1,720,964 research outputs found
Parameter optimization, microstructural and mechanical properties of fiber laser lap welds of DP1200 steel sheets
No full textIn this research, the effects of laser power, laser welding speed and laser incidence angle were evaluated in terms of weld geometry, microstructure, microhardness, fracture surfaces and tensile shear load in fiber laser welding joints of DP1200 steel sheets. Response Surface Methodology (RSM) was utilized to derive mathematical relationships between the process parameters and the tensile shear load after the tensile test. The optimum combination of process parameters was a laser power of 2800 W, a laser welding speed of 40 mm/s, and a laser incidence angle of 70 degrees . A thermal camera was used to record the laser welding process, and the cooling rates were evaluated by analyzing this data. The influence of cooling rate upon microstructure phase formation for DP1200 steel is investigated, with continuous cooling transformation (CCT) diagrams. Also, post -welding stress and displacement were simulated by Simufact Welding software. At high heat input (55.79 J/mm) occurred coarse dendritic martensitic lath growth while at low heat input (37.6 J/mm) fine dendritic martensitic structure was observed in the weld zone was obtained owing to the high rate of cooling. The microstructure consists of full martensite at a higher than 10 degrees C/s cooling rate. The findings reveal that the phases in FZ and HAZ, the morphology and martensite/bainite constituents differed related to the heat input and laser incidence angle, which ultimately affects the joint 's microhardness, fracture dynamics and tensile shear load
Effect of heat input on martensitic stainless steel laser clad characteristics on ductile cast iron
Get PDFLaser cladding is a surface modification technique used for repairing and enhancing substrate materials by depositing powder layers with a laser beam. This study investigates the effects of laser power, scanning speed, and heat input on the porosity, microhardness, microstructure, residual stress, and thermal behavior of Metco 42C martensitic stainless steel powder deposited on FGS600-3A ductile cast iron used in sheet metal forming molds. Characterization was conducted using optical microscopy, SEM, EDS, digital image processing, thermal imaging, and residual stress measurements via XRD and ESPI methods. The cladding zone exhibited a columnar dendritic martensitic structure, with coarser dendrites observed at high heat input (316.67 J/mm) compared to low heat input (78.57 J/mm). Increased heat input significantly affected porosity, with pore formation mechanisms including gas entrapment, lack of fusion, balling effect, and thermal contraction. Microhardness variation was attributed to carbon diffusion from the substrate, with a peak hardness of 946 HV0.05 in the transition zone. Residual stress analysis revealed compressive stress dominance at high heat input and tensile stress at low heat input. Thermal analysis indicated a peak temperature of 1771 degrees C in the first cladding layer, which also exhibited a higher risk of cracking. These findings highlight the influence of heat input on the mechanical and microstructural properties of the cladding, providing insights for optimizing laser cladding processes in industrial applications
Effect of energy input on porosity and microhardness in laser cladding coating on fgs600-3a ductile cast iron
No full textLaser cladding, which is surface modification technology, is based on melting with a laser beam by spraying powder on the base metal and generated by depositing the layers. In this study, the Metco 42C martensitic stainless steel powder material was cladded on the FGS600-3A ductile cast iron used in sheet metal forming molds. The effect of energy input on porosity and microhardness was investigated. The digital image processing method was used for porosity analysis. The energy input had a significant effect on the pore formation. The lower energy input (1.1 kW laser power, 14 mm/s scanning speed) resulted in lower porosity. The cladding thickness varied depending on the scanning speed parameter due to affecting powder efficiency, high thickness was obtained at 6 mm/s low scanning speed. In the upper layer of the cladding, high hardness values were achieved due to the martensitic phase formation. The bottom layers of cladding had lower hardness values because of the tempering of the hard martensitic phases by subsequent cladding processes. Significant increase in hardness at cladding zone was attributed to carbon transfer from the base metal. This remarkable increase in hardness was much higher at lowest energy input (1.1 kW laser power and 14 mm/s scanning speed). However, it is clear that this will increase the risk of crack formation because of brittleness. On the other hand, at the higher energy input, this significant increase in hardness is at a lower level due to rest-austenite formation and excessive annealing with subsequent cladding processes
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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