1,720,965 research outputs found
SVILUPPO, VALIDAZIONE E IMPLEMENTAZIONE DI APPROCCI LOCALI PER L'ANALISI DELLA DURABILITA' STRUTTURALE DI COSTRUZIONI SALDATE
No full textWelding represents a widespread practice in the modern engineering framework, due to the constant development of the joining technologies and the possibility to combine simple components to create high-performance engineering structures. However, it is a well-known fact that the durability of welded structures strictly depends on the strength of the joints composing them, especially when time-variant multiaxial fatigue loadings are involved. The nominal stress-based approaches provided in International Standards and Recommendations represent the most employed method to address the challenges of the fatigue durability assessment of welded structures. However, Standards do not necessarily provide accurate fatigue design references when complex un-classified geometries and multiaxial loading conditions are involved. On the other hand, it has been proven in the Literature that local approaches enable to overcome the limitations of nominal stress-based approaches, since they adopt criteria based on local stress and strains acting at the welds to assess the fatigue strength of welded structures. The Peak Stress Method (PSM) is a rapid FE-based local approach for estimating the Notch Stress Intensity Factors (NSIFs) at the weld toes and weld roots, which are assumed as sharp V-notches. By adopting the averaged Strain Energy Density (SED) as a fatigue failure criterion, the PSM enables to define a design stress, the equivalent peak stress, which can be exploited to estimate the fatigue lifetime of welded structures made of structural steels or aluminium alloys, in compliance with PSM-based fatigue design curves. Even though being recognized as more reliable than traditional methods based on the calculation of nominal stresses, local approaches still suffer from limited spreading in the modern industrial design practice, due to the high computational FE requirements and the need for specific knowledge. In order to address the aforementioned challenge and promote the adoption of the PSM in the modern engineering practice, in this manuscript, the entire analysis workflow of the Peak Stress Method (PSM) has been implemented in the Ansys® Mechanical FE environment as a custom fatigue analysis toolbox, the so-called "PSM App". The aim of the research has been to fully automate the application of the PSM to generic welded structures in order to support the FE analyst in the fatigue design of complex engineering structures. In order to achieve this target, first, the theoretical background of the PSM has been extended to improve the automation degree of the PSM analysis workflow. In addition, the applicability of the PSM has been extended to more commerical FE codes. Then, the fatigue strength of complex tube-to-flange steel arc-welded joints with reinforcement ribs inspired by the amusement park structures by Antonio Zamperla S.p.a has been investigated experimentally by performing fatigue tests under constant and variable amplitude uniaxial and multiaxial loadings. In addition, more fatigue data relevant to V-notched specimens made of E355 structural steel and tested under constant amplitude uniaxial and multiaxial loadings have been recently collected. The obtained experimental fatigue life data have been re-evaluated in terms of the equivalent peak stress and compared with fatigue lifetime estimations performed by means of the PSM-based fatigue design curves with the aim to validate the proposed fatigue design approach. Eventually, the "PSM App" has been employed to analyse a large variety of laboratory welded joints coming from the Literature and complex welded structures by Antonio Zamperla S.p.a., made of structural steel and aluminium alloys and subjected to constant and variable uniaxial and multiaxial fatigue loadings. As a result, the "PSM App" enabled to achieve a remarkable reduction in time and effort required to assess the fatigue durability of complex welded structures
Fatigue assessment of steel tube-to-flange welded joints with reinforcement ribs subjected to multiaxial loads according to the Peak Stress Method
Full text linkFatigue lifetime assessment of tube-to-flange arc-welded steel joints with reinforcement ribs under constant and variable amplitude multiaxial fatigue loadings according to the peak stress method
No full textWelded reinforcements are a widespread solution when increasing the stiffness and load bearing capacity of engineering
structures is of primary interest, particularly under in-service cyclic loadings which require a fatigue durability
assessment. However, experimental fatigue data available in the literature and the number of classified details reported in
Standards and Recommendations are limited. On top of that, the fatigue strength assessment of large-scale reinforced
welded structures generally involves complex geometries and variable amplitude multiaxial loadings. In this framework,
local approaches for the fatigue assessment of reinforced welded structures are applicable without limitations in the
complexity of geometries or loading conditions. In this investigation, the fatigue strength of complex Square Hollow
Section (SHS) tube-to-flange arc-welded joints with reinforcement ribs of S355 structural steel has been experimentally
investigated under constant and variable amplitude pure bending, pure torsion and in-phase as well as out-of-phase
combined bending and torsion loadings. The number of cycles to break-through has been adopted as a failure criterion
and the cracking behaviour of the tested specimens has been also investigated. Afterwards, the Peak Stress Method (PSM)
has been successfully adopted to assess the fatigue strength of the welded reinforcement ribs joining the tube and flang
Analytical expressions to estimate rapidly the notch stress intensity factors at V‐notch tips using the Peak Stress Method
No full textThe Peak Stress Method (PSM) enables a rapid estimation of the notch stressintensity factors (NSIFs) for the fatigue strength assessment of sharp V-notchesand notably welded joints. It takes advantage of the linear elastic peak stressescalculated at the V-notch tip using coarse finite element (FE) mesh patterns,thanks to properly calibrated coefficients depending on the V-notch openingangle, FE type, formulation, and FE mesh pattern typical of the employed FEcode. The original calibration was performed only for few master values ofopening angle; therefore, in the present study, the coefficients have been cali-brated by using Ansys®FE code for the full range of notch opening angles togeneralize the PSM. In particular, polynomial expressions have been fitted onthe results of FE analyses and implemented in a tool that automates the appli-cation of the PSM. Two case studies have been analyzed highlighting the bene-fits of the new polynomial expressions
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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