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Fracture toughness evaluation of natural rubber
No full textA method for estimating the fracture toughness of rubbur-like materials is presented. Experimental data of a notched natural rubber sheet is analysed by application of the path-independent J-integral. A finite element code for large elastic deformations is used to evaluate the deformed shape of the rubber at crack growth initiation. Discussed is a stability criterion based on the existence of a critical value of J in relation with the experimental results
MECHANICAL Analysis of Elastomeric Seals by Numerical Methods
No full textA procedure which permits the evaluation of the stress-strain field in an elastomeric seal is presented. Such a procedure is based upon a mechanical modeling of the elastomer and on the employ of finite elements which can cope with high strains. Finally, the above-mentioned procedure is checked against experimental results. The problems connected with the material modeling are examined. In aprticular, the monotonicity of the constitutive relation is discussed. The difficulties encountered in the numerical simulation of the elastomeric seal are investigated. In particular, the convergence problems are discussed. The procedure is applied to a rectangular seal with rounded edges, to an O-ring seal, and to a U-ring seal. The numerical isochromatic pattern is drawn automatically and is compared to the photoelastic one. The validity and limits of the proposed procedure are discussed with regard to the three seal configurations examined
L’importanza di alcuni parametri geometrici in guarnizioni elastomeriche di sezione rettangolare: studio numerico
No full textCon l'impiego di un programma di calcolo agli elementi finiti, viene esaminata l'influenza di alcuni parametri geometrici sull'andamento della pressione di contatto al bordo interno di una guarnizione dinamica, di sezione circa rettangolare, realizzata in materiale elastomerico. E' evidenziata la possibilità di modificare tale andamento in maniera più agevole di quanto possa avvenire negli anelli di tenuta O-Ring. E' proposta una formula empirica che fornisce l'influenza della curvatura della guarnizione sulla pressione di contatto massima. Essa consente di correggere i risultati ottenibili nell'ipotesi semplificativa che la sezione dell'organo di tenuta si trovi in condizioni di deformazione piana
Stress-Strain Fields in Compressed Elastomeric Seals and their Extension to Fracture Mechanics
No full textStress and deformation fields in a compressed elastomeric unit, and extension to fracture mechanic
Mechanical behaviour of two elastomeric seals for rlling element bearing units
No full textThe mechanical properties of a commercial elastomer in use for axial and radial rolling bearing seals have been experimentally determined by means of biaxial, uniaxial and compresison tests. A finite-element program has been developed for large hyperelastic deformations, and a numerical analysis of the stress-strain field in the seal investigated has been performed. In this program, mechanical properties of the rubber are described by means of an experimentally determined constitutive relationship. The numerical results have been verified in the experiments, but substantial additional work is required before the analytical methods can be used with complete effectiveness
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
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