1,720,985 research outputs found
Cold spraying of tailored aluminium foam precursors: Investigating the correlation between spraying conditions and foam morphology
Full text linkA Preliminary Study on the Sustainability of Metallization of Polymer Matrix Composites through Cold Spray
Full text linkChemical Machining of Copper-Based Aerospace Alloys Produced Through Additive Manufacturing: A Preliminary Approach to Improve Surface Quality
No full textAdditive Manufacturing (AM) is transforming the production of high-performance components, particularly in the aerospace sector. However, the surface quality of AM products often does not meet industry standards, necessitating additional treatments. Chemical machining processes are especially advantageous for preserving the intricate geometries of AM parts, yet their application can be challenging for certain metals due to the presence of alloying elements. The objective of this study is to evaluate the enhancement of surface properties, with a focus on roughness reduction, in GRCop-42 components fabricated via powder bed fusion technology, through the application of chemical machining treatments. Two distinct chemical machining solutions were considered: one formulated with ferric chloride and the other composed of a mixture of sulfuric and nitric acids. Furthermore, two experimental setups were implemented to assess the efficacy of ultrasound assistance during the chemical machining process. The results demonstrated that both chemical solutions effectively removed surface material, with the integration of ultrasound significantly accelerating the process. Surface roughness was reduced by up to 13 pct and the steepness of the surfaces was markedly decreased, achieving a nearly uniform finish. However, the utilization of ultrasound with the lower viscosity solution resulted in cavitation erosion, which created undesirable cavities on the surface
Integrating 3D printing of polymer matrix composites and metal additive layer manufacturing: surface metallization of 3D printed composite panels through cold spray deposition of aluminium particles
Full text linkThe integration of metals and polymers in the same component to couple the best properties and advantages of both these classes of materials can be useful for engineering applications. In this scenario, the aim of this paper is to integrate additive manufacturing of composites with cold spray deposition of metal particles: in particular, 3D-printed carbon fibre-reinforced plastics (CFRP) panels were coated with aluminium particles to couple the lightweight and high mechanical properties of CFRP with high wear resistance and hardness of metals. CFRP panels have been produced by using the Fused Filament Fabrication (FFF) technology, then the panels have been coated with aluminium particles by using a low pressure cold spray facility. Panels with various stratification sequences have been produced to investigate the feasibility of the process and to highlight the influence of the lay-up strategy on the whole process; the parameters of the cold spray process have been also optimized to ensure an effective deposition. Adhesion tests, distortion measurements, cross-section observations and surface coverage measurements have been chosen as response outputs to evaluate the effectiveness of the process and to assess the influence of the process parameters. The integration between FFF of CFRPs and cold spray deposition of aluminium particles has been proved, values of surface coverage close to 100% and good values of adhesion strength (close to 4 MPa) have been achieved; moreover, the presence of the fibres, giving a higher stiffness to the substrate, avoids the occurrence of distortion phenomena during the deposition. It was also proved that the printing parameters influence the deposition: an increase in the infill density from 30% to 50% leads to an increase in the adhesion strength up to 40%. In summary, the results obtained proved the feasibility of the process and allowed to enucleate directions of future research
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
Cold Sprayed Metallic Coatings on Fibre-Reinforced Composites: A Machine Learning Approach for the Optimization of the Process
No full textCold spray additive manufacturing (CSAM) is a promising process for producing metallic layers on different substrates, using powders as a feedstock material. The metallic powders are deposited through pressured gas that reaches supersonic velocities. Due to the low heat input required, as the powders remain in solid-state, this technology is particularly suitable to coat thermo-sensitive materials such as composites. In this scenario, machine learning techniques can be crucial to improve the quality and understanding of this manufacturing process. The aim of this work is to predict the deformation and penetration of a particle upon impact using machine learning techniques in order to assess the properties of the coating. A univariate linear regression method was chosen to verify the feasibility of Theory Guided Machine Learning (TGML) techniques to predict the characteristics of the coating. The training dataset was obtained from both experimental data and computational data. It was confirmed that TGML could be a good route to pursue in order to optimize this process
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
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