1,720,957 research outputs found
Ultrasonic and thermographic studies for CFRP inspections with real and simulated defects
No full textThis paper deals with an overview of improved UT control procedures, related to defect investigation on advanced CFRP composite elements for aeronautical structures; the inspection procedures were evaluated with different frequency probes, employing direct contact, water stream and immersion methods. In this work, ultrasonic and thermographic controls of CFRP components are presented for detection of different types of defects (real and artificial) in order to evaluate sensitivity and detectability techniques. This work presents a preliminary ultrasonic study on CFRP components employing different probes and tools.
For these aims, inspections of CFRP plates with artificial defects are optimized and compared to thermographic acquisitions with active pulsed technique, in order to calibrate Ultrasonic Technique tools and verify procedures for suitable results. In a second stage, improved ultrasonic scanning investigations are applied on real parts, containing real production defects in terms of small delamination and diffused porosity of T-shape stringer and resin/matrix excesses between layers, localized in the thin cap and web of structural civil aircraft stringers
Fatigue damage on CFRP plates under bending by thermographic and UT analysis, aided with FEM-DIC prediction
Full text linkIn this article, a combination of numerical and experimental methodology for delamination evolution analysis on unidirectional CFRP elements under fatigue is suggested. Fiber-reinforced composite structures exhibit continuous damage accumulation with degradation of effective mechanical properties during cyclic HCF loads. Since advanced composites applications are allowed after extensive experimental certification tests, proposed work is based on experimental procedures to better detect and predict damage initiation and growth, monitoring static displacements and strains under 4-points bending by digital image correlation and measuring compliance variation under fatigue. In addition, non-destructive investigation of composite plates is conducted during cycling tests by using infrared thermography and ultrasonic measurements to detect damage location and validate FEM predictions. Experimental results are analyzed and compared, employing also digital image correlation technique; in addition, thermographic and ultrasonic monitoring inspection with Matlab elaborated measurements are implemented to check results for fatigue damage analysis of same specimens
Advanced NDT methods and data processing on industrial CFRP components
Full text linkIn this work, enhanced thermal data processing is developed with experimental procedures, improving visualization algorithm for sub-surface defect detection on industrial composites. These materials are prone to successful infrared nondestructive investigation analyses, since defects are easily characterized by temperature response under thermal pulses with reliable results.
Better defect characterization is achieved analyzing data with refined processing and experimental procedures, providing detailed contrasts maps where defects are better distinguished. Thermal data are analyzed for different CFRP specimens with artificial defects and experimental procedures are verified on real structural aeronautical component with internal anomalies due to impact simulation. A better computation method is found to be useful for simultaneous defect detection by means of automatic mapping of absolute contrast, optimized to identify defect boundaries
Mechanical behaviour of AlSi10Mg lattice structures manufactured by the Selective Laser Melting (SLM)
No full textAdditive Manufacturing (AM), particularly Selective Laser Melting (SLM), has enabled design and production of complex metal lattice structures with specifically required properties, minimizing weight. The aim of this work is to provide insight into the influence of cell topology, cell size and beam diameter on deformation and failure behaviour of different SLM-manufactured AlSi10Mg alloy structures under static compressive loading. Design of experiment (DOE) analysis is performed to define geometrical features and dimensional characteristics of cell unit for specimen final configuration. A total of sixteen topological combinations was obtained, and forty-eight lattice specimens with three replicas for each cell type were manufactured with random order process to minimize manufacturing time variation and dependence. The full experimental testing results were analysed and compared in absolute terms and related to lattice density. Furthermore, a deep experimental microscopic analysis was conducted for a statistical analysis of representative beam diameters and real cell sizes for lattice samples. Additionally, micro-computed tomography (micro-CT) inspection was employed to analyse the local morphology and to characterize material distribution and in particular to verify defect presence (such as porosity and superficial anomalies) that may affect the mechanical behaviour
Advanced NDT procedures and thermal data processing on CFRP aeronautical components
No full textIn this work, active Pulsed Thermography (PT) was used to improve CFRP aeronautical parts
investigation in order to detect sub-surface defects. Composite materials are prone to
successful thermal/infrared NDT analyses, since defects are easily characterised by their
surface ‘footprints’ under thermal pulses with reliable results. Better defect characterisation is
achieved analysing data with better data processing and procedures, providing detailed
contrasts maps where defects’ edges are distinguished. Thermal data are analysed for different
specimens with artificial defects and experimental procedures are verified on real a failure in
structural aeronautical component. Finally, improved data processing allowed better
identifying the damaged areas on specimens
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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