Creep of fluoroplastic under the joint action of tension and hydrostatic pressure

Conclusions 1. The effect of hydrostatic pressure on the creep of Teflon has been investigated under isothermal conditions. The applicability of the principle of reduced variables for reduction of creep curves with respect to pressure has been shown.2. It has been ascertained that in the pressure region from atmospheric to 1600 kgf/cm² there are two subregions, which are separated by a transition at a pressure of 700–800 kgf/cm². It has been shown that in these subregions the occurrence of relaxation processes has different characters.3. A direct measurement of the free volume of Teflon has been made in the temperature range from 40 to 120°C. A sharp increase in free volume in the region of the temperature transition has been shown.Leningrad Technological Institute of the Refrigeration Industry. Okhtinsk Scientific and Industrial Union "Plastpolimer," Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 434–438, May–June, 1977.     

The effect of rate of deformation on the mechanical characteristics of plastics

An experimental investigation of the effect of the rate of deformation on the strength and modulus of elasticity of vinyl plastic and glass-reinforced laminate is described. It is established that when the rate of relative tensile deformation of vinyl plastic at 25°C is reduced from 2000×10^–6 sec^–1 to 5×10^–6 sec^–1, and that for glass-reinforced laminate from 1000×10^–6 sec^–1 to 1.3×10^–6 sec^–1, the decrease in the modulus of elasticity is about 40% and the decrease in ultimate strength 30 and 48%, as the case may be.Mekhanika polimerov, Vol. 1, No. 1, pp. 76–81, 1965     

Experimental study of young's modulus of glass-plastics

The results of study of Young's modulus of glass-plastics in the 10^–1–10⁵-Hz frequency range are presented. A stepwise variation in the modulus, which governs the relaxation process corresponding to a low-temperature internal-friction peak in the filler, is obtained.Rybinsk Institute of Aircraft Technology. Translated from Mekhanika Polimerov, No. 6, pp. 1089–1091, November–December, 1975.     

On the number of relaxation regions in polyformaldehyde

The mechanical relaxation of a polyformaldehyde homopolymer free from surface grease and the additives normally used as stabilizers has been studied at a frequency of 10^–2 Hz in the temperature region 77–413°K. Six relaxation regions are observed on the curve of tangent of angle of mechanical losses as a function of temperature.T. G. Shevchenko Kiev State University. Translated from Mekhanika Polimerov, No. 5, pp. 925–927, September–October, 1973.     

Dynamic properties of some polymer materials in loading and unloading

A series of quasi-static tests have been carried out on kapron fiber, vinyl plastic, and fluoroplastic specimens with small cross sections. Stress-strain diagrams have been obtained at strain rates from 1 · 10^–3 to 1 · 10² sec^–1. In the experiments the strain rate changed sign, which corresponded to loading and unloading. In each regime the strain rate remained constant. The experimental data are analyzed using the model of a standard linear viscoelastic solid.Mekhanika Polimerov, Vol. 3, No. 1, pp. 118–122, 1967     

Action of a powerful light beam on polypropylene film

The changes in the supermolecular structure of polypropylene films exposed to powerful light pulses have been investigated by optical microscopy. A pulse lasting 10^–3 sec produces melting of the polymer with subsequent recrystallization and the formation of a finely spherulitic structure. In connection with the change in supermolecular structure there is an increase in the breaking stress of the melted portion of the film. A pulse lasting 2·10^–8 sec causes melting and vaporization of individual parts of the spherulites in the irradiated region. The remainder of the polymer is such that orientation of the structural elements with respect to the radius—the maltese cross pattern of the original spherulites—is preserved.Mekhanika Polimerov, Vol. 2, No. 6, pp. 817–822, 1966     

Exact analysis of asymmetric random polling systems with single buffers and correlated input process

We introduce a simple approach for modeling and analyzing asymmetric random polling systems with single buffers and correlated input process. We consider two variations of single buffers system: the conventional system and the buffer relaxation system. In the conventional system, at most one customer may be resided in any queue at any time. In the buffer relaxation system, a buffer becomes available to new customers as soon as the current customer is being served. Previous studies concentrate on conventional single buffer system with independent Poisson process input process. It has been shown that the asymmetric system requires the solution ofm 2 ^m –1) linear equations; and the symmetric system requires the solution of 2 ^m–1–1 linear equations, wherem is the number of stations in the system. For both the conventional system and the buffer relaxation system, we give the exact solution to the more general case and show that our analysis requires the solution of 2 ^m –1 linear equations. For the symmetric case, we obtain explicit expressions for several performance measures of the system. These performance measures include the mean and second moment of the cycle time, loss probability, throughput, and the expected delay observed by a customer.     

Mass-spectrometric investigation of solid lubricating coatings subjected to friction in a deep vacuum

The life of solid lubricating coatings of the VNII NP type, based on molybdenum disulfides and various binders, has been experimentally investigated under deep vacuum conditions (10^–8–5 · 10^–9 torr) together with the composition of the gas released in the friction process. It is shown that both under atmospheric conditions and in a deep vacuum the life of the coatings depends on the chemical nature of the film-former. The depth of the vacuum also has an important influence on the life of the coatings, both the mechanism and the end result of this effect depending to a large extent on the physicochemical properties of the bind. On the interval 10^–1–10^–2 torr there is a sudden change in the life of the coating.Physicotechnical Institute of Low Temperatures, Academy of Sciences of the Ukrainian SSR, Khar'kov. Translated from Mekhanika Polimerov, No. 6, pp. 1070–1075, November–December, 1970.     

Effect of cycle asymmetry on the cyclic strength of polymers

Cyclic strength diagrams have been obtained for polymethyl methacrylate and kaprolon at different degrees of loading asymmetry (from a pure compression to a pure tension cycle) on the interval from –100 to +80° C at 2·10³ and 3·10⁵ cycles.M. I. Kalinin Leningrad Polytechnic Institute. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 948–951, September–October, 1968.     

Deformations and stresses around submicroscopic cracks in loaded polymers

Structure deformations upon loading of oriented films of polycaproamide (Kapron) or polypropylene when submicroscopic cracks (dimensions of hundreds of Ångstroms) have appeared in the samples in high concentration (up to 2 · 10¹⁵ cm^–3) have been studied by x-ray diffraction methods at low and large angles. It has been established that the appearance of submicro-cracks causes relieving of the regions adjacent to them along the loading axis (extent about 1000 Å) and an increase in stress in the lateral zone relative to the crack, which is manifested in an intensification of the stretching of these zones.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 51–58, January–February, 1972.     

Effect of temperature on the chemical relaxation process in rubbers

The effect of temperature on the chemical relaxation of rubbers has been investigated. With reference to nine industrial rubbers it has been shown that during storage in the stressed state (at =const) chemical relaxation is chiefly determined by two processes proceeding at different rates. Furthermore, the chemical relaxation of rubbers is determined not only by the rate constants of these two processes but also by the pre-exponential constants C_0i, the relationship between which varies with increase in temperature. It is possible to extrapolate the rate constants (k_i) and pre-exponential constants (C_0i) from elevated temperatures (110–50° C) to temperatures in the range 20–25° C. An equation is proposed that makes it possible to calculate the change in the elastic properties of rubbers in the stressed state at storage temperatures (20–25° C) by means of results obtained at elevated temperatures.Mekhanika Polimerov, Vol. 3, No. 3, pp. 448–454, 1967     

Dielectric investigation of the molecular mobility of silicone ladder polymers

Dielectric spectroscopy has been used to study the molecular mobility in polyphenylsilsesquioxane, polyphenylisobutylsilsesquioxane with a 1:1 ratio of phenyl to isobutyl groups, and poly-m-chlorophenylsilsequioxane on the temperature interval from –196 to 300°C at frequencies from 10² to 10⁶ Hz. The investigation was carried out in air and in a nitrogen atmosphere. The flexibility mechanism of silicone ladder polymers is considered and the development of molecular mobility is shown to be discrete.Institute of Heteroorganic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 3–7, January–February, 1976.     

Strength of glass laminates at low temperatures and high strain rates

The tensile strengths of glass laminates of various compositions under standard, high-speed and impact loading have been experimentally investigated in relation to the effect of low-temperature and stress raisers. As the loading rate increases (from 0.7 to 253 · 10³ kgf/cm². · sec) and the temperature falls to –196° C, the effective stress concentration coefficient decreases, which indicates that the glass laminates will perform adequately under these conditions.All-Union Scientific-Research Institute of Aviation Materials, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 836–841, September–October, 1970.     

Polymer fractography and fracture kinetics

The fractographic method makes it possible to determine the test temperature and time at which anomalies appear in the temperature-time dependence of the strength of polymethyl methacrylate and polycaprolactam by finding the conditions of disappearance of specular zones from the fracture surfaces of these polymers. For PMMA these values are –40°C and 10^–2 sec, for PCL –120°C and 10^–7 sec, respectively.For communication 1 see [2].Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 232–237, March–April, 1971.     

Dynamic modulus of polymethylmethacrylate saturated with carbon dioxide

The authors have devised a method for measuring the complex modulus of elasticity of non-plasticized polymethylmethacrylate of grade ST-1-110 in an atmosphere of carbon dioxide. The pressure of the saturated gas in the working chamber was varied between 4·10⁵ and 60·10⁵ N/m², and the experiments were performed at 18–90°C.S. M. Kirov Ural Polytechnic Institute, Sverdlovsk. Translated from Mekhanika Polimerov, No. 2, pp. 370–372, March–April, 1974.     

Failure of water-filled cylindrical glass-reinforced epoxy shells under internal impulsive loading

Conclusions 1. The explosive failure of water-filled, geometrically similar glass-reinforced epoxy shells, whose dimensions increase by a factor of 1.5–4.4, is not associated with an energetic scale effect. This is attributable to the imperfect similarity of the shells, since although their dimensions changed, the diameter of the glass reinforcing fibers remained the same.2. The relative mass of explosive required to fracture the shells is approximately 0.4%. With respect to this index, glass-reinforced epoxy is comparable to structural steels 20 and 17Mn1Si at R₀160 mm.3. The circumferential deformation of the shells at failure is about 4% and does not depend on the thickness of the shell wall, the dimensions of geometrically similar shells, or the initial strain rate on the interval 0.21 · 10³–1.2 · 10³ sec^–1. Thin-walled shells begin to fail from the outside surface, thick-walled shells from the inside surface.4. The modulus of elasticity of the GRE is 2.4 · 10⁵ kgf/cm² and does not depend on the strain rate on the interval 10^–3–1.5 · 10³ sec^–1. The material deforms elastically up to failure.Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 283–289, March–April, 1978.     

Relaxation and optical properties of cured epoxy resin

Epoxy resin cured with methyltetrahydrophthalic and maleic anhydrides has been tested in relaxation, creep, and compression at constant strain rate. The constants characterizing the relaxation properties and the approximate limits of the spectrum of most probable relaxation times have been determined; it is shown that the mechanical properties can be described by means of equations with two relaxation times. The residual optical effect has also been investigated. A linear relationship between the high-elastic strains and the path difference in the birefringent state is preserved at temperatures below the glass transition region.Read at Moscow State University polymer mechanics seminar.Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 15–23, January–February, 1970.     

Strength of boron fibers

The tensile and flexural strength and elastic properties of continuous boron fibers 95–105 µ in diameter obtained by depositing boron on a tungsten filament 10–12 µ in diameter have been investigated. The strength properties are primarily determined by the defects present at the boron sheath-core interface and for the fibers investigated have a limit of approximately 400 kgf/mm². Coarse surface or internal defects are capable of reducing the strength of the fibers to 200–250 kfg/mm².All-Union Scientific-Research Institute of Aviation Materials, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1126–1127, November–December, 1970.     

The dynamic properties of polyethylene and an acrylonitrile — Butadiene — Styrene material in a broad range of temperature and strain-rate variation

Conclusions The mechanical properties of an acrylonitrile-butadiene-styrene material and polyethylenes of densities =0.92 and 0.96 g/cm³ are studied within the temperature range of from 100 to –196°C and at strain rates of from 10^–3 to 1.3 · 10³ sec^–1. It is observed that under low-temperature and high-strain-rate conditions, the laws governing the mechanical properties of the acrylonitrile-butadiene-styrene material and polyethylenes are similar. Regions of strain rates and temperatures are found for which the behavior of the test materials is in good agreement with the Ree-Eyring equation, and, consequently, conforms to a temperature-time analogy. No embrittlement of the polyethylene is observed during tests at strain rates to 1.3 · 10³ sec^–1 and temperatures down to –196°C. In approximating these values of and T, the mechanical properties of polyethylenes will cease to be dependent on initial density.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, 1027–1033, November–December, 1978.     

Changes in the mechanical properties of polycarbonate produced by a powerful light flux

The effects of a laser beam on PC are examined in relation to the power and duration of the light pulse. In uniaxial tension there is a sharp change in the relative elongation of the irradiated specimens (pulse length 10^–3 sec); the elastic modulus and the molecular weight remain unchanged. Irradiation of PC with a giant pulse does not affect its mechanical properties.Mekhanika Polimerov, Vol. 4, No. 2, pp. 288–292, 1968