The Experts below are selected from a list of 57 Experts worldwide ranked by ideXlab platform
John Dangelo - One of the best experts on this subject based on the ideXlab platform.
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proposed refinement of superpave high temperature specification parameter for performance graded binders
Transportation Research Record, 2001Co-Authors: Mark Bouldin, Raj Dongre, John DangeloAbstract:A semiempirical approach developed to predict the viscoelastic response of a binder in repeated creep recovery tests is described. This model provides an avenue to predict the rut resistance (R) as a function of loading (time and load) and temperature from data at a single frequency or frequency sweeps when needed. Thus, it can be used to develop a grading procedure for asphalt binders that not only accurately captures the Delayed Elasticity of modified binders but also accounts for the effect of traffic speed and traffic loading. The current Superpave binder specification attempts to capture the relative high-temperature performance (i.e., resistance to rut) of a binder via the inverse shear loss compliance, 1/J" or G*/sin δ, at 10 rad/s. This parameter represents an improvement over the absolute viscosity because it is measured at a defined rate of deformation and accounts to some degree for the viscoElasticity of the binder via the phase angle. The parameter would correctly predict the relative R for a...
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proposed refinement of superpave high temperature specification parameter for performance graded binders with discussion and closure
Transportation Research Record, 2001Co-Authors: Mark G Bouldin, Raj Dongre, John DangeloAbstract:A semiempirical approach developed to predict the viscoelastic response of a binder in repeated creep recovery tests is described. This model provides an avenue to predict the rut resistance (R) as a function of loading (time and load) and temperature from data at a single frequency or frequency sweeps when needed. Thus, it can be used to develop a grading procedure for asphalt binders that not only accurately captures the Delayed Elasticity of modified binders but also accounts for the effect of traffic speed and traffic loading. The current Superpave binder specification attempts to capture the relative high-temperature performance (i.e., resistance to rut) of a binder via the inverse shear loss compliance, 1/J" or G*/sin delta, at 10 rad/s. This parameter represents an improvement over the absolute viscosity because it is measured at a defined rate of deformation and accounts to some degree for the viscoElasticity of the binder via the phase angle. The parameter would correctly predict the relative R for an ideally viscous material or an ideally elastic material. However, there is mounting evidence that at phase angles between 40 deg and 75 deg, the parameter may not fully capture the viscoelastic nature of many modified binders. Various authors have shown that the R of mixtures can be well described by models using data from dynamic creep experiments, in which the mix is subjected to a load followed by a relaxation period. More recently, Bahia proposed to capture their high-temperature performance by using a similar technique on neat binders.
Nirmal K. Sinha - One of the best experts on this subject based on the ideXlab platform.
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Stress exponent and primary creep parameters using single specimen and strain relaxation and recovery test
Materials Science and Engineering: A, 2009Co-Authors: Nirmal K. SinhaAbstract:Strain relaxation and recovery test (SRRT), requiring one specimen and viscous (permanent) strain, ɛv (≤0.001 per test) on full unloading during primary creep, is presented with results on gas-turbine engine materials: Ti-6246 at 600 °C, Discaloy at 500 °C, IN-738LC at 850 °C and Waspaloy at 732 °C. It is shown that a ‘steady-state’ in irreversible viscous flow develops during primary creep; the shape of the creep curve is controlled by time-dependent reversible Delayed elastic (anelastic) response. The average viscous strain rate during primary-creep, e˙v(av)(=ev/tSR) for load duration, tSR and corresponding ɛv can be used for the determination of the stress exponent, nv for viscous flow. It is shown that the value of nv for primary-creep is comparable to the stress exponent, nmin for minimum creep rate. Using a single specimen, SRRTs also allow determinations of Young's modulus, stress exponent, s for Delayed-Elasticity (anElasticity), about one-third to fourth of nv, and other parameters for the constitutive equation for primary creep—strictly before creep enhancement due to the onset of microcracking activities. Short-term and long-term SRRT data on Waspaloy indicated that the creep strain at minimum creep rate consists of a significant amount of recoverable strain (32% at 450 MPa and 38% at 650 MPa).
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stress relaxation at high temperatures and the role of Delayed Elasticity
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2005Co-Authors: Nirmal K. Sinha, Shoma SinhaAbstract:Abstract Closed-loop controlled isothermal ‘constant-strain’ stress relaxation tests (SRT) at different strains led to the conclusion that SRT cannot provide the anticipated viscous strain rate over a wide stress range; the stress exponent for power-law creep was found to depend on strain. The recovery phase after SRT showed that Delayed Elasticity, not the viscous flow, controls relaxation processes during the primary stages of stress relaxation irrespective of the level of constraint. Viscous flow controls stress relaxation only at longer times exhibiting ‘apparently’ asymptotic approach to a quasi-stable stress rate. Limitations of SRT can be explained by formulating the relaxation processes on the basis of a three-component rheological equation, derived from independent isothermal constant-stress strain relaxation and recovery tests (SRRT). Theoretical predictions were made for the time-dependent recoverable (Delayed elastic) and permanent components of strain as functions of time and imposed strain. Experimental results exhibiting the short-coming of conventional experimental and analytical approaches and the strength of present formulations are illustrated by using a titanium-based, α–β, Ti–6Al–2Sn–4Zr–6Mo alloy at 600 °C (0.45 T m ) as a test material.
Kazumasa Matusita - One of the best experts on this subject based on the ideXlab platform.
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Delayed Elasticity in relaxation process of glasses far below the glass transition temperature
Journal of the Ceramic Society of Japan, 1998Co-Authors: Manabu Koide, Kazumasa MatusitaAbstract:Deformations of pre-annealed lead-silicate glass fibers were measured by the fiber-bending method during loading and unloading below the glass transition temperature. Burger model consisting of Maxwell and Voigt elements was used for the evaluation of Elasticity, Delayed Elasticity and viscosity. In the loading process, it was found that the deformation due to the viscosity increases with time. However, the deformation due to the Delayed Elasticity increases rapidly for a short time and decreases with further increase in time, In the temperature range of the measurement, the viscosity of Maxwell element, representing pure viscosity decreases with increasing temperature. The viscosity of Voigt element consisting of the Delayed Elasticity decreases with increasing temperature and is one magnitude order lower than that of Maxwell element. The elastic constant of Voigt element consisting of the Delayed Elasticity decreases slightly with increasing temperature. In the unloading process, the Delayed Elasticity was analyzed, assuming that the Elasticity of Voigt element is the same as that in the loading process.
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Delayed Elasticity and viscosity of silicate glasses below the glass transition temperature
Thermochimica Acta, 1996Co-Authors: Manabu Koide, Takayuki Komatsu, Kazumasa MatusitaAbstract:The viscosity of pre-annealed lead-silicate glass was studied below the glass transition temperature using the fiber-bending method. The viscosities were determined under conditions of loading and unloading. The Delayed Elasticity and its effect on the viscosity were also investigated. In the case of equal loading and unloading times, the viscosity was the same for the loading and unloading processes and the Delayed Elasticity was larger within shorter periods and smaller for longer ones. In addition, the time necessary for the recovery of the Delayed Elasticity increases with increasing loading time.
Jean-christophe Sangleboeuf - One of the best experts on this subject based on the ideXlab platform.
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A relationship between non-exponential stress relaxation and Delayed Elasticity in the viscoelastic process in amorphous solids: Illustration on a chalcogenide glass
Mechanics of Materials, 2015Co-Authors: Yann Gueguen, Vincent Keryvin, Bruno Bureau, Tanguy Rouxel, Mickaël Le Fur, Hervé Orain, Catherine Boussard-plédel, Jean-christophe SangleboeufAbstract:Inorganic glasses are viscoelastic materials since they exhibit, below as well as above their glass transition temperature, a viscoelas-tic deformation under stress, which can be decomposed into a sum of an elastic part, an inelastic (or viscous) part and a Delayed elastic part. The Delayed elastic part is responsible for the non-linear primary creep stage observed during creep tests. During a stress relaxation test, the strain, imposed, is initially fully elastic, but is transformed, as the stress relaxes, into an inelastic and a Delayed elastic strains. For linear viscoelastic materials, if the stress relaxation function can be fitted by a stretched exponential function, the evolution of each part of the strain can be predicted using the Boltzmann superposition principle. We develop here the equations of these evolutions, and we illustrate their accuracy by comparing them with experimental evolutions measured on GeSe 9 glass fibers. We illustrate also, by simple equations, the relationship between any kind of relaxation function based on additive contribution of different relaxation processes and the Delayed elastic contribution to stress relaxation: the Delayed Elasticity is directly correlated to the dispersion of relaxations times of the processes involved during relaxation.
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Room temperature viscosity and Delayed Elasticity in infrared glass fiber
Journal of the European Ceramic Society, 2007Co-Authors: Cédric Bernard, Gaëlle Delaizir, Jean-christophe Sangleboeuf, Vincent Keryvin, P. Lucas, Bruno Bureau, Xianghua Zhang, Tanguy RouxelAbstract:Infrared transparent optical fibers from the Te-As-Se system (TAS) exhibit a viscoelastic behavior at room temperature. The study of the change of the radius of curvature of fibers, once the fibers are unrolled from the mandrel onto which they were rolled just after fiber-drawing, allows the determination of constitutive laws both for the stress relaxation kinetics and for the Delayed Elasticity process. Whereas, a linear Burger's model provides a good modelling of the stress relaxation stage, a stretched exponential function gives a better description for the Delayed Elasticity behavior. The room temperature viscosity of the fibers ranges from 3 × 1016 to 2 × 1017 Pa s and the time constant of the anelastic strain recovery process is from 4 to 15 days.
Tanguy Rouxel - One of the best experts on this subject based on the ideXlab platform.
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A relationship between non-exponential stress relaxation and Delayed Elasticity in the viscoelastic process in amorphous solids: Illustration on a chalcogenide glass
Mechanics of Materials, 2015Co-Authors: Yann Gueguen, Vincent Keryvin, Bruno Bureau, Tanguy Rouxel, Mickaël Le Fur, Hervé Orain, Catherine Boussard-plédel, Jean-christophe SangleboeufAbstract:Inorganic glasses are viscoelastic materials since they exhibit, below as well as above their glass transition temperature, a viscoelas-tic deformation under stress, which can be decomposed into a sum of an elastic part, an inelastic (or viscous) part and a Delayed elastic part. The Delayed elastic part is responsible for the non-linear primary creep stage observed during creep tests. During a stress relaxation test, the strain, imposed, is initially fully elastic, but is transformed, as the stress relaxes, into an inelastic and a Delayed elastic strains. For linear viscoelastic materials, if the stress relaxation function can be fitted by a stretched exponential function, the evolution of each part of the strain can be predicted using the Boltzmann superposition principle. We develop here the equations of these evolutions, and we illustrate their accuracy by comparing them with experimental evolutions measured on GeSe 9 glass fibers. We illustrate also, by simple equations, the relationship between any kind of relaxation function based on additive contribution of different relaxation processes and the Delayed elastic contribution to stress relaxation: the Delayed Elasticity is directly correlated to the dispersion of relaxations times of the processes involved during relaxation.
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Room temperature viscosity and Delayed Elasticity in infrared glass fiber
Journal of the European Ceramic Society, 2007Co-Authors: Cédric Bernard, Gaëlle Delaizir, Jean-christophe Sangleboeuf, Vincent Keryvin, P. Lucas, Bruno Bureau, Xianghua Zhang, Tanguy RouxelAbstract:Infrared transparent optical fibers from the Te-As-Se system (TAS) exhibit a viscoelastic behavior at room temperature. The study of the change of the radius of curvature of fibers, once the fibers are unrolled from the mandrel onto which they were rolled just after fiber-drawing, allows the determination of constitutive laws both for the stress relaxation kinetics and for the Delayed Elasticity process. Whereas, a linear Burger's model provides a good modelling of the stress relaxation stage, a stretched exponential function gives a better description for the Delayed Elasticity behavior. The room temperature viscosity of the fibers ranges from 3 × 1016 to 2 × 1017 Pa s and the time constant of the anelastic strain recovery process is from 4 to 15 days.