1,720,969 research outputs found
A concurrent multiscale model for simulating transverse crack propagation in fiber-reinforced composite materials
No full textCrack propagation modeling in functionally graded materials using Moving Mesh technique and interaction integral approach
No full textThis paper presents a novel FE modeling approach based on Moving Mesh technique to reproduce crack propagation mechanisms in Functionally Graded Materials. The moving mesh is consistent with the Arbitrary Lagrangian-Eulerian formulation, which is suited to handle growing random cracks, avoiding extensive remeshing processes. This approach is based on the Interaction Integral Method to extract the mixed-mode Stress Intensity Factors, which are necessary to establish crack onset conditions and propagation direction. Among the different available options for FGM, the incompatibility formulation is adopted. The proposed scheme reproduces the propagation mechanisms by moving the computational nodes around the crack tip, according to standard fracture criteria. Mesh regularization technique based on proper rezoning equations ensures the consistency of the motion, reducing mesh distortion. The reliability of the proposed method is evaluated through comparisons with experimental data and existing numerical approaches. The computational efficiency is checked through parametric analyses on mesh discretization and accuracy in the prediction of the crack path and fracture variables. The results show how the proposed method could represent a valid tool to simulate the propagation mechanisms in FGM, in which heterogeneous macro-properties involve complex crack paths
A multiscale analysis of instability-induced failure mechanisms in fiber-reinforced composite structures via alternative modeling approaches
No full textMultiscale techniques have been widely shown to potentially overcome the limitation of homogenization schemes in representing the microscopic failure mechanisms in heterogeneous media as well as their influence on their structural response at the macroscopic level. Such techniques allow the use of fully detailed models to be avoided, thus resulting in a notable decrease in the overall computational cost at fixed numerical accuracy compared to the so-called direct numerical simulations. In the present work, two different multiscale modeling approaches are presented for the analysis of microstructural instability-induced failure in locally periodic fiber-reinforced composite materials subjected to general loading conditions involving large deformations. The first approach, which is of a semi-concurrent kind, consists in the “on-the-fly” derivation of the macroscopic constitutive response of the composite structure together with its microscopic stability properties through a two-way computational homogenization scheme. The latter one is a novel hybrid hierarchical/concurrent multiscale approach relying on a two-level domain decomposition scheme used in conjunction with a nonlinear homogenization scheme performed at the preprocessing stage. Both multiscale approaches have been suitably validated through comparisons with reference direct numerical simulations, by which the ability of the latter approach in capturing boundary layer effects has been demonstrated
A crack growth strategy based on moving mesh method and fracture mechanics
Full text linkA numerical model based on moving mesh strategy is proposed to simulate the evolution of internal material discontinuities in a continuum medium. The approach combines concepts arising from structural mechanics and moving mesh methodology, which are implemented in a unified framework to predict crack growth on the basis of Fracture Mechanics variables. In particular, moving computational nodes are modified starting from a fixed referential coordinate system on the basis of a crack growth criterion to predict directionality and displacement of the tip front. The use of rezoning mesh methods coupled with a proper advancing crack growth scheme ensures the consistency of mesh motion with small distortions and an unaltered mesh typology. In addition, the moving grid is modified from the initial configuration in such a way that the recourse to re-meshing procedures is strongly reduced. The numerical formulation and its computational implementation show how the proposed approach can be easily embedded in classical finite element software. Finally, numerical examples in the presence of internal material discontinuities and comparisons with existing data obtained by advanced numerical approaches and experimental data are proposed to check the validity of the formulation.</p
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
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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