"Freezing" and "defreezing" effects in the photoelastic investigation of temperature stresses

The "freezing" and "defreezing" temperature limits of an optically active material based on an epoxy resin have been experimentally investigated. A method of determining the mean value of the optical coefficient when the material is heated on the "freezing" temperature range is considered. The lower "defreezing" temperature limit has been experimentally established. The results of the investigation are presented in the form of graphs.Translated from Mekhanika Polimerov, No. 3, pp. 501–506, May–June, 1976.     

Effect of the rate of deformation on the mechanical properties of compact bone tissue

Conclusions The results of this study show that the ultimate stress increases with increasing deformation rate from 10^–5 to 1 sec^–1 but the initial elasticity modulus remains virtually constant. A characteristic feature of bone tissue is the significant increase or even maximum in specific deformation energy for destruction in the range of deformation rates corresponding to normal physiological conditions for bone function. The deformation diagrams of human bone tissue for the same values of moisture content and deformation rate in tensile testing do not differ from the analogous curves for the bone tissue of cattle. Quantitatively, the ultimate stress ₁₁ and the initial elasticity modulus E₁ are 5–10% and 15–25% greater, respectively, than for cattle bone tissue, while the ultimate deformation eu is virtually the same. An increase in the moisture content of bone tissue leads to a more pronounced dependence of the mechanical parameters on the deformation rate.Translated from Mekhanika Kompozitnykh Materialov, No. 3, pp. 512–517, May–June, 1982.     

Effect of loading on intensity of fracture and deformation of polymers

An expression is proposed for the activation energy U = U₀ –a + b², by means of which it is possible qualitatively to describe the various cases of the kinetics of deformation and rupture in polymers.Scientific-Research Institute of Plastics, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 366–368, March–April, 1972.     

Inelastic deformation and fracture of disordered fiber-reinforced composites

Conclusions Simulation of the process of nonlinear deformation and failure in the structure of a unidirectional epoxy glass plastic under transverse loading has indicated that equilibrium regions of failure receiving only hydrostatic compressive loading may form. The development of this region explains the high (up to 40%) nonlinearity of deformation diagrams under transverse biaxial compressive loading. The regions of nonlinear deformation of the epoxy matrix affect less markedly the nonlinearity of the macroscopic s* diagrams. This fact and also the formation and avalanchelike propagation of regions of complete failure explain the linear form of many diagrams corresponding to tensile and shear loading in the transverse plane. The relations of the nonlinear theory of elasticity make it possible to describe with sufficient accuracy the entire set of the calculated diagrams.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 5, pp. 621–628, September–October, 1993.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 5, pp. 621–628, September–October, 1993.     

Viscoelasticity of a curing epoxy composition in the "critical branching" region

The curing of an epoxy resin in the "critical branching" region has been investigated by mechanical and infrared spectroscopy. It is shown that the effective molecular weight between network points (M_c) during the polymerization of an actual system can be determined from the relaxation spectrum in the curing stage investigated.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 154–158, January–February, 1976.     

Solution of the problem of the plane deformation of a tube made of physically nonlinear quadratic viscoelastic material

An exact solution is obtained for the problem of the plane deformation of a tube of quadratically nonlinear viscoelastic material characterized by four kernels. For given boundary pressures the solution contains functions determined from simple creep and relaxation tests for stresses and strains lying in the region of linearity of the relation. In accordance with the method of approximations for nonlinear materials [9], an approximation is given for a series of convolution integrals of increasing multiplicity in transforms and inverse transforms together with an error estimate.Moscow Institute of Electronic Engineering. Translated from Mekhanika Polimerov, No. 1, pp. 117–123, January–February, 1973.     

Compound vibrator method of determining the complex deformation characteristics of polymeric materials

The propagation velocities c and logarithmic decrements in the longitudinal and shear modes, used for calculating the complex deformation characteristics of polymeric materials, can be simultaneously determined by means of a compound vibrator with a mechanical clamp. Relations are obtained for determining c and when the other end of the specimen is free or fixed and with allowance for the mechanical losses in the measuring rod. The method has been tested on specimens of P-4020E polyethylene at various temperature.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 116–123, January–February, 1970.     

Analysis of the tensile deformation of glass-reinforced plastics

The deformation of an orthotropic glass-reinforced plastic is considered with allowance for the failure of the resin in the transverse layers.Ordzhonikidze Moscow Aviation Institute. Translated from Mekhanika Polimerov, No. 1, pp. 144–147, January–February, 1970.     

Study of the two-dimensional deformation of polymers

The effect of two-dimensional deformation on the mechanical properties of films made from the hydrochloride of polyisoprene rubber is studied. The laws determining the reversible deformation of films when _y=0 are investigated. The results obtained are discussed in relation to supramolecular structures in polymers.Mekhanika Polimerov, Vol. 1, No. 2, pp. 21–26, 1965     

Predicting the deformation properties of polymers

Physically well-founded relations, following from a consideration of the molecular-kinetic nature of the relaxation processes, are proposed for the time-temperature superposition principle. It is shown that the well-known Williams—Landel—Ferry relation is a particular case of more general formulas.V. I. Lenin Moscow State Pedagogical Institute, Problem Laboratory of Polymer Plastics. Translated from Mekhanika Polimerov, No. 6, pp. 1106–1109, November–December, 1971.     

A model of the deformation of a thick-walled composite ring under the action of pressure

A model is examined for the deformation of a ring of unidirectional composite under the action of pressure which permits one, to a first approximation, to take account of the nonlinearity of the - relationship on compression of the composite perpendicularly to the fibers. It is shown that this feature of the material leads to a considerable overloading of the ring coils from the side of the applied pressure. The results obtained qualitatively explain some of the known experimental evidence on the strength of thick-walled rings.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1087–1092, November–December, 1972.     

An experimental study of the deformation of multilayer cylindrical shells

Experimental results are presented on the deformation of two-layer and four-layer reinforced shells subject to static loading. The strains on the outside and inside surfaces are unequal at points remote from the region of the edge effect when the shell is subject to an internal pressure and an axial force.P. I. Baranov Central Institute for Aviation Engine Design. Translated from Mekhanika Polimerov, No. 5, pp. 943–944, September–October, 1973.     

Kinetics and consequences of "bleeding" of volatiles from plexiglas

The authors have studied the kinetics of "bleeding" during the heating of oriented and non-oriented plexiglas with accrued operating times of up to 16,000 h. They show that bleeding of the products of degradation of macromolecules from plexiglas is accompanied by a decrease in the volume of the polymer, which causes tensile stresses in the surface layers and may lead to surface cracking."Lenin Komsomol" Riga Red Banner Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 2, pp. 346–348, March–April, 1974.     

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     

Relation between fracture and deformation in oriented polymers

The development of submicroscopic cracking under load has been studied (by a small-angle X-ray scattering technique) in such oriented polymers as Kapron (Nylon 6), polypropylene, etc. The increase in crack density (N_cr) is compared with the variation of the tensile strain (). The observed correlation between and N_cr indicates that the processes of fracture and deformation of oriented polymers are closely connected. The presence of a similar correlation in loading-relaxation-repeat loading experiments establishes fracture as the primary process.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 43–47, January–February, 1970.     

Contribution to the theory of forced high-elastic deformation of polymer materials

The large reversible and irreversible deformations of network polymers are examined. Expressions are derived for the stress tensor and for the conventional tensile stress. The uniaxial homogeneous extension curve has a maximum and a minimum if it is assumed that the coefficient of friction depends exponentially on the applied stress. The "necking" condition is derived for uniaxial tension. The results are compared with the experimental data.Mekhanika Polimerov, Vol. 4, No. 2, pp. 255–262, 1968     

Dependence of the crystallization kinetics of cis-1,4-polybutadiene vulcanizates on the type and degree of deformation

The effect of tension and compression on the crystallization rate of cis-1, 4-polybutadiene vulcanizate has been investigated. The crystallization kinetics of deformed specimens were studied by measuring the stress relaxation. A linear relation, common to tension and compression, was observed between the logarithm of the crystallization half-period (log _1/2) and the true stress in the specimens before the onset of crystallization. The crystallization time of the unstressed specimen can be found from the intersection of the straight line with the log _1/2 axis. The dependence of log _1/2 on the degree of deformation is linear only in the region of relatively small strains.Lebedev All-Union Scientific-Research Institute of Synthetic Rubber, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 929–931, September–October, 1970.     

Characteristic features of the deformation process on creep and secondary creep of polymers under conditions of monaxial tensioning. Part I

Experiments carried out in the field of linear and nonlinear creep of a filled polyethylene and Teflon resin, including two complete cycles of creep and deformation recovery at monaxial tensioning, show that the bulk deformations (t) change nonmonotonically, and relationships computed by summation of terms containing a function of time cannot be used to approximate the deformation.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 399–405, May–June, 1974.     

The opening of a nonthrough longitudinal crack in a cylindrical shell taking account of elastoplastic deformation

In the context of an analog of the _k —model the problem of the stress-strain state of a shallow cylindrical shell with a nonthrough longitudinal crack is reduced to a system of singular integral equations that is solved by the small-parameter method. For a shell under an internal pressure we study the dependence of the opening of the crack on the geometric and physico-mechanical parameters of the shell.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 31, 1990, pp. 66–70.     

Effect of loading regime on the heating of plastics subjected to cyclic deformation

In cyclic loading in the W = const and ₀ = const regimes, as in the ₀ = const regime, both a low-temperature and a high-temperature thermal regime may exist, with an abrupt transition from the former to the latter. The effect of the loading regime on the temperature dependence of the hysteresis temperature rise T, which depends on the elastohysteresis properties of the material, results in the following relationship between the critical temperature rises: T ₀ ^c T _W ^c T ^c .Scientific-Research Institute of Plastics, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 465–469, May–June, 1969.