1,720,952 research outputs found
Numerical Simulation of Fatigue Crack Growth in a Stiffened Plate
No full textFatigue is the most common source behind failures of mechanical structures. In order to study the phenomena, experiments have been performed by Lloyd's Register and other tests have been presented in literature. Performing real life fatigue experiments requires a long time, a considerable amount of money and it is size limited. The solution is to create and validate numerical models which are accurate and reliable.This is the main reason why the research is focusing on the prediction of the crack growth, using numerical models. The reference geometry for this study is a plate with longitudinal stiffener, since a lack of knowledge about this shape has been noticed in literature.In order to better understand the current knowledge in the topic of fracture mechanics, an extensive literature review has been performed. Considering a plate with longitudinal or transverse stiffener, the crack always appears at the weld toe, and propagates with a charactheristic semi-elliptical shape. The empirical solutions needed to compute crack propagation are presented in the British Standard 7910 (BS7910), but additional correction factors have been described in literature Anderson, 2005, Bowness and Lee, 2000, Han et al, 2014 and Newman and Raju, 1981.An additional research has been performed about the 3D modeling using the finite element method. The standard FEM can be used to compute the Stress Intensity Factor (SIF) along with a dedicated "spider web" mesh around the crack front. A valid alternative is marked by the newly introduced XFEM method, which uses an element definition with additional terms; these terms are able to consider the crack discontinuity and the stress singularity at the crack tip.The empirical equations and the correction factors have been merged in 14 sets of equations. The objective of this first study is to assess the conservativeness of the solution proposed in the BS7910. A MATLAB empirical model has been created with the equations and the Paris law crack growth. The results of these models are compared to tests from literature and to the experiments from LR. An high accuracy is achieved using the set of equations from the BS7910 and using the correct load ratio.The FEM model has been created to define a new XFEM meshing technique able to supply accurate SIF results; finally, as demonstration of the accuracy of the XFEM models, the empirical equations has been compared with the 3D finite element models.An extensive mesh convergence study was performed, reaching a good agreement for the crack in a simple plate, both using the standard FEM method and the newly introduced XFEM solution. Finally, a comparison between the new XFEM mesh and the standard mesh in a plate with transverse stiffener was performed. This latest comparison highlighted a big discrepancy in the SIF solution for the surface point of the semi-elliptical crack. This difference was demonstrated to be the consequence of an erroneous stress distribution in the standard FEM model.The research has brought to the conclusion that the empirical model using the BS7910 is able to deliver accurate results, if the correct load ratio is considered. While in the FEM model analysis, it has been demonstrated that the empirical equation from Bowness and Lee, 2000 is not accurate at predicting the stress intensity factor at the surface point. This finding was revealed thanks to the use of the XFEM finite element method along with a detailed meshing technique
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
No full text“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
No full textWe 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
A Numerical Investigation of an Abnormal Phenomenon of Stress Intensity Factor (SIF) in a Cracked T-Butt Joint Accounting for Welding Effect
No full textIndustry design standards such as BS 7910 deployed some empirical formulas for the prediction of stress intensity factor (SIF) based on simulation results from traditional finite element method (FEM). However, such FEM simulation occasionally failed to convince people due to the large discrepancies compared with engineering practice. As a consequence, inaccuracy predictions via such formulas in engineering standards inevitably occur, which will compromise the safety of structures. In our previous research work, an abnormal phenomenon of SIF in a cracked T-butt joint accounting for welding effect has been observed. Compared with BS 7910, the calculation results of SIF at the surface points of welded specimens cannot be well predicted, with a large discrepancy appearing. In order to explore such problem with an abnormal increase at the surface points of cracked welded specimens, a numerical investigation in terms of SIF among BS 7910, XFEM, and FEM is performed in this paper. Numerical models on both a simple cracked plate without welding effect and a cracked T-butt joint with welding effect are developed through ABAQUS. Parametric studies in terms of the effects of varied crack depth to thickness ratio (a/T) and the effects of crack depth to crack half-length ratio (a/c) are carried out. Empirical solutions from BS 7910 are used for comparison. It is found that the XFEM can provide predictions of SIF at both the crack deepest point and crack surface point of a simple cracked plate as accurate as FEM. For a T-butt joint with a transverse stiffener, a large discrepancy in terms of the weld magnification factors (Mk) occurs at the crack surface point compared with empirical predictions. An exceptional increase of von Mises stress gradient in regions close to the weld-toe is found through the simulation of FEM, whereas a constant stress gradient is obtained through XFEM. The comparison results indicate an inappropriate prediction of SIF by the utilization of the empirical formulas in BS 7910. A more reasonable prediction of the SIF at the surface point of a crack is obtained by the XFEM. Therefore, further updating of the empirical solutions in BS 7910 for SIF accounting for welding effect is recommended.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport Engineering and Logistic
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
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