1,720,960 research outputs found
Numerical Investigation of Coefficient of Friction in Copper Powder Compaction Process at Micro Scale
No full text7th International Conference on Mechanical and Aerospace Engineering (ICMAE) -- JUL 18-20, 2016 -- London, ENGLANDguner, faruk/0000-0002-3438-0553; SOFUOGLU, HASAN/0000-0002-8433-4045WOS: 000390417000023Multi Particle Finite Element Method (MPFEM) which is a power full approach for particle systems analyzes particle interactions via different friction models. In this study, Amontons-Coulomb constant friction (ACM), Wanheim/Bay generalized friction (WBM) and Levanov's friction models (LFM) are utilized in MPFEM in order to obtain coefficient of friction at particle-particle and particle- die wall interactions in spherical copper powder compaction. Friction models are introduced into the analysis by user subroutines. Compaction processes at room temperature and at 270 degrees C were investigated by terms of coefficient of friction, shear stress and equivalent strain. Although equivalent strain curve of WBM and LFM are in good agreement, ACM resulted in higher equivalent strain and shear stress values. Coefficient of friction those were obtained with WBM and LFM varies in a reasonable range.IEE
An investigation of contact interactions in powder compaction process through variable friction models
No full textguner, faruk/0000-0002-3438-0553; SOFUOGLU, HASAN/0000-0002-8433-4045WOS: 000371100800001In this study, multiparticle finite element (MPFE) approach was used to analyze contact interactions of spherical copper particles in powder compaction process. To this goal, 74 spherical copper particles of 200 in diameter were modeled as individual elastic-plastic bodies, and randomly filled into a die cavity. Interparticle and die-wall-particle contact interactions were investigated, and coefficients of friction were obtained using variable friction models; Wanheim-Bay's general friction model and Levanov's friction model. Variable friction models were incorporated into FE analyses through user subroutines. It was found that the variation of contact stresses inside the die leads to different contact conditions at different zones. The range of coefficient of friction encountered in the analysis was found to be slightly higher in Levanov's friction model than that for Wanheim-Bay's general friction model. On the other hand, Levanov's model was found to be more appropriate for elevated temperature analyses. (C) 2015 Elsevier Ltd. All rights reserved
Effects of friction models on the compaction behavior of copper powder
No full textguner, faruk/0000-0002-3438-0553; SOFUOGLU, HASAN/0000-0002-8433-4045WOS: 000430522500015A comparative numerical and experimental analysis of metal powder compaction processes was presented. Closed-die compaction of spherical copper particles with a nominal diameter of 200 pm was analyzed using Multi Particle Finite Element Method (MPFEM). The von Mises material model associated with contact sensing algorithms was employed to investigate variation of coefficient of friction, and contact interactions between powder particles as well as particles with the die walls. Three different friction models (Amonton-Coulomb, Wertheim Bay, and Levanov) were used to provide a better insight and the latter two were integrated into the commercial finite element package via user-subroutines. To verify the established model, some compaction experiments were carried out. Optical, and scanning electron microscopy analyses were performed, and images obtained were compared with the numerical results. The values of the coefficient of friction obtained using Wanheim-Bay and Levanov friction models fall into the range of 0.04-0.07. From the stress distribution perspective, it was observed that the results obtained with Wanheim-Bay friction model were more conforming to experimental cases where high relative density compaction takes place while Levanov friction model was found to be preferable at low relative density compaction process
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
Physical modeling of extrusion process
Get PDFMany metal forming processes can be simulated by using the Physical Modeling Technique which requires an inexpensive and small amount of apparatus. The underlying principle behind the Physical Modeling Technique is to simulate the actual metal forming process by selecting a model material and die geometry that closely resemble the actual metal forming process. Typical modeling materials are PLASTICINE, wax and lead while the typical die models are usually made of aluminum, wood or plexiglass.
In two-dimensional analyses, a square or circular grid pattern is printed on the surface of the specimen using ink and a grid stencil. The common method of generating the grid pattern is to use different types of PLASTICINE instead of using ink. Therefore, alternating slabs of PLASTICINE of different colors automatically form the grid patterns.
In the first phase of this study, 16 types of PLASTICINE were tested, via standard compression tests, in order to determine their flow behavior and to identify a pair with similar behavior.
In the second phase of this study, three-dimensional extrusion process was studied by using two types of PLASTICINE as a modeling material while using plexiglass as chamber and die material. The friction coefficient of PLASTICINE was obtained by utilizing the ring compression test. Analysis of deformation patterns, using the well established Physical Modeling Technique, is normally carried out by prescribing a grid pattern on the surface of modeling material.
The extrusion experiments were conducted at the three different area reductions for three different semi-cone die angles. In each case, the plastic strain distributions were determined analyzing the deformed and undeformed grids.
The main objective of this study was to simulate the three-dimensional extrusion process by using PLASTICINE as a modeling medium. Since PLASTICINE is available in 16 different colors, it became necessary to characterize the mechanical behavior of 16 different types of PLASTICINE. The objective was also to identify color pairs of PLASTICINE with similar mechanical behavior and to use these color pairs for the three-dimensional extrusion process. Furthermore, the objectives were to determine the strain distributions of plastic strain components along the diameter of an extruded product and to determine the effects of the process variables, such as area reduction and semi-cone die angle, on the required forming load
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