1,720,983 research outputs found
Micromilling operation of AISI 52100: experimental and numerical analysis
No full textIn many industrial field the part miniaturization is a very important task for increasing the competitiveness in the market. For this reason industries and researchers focused their attention on the micro manufacturing processes. A wide range of different processes can be utilized for manufacturing micro components and micro products. Amongst them the micro cutting processes (i.e., micromilling, microturning and microdrilling) play an important role because of their high flexibility and ability in realizing complex shapes. Of course, it is very important to analyze advantages and limits of these manufacturing processes since these processes base the material transformation on different physical-chemical phenomena. Therefore, the comprehension of metallurgical aspects (phases, grain structure, etc.) influence on machinability of the micro cutting processes is fundamental. In this context, the present paper reports the preliminary part of a research aimed at developing a robust FE model to correctly simulate micromilling of hardened AISI 52100 steel samples with different metallurgical state and, consequently, initial hardness machined under different cutting conditions. The experimental data, coming from this preliminary experimental campaign, will be used for calibrating and validating an FE simulation strategy and a material model able to take into account the different material microstructures in order to increase the accuracy of the FE results
Evaluation of the environmental impact of direct hot rolling, ECAP and FSE for aluminum chips recycling
Full text linkWith the increasing global demand for aluminum, the environmental challenges associated with primary aluminum production, such as high energy consumption and greenhouse gas emissions, need innovative recycling solutions. Recently, unconventional aluminum recycling methods, known as Solid-State Recycling (SSR), have been developed. These processes bypass the melting stage, resulting in significant energy savings and reduced material losses. This paper presents a Life Cycle Assessment (LCA) study of the newly developed Direct Hot Rolling (DHR) process for recycling aluminum chips, focusing on the environmental impacts of chips degreasing and comparing DHR with other SSR methods. The DHR process, an emerging solid-state recycling (SSR) technology, offers a promising alternative to conventional methods by reducing energy use and emissions. However, the introduction of a degreasing phase is necessary to possibly scale the process for industrial applications, adding new environmental considerations. Using the SimaPro software with a “gate to gate” approach, this study evaluates the environmental performance of DHR both with and without the degreasing phase, to understand the environmental impact of this step. Then, based on data available in literature, the direct rolling process is compared with ECAP and FSE techniques. The results show that the degreasing process significantly contributes to aquatic and terrestrial ecotoxicity due to the chemicals used, highlighting a trade-off between material quality and environmental liability. On the other hand, DHR has a lower overall environmental impact if compared to ECAP and FSE. Additionally, DHR demonstrates significantly lower material losses compared to ECAP and FSE, making it more resource efficient
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
Direct hot rolling as a solid-state recycling process for green sheets production
Full text linkWith the increasing demand for sustainable solutions in the recycling of aluminum alloys, solid-state recycling (SSR) offers an energy-efficient alternative by avoiding the melting phase, which typically leads to high energy consumption and material loss. This study presents a novel SSR process utilizing direct hot rolling to recycle aluminum alloy chips (EN AW-5754). The main objective is to evaluate this process's feasibility and assess the recycled sheets' mechanical and microstructural properties. Aluminum alloy chips were produced from the turning process of EN AW-AA5754 bars. The chips were compacted and subsequently heat-treated at 400°C for 2 hours. The compacted samples were then hot rolled in multiple passes, with a final cold rolling step to achieve a final thickness of 0,8 mm. Mechanical properties and microstructure were analyzed using tensile testing machine and SEM-EBSD technique. The recycled samples demonstrated mechanical properties comparable to those of reference material. SEM/EBSD analysis revealed broken oxides and a layered grain structure due to the prior chips’ boundaries. Overall, the results confirm that direct hot rolling can be a viable recycling method for aluminum alloys, offering significant energy and material savings compared to conventional processes
Effect of material characterization via torsion tests on the accuracy of FEM simulations in the extrusion process
Full text linkThe Finite Elment Method codes are nowadays potent and useful tools for advancing the design and optimization of metal forming processes. This is particularly evident in sectors such as aluminum extrusion, where FEM contributes to both process enhancement and tool development, mitigating the high costs and time demands of experimental trials. However, accurate and reliable simulations require precise material flow stress modeling. In this context, the hot torsion test is considered the most suitable for material characterization as it allows for achieving the high strain levels typical of the extrusion process while maintaining stable temperature and strain rate conditions during testing. This work presents the characterization via torsion tests of four distinct alloys, all classified within the AA6082 series, obtained from different casting batches. The resulting data were subsequently employed as input for numerical simulations of an industrial extrusion process and compared with experimental results to assess the impact of flow stress modeling on the accuracy and reliability of the simulations
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
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