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Laser wire deposition additive manufacturing of Ti-6Al-4V for the aerospace industry
No full textAdditive manufacturing (AM) is an attractive solution to reduce processing cost of complex components. The interest of the aerospace industry into Ti-6Al-4V resides in its excellent strength to weight ratio and corrosion resistance properties. As of today, control of the process to structure to property relationship for AM technologies remains challenging. This research investigates the effects of some key laser wire deposition (LWD) parameters and various post deposition heat treatments on the developed microstructure and subsequent properties of the deposited Ti-6Al-4V materials. The effect of two different travel speeds on the structural development of thin Ti-6Al-4V deposits was investigated. A travel speed set at 1.4 mm/s promoted recrystallization of columnar prior β grains into horizontal prior β grains and a diffusion-controlled type of microstructure. A travel speed set at 7.2 mm/s resulted in higher cooling rates that produced a refined microstructure while no recrystallization of the prior β grains has been observed. Next the effect of five different post deposition heat treatments were investigated. A stress relief preserved the morphology of the deposited samples while annealing or HIP, followed or not by aging, coarsened the developed microstructure. The lower travel speed exhibited a strong anisotropy in elongation with lower values generated along the build direction as opposed to the isotropic results in elongation at higher travel speed. Moreover, samples processed at 7.2 mm/s produced high strength meeting the minimum wrought requirements as set by the AMS4911. Eventually, the grain boundary strengthening mechanism with regards to the α platelets thicknesses was found to be travel speed dependent. Thick samples were characterized by the deposition of multiple lateral beads within one layer. Thermal history was first investigated through the development of a FEM model reproducing the deposition process. Typical macrostructures and microstructures that developed post deposit were then investigated. Subsequent static tensile properties were found to be hardly meeting the cast minimum requirements as set by the ASTM F1108. No anisotropy in the impact toughness properties was observed. Eventually, HIP did not induce any major improvement of the mechanical properties for both thin and thick specimens and is not required for LWD applications. All the previous findings were eventually applied for the printing of a large Ti-6Al-4V aerospace component. The deposition strategy was presented. Destructive and non-destructive testing were done to check the printed part geometry and the process to structure to properties relationship. The printed part was characterized with a buy-to-fly ratio (BTF) of about 3.2:1 as opposed to a BTF ratio of 30.8:1 when using conventional subtractive processes.La fabrication additive (FA) des alliages a été identifiée par l'industrie aérospatiale comme étant une solution attrayante pour réduire le coût de production de pièces complexes. L'intérêt que porte l'industrie aérospatiale pour cet alliage réside dans son excellent rapport entre résistance mécanique et faible densité ainsi que pour son excellente résistance à la corrosion. À ce jour, l'enjeu réside dans le contrôle de la relation qui existe entre le processus utilisé, la microstructure développée et les propriétés mécaniques qui en découlent au travers de l'utilisation des technologies de FA. Ce projet a pour but d'évaluer les effets de certains paramètres du processus de déposition par fil et laser (DFL) ainsi que les effets de plusieurs traitements thermiques post déposition sur le développement de la microstructure et des propriétés des pièces imprimées en Ti-6Al-4V. L'effet de deux vitesses de déplacement sur le développement structurel des dépôts minces de Ti-6Al-4V a été évalué. Une vitesse de déplacement fixée à 1.4 mm/s favorise la recristallisation des ex-grains β colonnaires en ex-grains β horizontaux ainsi que le développement d'une microstructure contrôlée par diffusion. Une vitesse de déplacement fixée à 7.2 mm/s aboutis à des taux de refroidissement plus élevés qui favorisent le développement d'une microstructure raffinée, alors qu'aucune recristallisation des ex-grains β n'a pas été observée. Un traitement d'adoucissement permis de préserver l'effet des paramètres de déposition sur les différentes microstructures développées alors qu'un cycle de recuit ou de compression isostatique à chaud (HIP), suivi ou non d'un cycle de revenu, firent croitre la microstructure développée post déposition. La vitesse de déplacement plus lente résulta en une déformation anisotropique avec des valeurs inférieures mesurées le long de la direction de déposition à l'opposé des déformations isotropiques générées pour les échantillons produits à 7.2 mm/s. De plus les échantillons produits à 7.2 mm/s développèrent des résistances en contraintes élevées dépassant les exigences minimales des matériaux forgés telles que définies par la norme AMS4911. Enfin, le mécanisme de renforcement par joints de grains associé à l'épaisseur des lamelles α s'est avéré être dépendant de la vitesse de déplacement.Des échantillons épais furent caractérisés par la déposition latérale de plusieurs cordons pour chacune des couches. Un modèle par la méthode des éléments finis (MÉF) reproduisant la stratégie de dépôt fut développé pour étudier l'historique des cycles thermiques. Les macrostructures et microstructures représentatives des échantillons post déposition furent étudiées. Les propriétés de résistances en contraintes développées n'ont que très difficilement atteint les exigences minimales associées aux matériaux coulés telles que définies par la norme ASTM F1108. Aucune anisotropie ne fut observée à la suite des essais Charpy. Enfin, un cycle de HIP n'engendre aucune amélioration concrète des propriétés mécaniques à la fois pour les échantillons épais et fins et n'est pas nécessaire pour les échantillons produits par DFL.Enfin, tous les enseignements précédents ont été mis à contribution aux travers d'une application concrète d'impression d'une grande pièce en Ti-6Al-4V pour le domaine aérospatiale. La stratégie de déposition fut présentée. Des tests destructifs et non destructifs ont été effectués pour vérifier la géométrie de la pièce imprimée ainsi que la relation de structure à propriété qui s'est développée. La pièce imprimée fut associée à un rapport « acheter-pour-voler » (APV) ou plus connu comme étant le rapport « buy-to-fly » (BTF) en anglais de 3.2:1 à l'opposé d'un rapport de 30.8:1 lorsque fabriquée par des méthodes conventionnelles
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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