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31.
A. I. Slutsker V. L. Hilyarov Yu. I. Polikarpov D. D. Karov 《Physics of the Solid State》2010,52(8):1637-1644
An elementary event in the kinetics of fracture of polymers, i.e., breaking of a stressed skeletal bond in a chain molecule,
has been simulated by the decay of a loaded quantum anharmonic oscillator. The probability and the average time of expectation
of the escape of a particle from the potential well in the Morse potential under the action of a tensile force have been calculated
over a wide range of temperatures. It has been demonstrated that the escape of the particle occurs predominantly through the
tunneling mechanism at low and medium temperatures and through a combination of the tunneling (under-barrier) and over-barrier
(thermal-fluctuation) mechanisms with comparable contributions at high temperatures. The calculations have revealed that the
participation of the tunneling mechanism in the kinetics of fracture of polymers manifests itself in a low-temperature athermal
plateau in the temperature dependence of the breaking strength. A comparison between the calculated and experimental temperature
dependences of the breaking strength for the oriented polymer polycaproamide has shown that the calculated and experimental
results are in qualitative and quantitative agreement, which allows the conclusion that the tunneling mechanism can contribute
to the fracture of polymers. 相似文献
32.
A. I. Slutsker A. B. Sinani V. I. Betekhtin A. A. Kozhushko A. G. Kadomtsev S. S. Ordanyan 《Physics of the Solid State》2008,50(8):1450-1457
A series of silicon carbide ceramic samples with variable characteristics of the microporosity and strength, such as the ballistic strength σ B and the static strength σ S , are investigated. The dependences of the strength on the integral porosity for ceramic materials are determined. It is established that the strength (both σ B and σ S ) is directly proportional to the average length of the bridges between micropores. The mechanism of the influence of microporosity on the strength of the ceramic materials is elucidated. According to this mechanism, interpore bridges are concentrators of stresses and, hence, are broken when a load is applied to the ceramic material. Numerous breakings of bridges bring about the failure of the ceramic body. The average stress concentration coefficient is estimated as a function of the integral porosity of the ceramic material. It is demonstrated that the static strength of the ceramic material is determined by the presence of large micropores (50–100 μm). 相似文献
33.
A. S. Vlasov E. L. Zil’berbrand A. A. Kozhushko A. I. Kozachuk A. B. Sinani A. I. Slutsker V. I. Betekhtin S. S. Ordan’yan 《Technical Physics》2004,49(5):583-586
The kinetics of penetration of deformable striking rods into SiC ceramics with different void content is studied. The penetration
may be viewed as a two-stage process. At the first stage, the penetration rate is minimal and the rate of contraction of the
rod is maximal. At this stage, the penetration resistance of the ceramic is the highest. At the second (quasi-steady-state)
stage, the penetration kinetics is similar to the kinetics of penetration into a zero-strength medium and resistance to penetration
is largely inertial. At the first stage, the penetration resistance is shown to correlate with the hardness of the ceramic
and depend strongly on the void content. 相似文献
34.
35.
D. W. Tomlin C. M. Roland L. I. Slutsker 《Journal of Polymer Science.Polymer Physics》1993,31(10):1331-1337
X-ray scattering from a series of poly(ethylene terephthalate) (PET) fibers spun at differet speeds is analyzed to probe the morphology in the direction transverse to the fiber axis. Both the apparent crystal modulus, determined from the change in wide-angle X-ray scattering angle with fiber stretching, and the transverse degree of crystallinity indicate there is a substantial interfiberillar amorphous content. In the PET fiber spun at conventional speeds, only roughly one-quarter of the fiber cross-section is actually occupied by fibrils. The transverse crystallinity increases for fibers spun at speeds sufficient to cause crystallization in the spin line. The X-ray moduli and fibril diameters are correspondingly larger in these high speed spun fibers. © 1993 John Wiley & Sons, Inc. 相似文献
36.
A. G. Makarov G. Ya. Slutsker I. V. Gofman V. V. Vasil’eva 《Physics of the Solid State》2016,58(4):840-846
The initial stage of stress relaxation, i.e., a decrease of the stress with time in an extended solid at a fixed length of the specimen, has been studied in oriented fibers of a linear polymer, polypropylene, chosen as the object of investigation. Experimental data have been obtained, and the stress in the object from the beginning of tensile loading of the specimen has been analyzed. It has been found that the stress relaxation caused by thermal fluctuation conformational transitions in stretched chain polymer molecules occurs from the beginning of the stretching of the polymer fiber. The time dependence of the stress relaxation of polypropylene fibers in all initial stages of deformation of the fibers has been elucidated. 相似文献
37.
Dielectric losses in poly(vinyl acetate) and poly(ethyleneterephthalate) polar polymers are measured in wide ranges of frequencies
and temperatures. The temperature dependences of the frequency of activation transitions of two types, small-scale and conformational,
are derived. For conformational transitions, it is revealed that the temperature dependence of their frequency exhibits nonlinear
behavior (in Arrhenius coordinates); it determines the temperature dependence of barriers to transitions and the defreezing
temperature of conformational dynamics (∼300 K for poly(vinyl acetate) and ∼370 K for poly(ethyleneterephthalate)). This temperature
is found to be close to the temperatures of the quantum defreezing of the molecular dynamics of poly(vinyl acetate) and poly(ethyleneterephthalate)
(∼300 and 400 K) according to IR spectroscopy data. It is assumed that a decrease in the barrier to the conformational transitions
that provide defreezing of the conformational dynamics is caused by a decrease that occurs in the rigidity of polymer molecules
owing to quantum defreezing of the vibrational molecular dynamics of the polymers. 相似文献
38.
Deformation of supermolecular structure elements of oriented crystalline polymers and nucleation of initial submicroscopic cracks induced by stress have been studied by the small-angle x-ray scattering technique. It is shown that the intrafibrillar amorphous interlayers have low strength and high deformability. The rupture of the weakest amorphous interlayers leads to nucleation of initial submicrocracks. The influence of submicrocracks on deformation around such cracks is revealed. The micromechanics of deformation and fracture of polymers is discussed. 相似文献
39.
Analysis of the energy distribution in an ensemble of quantum anharmonic oscillators loaded by an external force in a wide
temperature range (from T = 0) is carried out using a general approach based on the virial theorem. At T = 0, anharmonic effects are observed: a linear variation of zero-point energy of an oscillator under loading (energy decrease
during extension and increase under compression) and a linear variation of the average kinetic and potential energy components.
At high temperatures, at which the dynamics of the oscillators becomes classical, the anharmonic effects are manifested in
a linear variation in the vibrational energy and a linear variation in the average kinetic and potential energy components
upon an increase in force. Mutually compensating variation in the average kinetic and potential energy components of the internal
dynamic energy of an oscillator (energy redistribution upon loading) takes place both at low and high temperatures. 相似文献
40.
A. I. Slutsker 《Physics of the Solid State》2005,47(5):801-811
Experimental studies of the fracture kinetics of solids have shown that the process culminating in fracture of a stressed solid comprises a sequence of elementary events in which stressed atomic bonds are ruptured by local energy fluctuations. This recognition sparked investigations into elementary fracture events and into the fluctuations themselves that are responsible for bond rupture. Currently, only computer simulation of the dynamics of atoms offers the possibility of tracing, in considerable detail, the evolution of fluctuation events characterized by very short duration (~10?13?10?12 s). An analysis is made of the results obtained in computer simulation experiments on the temporal and spatial localization of atomic-energy fluctuations and atomic-bond strains, fluctuation migration, the mechanism of fluctuation formation, the role of anharmonicity in atomic interactions, and the magnitude of the volume activated in an elementary fracture event. 相似文献