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11.
V. V. Shpeizman P. N. Yakushev N. N. Peschanskaya Zh. V. Mukhina A. S. Shvedov V. G. Cheremisov A. S. Smolyanskii 《Physics of the Solid State》2012,54(6):1229-1234
The rate and magnitude of the deformation in polymers under constant compressive stresses at room temperature have been measured. The use of laser interferometer has made it possible to perform measurements at small intervals of variations in the specimen length Δl = 0.325 μm, and the analysis of the form of beats has made it possible to estimate oscillations of the strain rate in nanoscale displacements. It has been shown that the average strain rate of polymers continuously varies and no creeping interval with a constant rate is observed. At all stages of smooth variations in the average rate, jumps of its current values corresponding to Δl from several nanometers to a hundred and more nanometers have been found. Changes in the structure with an increase in the deformation manifest themselves in an increase in the size of nanoscale jumps and in a complication of their shape. 相似文献
12.
V.?V.?Shpe?zman N.?N.?Peschanskaya T.?S.?Orlova B.?I.?Smirnov 《Physics of the Solid State》2009,51(12):2458-2462
Inhomogeneity of the microplastic strain rate (deformation jumps) of a biomorphic SiC/Al composite under uniaxial compression
has been studied by laser interferometry on the nanometer level. The value of strain rate jumps has been calculated from the
deviation of the form of separate beats in the interferogram of a deformation from the standard form corresponding to a constant
strain rate within one beat. In addition to strain rate oscillations extended by 100–180 nm along the displacement (the variation
in the length of the specimen), peaks of small width and amplitude with a distance of 10–20 nm between them are observed,
as well as peaks with a width of ∼ 50 nm. These peaks may be associated with the sizes of structural formations of an aluminum
alloy (grains, subgrains, precipitates, etc.) or with the sizes of SiC nano- and microcrystals situated separately from large-grain
crystals and surrounded by residual carbon. The results of this work offer hope to the possibility of enhancing plasticity
and strength of biomorphic composites by increasing the fraction of fine-grain elements (< 1.5 μm) in their structure. 相似文献
13.
The parameters of microdeformation jumps for copper, aluminum, titanium, and Armco iron with the initial (annealed) structure and after equal-channel angular pressing are investigated in a creep mode under low compressive stresses. The strain rate is measured with a laser interferometer in 0.15-μm linear displacements. It is demonstrated that the values of the microstrain rate and the mean sizes of jumps for the annealed metals are larger than those for the metals subjected to severe deformation. It is revealed that there is a correlation between the jumps of microplastic deformation and the size of nanometal grains. The inference is made that, for nanostructured metals, as for other materials, the structural heterogeneity is one of the factors responsible for the jumplike deformation. 相似文献
14.
Using precision interferometric methods, we were able to record changes in the characteristics of discontinuous creep of glassy
polymers brought on by preliminary treatment with weak external fields. For the example of a polymer composite we have shown
that the long-period application of small loads and a constant magnetic field greatly reduces the nonuniformity of the creep
rate at large stresses, i.e., it decreases the suddenness of abrupt deformations. After separating the effects of the magnetic
and force fields, we concluded that the effects resulting from not only stress but also magnetic fields have partially reversible
character. Our data confirm that a constant magnetic field affects the local potential barriers that inhibit strain in nonmagnetic
materials.
Fiz. Tverd. Tela (St. Petersburg) 40, 681–683 (April 1998) 相似文献
15.
N. N. Peschanskaya P. N. Yakushev V. M. Egorov V. A. Bershtein L. Bokobza 《Physics of the Solid State》2002,44(9):1684-1688
The morphological nature of discontinuous (jumplike) deformation is studied. Recording creep behavior of materials using a laser interferometer permits one to determine the parameters of deformation jumps on a micron scale. The objects of investigation were poly(dimethylsiloxane) (PDMS) and a composite material consisting of PDMS and quartz (SiO2). It is shown that the height and sharpness of jumps depend on the composition of the material and the stage of deformation. An analysis of differential scanning calorimetry (DSC) curves of the materials in the deformed and initial states suggests that deformation results in ordered domains in rubberlike polymers. This confirms the assumption that deformation jumps reflect the presence and the evolution of structural inhomogeneities in amorphous polymers. 相似文献
16.
N. N. Peschanskaya 《Physics of the Solid State》2001,43(8):1478-1482
The variation of step deformation kinetics in solids is studied as a function of morphological factors. Oscillations of creep rate at micrometer increments of the amount of deformation, which reflect the step nature of the process, are investigated from an interferogram. It is shown that the plasticization of polymethyl methacrylate by dibutyl phthalate blurs the steps, while their height varies insignificantly. The results are explained using the concept of the netlike structure of amorphous polymers. The data obtained confirm the universal nature of jumps as a mode of evolution of deformation in various solids. The jumps reflect the cooperative nature of motion of kinetic units, and the regular variation of the characteristics of the jumps lends support to the definition of creep as a process of structural self-organization. 相似文献
17.
The authors have investigated changes in the lifetimes of polymethylmethacrylate, polyethylene, and polystyrene resulting from prestressing. They show that, according to the temperature, stressing can cause either an increase or a decrease in the lifetime.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 176–178, January–February, 1972. 相似文献
18.
N. N. Peschanskaya P. N. Yakushev L. P. Myasnikova V. A. Marikhin M. J. Jacobs 《Physics of the Solid State》1997,39(3):505-509
The study of stepped creep, previously discovered with micron-size deformation increments (ɛ) of polymers, in the form of a variation of the rate near the average value is continued. A scheme based on a laser interferometer
was used to record the creep; this made it possible to perform precise measurements. Attention was focused on the degree of
scatter of the rate h in the process of deformation of polyethylene fibers. It is shown that the creep rate of textured fibers is extremely nonuniform
and pulsates continuously, forming beats of different periods, i.e., deformation jumps of different height. The ratio of h of the highest to the lowest rate for arbitrarily chosen small increments of the deformation has a maximum near the start
of the “flow” stage and prior to fracture. The h-ɛ curve shifts along the deformation scale as the polymer structure changes, but the form of the curve and the overall level
of h change very little. It is also established that the value of h for identical deformations is higher in more highly oriented polymers, and the value of h is higher in cross-linked structures than in unmodified structures. It is proposed that h reflects not only the deformation heterogeneity, but also influences crack formation during the creep process.
Fiz. Tverd. Tela (St. Petersburg) 39, 580–585 (March 1997) 相似文献
19.
N. N. Peschanskaya P. N. Yakushev V. A. Bershtein M. Keating T. Krizan 《Physics of the Solid State》2005,47(5):949-953
This paper reports on the results of research into the jumplike deformation of two polymers based on poly(oxymethylene) (POM) with structural aggregates (spherulites) of different micrometer-scale sizes at a temperature of 290 K, as well as of polyimide (PI) and a PI + graphite composite at temperatures of 290 and 690 K. The creep rate under compression is measured with a laser interferometer in 0.3-μm deformation increments. It is found that, in the course of deformation on the micrometer scale, the creep rate varies nonmonotonically. Periodic variations of the creep rate correspond to a jumplike (stepwise) behavior of the creep. It is shown that the mean jumps in the microdeformation correspond to the mean sizes of poly(oxymethylene) grains and graphite particles in polyimide. The results obtained are in agreement with previously drawn conclusions: the deformation jumps are determined by the scale of ordered microaggregates typical of the structure under investigation. 相似文献
20.
The inhomogeneity in the creep rate of polymers on different scales of deformation has been studied by laser interferometry.
The main results have been obtained for the amorphous-crystalline polymer polytetrafluoroethylene. The deformation characteristics
are the oscillation periods of the rate (jumps of deformation), oscillation amplitudes of the rate, and the scatter of these
quantities. Application of computer methods for processing of the results has made it possible to determine the difference
and similarity between jumpwise deformations on different structural levels, including the nanolevel. For a more distinct
separation of deformation levels, the measurements have been made in a magnetic field and outside the magnetic field. Deformation
jumps have been found on five levels: from 4 nm to more than 10 μm. Introduction of a sample into a magnetic field changes
the characteristics of jumps; in this case, the scatter in the values of jumps always increases, whereas their average value
varies differently on different scale levels. The measurement of the parameters of deformation jumps on different scales allows
one to study the laws of the development of the deformation process and the evolution of structural inhomogeneities. 相似文献