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Coupled fracture mode of a cracked plate under anti-plane loading
No full textThe existence of three-dimensional effects at cracks has been known for many years, but understanding has been limited, and for some situations still is. Despite increased understanding, three-dimensional effects are sometimes ignored in situations where they may be important. The purpose of the present investigation is to study a coupled fracture mode generated by a nominal anti-plane (Mode III) loading applied to linear elastic plates weakened by a straight through-the-thickness crack. With this aim accurate 3D finite element (FE) analyses have been performed. The results obtained from the highly accurate finite element models have improved understanding of the behaviour of through cracked plates under anti-plane loading. The influence of plate bending is increasingly important as plate thickness decreases. It appears that a new field parameter, probably a singularity, is needed to describe the stresses at the plate surfaces. Discussion on whether KIII tends to zero or infinity as a corner point is approached is futile because KIII is meaningless at a corner point. Calculation of the strain energy density (SED) in a control volume at the crack tip allows us to predict the most critical point through the plate thicknes
Corner point singularities under in-plane and out-of-plane loading: A review of recent results
No full textThe linear elastic analysis of homogeneous, isotropic cracked bodies started in the 1900s. The existence of three dimensional corner point effects in the vicinity of a corner point where a crack front intersects a free surface was investigated in the late 1970s. An approximate solution by Bažant and Estenssoro explained some features of corner point effects but there were various paradoxes and inconsistencies. Results derived from finite element models showed that the analysis is incomplete. The stress field in the vicinity of a corner point appears to be the sum of two different singularities (i.e. stress intensity factors and corner point singularities). In this paper some recent results for the corner point singularities under in and out of plane loadings is reviewed and discussed
Coupled fracture modes under anti-plane loading
Full text linkThe linear elastic analysis of homogeneous, isotropic cracked bodies is a Twentieth Century
development. It was recognised that the crack tip stress field is a singularity, but it was not until the introduction
of the essentially two dimensional stress intensity factor concept in 1957 that widespread application to practical
engineering problems became possible. The existence of three dimensional corner point effects in the vicinity of
a corner point where a crack front intersects a free surface was investigated in the late 1970s: it was found that
modes II and III cannot exist in isolation. The existence of one of these modes always induces the other. An
approximate solution for corner point singularities by Bažant and Estenssoro explained some features of corner
point effects but there were various paradoxes and inconsistencies. In an attempt to explain these a study was
carried out on the coupled in-plane fracture mode induced by a nominal anti-plane (mode III) loading applied
to plates and discs weakened by a straight crack. The results derived from a large bulk of finite element models
showed clearly that Bažant and Estenssoro’s analysis is incomplete. Some of the results of the study are
summarised, together with some recent results for a disc under in-plane shear loading. On the basis of these
results, and a mathematical argument, the results suggest that the stress field in the vicinity of a corner point is
the sum of two singularities: one due to stress intensity factors and the other due to an as yet undetermined
corner point singularity
Analytical and numerical modelling of the Swift effect in elastoplastic torsion
Full text linkTorsion tests are widely used to investigate the elastoplastic behaviour of metallic materials, particularly when large strains are involved, up to the specimen’s fracture. Such tests induce multiaxial inhomogeneous stress/strain and damage fields into the specimen. In this paper, elastoplastic torsion at room temperature of uniform isotropic circular solid and tubular metallic specimens is investigated in the finite strain range, both in analytical and numerical forms. The paper reports preliminary results of an on-going research project at the University of Bergamo [1]. Particular emphasis is given to the evaluation of the so-called Poynting (in the elastic domain) and Swift (in the plastic range) effects [2,3], i.e. the recorded axial length variation of the specimen that may appear under free-end torsion
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
Some practical crack path examples
Full text linkIt is well known that many engineering structures and components, as well as consumer items,contain cracks or crack-like flaws. It is widely recognised that crack growth must be considered both in designand in the analysis of failures. The complete solution of a crack growth problem includes determinationof the crack path. Macroscopic aspects of crack paths have been of industrial interest for a very long time.At the present state of the art the factors controlling the path taken by a crack are not completely understood.Eight brief case studies are presented. These are taken from the author’s professional and personal experienceof macroscopic crack paths over many years. They have been chosen to illustrate various aspects ofcrack paths. One example is in a component from a major structure, three examples are in laboratory specimens,and four are in nuisance failures. Such nuisance failures cause, in total, a great deal of inconvenienceand expensive, but do not normally receive much publicity
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