room and elevated temperature
Get PDFThe objective of the present study is to evaluate the anisotropy influence on the mechanical and microstructural characteristics of AZ31B magnesium alloy sheets deformed at room and elevated temperature. To this aim, uniaxial tensile tests were carried out along the rolling, transverse and diagonal direction in the range of temperatures from room temperature to 300°C at 0.1 s-1. The Lankford coefficients, ultimate tensile strength, diffuse necking strain and fracture strain values were evaluated as a function of the testing temperature and specimen orientation. Furthermore, microstructural features were analysed as well as micro-hardness was measured for each testing condition to assess the post-deformation characteristics
Anisotropy influence on the failure of Ti6Al4V sheets deformed at room and elevated temperature
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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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Influence of temperature and deformation on phase transformation and vickers hardness in tailored tempering process: Numerical and experimental verifications
No full textHot stamping of quenchenable ultra high strength steels currently represents a promising forming technology for the manufacturing of safety and crash relevant parts. For some applications, such as B-pillars which may undergo impact loading, it may be desirable to create regions of the part with softer and more ductile microstructure. In the article, a laboratory-scale hot stamped U-channel was produced with segmented die, which was heated by cartridge heaters and cooled by chilled water recirculation independently. It can be concluded that in order to satisfy tailored mechanical properties by introducing regions, which have an increased elongation for improved energy absorption, the minimum die temperature should be no less than 450C. Optical micrographs were used to verify the microstructure of the as-quenched phases with respect to the heated die temperatures. For the cooled die region, the microstructure was predominantly martensite for all the die temperatures interested. With the increase of heated die temperature, there was a decrease of Vickers hardness in the heated region due to the increasing volume fractions of bainite. The finite element (FE) model was developed to capture the overall hardness trends that were observed in the experiments. The trends between the simulations and experiments were very similar, with acceptable differences in the magnitude of Vickers hardness. The transition widths were measured and simulated and there was a quite good agreement between experiment and simulation with almost the same value of 10 mm by taking heat conduction into accoun
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