1,720,959 research outputs found
Analysis of Composite End Notch Flexure Specimen using13; Various Plate Theories
No full textAbstract: Mathematical formulation for the stress analysis of symmetric multidirectional end notch flexure (ENF) specimen, using classical plate theory, first,second, 13; and third-order shear deformation plate theories under generalized plane stress and cylindrical bending conditions, is developed to determine the mode II interlaminar fracture toughness of symmetric 13; multidirectional composites. In the present formulation,13; appropriate matching conditions are applied at the crack tip and these matching conditions at the crack tip are derived by enforcing the displacement continuity at the13; crack tip in conjunction with the variational equation. Compliance approach is used to calculate strain energy release rate (SERR). Generalized plane stress model 13; and cylindrical bending model are applicable and close 13; to each other for unidirectional and cross-ply composite 13; ENF specimens. For multidirectional ENF specimens, the13; appropriate compliance/SERR values, obtained from the combination of compliance/SERR values of generalized 13; plane stress and cylindrical bending models,appear to be 13; reasonable and encouraging. For unidirectional and cross-ply composite ENF specimens, classical and first order 13; plate theories give similar SERR under generalized plane 13; stress and cylindrical bending conditions where as for multidirectional ENF specimen they give similar SERR 13; only under generalized plane stress condition. In general, 13; second and third order plate models of ENF specimen are found to be good for unidirectional, cross-ply composite 13; ENF specimens and reasonably good for multidirectional composite ENF specimens in determining the interlaminar 13; fracture toughness (or SERR) and interlaminar shear 13; stress distribution ahead of the crack tip
Analysis of Composite Double Cantilever Beam Specimen using13; Various Plate Theories
No full textMathematical formulation for the analysis of symmetric multidirectional double cantilever beam (DCB) specimen using classical plate theory, first and higher order shear13; deformation plate theories under both generalized plane stress and cylindrical bending conditions is developed to determine the mode I interlaminar fracture toughness of symmetric multidirectional composites. In the present formulation, appropriate matching conditions are applied at the crack tip and these matching conditions at the crack tip are derived by enforcing the displacement continuity at the crack tip in conjunction with the variational equation. Variationally derived matching conditions at the crack tip enforce the shear force to be13; discontinuous at the crack tip. Strain energy release rate (SERR) is calculated using compliance approach. Generalized plane stress and cylindrical bending models are applicable and close to each other for unidirectional and cross-ply composite DCB specimens, where as they differ with each other for composite DCB specimens with angle-ply layers. For multidirectional DCB specimens, appropriate compliance/SERR values are obtained from the13; combination of compliance/SERR values of generalized plane stress and cylindrical bending models and appear to be 13; reasonable and encouraging. Performances of first and 13; higher order plate theory models of DCB specimen are close to each other in predicting the SERR. However, higher order plate theory models of DCB specimen are necessary to determine the proper interlaminar normal stress distribution ahead of the crack tip
Analysis of composite ENF specimen using higher order beam theories
No full textMathematical modelling, for the stress analysis of symmetric composite end notch flexure (ENF) specimen, has been presented using classical beam theory, first, second, and third order shear deformation beam theories to determine the strain energy release rate (SERR) for symmetric composites under mode II interlaminar fracture. In the present formulation, appropriate matching conditions have been applied at the crack tip and these matching conditions at the crack tip have been derived by enforcing the displacement continuity at the crack tip in conjunction with the variational equation. Compliance method has been used to calculate the SERR. Beam models under plane stress and plane strain conditions agree with each other with good performance to analyze the unidirectional and cross-ply composite ENF specimens, whereas for multidirectional composite ENF specimen, only the beam model under plane strain condition appears to be applicable with moderate performance. Third order shear deformation beam model of ENF specimen has been found to be better than other beam models in determining the SERR for unidirectional, cross-ply and multidirectional composites under mode II interlaminar fracture
Fracture Behavior of Multidirectional DCB Specimen:Higher-Order Beam Theories
Get PDFMathematical models, for the stress analysis of symmetric multidirectional double cantilever beam �DCB� specimen using classical beam theory, first and higher-order shear deformation beam theories, have been developed to determine the Mode I strain energy release rate �SERR� for symmetric multidirectional composites. The SERR has been calculated using the compliance approach. In the
present study, both variationally and nonvariationally derived matching conditions have been applied at the crack tip of DCB specimen. For the unidirectional and cross-ply composite DCB specimens, beam models under both plane stress and plane strain conditions in the width direction are applicable with good performance where as for the multidirectional composite DCB specimen, only the beam model under plane strain condition in the width direction appears to be applicable with moderate performance. Among the shear deformation beam theories considered, the performance of higher-order shear deformation beam theory, having quadratic variation for transverse displacement over the thickness, is superior in determining the SERR for multidirectional DCB specimen
Higher-Order Beam Theories for Mode II Fracture of Unidirectional Composites
No full textMathematical models, for the stress analyses of unidirectional end notch flexure and end notch cantilever specimens using classical beam theory, first, second, and third-order shear deformation beam theories, have been developed to determine the interlaminar fracture toughness of unidirectional composites in mode II. In the present study, appropriate matching conditions, in terms of generalized displacements and stress resultants, have been derived and applied at the crack tip by enforcing the displacement continuity at the crack tip in conjunction with the variational equation. Strain energy release rate has been calculated using compliance approach. The compliance and strain energy release rate obtained from present formulations have been compared with the existing experimental, analytical, and finite element results and found that results from third-order shear deformation beam theory are in close agreement with the existing experimental and finite element results
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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