1,720,966 research outputs found
Laser cladding of Ti-6Al-4V with carbide and boride reinforcements using wire and powder feedstock
No full textThe growth in the use and wear of Ti-based alloy components in mining and offshore explorations has led to a search for techniques to re-engineer such components for reuse. The most desirable method of restoring/protecting the component surfaces is by hard-facing to enhance longevity in service.
Laser cladding is one of the viable techniques to achieve a thick coating on such components which involves the addition of reinforcing particulates to improve surface properties such as hardness, wear and erosion resistance amongst others. A fundamental study and understanding of the resultant microstructure-property of the laser clad, hard-facing composite becomes necessary.
In this study, laser cladding of Ti-6Al-4V wire with Spherotene particulate reinforcement and laser cladding of modified pre-blend of Ti-6Al-4V and TiB_2 powder were undertaken. The resulting physical and microstructural characteristics, hardness, and performance characteristics of laser clad composites were investigated. Samples from the as-deposited laser clad composites were characterised using optical microscopy, scanning electron microscopy (with chemical microanalysis) and X-ray diffraction. Performance characteristics were examined via erosion testing of the laser clad Ti-6Al-4V/Spherotene using plain and abrasive water jetting, and tensile testing of the laser clad Ti-6Al-4V/TiB_2 composite.
The results showed that a crack and pore free clad containing as high as 76 wt.% Spherotene in the Ti matrix was achieved at an energy density of 150 J.mm^-2, 275 mm/min traverse speed, 700 mm/min wire feed rate and 30 g/min powder feed rate. The microstructure of the laser clad Ti-6Al-4V/Spherotene is characterised by nano-sized precipitates of reaction products (W and TiC) uniformly distributed in a beta-Ti solid solution matrix. Matrix hardness is enhanced by the presence of the reaction products in the Ti ranging between 410-620 kgf.mm^-2. Moreover, the modication made to the 90 wt.% Ti-6Al-4V/10 wt.% TiB2 feedstock by attaching the TiB2 to Ti-6Al-4V
allowed uniform distribution of reinforcing element in the deposited composite. The composite microstructure on solidication is characterised by TiB eutectic needle-like
features uniformly distributed in a Ti-rich primary phase. The hardness of the composite ranged between 440-480 gf.mm^-2. Tensile tests showed that the mean elastic modulus of Ti-6Al-4V/TiB_2 composite is 145 GPa, which is a 27% improvement when compared to that of Ti-6Al-4V. Erosion test indicated that the Ti-6Al-4V/Spherotene composite offered as high as 13 and 8 times resistance of that of Ti-6Al-4V when subjected to PWJ and AWJ impacts respectively
Laser cladding of Ti-6Al-4V with carbide and boride reinforcements using wire and powder feedstock
Get PDFThe growth in the use and wear of Ti-based alloy components in mining and offshore explorations has led to a search for techniques to re-engineer such components for reuse. The most desirable method of restoring/protecting the component surfaces is by hard-facing to enhance longevity in service.
Laser cladding is one of the viable techniques to achieve a thick coating on such components which involves the addition of reinforcing particulates to improve surface properties such as hardness, wear and erosion resistance amongst others. A fundamental study and understanding of the resultant microstructure-property of the laser clad, hard-facing composite becomes necessary.
In this study, laser cladding of Ti-6Al-4V wire with Spherotene particulate reinforcement and laser cladding of modified pre-blend of Ti-6Al-4V and TiB_2 powder were undertaken. The resulting physical and microstructural characteristics, hardness, and performance characteristics of laser clad composites were investigated. Samples from the as-deposited laser clad composites were characterised using optical microscopy, scanning electron microscopy (with chemical microanalysis) and X-ray diffraction. Performance characteristics were examined via erosion testing of the laser clad Ti-6Al-4V/Spherotene using plain and abrasive water jetting, and tensile testing of the laser clad Ti-6Al-4V/TiB_2 composite.
The results showed that a crack and pore free clad containing as high as 76 wt.% Spherotene in the Ti matrix was achieved at an energy density of 150 J.mm^-2, 275 mm/min traverse speed, 700 mm/min wire feed rate and 30 g/min powder feed rate. The microstructure of the laser clad Ti-6Al-4V/Spherotene is characterised by nano-sized precipitates of reaction products (W and TiC) uniformly distributed in a beta-Ti solid solution matrix. Matrix hardness is enhanced by the presence of the reaction products in the Ti ranging between 410-620 kgf.mm^-2. Moreover, the modication made to the 90 wt.% Ti-6Al-4V/10 wt.% TiB2 feedstock by attaching the TiB2 to Ti-6Al-4V
allowed uniform distribution of reinforcing element in the deposited composite. The composite microstructure on solidication is characterised by TiB eutectic needle-like
features uniformly distributed in a Ti-rich primary phase. The hardness of the composite ranged between 440-480 gf.mm^-2. Tensile tests showed that the mean elastic modulus of Ti-6Al-4V/TiB_2 composite is 145 GPa, which is a 27% improvement when compared to that of Ti-6Al-4V. Erosion test indicated that the Ti-6Al-4V/Spherotene composite offered as high as 13 and 8 times resistance of that of Ti-6Al-4V when subjected to PWJ and AWJ impacts respectively
Additive manufacturing in the oil and gas industries : a review
Get PDFAdditive manufacturing (AM), also known as 3D printing, is a process for creating prototypes and functional components achieved by consolidation of material layer upon layer. Applications of AM technologies have been witnessed in the healthcare, automotive, architecture, power generation, electronics and aviation industries. Some of the main benefits of AM include effective material utilisation, new design possibilities, improved functionality of the products and flexible production. The opportunities for the applications of additive manufacturing in the oil and gas industries are only just being explored. In this study, a review of the potential opportunities of AM technologies in oil and gas industries was reported. The adoption of the AM technologies necessitated the need for a rethink on design for manufacture and assembly of oil and gas component parts such as high-tech end burners, metal fuel nozzles, and submersible pump components amongst others. The possibility of employing AM technologies on-site for the production of spare parts for replacement of damage components in oil and gas equipment and facilities is commendable, as this brings about reduction in production downtime and replacement cost. The future of AM in the oil and gas industries is highly promising, however before AM can actualize its full-fledged potentials in these industries, further research is required in the area of new materials development and processing, improved surface finish of AM fabricated parts, enhanced fabrication speed and parametric optimisation to improve the mechanical properties of the fabricated components
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
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