1,720,961 research outputs found
How many critical planes? A perspective insight into structural integrity
No full textThe topic of material fatigue is a subject extensively investigated within both scientific and industrial worlds. Fatigue-induced damage remains a critical concern for a variety of components, encompassing both metallic and non-metallic materials, often leading to unexpected failures during their operational lifecycle. In cases necessitating the assessment of multiaxial fatigue, critical plane methodologies have emerged as a valuable approach. These methodologies offer the means to pinpoint the component's critical regions and anticipate early-stage crack propagation. Nevertheless, the conventional technique (i.e., plane scanning method) for computing critical plane factors is a time-intensive process, reliant on nested iterations, predominantly suited for research purposes. In numerous cases, where the critical area within a component is unknown in advance (i.e., primarily due to complex geometries and loading conditions) the method proves impractical. Furthermore, the plane scanning method does not provide a deep comprehension of the critical plane concept; indeed, it is just a numerical artifice for calculating stress and strain quantities on different planes. Recently, the authors introduced an efficient algorithm for evaluating critical plane factors. This algorithm is based on a closed form solution and is applicable to all instances where the maximization of a specific parameter, based on stress or strain components, is required. The methodology relies on tensor invariants and coordinates transformation principles thus enhancing the investigation of various critical plane methods. The paper addresses two formulations of the Fatemi-Socie critical plane factor and discusses how the number of critical planes depend on the loading conditions the component is subjected to. By the use of a closed form solution a deep insight of critical planes orientation can be achieved
Frequency analysis of random fatigue: Setup for an experimental study
No full textThe frequency-domain approach to fatigue life estimation in random loading has been largely investigated due to its computational advantages, and several methods for the frequency translation of the most common time-domain methods have been proposed. Between the most known frequency methods, there are Bendat's method, valid for narrow-band signals, and Dirlik's formula, which ifis considered the best result for wide-band signals. However, a great part of the frequency methods takes the rainflow count as a reference time-domain method and uses the rainflow damage computation as the exact value to emulate. Therefore, very few experimental data for the fatigue life of mechanical components subject to random loads are available in the literature. This work presents the setup for a series of experimental tests for specimens subjected to random loads, aiming at achieving experimental data to compare with the results provided by frequency methods. After a brief description of the materials used for the setup, the two-step test concept is described: first, the specimen will be subjected to random loads obtained by a certain power spectral density for an amount of time which should nominally cause a 30% of damage; then, the fatigue test will be ended on a resonance testing machine to compute the actual residual fatigue life of the specimen; this two-step testing also allows to reduce the time requested for the tests. The test bench developed for the experimental investigation is described in the paper, together with the results of some preliminary tests, aimed at verifying the feasibility of the conceived procedure
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
Frequency analysis of random fatigue: Setup for an experimental study
Full text linkThe frequency-domain approach to fatigue life estimation in random loading has been largely investigated due to its computational advantages, and several methods for the frequency translation of the most common time-domain methods have been proposed. Between the most known frequency methods there are the Bendat's Method, valid for narrow-band signals, and the Dirlik's formula, which is considered the best result for wide-band signals. However, the great part of the frequency methods takes the rainflow count as a reference time-domain method and uses the rainflow damage computation as the exact value to emulate. Therefore, very few experimental data for fatigue life of mechanical components subject to random loads are available in the literature. This work presents the setup for a series of experimental tests for specimens subjected to random loads, aiming at achieving experimental data to compare with the results provided by frequency methods. After a brief description of the materials used for the setup, the two-step test concept is described: firstly, the specimen will be subjected to random loads obtained by a certain PSD for an amount of time which should nominally cause a 30% of damage; then, the fatigue test will be ended on a resonance testing machine to compute the actual residual fatigue life of the specimen; this two-step testing also allows to reduce the time requested for the tests. The test bench developed for the experimental investigation is described in the paper, together with the results of some preliminary tests, aimed at verifying the feasibility of the conceived procedure
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
Numerical-experimental characterization of the dynamic behavior of PCB for the fatigue analysis of PCBa
Full text linkIn today's highly digitized and mechatronics-based world, the need for reliable and cost-effective electronic components has become essential. The reliability of these components is not only based on their electrical and circuit aspects but also on their structural properties. This paper presents a study carried out on two-layer Printed Circuit Boards (PCBs) of rectangular shape, which are representative of many industrial applications. The aim of this study is to compare different numerical models, developed in Ansys Workbench and in a FEM software specifically designed for circuit boards, with experimental tests to determine the most interesting ones for further studies on Printed Circuit Board Assemblies (PCBAs). The comparison includes both static and dynamic behaviors, tested through isostatic bending tests and dynamic analyses with a shaker and a fiber optic laser. The models developed are capable of reproducing statics and dynamics of PCBs with varying degrees of accuracy and numerical complexity. However, increasing the details of the models does not always correspond to an increase in accuracy in reproducing the dynamic behavior. Prior to the experimental dynamic analysis, the influence of constraints’ modeling strategies and damping on the first eigenmode was studied, and the results were used to set up tests and simulations to achieve more consistent results. Future work will extend the dynamic characterization to PCBAs by populating the studied PCBs with components, and continue with the study of predictive models for their structural reliability
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