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A study on combined torsion and axial load fatigue limit tests with stresses of different frequencies
No full textThe aim of this paper is to investigate the high cycle fatigue behaviour of metals in the case of multiaxial loading where the stresses are
of different frequencies. In particular, combined axial load and torsion fatigue tests were performed on specimens made of quenched and
tempered steel. This material has been chosen because it is commonly employed for the production of mechanical components intensively
stressed under lengthy fatigue loads. Two frequency ratios between the shear stress and the normal stress are examined and the resulting
fatigue limits from these tests are compared to the results from tests where the shear and normal stress are of the same frequency and inphase.
Moreover, different multiaxial fatigue limit criteria, based on the critical plane concept and on the so-called integral approach, are
used to analyse the obtained experimental results. In general, better agreement between predictions and experimental results is achieved
by the criteria of the integral approach category
Use of multiaxial fatigue criteria and shakedown theorems in thermo-elastic rolling-sliding contact problems
No full textIn this paper two multiaxial fatigue criteria, the Dang Van and the Liu-Zenner criteria, are applied to rolling-sliding line contact problems taking into account both mechanical and thermal contact loads. The results of this analysis are summarized in maps, here called contact fatigue maps, similar to the so-called shakedown maps introduced by Johnson, but drawn to provide fatigue limits. These maps enable a general comparison of the contact fatigue limits obtained by the two multiaxial fatigue criteria and can be used as a design tool against high-cycle fatigue damage in rolling/sliding contacts. Shakedown maps are also provided and a comparison between contact fatigue and shakedown maps is discussed
Independence of the torsional fatigue limit upon a mean shear stress
No full textThe influence of a superimposed mean shear stress on the high-cycle fatigue endurance limit of metals is a question that has been discussed for a long time but general agreement between among researchers has not yet been reached. Though seemingly a question of minor importance, the hypothesis on such effect is a critical issue in the formulation of high-cycle multiaxial fatigue criteria. The available experimental data referring to fatigue tests on steels in which a static shear (torsional) stress is superimposed to cyclic torsion have been reviewed, showing that in most cases the effect of static shear stress is negligible as long as the maximum shear stress does not exceed the static shear yield strength. The limited amount of relevant experimental data found in the literature has led the present authors to perform torsion fatigue tests on a quenched and tempered steel, commonly employed in highly stressed mechanical components, with different levels of superimposed mean shear stress. The statistical analysis of the test results shows that no significant effect of the superimposed static shear stress may be observed
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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