1,720,977 research outputs found
Extending fatigue life of industrial low-pressure FV566 turbine blades: efficacy of a lifetime extension strategy to extend service life
No full textThe fir-tree-root-fillets of turbine blades are prone to fatigue cracking on the notch surfaces and pose a potential risk of fatigue failure before expected service life due to increasing exposure to start-stop fatigue loading conditions. Turbine systems are additionally subjected to 10 % over-speed testing annually. Turbine blades are being replaced at high cost due to the serious safety risk in the case of catastrophic failure. The efficacy of a proposed lifetime-extension strategy involving grinding out existing cracks, identifiable via non-destructive testing (thus changing the notch geometry), followed by T0 shot peening and the effect of additional overload cycles was investigated. FV566 martensitic stainless-steel material extracted from ex-service turbine blades was tested and the characteristic baseline material microstructure, mechanical properties and fatigue behaviour examined. Single edge notch bend and U-notch specimens (with industry representative geometries) were subjected to 3-point bending fatigue loading in the low cycle fatigue regime. A finite element model of the test specimens with elastic-plastic material modelling was developed to calculate required loads and stress and strain distributions in the notch field with various U-notch geometries. The effects of industry representative ‘as-received’ and polished notch surface conditions on the crack initiation behaviour was investigated. The effect of relatively small industry representative overloads up to 150 % of the maximum baseload every 150 baseload cycles were compared with constant amplitude loading and the effect on initiation behaviour and crack growth rates examined. Various U-notch geometries expected after grinding out existing cracks were fatigue tested at different strain ranges to establish the influence of notch geometry on fatigue behaviour. T0 industrial representative shot peening was applied to U-notched specimens and the residual stress profiles obtained via XRD. The effect shot peening on fatigue behaviour was investigated for various loading conditions (including overload) and notch geometries. A lifetime prediction method was developed which was capable of accounting for the application of the proposed lifetime extension strategy and was compared with experimental testing. Early crack initiation was observed in the as-received notch surface condition due to the presence of corrosion pits. A polished surface condition increased the number of cycles to crack initiation. The presence of an overload 110 % or less of the maximum baseload every 150 baseload cycles did not affect fatigue life. An overload of 150 % retarded both long and short crack growth rates, attributed to compressive residual stress ahead of the crack tip, resulting in an overall increase in fatigue life. Additionally, a compressive residual stress induced in the notch field increased the number of cycles to crack initiation, improving fatigue life overall. Shot peening damaged the notch surface causing pre-existing cracks and early crack initiation. However, the compressive residual stress field from shot peening significantly retarded short crack growth and increased overall fatigue life. After 1.2 % total strain range the lifetime extension benefit from shot peening was diminished. Notch geometry was not found to have a notable difference on fatigue life when tested at identical strain ranges. The lifetime extension strategy was found to increase the overall life of Unotch samples assuming the strain range remained constant throughout the test. The lifetime prediction model was able to predict the number of cycles to failure for a sample subjected to the lifetime extension strategy and offer a lifetime prediction that accounts for a likely increase in strain range after changing the notch geometry. The service life of turbine blades may be improved by adopting the lifetime extension strategy. Finite Element modelling of actual turbine blade geometry with industry relevant loading conditions is required to establish the increase in strain range expected from grinding out existing cracks in-situ. Further experimentation is then required to apply the method developed in this thesis to actual turbine blade geometry prior to incorporating the lifetime extension strategy as a maintenance procedure
Dataset to support the thesis entitled: "extending fatigue life of industrial low-pressure FV566 turbine blades: Efficacy of a lifetime extension strategy to extend fatigue life"
No full textDataset containing the original values of results and graphs throughout the thesis titled extending fatigue life of industrial low-pressure FV566 turbine blades: Efficacy of a lifetime extension strategy to extend fatigue life</span
Dataset to support the article 'Fatigue crack growth behaviour and life prediction following a lifetime extension strategy in the low-cycle fatigue regime for FV566 turbine blade steel'
No full textThis dataset contains:
The Excel spreadsheet file containing the results that were used to create the graphs in the paper.
The .mp4 file M08_7_Crack_evolution - Short crack growth evolution on the shot peened notch after an extension strategy
The .mp4 file M08_9_Crack_evolution - Short crack growth evolution on the shot peened notch after an extension strategy with overloads
The figures are as follows:
Fig. 4 Short crack data obtained by observing and measuring cracks using microscopy. Note all the data inlcudes arrested crack growth for representative comparison.
Fig. 5A-B The total number of initiation and total number of coalescence events which formed the primary crack only, versus the lifetime percentage for two samples subjected to the lifetime extension strategy.
Fig. 5C The measurement for each crack on each replica in micrometers for the constant amplitude loading sample subjected to the lifetime extension strategy. All measurements were converted into the lengths used for application in Microsoft powerpoint. The location of each crack is also inlcuded in this data.
Fig. 5D The measurement for each crack on each replica in micrometers for the sample subjected to overloads with OLR of 1.56 every 150 baseload cycles and the lifetime extension strategy. All measurements were converted into the lengths used for application in Microsoft powerpoint. The location of each crack is also inlcuded in this data.
Fig. 6A The total number of cracks (initiation events minus coalescence events) for two samples subjected to the lifetime extension strategy for each replica record.
Fig. 6B The total number of cracks (initiation events minus coalescence events) for samples with various loading and surafce conditions taken from the replica records.
Fig. 7 Number of cycles to failure versus strain range at the notch surafce in % for polished, shot peened and samples subjected to the lifetime extension strategy.
Fig. 8 The cycles to failure versus strain range separated into eleastic, plastic and total strain range at the notch surface for polished and shot peened samples, with the equivalent Coffin-Manson curves calculated based upon the lifetime data obtained.
Fig. 9 The difference between the shot peened and polished prediction using the Coffin-Manson constants obtained as lifetime extension from shot peening. The theoretical lifetime extension from shot peening based upon the Coffin-Manson prediction versus percentage lifetime is also shown.
Fig. 11 The average lifetime of samples with various surface and loading conditions, split into three main phases of lifetime (Initiation, short crack and remaining life).
Fig. 12 The average lifetime of samples with various surface/loading conditions compared with the lifetime extension strategy prediction and experimental results from samples subjected to the lifetime extension strategy.
Fig. 13 The predicted life versus the lifetime found through experimentation for polished, shot peened samples, and samples subjected to the lifetime extension strategy.
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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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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