1,721,189 research outputs found
Eigenstrain modelling of residual stress generated by arrays of Laser Shock Peeing shots and determination of the complete stress field using limited strain measurements
Full text linkThis paper presents a hybrid explicit finite element (FE) /eigenstrain model for predicting the residual stress generated by arrays of adjacent/overlapping laser shock peening (LSP) shots where the use of a completely explicit FE analysis may be impractical. It shows that for a given material, the underlying eigenstrain distribution (in contrast to the resulting stress field) representing a laser shock peen is primarily dependent on the parameters of the laser pulse and the number of overlays rather than the precise component geometry. Consequently the residual stress introduced by complex laser peening treatments can be built up by using static FE models and superposition of individual eigenstrain distributions without recourse to further computationally demanding explicit FE analyses. It is found that beneath a small patch of LSP array the magnitude of the compressive residual stress is higher than for a wider array of LSP shots and that with increasing numbers of layers the compressive stress increases as does the depth of the compressive zone. The model predictions for the eigenstrain distributions are compared well with experimental measurements of plastic strain (full-width-at-half-maximum) obtained by neutron diffraction. The eigenstrain method is also extended to construct the full residual stress field using measured residual elastic strains at a finite number of measurement locations in a component.<br/
Mapping fibre failure in situ in carbon fibre reinforced polymers by fast synchrotron X-ray computed tomography
No full textFast, in situ synchrotron X-ray computed tomography (CT) has been used to capture damage evolution, particularly fibre failures, before final fracture (within 99.9% of the ultimate tensile stress) in cross-ply carbon fibre/epoxy coupons under continuous monotonic tensile loading for the first time. It is noteworthy that fewer than 8% of the 0° fibres have fractured at 99.9% of the failure load. The majority of fibre breaks appear as isolated events, although some instances of multiple adjacent breaks (clusters) do occur at intermediate and high stress levels. Contrary to conventional wisdom, a cluster of failed fibres would always occur in a burst as a singular failure event: clusters were never seen to accumulate additional broken fibres as load increased suggesting low-level stress concentration local to fibre breaks. Several instances of multiple fractures along individual fibres were observed, providing an estimation of the critical stress transfer length between the fibre and matrix. The factors affecting fibre failure appear to be complex, with distinct sample-to-sample variability being identified for the length-scales tested. This highlights the need for improved understanding of the mechanisms that contribute to final failure, particularly criteria controlling the arrest or otherwise of clustered fracture events
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
Time-lapse helical X-ray computed tomography (CT) data of tensile fatigue damage in GFRP
No full textThe X-ray CT data here is published with the paper -
Wang, Y.; Mikkelsen, L.P.; Pyka, G.; Withers, P.J. Time-Lapse Helical X-ray Computed Tomography (CT) Study of Tensile Fatigue Damage Formation in Composites for Wind Turbine Blades. Materials 2018, 11, 2340.
https://doi.org/10.3390/ma11112340
More information about the data and the material can be found in the paper above.
If using the data here, please cite the above paper.
Contact details for author: Ying Wang, [email protected]</p
Comparison of the mechanical behaviour of standard and auxetic foams by X-ray computed tomography and digital volume correlation
Full text linkThe tensile behaviour of standard and auxetic polyurethane foams are contrasted by digital volume correlation of 3D images collected by in situ X-ray computed tomography (CT). It was found that subset sizes of 32 and 64 voxels for the auxetic and standard foams were optimal for strain resolutions in the order of 0.1%. For the standard foam, good uniformity of strain was observed at low strains giving a tangent Poisson's ratio of 0.5. Some heterogeneity of strain was observed at higher strains, which may be related to the fixtures. The behaviour of the auxetic foam was totally different, with strain being spatially heterogeneous with transverse strains both positive and negative but giving a negative Poisson's ratio on average. This suggests that the unfolding tendency of some groups of cells was higher than others because of the complex frozen starting microstructure. Further different methods of deriving Poisson's ratio gave different results. Besides revealing interesting microstuctural mechanisms of transverse straining, the study also shows digital volume correlation of tomography sequences to be the perfect tool to study complex mechanical behaviour of cellular material
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
The DR3 Risø reactor as a user facility for applied neutron scattering experiments: Texture, internal strain and applied small angle scattering
No full textStress development during the formation of ceramic membranes:Part I: stress development during drying
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