1,721,001 research outputs found
Understanding the effect of notches in orthotropic solids subjected to static loads
No full textThe main aim of the present paper is to propose and validate a new and simple diagram able to explain the effect of geometrical variations in orthotropic solids under static loads. The derived approach accounts for the effect of the local geometry of the notch as well as for the relevant material properties and highlights the parameters drawing the demarcation line from notch insensitivity, incomplete notch sensitivity and full notch sensitivity. In particular, it is demonstrated that when the notch depth is smaller than a characteristic length, aF, the notch does not have a detrimental effect and the design of the mechanical part can be carried out disregarding the geometrical variation. Differently, when the notch depth is larger than aF, full notch sensitivity or incomplete notch sensitivity can occur, depending on the actual value of the notch root radius. The soundness of the proposed diagram is checked against experimental data previously published in the literature and related to short fibre reinforced composites
TENSILE AND COMPRESSIVE QUASI-STATIC BEHAVIOUR OF 40% SHORT GLASS FIBRE - PPS REINFORCED COMPOSITES WITH AND WITHOUT GEOMETRICAL VARIATIONS
No full textIn this work, a comprehensive experimental investigation was carried out to characterise the quasi-static tensile
and compressive behaviour of notched and plain specimens made of 40% wt. glass fibre-Polyphenylenesulphide
(40GF-PPS) short fibre reinforced composite.
To this end, plain and notched specimens (with notch radius ranging from 0.25 mm to 10 mm) were manufactured
with two different fibre orientation angles (0◦ and 90◦) and tested under tension and compression,
allowing to observe the effect of the notch root radius and the notch geometry. In addition, a careful analysis was
carried out both at the macroscopic and microscopic level to compare the fracture behaviour of plain and
notched specimens. Finally, a Generalised-Stress-Intensity-Factor-based approach was adopted to correlate the
tensile strength of notched specimens. On the contrary, the compressive strength of the notched samples was
rationalised in terms of the nominal net-stress, thanks to the limited notch sensitivity exhibited by the material
during the compression tests
Effect of material orthotropy on the notch stress intensity factors of sharp V-notched plates under tension
No full textIn this paper, an analytical and numerical study is carried out on the role played by the elastic properties of orthotropic materials on the Notch Stress Intensity Factors (NSIFs) of pointed V-notches on plates under tension. In the first part of the work, new analytical solutions are presented to approximate the NSIFs of shallow and deep symmetric notches in Double Edge Notched plates under Tension (DENT). Subsequently, a comprehensive numerical study is carried out on finite size notches considering different orthotropic materials, with the aim to make explicit the effect of material orthotropy on the NSIFs. Eventually, based on a best fitting procedure of the numerical results, accurate expressions for the NSIFs are provided, and their degree of accuracy is discussed against data from the literature and results from ad hoc numerical analyses
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
On the correlation of temperature harmonic content with energy dissipation in C45 steel samples under fatigue loading
Full text linkFatigue damage onset involves a transformation of mechanical energy. This is in part spent into work of plastic deformation and fracture and in part transformed into heat. Therefore, different thermomechanical heat sources are activated during a fatigue loading cycle, resulting in a temperature modulation that can be characterized by its frequency content. Several studies have monitored the temperature on samples undergoing high-cycle fatigue, measuring specific thermomechanical metrics which could serve as indicators of damage evolution. The present work evaluates the harmonic content of temperature, to investigate its correlation with the material dissipation. The harmonic terms investigated are the amplitude and phase of temperature at the loading frequency (First Harmonic) and at twice the loading frequency (Second Harmonic). The paper reviews the mechanisms linking the evolution of heat dissipation to changes in these four parameters. The theoretical analysis is supported by an experimental campaign carried out on C45 steel tensile specimen subject to R=−1 and R=0.1 loading ratios. The harmonic metrics are evaluated analyzing both their spatially averaged value and their spatial dispersion, to check for the formation of localized heat dissipation zones in early fatigue life. The study shows that the phase of the Second Harmonic signal has a peculiar bimodal distribution that can be correlated to either a thermoelastic or dissipative prevailing effect. This behavior evolves towards a unimodal dissipative behavior when the load amplitude is increased, thus proposing the Second Harmonic phase parameter as an effective indicator for monitoring internal intrinsic dissipation in the material
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
Investigation of the crack tip stress field in a stainless steel SENT specimen by means of Thermoelastic Stress Analysis
Full text linkThe present paper evaluates the Thermoelastic and Second Harmonic signals acquired on a fatigue cycling Single Edge Notched Tension sample made of stainless steel AISI 304L. Three load ratios are in particular investigated: R=-1, 0, 0.1. The thermoelastic signal is used to evaluate the Stress Intensity Factor via two approaches: the Stanley-Chan linear interpolation method, and the over-deterministic least square fitting method using a Williams’ series expansion stress function. Some outputs of the present investigation include: the evaluation of an iterative procedure to localize the crack tip position from thermoelastic maps; an evaluation of the influence of the number of terms retained in the William’s solution (up to 20), in relation with the extent of the least-square fitting data input area, on the values of Stress Intensity Factor and T-stress; some insights on the influence of negative R-ratios and crack-closure. The present study also proposes an original interpretation of the Second Harmonic signal observed on the wake of the crack, which enables also the possibility to use this parameter to reveal the presence and extent of crack-closure
Static strength assessment of short glass fibre-reinforced polyphenilenesulphide in presence of notches according to different approaches
Full text linkIn this paper the static behaviour of polyphenylenesulfide reinforced by 40% wt. short glass fibre net-shaped
plain and notched specimens was investigated. The specimen geometries were obtained by injection moulding
and the experimental results were compared with data obtained from machined specimens with the same material and geometries. All data were reanalysed according to several models available in the literature for
orthotropic materials, to find a rapid and efficient assessment tool for predicting the strength of short glass fibre
reinforced materials in the early design stages. To this end, approaches based on orthotropic linear elastic stress
analysis were considered, namely the linear elastic peak stress criterion, the nominal net-stress criterion, the
point stress criterion, the average stress criterion, the strain energy density criterion, the generalized stress intensity factor-based approach, the inherent flaw model, the damaged zone criterion and the Hitchen criterion.
Among the models, the average stress criterion and the generalized stress intensity factor-based approach provided the most accurate predictions of the static strength, ranging from − 10% to +9% and from − 19% to +2%, respectively, compared to the experimental data
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