1,720,960 research outputs found
ADVANCED STRESS ANALYSIS OF LONG FIBRE COMPOSITE COMPONENTS MADE WITH ADDITIVE MANUFACTURING
Full text linkAdditive Manufacturing (AM), commonly known as 3D printing, has revolutionized traditional manufacturing by enabling the production of intricate and customized structures. It brings advantages such as the creation of components with complex geometries and the potential for cost savings, especially in scenarios with low production volumes. However, drawback of this technology exists, notably the propensity for unwanted porosity in parts. Among the various technologies falling under the umbrella of Additive Manufacturing, this thesis focuses on Fused Deposition Modeling (FDM), prevalent in the field of composite materials. The main contributions of the thesis include the development of several analytical models that consider the effects of defects and design features introduced by FDM manufacturing processes. These models specifically address stress states in composite bodies, focusing on factors like porosities and localized reinforcements. The analytical models are validated against Finite Element methods, demonstrating their reliability in describing stress field in the studied areas.
Despite the challenges posed by AM, the analytical models presented in this thesis serve as a robust foundation for developing effective tools to predict the elastic behavior and fatigue life of components manufactured using additive manufacturing technology, particularly in the context of FDM
Recent Advances in the Analytical Stress Field Solutions for Radiused Notches in Orthotropic Solids
Full text linkThe main aim of this work is to provide a brief overview of the analytical solutions available to describe the in-plane and out-of-plane stress fields in orthotropic solids with radiused notches. To this end, initially, a brief summary on the bases of complex potentials for orthotropic elasticity is presented, with reference to plane stress or strain and antiplane shear problems. Subsequently, the attention is moved to the relevant expressions for the notch stress fields, considering elliptical holes, symmetric hyperbolic notches, parabolic notches (blunt cracks), and radiused V-notches. Eventually, examples of applications are presented, comparing the presented analytical solutions with the results from numerical analyses carried out on relevant cases
An averaged strain energy density based approach to predict the static notch effect in short fibre composites. Part 2: experiments and validation
No full textIn this paper, an Averaged Strain Energy Density (ASED)-based equivalent stress parameter, derived from the theoretical framework presented in the companion paper, is employed to assess the static strength of notched, short glass fibre-reinforced composites. To this end, quasi-static tensile tests were conducted on specimens composed of 40 wt% short glass fibre-reinforced polyphenylene sulfide (SGF-PPS), which were manufactured via injection moulding with various notch geometries. Additionally, data from previous studies on notched specimens of milled 40 wt% SGF-PPS and 20 wt% short carbon fibre-reinforced polyamide (SCF-PA) were analysed. Computed tomography revealed that the injection moulding process significantly influenced fibre distribution, particularly in the vicinity of the notches. Furthermore, post mortem scanning electron microscopy analyses across all materials identified fibre–matrix debonding, matrix plastic deformation and fibre failure as the primary damage mechanisms. While these mechanisms were independent of notch geometry, they were strongly influenced by the fibre orientation. The results demonstrated that the ASED-based equivalent stress parameter successfully correlates the experimental static strength data within a narrow scatter band, thus being an effective criterion for the assessment of the notch effect of SFCs under static loadings
An averaged strain energy density based approach to predict the static notch effect in short fibre composites. Part 1: Theoretical formulation
No full textIn this work the Averaged Strain Energy Density (ASED) criterion is reformulated for notched bodies made of orthotropic materials and proposed as an effective approach to predict the static notch effect in short fibre composites. The first part of this study focuses on the theoretical formulation, with the aim to provide a new set of analytical solutions for the ASED evaluated over a well-defined control volume close to U- and blunt V-shaped notches in orthotropic plates under Mode I loading conditions. The analytical solutions presented are derived taking advantage of some recent expressions for the stress distribution near blunt notches in orthotropic solids, as developed by the authors. Key parameters considered include the notch tip radius, notch opening angle and the elastic properties of the orthotropic material. As also discussed in the second part of this contribution, the ASED approach offers insights into the notch sensitivity of short fibre composites, providing a foundation for further investigation into the mechanical behaviour of this class of materials
Three-Dimensional Stress Fields in Thick Orthotropic Plates with Sharply Curved Notches under In-Plane and Out-of-Plane Shear
Full text linkIn this paper, an analytical solution for the stress fields in the close neighbourhoods of radiused notches in thick orthotropic plates under shear loading and twisting is provided. In the first step, the equations of the three-dimensional theory of elasticity are successfully reduced to two uncoupled equations in two-dimensional space. Later, the 3D stress field solution for orthotropic plates with radiused notches is presented and its degree of accuracy is discussed by comparing theoretical results and numerical data from 3D FE analyses. The solution proposed can be satisfactorily used to characterise the stress field in plates made with polymeric composite materials, such as fibre-reinforced polymers and natural composites
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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