1,720,968 research outputs found
Fiber laser surface remelting of a nickel-based superalloy by an integrated rectangular laser spot
No full textIn some specific industrial applications employing nickel-based superalloy components, a surface enhancement of product tribological properties is required. In this work, the effects of a Laser Surface Remelting on a nickel-based superalloy was investigated. An Ytterbium fiber laser, with maximum power of 4 kW, and a focusing segmented mirror, which produces an integrated laser beam (in a knife blade or rectangular spot) as well as a laser intensity homogenization, were used. Different values of laser power and scanning speed were tested. Remelted tracks, having a width of 8 mm, were characterized in terms of surface visual inspection, morphology, metallographic examination as well as longitudinal and transverse micro-hardness. Moreover, a comparison was performed between properties of the remelted material and the base alloy. The particular optical setup allowed the width of the molten tracks remained almost constant also varying the process parameters. The quality of the treated surface, for a given power, improved with increasing scanning speed, even if the depth of the molten area reduced. Micro-hardness increased of about 14% because of the formation of very fine columnar-dendritic grains, due to the rapid remelting and resolidification. Process efficiency was also evaluated by two different parameters: the analysis of both allowed to state that, keeping the laser power constant, the efficiency of the process increased almost linearly with the speed
Enhancing coatings mechanical performance by advanced laser deposition of WCCoCr-colmonoy composites
Full text linkThe manufacturing industry's focus on achieving surfaces with advanced mechanical performance is driven by objectives of competitiveness, sustainability, and efficiency. This study explores the use of Directed Energy Deposition-Laser Beam (DED-LB) process to create Metal Matrix Composites (MMCs) coatings with high mechanical properties, consisting of a nickel-based alloy (Colmonoy 227-F) reinforced with WC-Co-Cr particles, deposited on a 316 L steel substrate. The specific aims of this research are to optimize the DED-LB process parameters and investigate the effect of different reinforcement percentages on the mechanical properties of MMC coatings. The objectives include evaluating the microstructural integrity, hardness, and material distribution of coatings with varying WC-Co-Cr reinforcement levels. The DED-LB technique offers advantages such as localized heat input, rapid cooling rates for finer microstructures, and controlled bonding between substrate and coating. Particularly, it allows for the creation of MMCs, including ceramic-reinforced ones, known for their enhanced mechanical properties. However, managing the dissolution of ceramic reinforcement within the metal matrix remains a challenge. In this research, two reinforcement percentages (10 % and 40 % WC-Co-Cr) were investigated to optimize the process parameters and enhance mechanical properties. Microstructural analysis showed that coatings with 10 % reinforcement maintained a spherical morphology, while 40 % exhibited a slight dispersion of individual carbide grains within the matrix. Vickers hardness tests indicated hardness values of 375 ± 15 HV for 10 % and 490 ± 10 HV for 40 %, with the pure matrix hardness measured at 325 ± 10 HV. This demonstrates the reinforcement effect in both composite coatings. Chemical composition analysis confirmed proper distribution of elements. The study demonstrates that MMC coatings produced through laser deposition with optimized parameters exhibit favorable microstructures, increased hardness, and correct material distribution. The scientific novelty of this work lies in demonstrating that a high level of reinforcement (40 %) can be incorporated without metallurgical defects, enhancing the mechanical properties significantly beyond typical reinforcement levels. These findings are essential for improving mechanical performance and wear resistance in high abrasive load applications. The research contributes valuable insights into optimizing DED-LB processes for advanced MMC coatings, crucial for sustainable and efficient manufacturing practices
Cold Spray Defects: An Investigation on Very Low Scanning Speeds
No full textThe Cold Spray process is one of the best options for restoring damaged aerospace components, made of different metal alloys, including aluminum-based ones. Among the most important process parameters there are gas temperature, gas supply pressure, particle size.type of the powder and the transverse scanning speed of the gun, during processing. This last parameter represents a key factor, still poorly studied. In particular, for very low translation speeds (< 30 mm/sec), the process is capable of obtaining single-pass thicknesses exceeding 0.5 mm. Moreover, low speeds are necessarily used when particular levels of detail have to be achieved. On the other hand the authors experienced that very low transverse speeds also imply defects such as coating deficiencies at the interface between base material and coating or between the deposition layers themselves. In this paper, the results are presented regarding an experimental study on the influence of low speeds, on the porosity of the interface, for depositions of aluminum-based alloys on substrate made of the same material. The experimental study pointed out the presence of evident defects, probably related to the low scanning speed
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
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