The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform
R N J Saal - One of the best experts on this subject based on the ideXlab platform.
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a study on the significance of the Ductility Test for bitumen
Journal of Chemical Technology & Biotechnology, 2007Co-Authors: R N J SaalAbstract:An analysis of the primary factors governing the Ductility of bitumens, as determined by the well-known Test, is given. Two phenomena should be distinguished: (1) brittle fracture (Ductility 0–1 cm.); (2) thread formation (Ductility > 1 cm.). Brittle fracture occurs if the stiffness of the bitumen at 10 sec. is higher than 107 N/sq. m.; this limiting value has been deduced both theoretically and experimentally. Thread formation occurs at lower stiffnesses. For bitumens of medium penetration index (P.I.) (P.I. between —2 and +2), thread formation must be considered as being largely due to a rise in temperature in the thread formed, resulting from the large amount of energy introduced during stretching. For high-P.I. bitumens (P.I. > 2) the Ductility behaviour must be attributed partly to the said rise in temperature, but mainly to thixotropy due to breakdown of the structure during stretching. Low-P.I. Newtonian-type bitumens (P.I. less than —2), which under normal conditions have ductilities of either 0 or more than 100, may also show intermediate values if the energy of stretch is increased by appropriate means. If we consider that neither the rise in temperature nor the thixotropic breakdown occurs in the practical use of bitumen, we may draw the conclusion that the significance of the Ductility Test is very doubtful, and that Tests more adapted to practical circumstances should be preferred for the evaluation of bitumens.
Fang Yu - One of the best experts on this subject based on the ideXlab platform.
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Shear performance of prestressed ultra high strength concrete encased steel beams
Construction and Building Materials, 2014Co-Authors: Dali Yao, Jinqing Jia, Feng Wu, Fang YuAbstract:Due to the high compressive strength and durability properties of ultra high strength concrete, prestressed ultra high strength concrete beam was used extensively in bridge engineering, but it possessed obvious brittle behavior. Encasing structural steel into it was a good way for alleviating the problem of brittleness. The purpose of this study was to investigate shear performance of prestressed ultra high strength concrete encased steel beams. A total of fifteen prestressed ultra high strength concrete encased steel beams and seven prestressed ultra high strength concrete beams were Tested to shear failure under simply supported three-point loading conditions. The primary variables of this investigation included the presence or not of structural steel, shear span-depth ratio, degree of prestress, ratio of stirrup and thickness of web. The shear performance was evaluated based on cracking pattern, load-deflection behavior and shear Ductility. Test results showed that prestressed ultra high strength concrete encased steel beams had higher residual shear capacity and post-cracking stiffness as well as by far better shear Ductility than prestressed ultra high strength concrete beams. In addition, influence of experimental parameters on the shear performance of prestressed ultra high strength concrete encased steel beams and prestressed ultra high strength concrete beams also was discussed and compared, respectively. © 2013 Published by Elsevier Ltd. All rights reserved.
Dali Yao - One of the best experts on this subject based on the ideXlab platform.
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Shear performance of prestressed ultra high strength concrete encased steel beams
Construction and Building Materials, 2014Co-Authors: Dali Yao, Jinqing Jia, Feng Wu, Fang YuAbstract:Due to the high compressive strength and durability properties of ultra high strength concrete, prestressed ultra high strength concrete beam was used extensively in bridge engineering, but it possessed obvious brittle behavior. Encasing structural steel into it was a good way for alleviating the problem of brittleness. The purpose of this study was to investigate shear performance of prestressed ultra high strength concrete encased steel beams. A total of fifteen prestressed ultra high strength concrete encased steel beams and seven prestressed ultra high strength concrete beams were Tested to shear failure under simply supported three-point loading conditions. The primary variables of this investigation included the presence or not of structural steel, shear span-depth ratio, degree of prestress, ratio of stirrup and thickness of web. The shear performance was evaluated based on cracking pattern, load-deflection behavior and shear Ductility. Test results showed that prestressed ultra high strength concrete encased steel beams had higher residual shear capacity and post-cracking stiffness as well as by far better shear Ductility than prestressed ultra high strength concrete beams. In addition, influence of experimental parameters on the shear performance of prestressed ultra high strength concrete encased steel beams and prestressed ultra high strength concrete beams also was discussed and compared, respectively. © 2013 Published by Elsevier Ltd. All rights reserved.
Hussain U Bahia - One of the best experts on this subject based on the ideXlab platform.
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critical problems with using the asphalt Ductility Test as a performance index for modified binders
Transportation Research Record, 2013Co-Authors: Hassan A Tabatabaee, Cristian Clopotel, Amir Arshadi, Hussain U BahiaAbstract:Despite the adaptation of advanced binder rheology characterization methods by many agencies, the asphalt Ductility Test is still being used in some specifications in the United States and a few other countries as a performance indicator for asphalt modification. In this study, binder properties known to reflect rutting and fatigue resistance were examined in a set of binders modified with two types of commonly used elastomeric polymer modifiers. The results showed no correlations with binder Ductility. Additionally, a Test procedure was developed by using a dynamic shear rheometer (DSR) as a surrogate to the conventional Ductility Test, results of which showed that both elastomeric modified binders are much more ductile than conventional binders, even when conventional Ductility showed a loss of Ductility. Finite element modeling was used to show the significant effects of decreasing true strain rates with elongation on the sample's stress and strain state attributable to the constant crosshead speed in ...
J.c. Lippold - One of the best experts on this subject based on the ideXlab platform.
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Effect of Multiple Postweld Heat Treatment on the Weldability of Alloy 718
Superalloys, 1997Co-Authors: J.w. Hooijmans, J.c. LippoldAbstract:This paper describes the effect of multiple postweld heat treatment thermal cycles on the weldability of both cast and wrought Alloy 7 18. The liquation cracking susceptibility of specially-melted alloys containing a range of niobium and boron contents was evaluated using the hot Ductility Test. Cracking susceptibility increased as a function of both composition and thermal cycling for the cast materials, while the wrought materials showed only a small influence of composition and effectively no deleterious effects from the multiple thermal cycles. Superalloys 718,625, 706 and Various Derivatives Edited by E.A. Loria The Minerals, Metals & Materials Society, 1997
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An evaluation of heat-affected zone liquation cracking susceptibility. I: Development of a method for quantification : a material-specific quantification of liquation cracking susceptibility was developed using the hot-Ductility, spot- and longitudin
Welding Journal, 1993Co-Authors: J.c. Lippold, W. A. BaeslackAbstract:A new methodology has been developed for quantifying heat-affected zone (HAZ) liquation cracking susceptibility. This methodology characterizes a thermal crack-susceptible region (CSR) in the HAZ. The thermal CSR was theoretical by derived based on the Ductility of a material during welding as obtained from the Gleeble hot-Ductility Test and the criteria assumed in the development of liquation cracking theories. This CSR was experimentally verified using longitudinal- and spot-Vare-straint Tests performed on A-286 and Type 310 stainless steels. The thermal CSR is material-specific and represents a true quantification of liquation cracking susceptibility
