1,720,984 research outputs found
Characterization of PLA parts made with AM process
No full textThe main objective of the presented work is to evaluate the thermal behavior of Poly-lactic acid (PLA) parts made with a Fused Deposition Modelling (FDM) process. By using a robust framework for the testing sequence of PLA parts, with the aim of establishing a standard testing cycle for the optimization of the part performance and quality. The research involves study the materials before and after 3D printing. Two biodegradable PLA polymers are investigated, characterized by different colors (one black and the other transparent). The study starts with the examination of each polymeric material and measurements of its main thermal properties
Friction Stir Welding of Ti6Al4V complex geometries for aeronautical applications: a feasibility study
Get PDFWhile Friction Stir Welding (FSW) of aluminium alloys can be considered a mature technology, even for complex joint morphologies, as T joints welded “in transparency”, welding of hard material still presents several open issues. In fact, welding of titanium alloys is a challenging process due to the chemical, mechanical and thermal characteristics of such materials which are subjected to atmosphere contamination resulting in joint hydrogen, oxygen and nitrogen embrittlement; additionally, due to the high melting temperature, large distortion and residual stress are found in joints obtained by traditional fusion welding processes as gas metal arc welding, electron beam welding and laser welding. In this way a solid-state process, as FSW, represents a valid choice in order to overcome problems related to the material melting. It should be noticed that FSW of titanium alloys is definitely more complex than the same process referred to aluminium alloys. In the proposed paper, a feasibility study on the production of Ti6Al4V T-joints in one welding pass, i.e. the so-called transparency welding, is presented. The main process parameters, i.e. tool rotation and feed rate have been fixed, and the main metallurgical and mechanical properties of the joint have been analysed. Macro and micro observations of the joints have been performed relating the final microstructure to the input process parameters utilized
Investigating the influence of deposition techniques and processing conditions on AA2024/SiC FSW joints: Evaluation of microstructural and mechanical properties
Get PDFFriction Stir Welding (FSW) has become a mature technology for most metal alloys. The current frontier is the
development of in-situ alloyed or reinforced materials to further spread the field of application of this technique.
In the paper, SiC-reinforced 2024-T3 aluminum joints were produced by integrating micro-size SiC particles by
creating proper features in the sheets. A new joint design was proposed in order to overcome the issues of powder
dispersion occurring with the more conventional hole design. The influence of distinct parameters viz., tool
rotation speed, traverse speed, and joint configuration on SiC dispersion, microstructure, and mechanical
properties of the prepared joints has been corroborated. Standard FSW was also carried out for comparison. The
rotation and travel speeds varied ranging 700–1100 rpm and 50–90 mm/min, respectively. The distribution of
reinforcement particles in various zones of the FSW process was examined by using optical microscopy (OM) and
scanning electron microscopy (SEM). It was found that the velocity ratio variation influences the heat generation
and thereby the microstructural and mechanical properties owing to distinct SiC particulate dispersion
throughout the joint area. The welded joints produced at the 1100 rpm and 70 mm/min (S1100–70) combination
exhibit an increment in hardness by 30 % as compared to base material resulting from grain size reduction and
better dispersion of SiC powder. Finally, the analysis of power consumption and temperature during the process
was carried out. These additional measurements were crucial in determining the overall performance and
feasibility of using SiC powder in the welding process
Study of PMMA materials for a digital optical module
No full textThis work illustrates the material characterization to realize of a prototypal polymeric cover of a Digital Optical Module for the Hyper-Kamiokande neutrino experiment. The cover was made of a high transmittance poly-methyl methacrylate (PMMA), used as a glass substitute. The main objective of the present research is to investigate the structural and optical properties of PMMA, evaluating the respect of the project specification
Effect of Rotational Speed on Mechanical Properties of AA5083/AA6082 Friction Stir Welded T-Joints for Naval Applications
Get PDFThis study evaluates the influence of rotational speed on the mechanical and microstructural properties of T-joints fabricated via friction stir welding (FSW) using dissimilar aluminum alloys, AA5083 and AA6082, for naval applications. Three types of joints were produced by maintaining a constant traverse speed of 100 mm/min and varying the tool rotational speed at 500, 700, and 900 rpm. Mechanical performance was assessed through pull-out tests and microhardness measurements. The joints fabricated at 500 rpm demonstrated superior mechanical properties, including a more uniform hardness distribution and higher pull-out strength, attributed to optimized material mixing and heat input at this speed. In contrast, higher rotational speeds led to defect formation, such as wormholes, and compromised mechanical performance. These findings underscore the importance of optimizing rotational speed to enhance joint quality, making FSW a viable solution for manufacturing durable, lightweight structures in demanding marine environments
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
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