1,721,010 research outputs found
A numerical study on effects of randomly distributed subsurface hydrogen pores on fretting fatigue behaviour of aluminium AlSi10Mg
No full textsponsorship: The author gratefully acknowledges the financial support provided by the University of Leuven (KU Leuven) under grant number STG/18/010. (University of Leuven (KU Leuven)|STG/18/010)status: Published onlin
Local approach of strain rate dependent damage and failure in dual-phase steel automotive crash boxes
No full textAutomotive lightweight design has prompted the use of advanced high strength steels in structural and safety relevant components, such as crash boxes, due to their attractive combination of strength, formability and ductility. However, the formation of cracks between the progressive folds of a crash box during impact loading impedes the energy absorption, and therein its crashworthiness potential. Prediction of such complex damage phenomena is challenging on account of the complicated dependency of the material’s fracture behaviour on local loading conditions such as stress state and deformation history. Varying strain rate and temperature during the impact event compound the problem, as it heavily influences the local elastoplastic response preceding failure. A local approach to fracture, based on a combined experimental-numerical study, allows the transferability from the material to the structural scale. A lab-scale experimental design encompassing a wide range of stress states, strain rates and temperatures specifically tailored to a crash event is instrumental in offering valuable insights on the effect of these loading conditions on plasticity, damage and fracture behaviour. A hybrid damage mechanics model combining both coupled and uncoupled material modelling approaches compliments the experiments in evaluating the loading factor dependent material behaviour. The work is demonstrated on a dual-phase (DP1000) steel. Next to the detrimental effect of stress triaxiality on damage and fracture, DP1000 reveals unusual non-monotonic relationships between flow strength and ductility properties, on the one hand, and temperature and strain rate, at the other. The research advances the knowledge on crack formation mechanics during crushing loading
Fretting fatigue under variable amplitude loading
Get PDFTese (doutorado) — Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, Programa de Pós-Graduação em Ciências Mecânicas, 2022.Agência Nacional de Energia Elétrica (ANEEL).Generally, the fretting fatigue problem is treated with constant amplitude
loading. However, this condition is not the reality for industrial applications.
Although there are few studies on fretting fatigue under variable amplitude
loadings, they use a simplistic approach to life estimation (unable to capture the
effects of the complex multiaxial and non-proportional stress field that exists
under the contact interface) and only the bulk fatigue load has its amplitude
alternating. The objective of this work is to propose a numerical methodology
for the life assessment of components subjected to fretting fatigue under variable
amplitude loading and to study the effects of these loads. For this, experimental
tests were carried out by applying H-L (High-Low) and L-H (Low-High) loading
blocks to the tangential load, that is, the contact normal load and the amplitude
of the bulk fatigue load were kept constant while the tangential load has its
alternating amplitude. The numerical methodology proposed for fretting fatigue
life assessment includes the wear effect and crack propagation. The multiaxial
fatigue parameter SWT, the theory of critical distance TCD, and Miners’ linear
rule were used to compute the damage in the crack nucleation phase. The
node-displacement algorithm based on Archard’s law was applied to account
wear. In the crack propagation phase, the CDM (critical direction method)
was used to estimate the crack initiation angle considering the worn contact
surface, and then the crack is modeled and propagated. The still limited
range of experimental data done in this work for fretting fatigue under varying
loading blocks seems to indicate that the loading sequence has an effect on the
accumulated fatigue damage, mainly to the H-L loading sequences. Based on
this observation, a new non-linear damage model was proposed. Using this new
damage model, the life estimation results were within a scatter band of 1.2.Faculdade de Tecnologia (FT)Departamento de Engenharia Mecânica (FT ENM)Programa de Pós-Graduação em Ciências Mecânica
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
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
Numerical modelling of dynamic ductile fracture propagation in different lab-scale experiments using GTN damage model
No full textsponsorship: The author gratefully acknowledges the support of the Research Foundation Flanders (FWO) via PhD fellowship grant 1SB6420N.. (Research Foundation Flanders (FWO) via PhD fellowship|1SB6420N)status: Published onlin
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