scholarly journals FEATURES OF QUANTITATIVE MEASUREMENTS OF THE DYNAMIC MODULE OF ELASTICITY OF BINDERS IN OPTIMIZATION OF PRODUCTION TECHNOLOGY SEROGYPSUM COMPOSITE

2021 ◽  
pp. 86-92
Author(s):  
V.I. Tarasevych ◽  
◽  
Yu.G. Gasan ◽  
V.B. Dolgoshey ◽  
◽  
...  
Keyword(s):  
Time Dependence ◽  
Structure Formation ◽  
Elastic Properties ◽  
Physicochemical Characteristic ◽  
Resonance Method ◽  
Acoustic Resonance ◽  
Mechanical Action ◽  
Bending Vibrations ◽  
Damping Decrement ◽  
Kinetics Of

The paper considers the issues of studying the structure formation of binders during hardening to determine the optimal moments of mechanical action on gypsum concrete specimens, which makes it possible to optimize the technology of their impregnation with sulfur melt. The time dependence of the elastic modulus of a hardening, binder is its important physicochemical characteristic, since it is used to objectively identify the stages of structure formation, to simulate the processes occurring at each of the stages. It is noted that the method of acoustic resonance of bending vibrations, in the case of hardening binders, needs correction with respect to the measurement technique and interpretation of the results obtained. The kinetics of the resonance frequency of a sample consisting of a rigid cell and a dispersion poured into it is a function of the elastic properties of the cell, the dispersion itself, the contact zone of the dispersion with cell and therefore cannot be used for either qualitative or quantitative analysis of the kinetics of hardening. Taking into account the elasticity of cuvette is necessary to obtain reliable information. It has been established that in the presence of shrinkage or significant expansion of the binder, the study of structure formation by the resonance method should be carried out in plastic cuvettes. Regardless of shrinkage, the use of a cuvette requires compulsory consideration of its elastic properties. It is advisable to objectively distinguish the stages of structure formation on the basis of the kinetics of not the dynamic modulus of elasticity itself, but the rate of its change. The time dependence of the logarithmic damping decrement is also an important characteristic of the concrete structure. The studies carried out make it possible to obtain serogypsum composites with the necessary performance characteristics and to manufacture elements of architectural décor, wall fencing products of increased aesthetics, durability and reliability from them.

Elastic Properties of Steps at Interphase Boundaries

1991 ◽  
Vol 238 ◽  
Author(s):  
G. J. Shiflet
Keyword(s):  
Energy Density ◽  
Elastic Properties ◽  
Mathematical Analysis ◽  
Strain Energy ◽  
Chemical Processes ◽  
Diffusion Kinetics ◽  
Interphase Boundaries ◽  
Kinetics Of ◽  
Maximum Stresses

ABSTRACTStresses are introduced in crystals at interphase boundaries where steps improve the registry of atoms. A model and mathematical analysis based on an approach previously taken by van der Merwe and Shiflet1–4 of the problem incorporating a coherent step are presented. Computed distributions of stresses, strains, dilatation and energy density in the form of contours and nets are given for a coherent monatomic step. It is concluded that the maximum stresses are quite large and the fields decay fairly rapidly with distance from the steps, the gradient of dilatation around steps will significantly affect diffusion kinetics of impurities and the strain energy seems too low to significantly enhance chemical processes.

Radiation damage in polyethylene as studied by electron spin resonance

1961 ◽  
Vol 262 (1309) ◽  
pp. 207-218 ◽  
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Alkyl Radical ◽  
Room Temperature ◽  
Chemical Properties ◽  
Resonance Method ◽  
Alkyl Radicals ◽  
Spin Resonance ◽  
Physical And Chemical ◽  
Kinetics Of

The electron spin resonance method was employed to study the nature, concentration and kinetics of the disappearance under varying conditions of radicals produced in polyethylene by fast electron irradiation at 77°K. The predominant radical species at 77°K is the alkyl radical —CH 2 —ĊH—CH 2 —. On being warmed to room temperature it disappears rapidly, revealing a more stable un­identified radical. The kinetics of the decay at room temperature of both radicals was observed. Their stabilities were found to vary in polyethylene samples of differing physical and chemical properties. G values for these radicals are given. Comparison was made with spectra obtained under similar conditions with two pure paraffins and a pure olefin to evaluate the effect of crystallinity branching, molecular weight and unsaturation. In the olefin there is evidence for a build-up of allyl radicals due to the encounter of an alkyl radical with main chain unsaturation. This supports the view that alkyl radicals are mobile, and cross-linking occurs when two such radicals meet.

DELAYED RESPONSE IN TRACER EXPERIMENTS AND FRAGMENT-CARRIER APPROACH TO TRANSIT TIME DISTRIBUTIONS IN NONLINEAR CHEMICAL KINETICS

2002 ◽  
Vol 12 (11) ◽  
pp. 2599-2618 ◽  
Author(s):  
MARCEL O. VLAD ◽  
JOHN ROSS ◽  
FEDERICO MORAN ◽  
YOEL RODRIGUEZ
Keyword(s):  
Time Dependence ◽  
Transit Time ◽  
Evolution Equations ◽  
Kinetic Equations ◽  
Mass Action ◽  
Rate Coefficients ◽  
Delayed Response ◽  
Linear Superposition ◽  
Highly Nonlinear ◽  
Kinetics Of

A delayed response tracer experiment is suggested, based on the following constraints: (1) The kinetics of the process can be expressed by local evolution equations without delays, for example by the mass action law. (2) The kinetic isotope effect can be neglected, that is, the rate coefficients for labeled and unlabeled chemicals are the same. (3) The total fluxes of the various chemicals are generally time dependent, but are not modified by the presence of the labeled compounds. (4) The experiment consists in the measurement of the time dependence of the fractions βu, u = 1, 2,… of labeled chemicals in the output fluxes as functionals of the time dependence of the fractions αu, u = 1, 2,… of labeled chemicals in the input fluxes, which are controlled by the researcher. We show that the output fluxes are related to the input fluxes by a linear delayed superposition theorem: βu(t) = ∑u′ ∫ χuu′(t,t′)αu′(t′)dt′, where χuu′(t,t′), is a delayed susceptibility function, which is related to the probability density of the transit time, that is, the time necessary for a molecular fragment to cross the system. This linear superposition law is not the result of a linearization procedure and holds even if the underlying kinetic equations are highly nonlinear. We establish a relationship between the transit time probability densities and the lifetime distributions of the various species in the system. The law permits extracting information about the mechanism and kinetics of chemical processes from response experiments.

Characterization of impact fatigue damage in CFRP composites using nonlinear acoustic resonance method

2020 ◽  
Vol 253 ◽  
pp. 112804 ◽  
Author(s):  
Qin Wei ◽  
Liyong Zhu ◽  
Jianguo Zhu ◽  
Lijun Zhuo ◽  
Wenfeng Hao ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Resonance Method ◽  
Acoustic Resonance ◽  
Impact Fatigue ◽  
Cfrp Composites ◽  
Nonlinear Acoustic
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