1,720,958 research outputs found
Experimental Studies on AA6063-Cu Dissimilar Friction Stir Welding Using Inconel 601 Tool
No full textAA6063-Cu dissimilar friction-stir welding was performed in the present work. Owing to excellent high temperature strength, and adequate wear resistance, nickel based super alloy Inconel 601 was used as FSW tool.
Two weld specimens were prepared at constant tool rotational speed but varied weld speed, and tool offset distance. Microstructural characteristics along with mechanical properties of the welded specimen including tensile strength, and micro-indentation hardness were studied.
Intermetallic compounds were found to be formed at the weld interfacial region. Lamellar intercalated microstructure with predominant flow pattern was observed in the stirred zone. Dispersed copper (layered or bulk) was observed over aluminum matrix. Distribution of copper and aluminum over the weld surface as well as interfacial region was studied through Electron Probe Micro Analyzer (EPMA). Maximum tensile strength attained ~103MPa, corresponded to the weld specimen obtained at tool rotation=1120 RPM, weld speed=100mm/min, and tool offset=0.95mm. Fractographic analysis of the same specimen revealed brittle fracture mechanism with predominant cleavage planes. Moreover, maximum micro-hardness (~68.54HV) was obtained approximately at weld center
Experimental Studies on Wire Arc Additive Manufacture of SS 308L and Inconel 718 Part
No full textWire Arc Additive Manufacturing (WAAM) belongs to the category of Direct Energy Deposition (DED)-based Additive Manufacturing (AM) in which the feedstock material is in the form of metallic wire. The wire melts under the action of a welding arc; the molten material is deposited on a substrate. Successive bead deposition in a layer-upon-layer manner (along the build direction) develops the final 3D part. In order to build a cross-section/ layer, multiple beads need to be deposited one-after- another onto the horizontal plane in accordance with a given pattern. WAAM is characterized by its high material deposition rate (when compared to the powder- based AM techniques) and is suitable towards fabricating parts which are medium- to-large sized, possessing low-to-medium level of design intricacy. The present dissertation focuses on microstructure and mechanical property characterization of Cold Metal Transfer (CMT) + Metal Inert Gas (MIG) welding based WAAMed SS 308L and Inconel 718 parts. The complex heat interaction phenomena that take place during execution of WAAM process is also studied herein. In the first part of the dissertation work, the SS 308L-T1 wire is utilized to fabricate a 3D slab (149 22 125 mm3). Evolution of location-dependent microstructure and thereby anisotropic static mechanical properties (tensile properties and microhardness) is witnessed. WAAMed SS 308L as fabricated microstructure is composed of grain boundary ferrite of varied morphologies (vermicular/ skeletal and lathy) within the inter-dendritic regions of austenite. The average value of the Ultimate Tensile Strength (UTS) of the horizontally-cut specimens (~ 542 MPa) exceeds to that of the vertically-cut specimens (~ 520 MPa). Post-heat treatment (at 1200 °C, 4 h + furnace cooling) causes significant grain growth; therefore, reduction in the microhardness value from 178 HV0.1 to 143 HV0.1 is witnessed. It is also experienced that the proportion of ferrite phase gets reduced considerably upon the said post-heat treatment. In the second part of the dissertation, an attempt is made to fabricate a 3D slab (15 25 18 mm3) of Inconel 718 through CMT + MIG based WAAM. WAAMed Inconel 718 exhibits dendritic microstructure decorated with Laves phase, phase and MC- type carbides. In the as fabricated condition, the average value of the UTS along horizontal direction obtained is ~ 824 MPa. Post-heat treatment cycle attempted herein consists of homogenization (at 1080 °C, 1.5 h + air cooling) followed by solution treatment (at 980 °C, 1 h + air cooling) and finally, double stage ageing – the first stage ageing is at 720 °C, 8 h + furnace cooling and the second stage ageing is at 620 °C, 8 h + air cooling. It is experienced that detrimental Laves phase is completely dissolved during homogenization treatment although residues of phase is witnessed after the solution treatment. Ageing treatment causes precipitation of the strengthening phase ′′ (Ni3Nb). Thus, post-heat treatment imparts 50 % improvement in the UTS and 85 % increment in the microhardness value when compared to the as fabricated condition. However, post-heat treatment lowers ductility. In comparison with the as fabricated specimen, better wear resistance is attributed to the post-heat treated specimen as evidenced through the dry sliding wear test (at room temperature). The wear rate of the as fabricated specimen obtained is ~ 0.0035 mm3/Nm; on the other hand, the post-heat treated specimen corresponds to the wear rate of ~ 0.0025 mm3/Nm
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
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