1,720,966 research outputs found
Friction stir consolidation of aluminium chips: A new approach to overcome the inhomogeneous properties of the consolidated billet
Full text linkThe need to improve the recycling process of metals to achieve sustainability goals is reflected in the growing interest in solid-state recycling approaches. One of these is the Friction Stir Consolidation (FSC), able to directly transform chips into consolidated billets. The main features of this process are the pressure and the rotational speed of the tool which compresses and heats up the chips collected inside a designed die. During the consolidation process, the friction between the tool and chips surfaces plays an important role because it is the main source of heat, therefore the heat transfer starts near the tool to the bottom of the billet resulting in an inhomogeneous material property. This aspect leads to both inhomogeneous microstructure and hardness characterization of the consolidated billet. To improve the effectiveness of the friction stir consolidation recycling process, this study focused on a numerical approach by proposing a new setup in which the structure where the die and the chips are placed on, namely backing plate, was heated up aiming to activate a heat flow also from the bottom
A generalized parametric model for the bonding occurrence prediction in friction stir consolidation of aluminum alloys chips
Full text linkOver the last years solid state processing has been applied as an environmentally friendly recycling method for metal scrap. These approaches, by skipping the melting step, allow substantial energy and resource savings with respect to conventional remelting routes. Specifically, several processes relying on solid bonding phenomenon have been applied to recycle aluminum alloys chips. In this paper, the Friction Stir Consolidation recycling process is considered as solid-state recycling approach to turn chips of three different aluminum alloys namely AA2024, AA6082 and AA5083, into consolidated billet. The paper aims both at validating a new solid bonding criteria specifically designed for Friction Stir Consolidation as well as at proposing a general model to characterize the bonding criterion for each single considered material. In this regard, a correlation analysis and a new parametric model has been developed aiming to understand which material properties were involved in solid bonding occurrence and to predict the bonding limit curve vs temperature by means of material thermomechanical properties. The identified criterion and parametric model have been validated by implementing these on the bonding prediction occurrence in Friction Stir Consolidation of AA5083 aluminum chips. Results revealed that just on the basis of some mechanical and thermal properties of the material to be recycled it is possible to identify the threshold for the actual bonding of the material at different temperature levels and, therefore, properly design the recycling process by means of numerical simulation implementation
Recycling magnesium alloy AZ31B chips via friction stir consolidation: A sustainable approach
Full text linkThe growing demand for lightweight alloys has resulted in significant environmental challenges due to the exponential growth of machining waste, such as magnesium alloy chips. Conventional recycling techniques for these chips are often associated with oxidation losses, energy inefficiencies, and elevated greenhouse gas (GHG) emissions. Friction Stir Consolidation (FSC) emerges as a sustainable and solid-state recycling technique that mitigates these drawbacks by consolidating magnesium alloy chips directly into solid billets. This study investigates the FSC process applied to AZ31B magnesium chips, focusing on the influence of processing time on the quality of the consolidated billets. An experimental campaign was conducted with four distinct consolidation times, evaluating the mechanical properties and energy consumption of the process. Additionally, numerical simulation was performed to analyze the process mechanics. The results revealed that FSC successfully produced consolidated billets, with the highest consolidation level achieved at a process time of 60 seconds. Hardness analysis revealed a decreasing trend from the top to the bottom of the billet, with maximum values below those of the base material
Effect of process parameters on the mechanical properties of wires produced from A356 aluminum alloy chips by Continuous Friction Stir Extrusion: Experiments and numerical simulation
Full text linkRecycling of metals is becoming crucial from an economic and environmental point of view. The solid-state recycling process Continuous Friction Stir Extrusion was used to produce wires out of A356-T6 chips. The mechanical properties of the produced wires were explored by varying the main process parameters. Characterization involved Vickers hardness tests, tensile tests, grain size measurements, and fracture surface analysis. It has been found that it is possible to achieve 77 % of the Ultimate Tensile Strength (UTS) and 92 % of Vickers hardness with respect to the as-fabricated A356 alloy. The average grain size increases with the tool rotational with values ranging from about 9 mu m to about 11 mu m. A 3D dedicated numerical model was used to predict the distributions and histories of primary field variables, and to calculate the Piwnik-Plata parameter, fostering a more in-depth understanding of the process mechanics. This allows for the precise prediction of unacceptable product quality of the bonding when the Plata and Piwnik parameters are low. Predicted temperature close to the rotating tool should reach 400 degrees C while the cochlea temperature should be below 100 degrees C for sound wires production thus avoiding early chip bonding and process failure
Material flow analysis in friction stir consolidation during recycling aluminum alloy chips
Full text linkFriction stir consolidation (FSC) is a solid-state process primarily employed to recycle
aluminum machining scrap with the aim to meet the increasing demand of aluminum within the
framework of sustainability goals. This technology has recently drawn the attention of many
researchers due to its potential beyond the recycling approach to offer plausible new routes for
alloying and upcycling metal scraps. Concerning the FSC process, a rotating tool with a certain
force is applied to a given batch of chips mass enclosed inside a die chamber turning it into a
consolidated billet by friction and stirring action of the tool. The obtained samples are
characterized by non-homogenous properties as the non-symmetric nature of the process and
therefore different strain levels occur while producing the recycled billet. This study was focused
on developing a proper experimental setup to visualize material flow supported with preliminary
numerical simulation. The adopted approach led to reveal the deformation during the FSC process
in different billet regions by visualizing the shape change of the pre-embedded copper marker in
the billet
An insight into friction stir consolidation process mechanics through advanced numerical model development
Full text linkFriction stir consolidation (FSC) is a solid-state process adopted to recycle machining
scraps with aim to reduce the adverse impact of obtaining metals from their primary source. FSC
was also applied to offer plausible new routes for alloying and upcycling from powder and scrap
metal and thus drew the attention of many researchers. During FSC process, a rotating tool with a
certain force is applied to a given chips batch enclosed in a die chamber turning it into a
consolidated billet. It is assumed that favorable process conditions for chips bonding are acquired
by the combined effect of friction, stirring action, and pressure of the tool. However, the real
process is quite complex, and it can be understood only by developing proper solid bonding criteria
through numerical modeling that can forecast the consolidation process. Therefore, in this
research, an attempt was made to implement different existing bonding criteria. Some of these
were good enough to predict favorable conditions for sound bonding of particular case studies,
however a uniform criteria with a single threshold value that is applicable to all case studies could
not be achieved. Therefore, this study suggests for a new approach to accurately predict the
bonding integrity of the FSC process
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
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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