Littérature scientifique sur le sujet « Smooth bars »
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Articles de revues sur le sujet "Smooth bars"
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VOLINO, RALPH J., MICHAEL P. SCHULTZ et KAREN A. FLACK. « Turbulence structure in boundary layers over periodic two- and three-dimensional roughness ». Journal of Fluid Mechanics 676 (15 mars 2011) : 172–90. http://dx.doi.org/10.1017/s0022112011000383.
Texte intégralRésumé :
Measurements are presented from turbulent boundary layers over periodic two- and three-dimensional roughness. Cases with transverse rows of staggered cubes and cases with solid square transverse bars of two sizes were considered. Previous results by Volino, Schultz & Flack (J. Fluid Mech. vol. 635, 2009, p. 75) showed outer-layer similarity between cases with three-dimensional roughness and smooth walls, and deviations from similarity in cases with large two-dimensional transverse bars. The present results show that differences also occur with small two-dimensional bars and to a lesser extent when the bars are replaced with rows of staggered cubes. Differences are most apparent in correlations of turbulence quantities, which are of larger spatial extent for the rough-wall cases. The results with the staggered cubes indicate that part of the periodic roughness effect is caused by the repeated disturbance and recovery of the boundary layer as it encounters a row of roughness followed by a smooth surface. A larger effect, however, is due to the blockage caused by the two-dimensional transverse bars, which extend across the entire width of the boundary layer. The small two-dimensional bars have a larger effect than the staggered cubes, in spite of the bar height being only 11 viscous units and 1/7 of the cube height. The effect of the small bars extends well into the outer flow, indicating that effects observed previously with larger bars were not due only to a thickening of the roughness sublayer. The observed differences between the rough- and smooth-wall results are believed to be caused by large-scale attached eddies which extend from the roughness elements to the edge of the boundary layer.
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Hayashi, Taro. « Orders of automorphisms of smooth plane curves for the automorphism groups to be cyclic ». Arabian Journal of Mathematics 10, no 2 (18 mai 2021) : 409–22. http://dx.doi.org/10.1007/s40065-021-00321-5.
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AbstractFor a fixed integer $$d\ge 4$$ d ≥ 4 , the list of groups that appear as automorphism groups of smooth plane curves whose degree is d is unknown, except for $$d=4$$ d = 4 or 5. Harui showed a certain characteristic about structures of automorphism groups of smooth plane curves. Badr and Bars began to study for certain orders of automorphisms and try to obtain exact structures of automorphism groups of smooth plane curves. In this paper, based on the result of T. Harui, we extend Badr–Bars study for different and new cases, mainly for the cases of cyclic groups that appear as automorphism groups.
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Stone, L. S., J. Lorenceau et B. R. Beutter. « Smooth Pursuit of a Partially Occluded Object ». Perception 25, no 1_suppl (août 1996) : 150. http://dx.doi.org/10.1068/v96l0201.
Texte intégralRésumé :
There has long been qualitative evidence that humans can pursue an object defined only by the motion of its parts (eg Steinbach, 1976 Vision Research16 1371 – 1375). We explored this quantitatively using an occluded diamond stimulus (Lorenceau and Shiffrar, 1992 Vision Research32 263 – 275). Four subjects (one naive) tracked a line-figure diamond moving along an elliptical path (0.9 Hz) either clockwise (CW) or counterclockwise (CCW) behind either an X-shaped aperture (CROSS) or two vertical rectangular apertures (BARS), which obscured the corners. Although the stimulus consisted of only four line segments (108 cd m−2), moving within a visible aperture (0.2 cd m−2) behind a foreground (38 cd m−2), it is largely perceived as a coherently moving diamond. The intersaccadic portions of eye-position traces were fitted with sinusoids. All subjects tracked object motion with considerable temporal accuracy. The mean phase lag was 5°/6° (CROSS/BARS) and the mean relative phase between the horizontal and vertical components was +95°/+92° (CW) and −85°/−75° (CCW), which is close to perfect. Furthermore, a \chi2 analysis showed that 56% of BARS trials were consistent with tracking the correct elliptical shape ( p<0.05), although segment motion was purely vertical. These data disprove the main tenet of most models of pursuit: that it is a system that seeks to minimise retinal image motion through negative feedback. Rather, the main drive must be a visual signal which has already integrated spatiotemporal retinal information into an object-motion signal.
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Silling, S. A. « Two-Dimensional Effects in the Necking of Elastic Bars ». Journal of Applied Mechanics 55, no 3 (1 septembre 1988) : 530–35. http://dx.doi.org/10.1115/1.3125825.
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Numerical solutions for incompressible hyperelastic bars undergoing smooth necking in plane strain show complex phenomena in which two-dimensional effects are inherently important. In long bars, the two-dimensional effects are confined to a transition zone between the necked and non-necked phases. In spite of the two-dimensional effects, the nominal stress in necked long bars is close to the Maxwell stress under certain conditions. For very long bars there are necked equilibrium deformations in which the overall stretch is less than that of the maximum in the constitutive relation.
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Leonardi, S., P. Orlandi, L. Djenidi et R. A. Antonia. « Heat transfer in a turbulent channel flow with square bars or circular rods on one wall ». Journal of Fluid Mechanics 776 (13 juillet 2015) : 512–30. http://dx.doi.org/10.1017/jfm.2015.344.
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Direct numerical simulations (DNS) are carried out to study the passive heat transport in a turbulent channel flow with either square bars or circular rods on one wall. Several values of the pitch (${\it\lambda}$) to height ($k$) ratio and two Reynolds numbers are considered. The roughness increases the heat transfer by inducing ejections at the leading edge of the roughness elements. The amounts of heat transfer and mixing depend on the separation between the roughness elements, an increase in heat transfer accompanying an increase in drag. The ratio of non-dimensional heat flux to the non-dimensional wall shear stress is higher for circular rods than square bars irrespectively of the pitch to height ratio. The turbulent heat flux varies within the cavities and is larger near the roughness elements. Both momentum and thermal eddy diffusivities increase relative to the smooth wall. For square cavities (${\it\lambda}/k=2$) the turbulent Prandtl number is smaller than for a smooth channel near the wall. As ${\it\lambda}/k$ increases, the turbulent Prandtl number increases up to a maximum of 2.5 at the crests plane of the square bars (${\it\lambda}/k=7.5$). With increasing distance from the wall, the differences with respect to the smooth wall vanish and at three roughness heights above the crests plane, the turbulent Prandtl number is essentially the same for smooth and rough walls.
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Nord, K. J., et T. J. Chung. « Fracture and surface flaws in smooth and threaded round bars ». International Journal of Fracture 30, no 1 (janvier 1986) : 47–55. http://dx.doi.org/10.1007/bf00034578.
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Nemes, J. A., et J. Eftis. « Constitutive modeling of the dynamic fracture of smooth tensile bars ». International Journal of Plasticity 9, no 2 (janvier 1993) : 243–70. http://dx.doi.org/10.1016/0749-6419(93)90031-k.
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Arani, Kamyar Karbasi, Mohammad S. Marefat, Marco Di Ludovico, Andrea Prota et Gaetano Manfredi. « Hysteretic cyclic response of concrete columns reinforced with smooth bars ». Bulletin of Earthquake Engineering 11, no 6 (5 juin 2013) : 2033–53. http://dx.doi.org/10.1007/s10518-013-9469-9.
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Rimal, Hariram, Piyush Pradhan, Dipendra Gautam et Rajesh Rupakhety. « Seismic Fragility of Aging Elevated Water Tank with Smooth Bars Considering Soil Structure Interaction ». Buildings 13, no 1 (20 décembre 2022) : 4. http://dx.doi.org/10.3390/buildings13010004.
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The functionality of elevated water tanks is pivotal to assure after an earthquake as water supply is expected to be uninterrupted. Although elevated water tanks with deformed bars are widely studied, limited works exist for water tanks with smooth bars, although such tanks comprise a considerable fraction, even in the high seismic regions. To quantify the seismic vulnerability of aging elevated water tanks with smooth bars, we created analytical fragility functions for full, half, and empty reservoir conditions, considering fluid–structure and soil–structure interactions. The sum of findings reflects that soil flexibility and the amount of water present in the tank have a significant effect on overall seismic fragility, especially at higher damage states. The tanks are found to be most vulnerable when they are fully filled with water. The effect of soil flexibility is more pronounced at higher damage states. The difference between the fragility of flexible base and fixed base structures is found to increase with increasing ground motion intensity and it is the highest for the empty tank condition.
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Caruso, Claudia, Rita Bento, Romain Sousa et António A. Correia. « Modelling strain penetration effects in RC walls with smooth steel bars ». Magazine of Concrete Research 71, no 17 (septembre 2019) : 894–906. http://dx.doi.org/10.1680/jmacr.18.00052.
Texte intégralThèses sur le sujet "Smooth bars"
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Führing, Sven [Verfasser], et Bernhard [Akademischer Betreuer] Hanke. « Positive Scalar Curvature and a Smooth Variation of Baas-Sullivan Theory / Sven Führing. Betreuer : Bernhard Hanke ». Augsburg : Universität Augsburg, 2013. http://d-nb.info/1077703112/34.
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Blychert, Ida. « Smoothieböcker är bara för kvinnor. En diskurs- och semiotisk analys av sju framsidor på smoothieböcker ». Thesis, Malmö universitet, Fakulteten för kultur och samhälle (KS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-21743.
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I denna uppsats analyseras sju stycken framsidor på smoothieböcker publicerade mellan år 2007 och 2016. Syftet är att undersöka hur dessa riktar sig till en kvinnlig målgrupp genom sin formgivning. Uppsatsen grundar sig i ett genusvetenskapligt perspektiv som kompletteras med teorier kring semiotik, färg, typografi och bild. Analysen sker i två steg där en semiotisk analys följs av en diskursanalys. I denna kan tre stycken diskurser kring kvinnligheten och smoothietrenden urskiljas: 1) Nyttighet, 2) Lyx, avslappning och njutning och 3) Kvinnligheten. Dessa budskap förstärks även genom färg- och typografival samt titelformuleringar på framsidorna. Slutligen problematiseras dessa resultat genom en diskussion kring vad detta kan ha för konsekvenser på såväl samhälle som individen samt designerns ansvar i formgivningen.
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Lion, Nicolas. « Caractérisation mécanique de la glace aéronautique sous chargement rapide et développement d'une loi de comportement pour simuler des impacts de glace ». Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI028.
Texte intégralRésumé :
Afin de garantir la sécurité des voyageurs et des appareils, de nombreuses études ont été financées ces dernières années par l'industrie aérospatiale et aéronautique en vue de caractériser expérimentalement puis de simuler numériquement l'ingestion par les moteurs d'avion de projectiles en tout genre. La glace est un exemple de projectiles susceptibles d'impacter les moteurs d'avion pendant leur fonctionnement. Notre travail s'inscrit directement dans ce cadre de recherche avec l'objectif de caractériser expérimentale la glace aéronautique à haute vitesse et de développer un modèle qui permettra de simuler des impacts de glace sur une structure. Une synthèse des divers travaux et recherches existants sur le matériau glace permet de faire le point sur les connaissances actuelles du matériau glace et d'en pointer les faiblesses, notamment l'absence de données expérimentales sur les glace aéronautique. Les protocoles de fabrication de différent types de glace, le protocole d'usinage des échantillons, la méthode de transport, des banc d'essais sur presse électromécanique et sur barres d'Hopkinsons ont été développé. Ils permettent de mieux cerner les mécanismes du comportement de la glace à hautes vitesses de déformation (en mettent en évidence le rôle de la microstructure, le rôle de la température et l'influence de la vitesse de déformation). La dernière partie détaille un modèle de comportement et de rupture général applicable aux matériaux fragiles et plus particulièrement à la glace sous impact. Il s'agit d'une loi de comportement élasto-endommagebale avec endommagement de type Mazars, associé aux modifications de Chuzel pour son utilisation en dynamique rapide. La méthode d'identification des paramètres de la loi à partir des essais est également présentée. L'implémentation de la loi dans le code commercial LS-Dyna est validée sur des cas simples avant que les résultats numériques ne soient confrontés aux résultats expérimentaux. Cette comparaison a mis en lumière un défaut inhérent au modèle d'endommagement de type Mazars une correction du modèle est donc proposéeIn order to guarantee the safety of passengers and aircrafts, numerous studies have been financed in recent years by the aerospace and aeronautics industry in order to characterize experimentally and then numerically simulate the ingestion by the aircraft engines of projectiles. Ice is an example of projectile that can impact aircraft engines during the fly. In this research framework, our work objectives are the high-speed experimental characterization of aeronautical ice and the developpement of a model that will simulate ice impacts on a structure. A synthesis of the various existing research and work on ice makes possible to take stock of the current knowledge of the ice material and to point out its weaknesses, in particular the lack of experimental data on aeronautical ice. Production protocols for different types of ice, sample processing protocol, transport method, electromechanical press test bench and split Hopkinson bars were developed. They make it possible to better understand the behavior of ice at high deformation velocities (influence of microstructure, influence of temperature and influence of deformation velocity). The last part details a model of behavior and general rupture applicable to fragile materials and more particularly to the ice under impact. It is a law of behavior elasto-damagebale with Mazars damage type, associated with modifications of Chuzel for its use in fast dynamics. The method of identifying the parameters of the law from the tests is also presented. The implementation of the law in the commercial code LS-Dyna is validated on simple cases before the numerical results are compared to the experimental results. This comparison has highlighted a defect inherent in the Mazars model of damage. A correction of the model is therefore proposed
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Kheireddin, Bassem A. « Investigation Of The Friction Factor Behavior for Flat Plate Tests Of Smooth And Roughened Surfaces With Supply Pressures Up To 84 Bars ». 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-7190.
Texte intégralRésumé :
Annular gas seal clearances were simulated with closely spaced parallel plates
using a Flat?Plate tester. The device is designed to measure the pressure gradient along
the test specimen. The main function of the Flat?Plate tester is to provide friction factor
data and measure dynamic pressure oscillations. A detailed description of the test
facility is described, and a theory for determining the friction factor is reviewed. Three
clearances were investigated: 0.635, 0.381, and 0.254 mm. Tests were conducted at
three different inlet pressures (84, 70, and 55 bars), producing Reynolds numbers range
from 50,000 to 700,000. Three surface configurations were tested including smooth?on-smooth,
smooth?on?hole, and hole?on?hole. The Hole?pattern plates are identical with
the exception of the hole depth. The results indicate that, for the smooth?on?smooth
and smooth?on?hole configurations, the friction factor remains constant or increases
slightly with increasing Reynolds numbers. Moreover, the friction factor increases as
the clearance between the plates increases. However, the results from the hole?on-hole configurations are quite different. A "friction?factor jump" phenomenon was
observed, and the Helmholtz frequency was detected on the frequency spectra.
Livres sur le sujet "Smooth bars"
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Healthy in a hurry : Smoothie recipes, breakfast bars and grab & go snacks. North Charleston, South Carolina] : [CreateSpace], 2014.
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Blakeslee, Barbara, et Mark E. McCourt. The White Effect. Oxford University Press, 2017. http://dx.doi.org/10.1093/acprof:oso/9780199794607.003.0039.
Texte intégralRésumé :
The White effect is an illusion in which gray test patches of identical luminance placed on the black and white bars of a square-wave grating appear different in brightness/lightness. The effect has received much attention because the direction of the brightness change does not correlate with the amount of black or white border in contact with the gray test patch or its general vicinity. The test patch on the black bar appears lighter than the test patch on the white bar despite changes in test patch height or inducing grating spatial frequency. In addition, although the test patch shows a smooth change in brightness/lightness as its spatial position is varied relative to the inducing grating, spatial inhomogeneities in brightness/lightness within the test patch are also visible. A large number of “higher-level” explanations have been offered for the White effect; only the oriented-difference-of-Gaussians model can account for all of these properties.
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Shaw, William, et Sara Lewis. Superfood Breakfasts ! : 50 Smoothie Bowls, Power Bars and Energy Balls. Anness Publishing, 2016.
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Aziz, Erica Palmcrantz. Superfood Boost : Immunity-Building Smoothie Bowls, Green Drinks, Energy Bars, and More ! Skyhorse Publishing Company, Incorporated, 2018.
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Aziz, Erica Palmcrantz. Superfood boost : Immunity-building smoothie bowls, green drinks, energy bars, and more ! 2018.
Trouver le texte intégralChapitres de livres sur le sujet "Smooth bars"
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Martins-Robalino, A., et D. Palermo. « Comparative Experimental Study of the Flexural Behaviour of UHP-SFRC and ECC Beams Reinforced with Smooth Bars ». Dans Lecture Notes in Civil Engineering, 485–98. Singapore : Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-19-1004-3_40.
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Aston, Joshua N. « Community Policing ». Dans Torture Behind Bars, 178–90. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190120986.003.0008.
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Community policing is often referred to as neighbourhood policing, and this has been one of the major reforms in the police system. In this chapter, various community policing initiatives and reforms undertaken by the police in various states of India have been discussed. By such experiences through different schemes, it has been proved that community policing is of utmost importance, and it is advantageous towards having a smooth functioning of society in particular and the government in general.
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Xu, X. X., Y. Su et Q. G. Cai. « STATISTICAL ANALYSIS OF CLEAVAGE IN PRECRACKED, NOTCHED AND SMOOTH BARS ». Dans Mechanical Behaviour of Materials VI, 87–92. Elsevier, 1992. http://dx.doi.org/10.1016/b978-0-08-037890-9.50409-9.
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« Epstein-Barr Virus-Associated Smooth Muscle Tumor ». Dans Diagnostic Pathology : Soft Tissue Tumors, 328–29. Elsevier, 2016. http://dx.doi.org/10.1016/b978-0-323-37675-4.50087-9.
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« Epstein-Barr Virus–Associated Smooth Muscle Tumor ». Dans High-Yield Bone and Soft Tissue Pathology, 311–12. Elsevier, 2012. http://dx.doi.org/10.1016/b978-1-4377-2520-9.10146-6.
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Seidman, Naomi. « Foreword to the 1933 Edition ». Dans Sarah Schenirer and the Bais Yaakov Movement, 234–35. Liverpool University Press, 2019. http://dx.doi.org/10.3828/liverpool/9781906764692.003.0019.
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AROUND FIFTEEN YEARS AGO, when our leader Mrs Sarah Schenirer first approached the Jewish world with the idea of Bais Yaakov, she had almost no supporters, and only very few Jewish parents understood what she wanted and what she was talking about. The Orthodox world was in despair over the problem of religious education for Jewish girls, and in any case could not believe that some humble, unknown woman would be able to overcome the obstacles and smooth the path....
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Migon, Piotr. « Slope Development in Granite Terrains ». Dans Granite Landscapes of the World. Oxford University Press, 2006. http://dx.doi.org/10.1093/oso/9780199273683.003.0013.
Texte intégralRésumé :
Rock slopes developed in granite may take different forms, as reflected in their longitudinal profiles. Field observations and a literature survey (e.g. Dumanowski, 1964; Young, 1972) allow us to distinguish at least five major categories of slopes: straight, convex-upward, concave, stepped, and vertical rock walls. In addition, overhang slopes may occur, but their height is seldom more than 10 m high and their occurrence is very localized. These basic categories may combine to form compound slopes, for example convex-upward in the upper part and vertical towards the footslope. Somewhat different is Young’s (1972) attempt to identify most common morphologies of granite slopes. He lists six major categories: (1) bare rock domes, smoothly rounded or faceted; (2) steep and irregular bare rock slopes of castellated residual hills, tending towards rectangular forms; (3) concave slopes crowned by a free face; (4) downslope succession of free face, boulder-covered section and pediment; (5) roughly straight or concave slopes, but having irregular, stepped microrelief; (6) smooth convex-concave profile with a continuous regolith cover. The latter, lacking any outcrops of sound bedrock, are not considered as rock slopes for the purposes of this section. Young (1972) appears to seek explanation of this variety in climatic differences between regions, claiming that ‘Variations of slope form associated with climatic differences are as great as or greater, on both granite and limestone, than the similarity of form arising from lithology’ (Young, 1972: 219). This is a debatable statement and apparently contradicted by numerous field examples of co-existence of different forms in relatively small areas. Slope forms do not appear specifically subordinate to larger landforms but occur in different local and regional geomorphic settings. For example, the slopes of the Tenaya Creek valley in the Yosemite National Park include, in different sections of the valley, straight, vertical, convex-upward, and concave variants (Plate 5.1). Apparently, multiple glaciation was unable to give the valley a uniform cross-sectional shape.
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Kimbel, William H., Yoel Rak, Donald C. Johanson, Ralph L. Holloway et Michael S. Yuan. « Elements of the Disarticulated Skull ». Dans The Skull of Australopithecus afarensis. Oxford University Press, 2004. http://dx.doi.org/10.1093/oso/9780195157062.003.0008.
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The 1970s collection of hominin cranial remains from Hadar is notoriously weak in its representation of the frontal bone. Besides the complete but distorted frontal of the A.L. 333-105 juvenile (Kimbel et al., 1982), only two very incomplete adult specimens provided glimpses of frontal morphology: A.L. 288-1 (Johanson et al., 1982b) and A.L. 333-125 (Asfaw, 1987). With the recovery of the almost complete frontal bone of A.L. 444-2, we are able to fill one of the last remaining gaps in our knowledge of the Hadar hominin adult skull. Another frontal specimen, A.L. 438-1b, contributes important information on the glabellar and supraglabellar regions, which are missing or poorly preserved in A.L. 444-2. The A.L. 444-2 frontal bone features prominent, laterally projecting supraorbital bars, strongly convergent temporal lines, and a transversely broad squama with only moderate postorbital constriction. The minimum distance between the temporal lines (30 mm) in the plane of the postorbital constriction is much smaller than the postorbital constriction itself (77 mm), creating on each side an extensive, almost horizontally inclined facies temporalis that, in coronal section, slopes gradually from the inferior temporal lines to the medial wall of the temporal fossa. In between the temporal lines, the supraglabellar region bears a mild hollow that grades smoothly onto the superior surface of the supraorbital bars. Neither a supratoral sulcus nor a trigonum frontale is present. The supraorbital bars are wide anteroposteriorly, measuring 16 mm at the right lateral break, about 42 mm lateral to the midline. The preserved portions of the anterior supraorbital margins are aligned coronally, forming right angles with the midsagittal line. At the lateral break on each side, the margin actually occupies a slightly more anterior plane than the middle part of the margin, suggesting an anteriorly prominent superolateral corner of the orbit. At the medial break through the left supraorbital, about 22 mm lateral to the midline, the anterior margin begins to swing out toward glabella (this area is damaged on the right side). The extent of anterior glabellar protrusion is suggested by the preserved supraglabellar plate, whose superior surface projects in the midline about 5 mm beyond the anterior supraorbital margins.
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CAHEN, MICHEL. « Indigenato Before Race ? Some Proposals on Portuguese Forced Labour Law in Mozambique and the African Empire (1926–62) ». Dans Racism and Ethnic Relations in the Portuguese-Speaking World. British Academy, 2012. http://dx.doi.org/10.5871/bacad/9780197265246.003.0009.
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Was blackness the key factor for labelling native people as ‘non-civilised’ and thus to be pushed into forced labour in Portuguese Africa? Without denying the importance of blackness as a stigmatising tool, this chapter argues, through a careful analysis of colonial law and practice, that the production of ‘nativeness’ was related to clear consciousness of Africans living outside the capitalist economy and social sphere. This helps us to understand that emerging forced labour represented not a smooth transition from slavery, but a rupture between two colonial ages and modes of production. Therefore, if colonial racism obviously used skin colour to construct a social bar, above all it used the definition of otherness as external to the capitalist sphere. Petty whites and natives could live side by side in suburban neighbourhoods, but in two impermeable spheres. Racism was pervasively present, but it was more social than racial.
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« Conservation, Ecology, and Management of Catfish : The Second International Symposium ». Dans Conservation, Ecology, and Management of Catfish : The Second International Symposium, sous la direction de MICHAEL L. FINE, EDWARD N. SISMOUR, SCOTT H. NEWTON, BISHOP T. BOSHER, AMANDA DH SULLIVAN, JOSEPH PAUL MIANO, ZACHARY N. GHAHRAMANI, YASHA J. MOHAJER et SHELLEY C. NELLIS. American Fisheries Society, 2011. http://dx.doi.org/10.47886/9781934874257.ch63.
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<em>Abstract</em>.—We have been examining proximate (functional morphology) and ultimate factors (survival from predation) relating to the pectoral spine in channel catfish <em>Ictalurus punctatus</em>. We briefly review functional morphology of the spine in channel catfish and then add new data on morphology in other ictalurids, including interpretation of the relatively smooth anterior and armored posterior profiles of the spine, functions of the various pectoral spine muscles, and new details about the mechanism of stridulatory sound production. Binding, locking, and production of stridulation sounds by the spine utilize derived processes on the spine base (dorsal, anterior, and ventral processes) that mate with counterparts within the pectoral girdle. Stridulation sounds are produced as a series of individual pulses during a forward pectoral fin sweep (abduction), and we provide evidence that each pulse is produced by a small amplitude forward movement, a slip-stick movement similar to bowing a violin. An anti-predator adaptation can work as a deterrent that reduces the probability of attack and as a defense that reduces the risk of mortality. Previous work indicated that the spine functions in defense. Intact channel catfish have a threefold greater chance of surviving a session with a largemouth bass <em>Micropterus salmoides</em> predator as comparably sized individuals with clipped spines. The question of whether the spine reduces the probability of attack had not been investigated. We presented bluegills <em>Lepomis macrochirus</em> and channel catfish to largemouth bass and found that largemouth bass consume more bluegills than channel catfish in a choice situation. Thus, experience with the pectoral spines likely deters attack, particularly if other species are available, and the spine increases the probability of surviving attack by complicating ingestion and possibly by the production of distress calls. Survival advantages accruing from the spine appear to have lead to the evolution of complex adaptations that permit locking and sound production.
Actes de conférences sur le sujet "Smooth bars"
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Childs, Dara W., Bassem Kheireddin et Stephen Phillips. « Friction Factor Behavior From Flat-Plate Tests of Smooth and Hole-Pattern Roughened Surfaces With Supply Pressures up to 84 Bars ». Dans ASME Turbo Expo 2010 : Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22227.
Texte intégralRésumé :
A flat-plate tester was used to measure the friction-factor behavior for a hole-pattern-roughened surface apposed to a smooth surface. The tests were executed to characterize the friction-factor behavior of annular seals that use a roughened-surface stator and a smooth rotor. Friction factors were obtained from measurements of the mass flow rate and static pressure measurements along the smooth and roughened surfaces. In addition, dynamic pressure measurements were made at four axial locations at the bottom of individual holes and at facing locations in the smooth plate. The test facility is described, and a procedure for determining the friction factor is reviewed. Three clearances were investigated: 0.635, 0.381, and 0.254 mm. Tests were conducted with air at three different inlet pressures (84, 70, and 55 bars), producing a Reynolds numbers range from 50,000 to 700,000. Three surface configurations were tested including smooth-on-smooth, smooth-on-hole, and hole-on-hole. The hole-pattern plates are identical with the exception of the hole depth. For the smooth-on-smooth and smooth-on-hole configurations, the friction factor remains largely constant or increases slightly with increasing Reynolds numbers. The friction factor increases as the clearance between the plates increases. The test program was initiated to investigate a “friction-factor jump” phenomenon cited by Ha et al. in 1992 in test results from a flat-plate tester where, at elevated values of Reynolds numbers, the friction-factor began to increase steadily with increasing Reynolds numbers. They tested apposed honeycomb surfaces. For the present tests, the phenomenon was also observed for tests of apposed roughened surfaces but was not observed for smooth-on-smooth or smooth-on-rough configurations. When the phenomenon was observed, dynamic pressure measurements showed a peak-pressure oscillation at the calculated Helmholtz frequency of the holes.
2
Zhang, Min, Dara W. Childs, James E. Mclean, Dung L. Tran et Hari Shrestha. « Experimental Study of the Leakage and Rotordynamic Coefficients of a Long Smooth Seal With Two-Phase, Mainly-Oil Mixtures ». Dans ASME Turbo Expo 2018 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75328.
Texte intégralRésumé :
Tests are conducted on a newly developed 2-phase annular seal stand (2PASS) at the Turbomachinery Laboratory of Texas A&M University. The test fluid is a mixture of silicone oil (PSF-5cSt) and air. Two spargers are used to produce mainly-oil mixtures by injecting air bubbles into the oil flow. The test seal is a smooth annular seal with inner diameter D = 89.306 mm, length-to-diameter ratio L/D = 0.65, and radial clearance Cr = 0.188 mm. Tests are performed with inlet gas-volume-fraction GVF = 0%, 2%, 4%, 6%, and 10%, rotor speed ω = 5, 7.5, 10, and 15 krpm, inlet temperature Ti = 39.4 °C, exit pressure Pe = 6.9 bars, and pressure drop PD = 31, 37.9, and 48.3 bars. The test seal is centered, and there is no intentional prerotation of the fluid at the seal inlet. The complex dynamic stiffness coefficients of the test seal are measured and fitted by the frequency-independent stiffness Kij, damping Cij, and virtual-mass Mij coefficients. Test results show that adding air into the oil flow does not change the seal’s mass flow leakage ṁ discernibly but significantly impacts the seal’s rotordynamic characteristics. Some planned 5 krpm cases with low inlet GVFs at PD = 31 and 37.9 bars are not accomplished due to stator instabilities, which are likely caused by negative stiffness of the test seals. For ω = 5 krpm when PD = 31 and 37.9 bars, direct stiffness K decreases from positive to negative as inlet GVF decreases. For all PDs and speeds, K increases as inlet GVF increases from zero to 10% except for 6% ≤ inlet GVF ≤ 10% when PD = 48.3 bars, where K decreases as inlet GVF increases. The K increment will increase a pump rotor’s natural frequency and critical speed. Increasing the rotor’s natural frequency would also increase the onset speed of instability (OSI) and improve the stability of the rotor. Adding air into the oil flow has little effect on cross-coupled stiffness k and direct damping C. Increasing inlet GVF has negligible effects on direct virtualmass M when ω ≤ 10 krpm and PD ≤ 37.9 bars, but generally decreases M when ω = 15 krpm or PD = 48.3 bars. Increasing inlet GVF has little effect on effective damping Ceff and does not change the seal’s resultant stabilizing force discernibly. Ceff = C − k/ω + mqω, where mq is the cross-coupled virtual-mass. Test results are compared to predictions from San Andrés’s [1] model. The model is based on a bulk-flow model and the Moody friction formula assuming that the liquid-gas mixture is isothermal and homogenous. The model reasonably predicts ṁ, C, and Ceff. All predicted K values are positive, while measured K values are negative for some test cases. Predicted k values are close to measurements when ω = 5 krpm and are larger than test results when 7.5 ≤ ω ≤ 15 krpm. M predictions are smaller than measurements, and the discrepancy between predicted and measured M values generally increases as inlet GVF increases.
3
Kim, Yun-Jae, Chang-Kyun Oh, Tae-Kwang Song et Do-Jun Shim. « Finite Element Ductile Failure Simulations of Tensile and Bend Bars Made of API X65 Steels ». Dans ASME 2007 Pressure Vessels and Piping Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/pvp2007-26218.
Texte intégralRésumé :
This paper presents a micro-mechanical model of ductile fracture for the API X65 steel using the Gurson-Tvergaard-Needleman (GTN) model. Experimental tests and FE damage simulations using the GTN model are performed for smooth and notched tensile bars, from which the parameters in the GTN model are calibrated. As application, the developed GTN model is applied to simulate small-sized, single-edge-cracked tensile and bend bars, via three-dimensional FE damage analyses. Comparison with experimental test data shows overall good agreements.
4
Itatani, Masao, Keisuke Tanaka, Isao Ohkawa, Takehisa Yamada et Toshiyuki Saito. « Fatigue Behavior of Circumferentially Notched Round Bars of Austenitic Stainless Steel Under Torsional and Axial Loads ». Dans ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-25472.
Texte intégralRésumé :
Fatigue tests of smooth and notched round bars of austenitic stainless steels SUS316NG and SUS316L were conducted under cyclic tension and cyclic torsion with and without static tension. Fatigue strength under fully reversed (R=−1) cyclic tension once increased with increasing stress concentration factor up to Kt=1.5, but it decreased from Kt=1.5 to 2.5. Fatigue life increased with increasing stress concentration under pure cyclic torsion, while it decreased with increasing stress concentration under cyclic torsion with static tension. From the measurement of fatigue crack initiation and propagation lives using electric potential drop method, it was found that the crack initiation life decreased with increasing stress concentration and the crack propagation life increased with increasing stress concentration under pure cyclic torsion. Under cyclic torsion with static tension, the crack initiation life also decreased with increasing stress concentration but the crack propagation life decreased or not changed with increasing stress concentration then the total fatigue life of sharper notched specimen decreased. It was also found that the fatigue life of smooth specimen under cyclic torsion with static tension was longer than that under pure cyclic torsion. This behavior could be explained based on the cyclic strain hardening under non-proportional loading and the difference in crack path with and without static tension.
5
Oh, Chang-Sik, Nak-Hyun Kim, Sung-Hwan Min et Yun-Jae Kim. « Finite Element Damage Analyses for Predictions of Creep Crack Growth ». Dans ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-25294.
Texte intégralRésumé :
This paper provides the virtual simulation method for creep crack growth test, based on finite element (FE) analyses with damage mechanics. Creep tests of smooth bars are used to quantify the constants of creep constitutive equation. The reduction of area resulting from creep tests of smooth and notched bar is adopted as a measure of creep ductility under multiaxial stress conditions. The creep ductility exhaustion concept is adopted for calculating creep damage, which is defined as the ratio of creep strain to the multiaxial creep ductility. To simulate crack propagation, fully damaged elements are forced to have nearly zero stresses using user-defined subroutine UHARD in the general-purpose FE code, ABAQUS. The results from 2D or 3D FE analyses are compared with experimental data of creep crack growth. It is shown that the predictions obtained from this new method are in good agreement with experimental data.
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Chan, Hoover, Christopher W. Tyler et Lei Liu. « Asymmetries in the perception of luminance increments and decrements at low contrasts ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.thaa6.
Texte intégralRésumé :
Studies of luminance increments and decrements have typically used transient pulses of localized stimuli. We employed two new paradigms to examine increment/decrement response asymmetries in grating stimuli presented with a smooth spatio–temporal envelope. For the first paradigm, we studied apparent width of the light and dark bars making up sinusoidal gratings as a function of contrast. In contrast ranges close to threshold, the light bars appeared up the three times wider than the dark bars, with a peak at contrast of ~3%. Similar asymmetries were seen over a range of spatial frequencies. For the second paradigm, the gratings were generated as only luminance increment bars from the grey background (or only luminance decrement bars). We found asymmetries in the response to increments and decrements than varied as a function of spatial frequency of the test grating. At low spatial frequencies, the visual system was more sensitive to decrements. At intermediate spatial frequencies, sensitivity was higher for increments than for decrements by a factor of ~2. Sensitivity to both become the same at high spatial frequencies.
7
Tran, Dung L., Dara W. Childs, Hari Shrestha et Min Zhang. « Preswirl and Mixed-Flow (Mainly-Liquid) Effects on Rotordynamic Performance of a Long (L/D=0.75) Smooth Seal ». Dans ASME Turbo Expo 2019 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90004.
Texte intégralRésumé :
Abstract Measured results are presented for rotordynamic coefficients and mass leakage rates of a long smooth annular seal (length-to-diameter ratio L/D = 0.75, diameter D = 114.686 mm, and radial clearance Cr = 0.200 mm) tested with a mixture of silicone oil (PSF-5cSt) and air. The test seal is centered, the seal exit pressure is maintained at 6.9 bars-g while the fluid inlet temperature is controlled within 37.8–40.6°C. It is tested with 3 inlet-preswirl inserts, namely, zero, medium, and high (the preswirl ratios, i.e., the ratio between the fluid’s circumferential velocity and the shaft surface’s velocity, are in ranges of 0.10–0.18, 0.30–0.65, and 0.65–1.40 for zero, medium, and high preswirls, respectively), 6 inlet gas-volume-fractions GVFi (0%, 2%, 4%, 6%, 8%, 10%), 4 pressure drops PD (20.7, 27.6, 34.5, 41.4 bars), and 3 speeds ω (3, 4, 5 krpm). The targeted test matrix could not be achieved for the medium- and high-preswirl inserts at PD ≥ 27.6 bars due to the test-rig stator’s dynamic instability issues. Spargers were used to inject air into the oil, and GVFi values higher than 0.10 could not be consistently achieved because of unsteady surging flow downstream from the sparger mixing section. Leakage mass flow rate ṁ and rotordynamic coefficients are measured, and the effect of changing inlet preswirl and GVFi are studied. The test results are then compared with predictions from a 2-phase, homogeneous-mixture, bulk-flow model developed in 2011. Generally, both measurements and predictions show little change in ṁ as inlet preswirl changes. Measured ṁ remains unchanged or slightly increases with increasing GVFi, but predicted ṁ decreases. Measured ṁ is comparable to predicted values but consistently lower. Dynamic-stiffness coefficients are measured using an ensemble of excitation frequencies and curve-fitted well by frequency-independent stiffness Kij, damping Cij, and virtual mass Mij coefficients. Planned tests with the medium and high-preswirl inserts could not be accomplished at PD = 34.5 and 41.4 bars because the seal stator became unstable with any finite injection of air. The test results show that the instability arose because the seal’s direct stiffness K became negative and increased in magnitude with increasing GVFi. The model predicts a drop in K as GVFi increases, but the test results dropped substantially more rapidly than predicted. Also, the model does not predict the observed strong tendency for K to drop with an increase in preswirl in moving from the zero-to-medium, and medium-to-high preswirl inserts. The authors believe that the observed drop in K due to increasing GVFi is not explained by either: (a) A reverse Lomakin effect from operating in the transition flow regime, or (b) The predicted drop in K at higher GVFi values from the model. A separate and as yet unidentified 2-phase flow phenomenon probably causes the observed results. The negative K results due to increasing GVFi and moving from the zero to medium, and medium to high preswirl observed here could explain the instability issue (sudden nonsynchronous vibration) on a high-differential-pressure helico-axial multiphase pump, reported in 2013. Effective damping Ceff combines the stabilizing effect of direct damping C, the destabilizing effect of cross-coupled stiffness k, and the influence of cross-coupled mass mq. As predicted and measured, increasing inlet preswirl significantly increases k and decreases Ceff, which decrease the seal’s stabilizing properties. Ceff increases with increasing GVFi — becomes more stable.
8
Madi, Yazid, Jacques Besson, Gre´goire Martin, Patrick Hornet et Mustafa Koc¸ak. « Fracture Behaviour of Mis-Matched Dissimilar Welds : Numerical Simulation Using Local Approach ». Dans ASME 2002 Pressure Vessels and Piping Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/pvp2002-1100.
Texte intégralRésumé :
The safety assessment of welded structures still remains an important industrial problem. In this study, a simple diffusion bonded bi-material jonction has been made in order to analyse the mismatch effect. It consists of an assembly of ferritic and austenitic steels which are representative of nuclear pressure vessel. Each material has been tested using smooth and notched tensile bars. These tests were used to adjust the parameters of local approach based on the Rousselier model. Bi-material structures including notch tensile bars, Charpy specimens and single-edge notch bend specimens were tested and simulated using the Finite Element method. The correct test/computation agreement shows that the adjusted parameters on the homogeneous specimens can be transferred to heterogeneous structures.
9
Zhang, Min, Dara W. Childs, Dung L. Tran et Hari Shrestha. « A Study on the Leakage and Rotordynamic Coefficients of a Long-Smooth Seal With Laminar-Two-Phase, Mainly-Oil Mixtures ». Dans ASME Turbo Expo 2019 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91824.
Texte intégralRésumé :
Abstract This paper conducts a comprehensive study on the effects of the air presence in the oil on the leakage and rotordynamic coefficients of a long-smooth seal (inner diameter D = 89.306 mm, radial clearance Cr = 0.140 mm, and length-diameter ratio L/D = 0.65) under laminar-two-phase flow conditions. The mixture consists of air and silicone oil with inlet GVF (gas volume fraction) up to 10%. Tests are performed at inlet temperature Ti = 39.4 °C, exit pressure Pe = 6.9 bars, pressure drop PD = 31 and 37.9 bars, and rotor speed ω = 5, 7.5, and 10 krpm. The test seal is always concentric with the rotor, and no intentional fluid pre-rotation is provided at the seal inlet. The complex dynamic stiffness coefficients Hij of the test seal are measured and fitted by the frequency-independent direct stiffness K, cross-coupled stiffness k, direct damping C, cross-coupled damping c, direct virtual-mass M, and cross-coupled virtual-mass mq coefficients. Under laminar flow conditions, increasing inlet GVF has negligible effects on K, k, C, and effective damping Ceff, while it decreases c and M. These trends are correctly predicted by San Andrés’s bulk-flow model with laminar flow friction formula. As inlet GVF increases, measured leakage flow rate ṁ increases slightly. In general, the predictions of K, k, C, c, Ceff, and ṁ are reasonably close to measurements.
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Zhang, Min, et Dara W. Childs. « Experimental Study on the Leakage and Rotordynamic Coefficients of a Long Smooth Seal at Laminar Flow Conditions ». Dans ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88717.
Texte intégralRésumé :
This paper experimentally investigates the performance of a long smooth seal (length-diameter ratio L/D = 0.65 and radial clearance Cr = 0.140 mm) under laminar flow conditions. Tests are carried out at shaft speeds ω up to 10 krpm, pressure drops PD up to 48.3 bars, exit pressure Pe = 6.9 bars, and inlet temperature Ti = 39.4 °C. The seal is centered. Since there is no validated friction formula published for a liquid seal in the transitional regime, this paper uses San Andrés’s bulk-flow model with laminar-flow friction formula to produce predictions. Test results show that under laminar flow conditions, increasing ω decreases measured direct stiffness K, increases measured cross-coupled stiffness k, barely changes measured direct damping C, and generally increases measured cross-coupled damping c. The model correctly predicts these trends, and the predictions of K, k, C, and c are reasonably close to test results. Measured direct virtual-mass M values are normally larger than predictions. This paper also judges two cases with high PD or high ω to be in the transitional regime. For these cases, the predictions of K, k, C, and c based on the laminar-flow friction formula are significantly different from test results. This discrepancy further strengthens the judgment that the flow in these cases is transitional. For all test cases, measured leakage mass flow rate ṁ and measured effective damping Ceff are not sensitive to changes in ω, but increase as PD increases. The model with the laminar-flow friction formula adequately predicts ṁ and Ceff even when the flow within the seal annulus is at the start of the transitional flow regime. Also, Ceff predictions are lower than test results, allowing a safe margin for the pump design.
Rapports d'organisations sur le sujet "Smooth bars"
1
Andrawes, Bassem, Ernesto Perez Claros et Zige Zhang. Bond Characteristics and Experimental Behavior of Textured Epoxy-coated Rebars Used in Concrete Bridge Decks. Illinois Center for Transportation, janvier 2022. http://dx.doi.org/10.36501/0197-9191/22-001.
Texte intégralRésumé :
The deterioration of bridge decks is a problem typically associated with the corrosion of the reinforcing steel. This issue was partially controlled during the 1970s with the incorporation of the epoxy-coating protection system. However, research later demonstrated that the smooth surface resulting from the epoxy-coating application reduces most of the friction between the rebar and the surrounding concrete. Consequently, forces acting on the rib faces are reconfigured in such a way that the radial components increase, triggering the early development of cracks. To mitigate both the reduction of bonding and the formation of cracks, the Illinois Department of Transportation proposed a new type of coated bars: textured epoxy-coated (TEC) bars. Over the last few years, different projects have been executed to understand and improve the characteristics of TEC rebars. This report is a continuation of research performed at the University of Illinois Urbana-Champaign to evaluate the bond behavior of TEC bars. The experimental program starts by characterizing, qualitatively and quantitatively, the roughness of the TEC rebars. Next, their bond-slip interaction embedded in concrete is evaluated through pull-out tests. Finite element models of these tests are developed to validate the behavior observed as the textured reinforcement loses anchorage with concrete. Based on these results, the experimental program then aims to study the impact of the drying shrinkage, temperature change, and flexural demands on two large-scale bridge deck specimens reinforced, individually, with TEC and standard epoxy-coated bars. The results collected from both specimens using digital image correlation and strain gauges are compared to explore the differences exhibited by the traditional and the new type of reinforcement coatings in terms of stress distribution in bridge decks. Finally, given the specialized equipment and time-consuming procedure needed to calculate the roughness parameters of TEC bars, an empirical, weight-based approach is developed as a rapid method for assessing the rebars’ roughness on-site.
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STUDY ON MICROMECHANICAL FRACTURE MODELS OF STRUCTURAL STEEL AND ITS WELDS. The Hong Kong Institute of Steel Construction, juin 2021. http://dx.doi.org/10.18057/ijasc.2021.17.2.2.
Texte intégralRésumé :
Steel structures have been widely used in constructions due to their advantages of lightweight, high strength, short construction time and high recycling and reuse potential. Fracture failure in steel structures should be prevented to avoid collapse of the whole structures. Micromechanical fracture models can capture the fracture initiation mechanisms and therefore can be used to predict ductile fractures in steel. Twelve smooth round bars were carried out to obtain the material properties and 36 notched round bars were tested to calibrate the parameters of stress modified critical strain (SMCS) model and the void growth model (VGM) for structural steels (Q235B and Q345B) and the corresponding welds. Specimens were extracted from the base metal, the weld metal and the heat affected zone (HAZ) to investigate fracture behaviour in different parts of the welded joint. Scanning electron microscope (SEM) measurements were taken and finite element models were developed to calibrate the models. The test results and calibrated parameters are reported. Moreover, the calibrated models are applied to analyses the fracture behaviour of welded joints and their accuracy are validated. The calibrated and validated models can be used for further numerical fracture analysis in welded steel structures.