1,720,955 research outputs found
Buckling of 3D-Printed Cylindrical Shells with Corrugated Surface
No full text3D-printing technology opens broad possibilities to manufacture structural shapes which could not be always possible by other methods. In the field of lightweight shells it allows to investigate structures with higher buckling loads than conventional shells. The buckling behavior of 3D-printed shells is studied in this paper where the shape of the cylindrical shells is modified by adding corrugation in the axial or circumferential directions. The shells are characterized by the amplitude of the corrugation and the number of the sinusoidal waves. Their elastic mechanical behavior is analyzed up to the buckling load. The numerical analysis shows that the modified surface can significantly improve the buckling load and reduces the sensitivity towards geometric imperfections. Prototypes of the shells were manufactured and tested to validate the numerical model. Regardless the experimental scatter, the average buckling load of the optimized corrugated shell twice exceeds the buckling load of the reference circular shell. At the same time stiffness and mass of the shell remain the same.Aerospace Structures & Computational Mechanic
An experimental vibration-buckling investigation on classical and variable angle tow composite shells under axial compression
No full textTwo laminated composite shells, one with a conventional straight fiber laminate denoted the classical laminated shell and the second one with a variable angle tow reinforced composite, had been excited and their natural frequencies and mode shapes had been measured and monitored as a function of the axial compression load. Then, the in-situ buckling loads of the two tested specimens were predicted using the Vibration Correlation Technique (VCT) and compared with actual experimental buckling loads and Finite Element buckling predictions, yielding matching, consistent and repeatable results. It was shown that the VCT predicts the actual in-situ buckling loads of laminated composite thin walled cylindrical shells with a high accuracy, yielding 96% and 98.6% of the experimental buckling load, for the classical and variable angle tow composite shells, respectively. These results, although based on only two specimens, join the relatively small data base published in the literature, proving the nondestructive nature of the VCT approach, making it an adequate method for application on thin-walled structures, like shells. In addition, some testing recommendations are presented, to effectively enable the successful application of the VCT for in-situ buckling prediction of the buckling sensitive structures, like composite cylindrical shells
Mechanical Response of Variable and Constant-Stiffness Cylindrical Shells for Launcher Structures
No full textThe ability to steer the carbon fibre tape, varying the tow angle can open new designs of cylindrical shells – the main structural component of the space launcher vehicles. This research presents experimental and numerical investigation of two carbon-epoxy cylindrical shells – a cylinder with conventional layup made of unidirectional prepreg and a variable-stiffness cylinder manufactured by applying advanced fibre placement technology. The shells were tested in compression until buckling, measuring load-shortening and capturing the buckling shape by digital image correlation systems. For the purpose of modelling the variable-stiffness cylinder, a simplified stiffness approximation approach was applied. The obtained load-shortening curves and buckling shapes demonstrated good correlation with non-linear numerical models. The results of the investigation contributes to the understanding the phenomenon of buckling of variable-stiffness cylindrical shells, and the influence of initial geometric imperfections and thickness variations.Aerospace Structures & Computational Mechanic
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
Bending of composite cylindrical shells with circular cutouts: Experimental validation
No full textAn experimental study of unstiffened graphite-epoxy cylindrical shells with cutouts subjected to bending load is presented. Two cylinders were tested: a classical laminated cylinder with constant-stiffness and a fiber-steered cylinder with variable stiffness in circumferential direction. Both cylinders were tested until collapse in displacement control. Displacements and strains were measured by displacement sensors, strain gauges, and two digital image correlation systems. Analysis of the test data indicates that the highest stressed area was the edges of the cutouts where local displacements created large compression strains. The experimental data were compared with progressive damage analysis results obtained with a finite element analysis that included measured geometrical imperfections. The research contributes to the knowledge of variable-stiffness composite structures and their applications in aircraft fuselages
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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