1,720,953 research outputs found
Residual Stress and Distortion in Machined Wrought and Additively Manufactured Metallic Components
No full textThe described research aims to elucidate the factors that influence post-machining residual
stress and part distortion in machining of wrought (rolled and heat-treated) aluminum al-
loys and additively manufactured stainless steel components. At present, even with carefully
designed machining process parameters, part distortions that arise in wrought aluminum
alloys due to the presence of inherent residual stress (IRS) makes it difficult to produce
high aspect-ratio thin-walled monolithic components requiring increasingly stringent toler-
ances. Lack of understanding on the effects of IRS during high-speed machining (HSM)
inhibits it’s adaption into the manufacturing work flow to determine appropriate process
parameters or tool path strategy necessary for competitive economic production that avoids
trial-and-error machining strategies with such parts. This work intends to shed light on the
influences of inherent material characteristics, such as IRS and inhomogeneous/anisotropic
material properties, on the machining response (due to coupled effects of IRS and MIRS)
in both wrought and additively manufactured metallic components. It is first hypothesized
that coupling between IRS and MIRS contributes to final part residual stress and distortion.
This coupling, contrary to assumptions prevalent in the existing literature, is believed to not
simply allow for superposition of the inherent and machining contributions, but rather call
for a nonlinear relationship that is dependent on various factors. In the presented work, the
effects of IRS and material inhomogeneity and anisotropy are analyzed through computa-
tional studies and experimental validations made possible through industrial collaborations.
The work described herein, first, studies the effect of IRS and MIRS on the final-state of
residual stress (FRS) and post-machining part distortion and suggests that there is indeed a
nonlinear coupling that exists between IRS and MIRS. Analyses have been performed using
2D orthogonal cutting and 3D end-milling computational models. The material model, val-
idated using the 2D model based on observations from published literature, is used in both
the 2D and 3D case studies. IRS in the wrought material has been modeled by employing
an iterative stress reconstruction algorithm (ISRA) to generate a compatible IRS field that
encompasses the entire wrought material based on limited experimental measurements. The
results from the 2D case studies support the existence of a nonlinear coupling between IRS
and MIRS that subsequently determines the FRS. The 3D case studies reveal distortion re-
sults that elucidate the coupling effect even further by showing that IRS not only influences
the distortion of the final part, but that the degree of influence is dependent on the coupling
of the IRS profile and the HSM tool path. The presence of said coupling can thus either
magnify or reduce the final part distortion. The above established model is further devel-
oped to simulate machining of a 2 mm thin-walled part of the same material. To compare
and validate the predictive capability of the computational model, corresponding machining
experiments are performed, followed by coordinate measuring machine (CMM) distortion
analysis on the thin wall. In order to characterize the material IRS and subsequently in-
corporate it appropriately in the computational model via ISRA, Neutron Diffraction (ND)
stress measurements are performed at various locations on a plate of the same material,
from which smaller blocks are extracted for machining. High-speed machining simulations
are performed and the results are compared with the CMM measurements. Results indi-
cate that the presence of IRS in the material significantly influences the distortion profile.
Idealized material removal by element deletion simulation shows that IRS alone does not
induce significant distortion in these specific parts whereas the coupling between IRS and
MIRS is the prominent driver. The presence of IRS also tends to drive the distortions to-
wards experimentally measured result. It is also hypothesized that additively manufactured
parts that require post-process machining also experience similar coupling between IRS (in
the substrate and the build) and MIRS, which likewise is believed to significantly affect
post-machining part distortion. To test this hypothesis, first, a continuously coupled com-
putational fluid dynamics (CFD) and finite element analysis (FEA) framework is developed
in collaboration with other researchers. This model, involving directed energy deposition
(DED) builds, is employed to simulate manufacture of single-layer and double-layer, single-
bead DED builds. Corresponding experiments are performed to create samples, followed
by geometry scanning and ND stress measurements to compare with the simulation results.
The predicted final stress profiles agree well with experimentally measured profiles obtained
via ND stress measurements. Subsequently, the geometry and stress profile obtained from
the coupled CFD-FEA framework is employed to simulate an interlayer machining operation
in order to study the influence of IRS and inhomogeneous microstructure on post-machining
residual stress and distortion. A kinetic Monte-Carlo based microstructure prediction model
is calibrated and employed to obtain the microstructure in the build. The predicted mi-
crostructure is compared with EBSD measurements for validation. The microstructure is
then incorporated into the FEA model to create a representative volume element (RVE)
with varying strengths for grains of different sizes, based on a combined Johnson Cook - Hall
Petch material model. It is found that IRS and inhomogeneous microstructure influences
the part distortion after machining. IRS shows a greater influence on distortion compared
to microstructure. Finally, the IRS is found to influence the bulk behavior of the material
more significantly, whereas, the microstructure influences the local behavior of the material.
With this new understanding of the influence of various factors on post-machining stress and
part distortion, machining operations can be improved further to reduce waste and improve
part compliance to tight tolerances, including in new hybrid manufacturing markets
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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