1,720,965 research outputs found
Effective Modeling of Interlaminar Damage in Multilayered Composite Structures Using Zigzag Kinematic Approximations
No full textThe chapter gives an overview of the main approaches formulated to model
interlaminar damage and imperfections in layered structures using zigzag kinematic approximations and concentrates on the models which have been extended
to analyze delamination damage progression. The zigzag theories are structural
theories which assume different kinematic fields in the layers, to account for
zigzag effects associated to their elastic mismatch, and use a fixed number of
variables that is independent of the number of layers. Interfacial imperfections,
interlayer damage, and delaminations are included using the compliant layer
concept, imperfect interfaces, or by adding additional variables. Delamination damage progression is studied using continuum mechanics and fracture mechanics techniques. The focus of the presentation is on the theoretical aspects and uses
simple examples and applications to discuss and compare the different formulations and show relevant behaviors
The Effects of a Large Elastic Mismatch on the Decohesion of Thin Films from Substrates
No full textAnalytical and semi-analytical solutions are presented for energy
release rate and mode mixity phase angle of an edge-delaminaton crack between
a thin layer and an infinitely deep substrate. The solutions apply also to systems
with an exceptionally large mismatch of the elastic constants, such as those
which are used nowadays for various industrial and structural applications, and
allow to investigate the role played by substrate/layer compressibility
Direct evaluation of the modification coefficient kmod for the static-fatigue design of annealed glass panes under wind load
No full textMost standards reduce the design strength of glass through a modification coefficient that accounts for static fatigue caused by subcritical propagation of surface cracks. For wind pressures on glass plates, the coefficient is derived assuming nominal durations of maximum wind gusts or cumulative winds, which are defined based on tradition and practice. Here we derive closed-form expressions for the modification coefficient using a fracture mechanics approach which incorporates the time histories of wind velocity or their probabilistic distributions. The coefficient depends on the duration of the action and becomes constant for typical design lives. A consistent nominal duration is then defined by referring to a wind with fixed reference velocity which produces the same damage of the actual action. The approach, applicable to the European context, has been applied to data recorded in Italy. The results are compared with prescriptions from various standards showing that they are in general non-conservative
Orthotropic strip with central semi-infinite crack under arbitrary loads applied far apart from the crack tip. Analytical solution
No full textAn exact analytical solution is derived for the problem of a homogeneous orthotropic strip with a
central semi-infinite crack loaded by a self-balanced system of forces applied far enough from the
crack tip to be considered as applied at infinity. The general solution is expressed as superposition of solutions for four elementary loads. The mode I and mode II stress intensity factors are
obtained in terms of two functions, one for the opening mode and one for shear, which depend on
a single parameter and are expressed as single integrals
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
The effective crack extension and its implications on the single cantilever beam test for sandwich composites
No full textThe response of Single Cantilever Beam sandwich specimens may be analyzed effectively through one-dimensional theories accounting for the actual deformation of the core and its effects on fracture parameters and compliance. The model of a beam on an elastic Winkler foundation describes the detaching facesheet as an Euler-Bernoulli beam resting, in the bonded region, on an elastic foundation which generates oscillating deflections with characteristic length 1/lambda. Modified beam theory (MBT) describes the debonded part of the face sheet as a cantilever beam, built-in at the debond tip, with an effective length which is longer than the actual detached length, by a quantity Delta. If Delta = 1/lambda. the two models predict the same energy release rate and similar load-point displacements. Effective crack extension and characteristic length depend on the thicknesses and elastic constants of facesheets and core and may be derived through experimental measurements of the specimen compliance at various increments of crack growth, as prescribed by experimental protocols. In the theoretical analyses, Delta is typically assumed, either by directly using formulas proposed for other specimens or by calibrating their parameters to case specific finite element results. In this paper, we investigate the applicability of such formulas to a wide selection of sandwich composites for naval and aeronautical applications having thicknesses or materials other than those used for the original fitting; we then highlight their limitations and effects on the design of experimental protocols for material characterization. The applicability of a recent isotropic-elasticity based formula for Delta is then verified using extensive data from the literature and novel finite element (FE) results for typical sandwich composites. Finally, a novel elasticity solution for the load-point displacement of a layer on a half plane is derived which supports the test data reduction procedure for Delta
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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