Effect of hydrostatic pressure on the strength properties of polymer materials

On the assumption that the strength characteristics of homogeneous polymer materials depend on the specific volume, equations are derived for the dependence of the strength or high-elastic limit on the hydrostatic component of the stress tensor and temperature. The ultimate strengths in simple tension, compression and shear are considered in relation to brittle and plastic fracture.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 449–454, May–June, 1969.     

Effect of liquid media on the deformation of the surface layers of a polymer-metal pair in sliding friction

The relation between the high-elastic component of polyurethane deformation and the deformation of the surface layers of metals has been investigated for sliding friction in various media. The surface layers of polymer and metal are plastically deformed. There is a certain correlation between the coefficient of friction and the amount of deformation.Kiev Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 1, pp. 147–149, January–February, 1970.     

A rheological model of polymers and glass-reinforced plastics

Network polymers and the corresponding glass-reinforced plastics are investigated for a homogeneous uniaxial state of stress and constant temperature. A physical law relating the high-elastic strain and the stress in explicit form with once-determined structural constants is obtained for the damped (bounded) creep regime. The theoretical solutions are compared with the experimental data for a glass-reinforced plastic based on unsaturated polyester resin and glass mat reinforcement.Institute of Engineering Mechanics, Bulgarian Academy of Sciences, Sofia. Translated from Mekhanika Polimerov, No. 5, pp. 851–857, September–October, 1971.     

Some laws of plastics friction

The dependence of the actual contact area S of plastics on temperature, specific load, and sliding speed has been investigated. The value of S increases exponentially with the specific load, the maximum value at large specific loads being less than the nominal contact area. The temperature dependence of S under static conditions between 20 and 130° C is attributable to the decrease in the static modulus of elasticity of the plastic near the glass transition point and to the development of high-elastic and plastic deformations at elevated temperatures. There is practically no change in S as the sliding speed varies from 10^–3 to 10 cm/min; at the same time the force of friction increases slightly.Mekhanika Polimerov, Vol. 3, No. 6, pp. 1078–1081, 1967     

Deformation and sliding friction of polyurethane in the presence of a lubricant

The relation between coefficient of friction and elastic and high-elastic strains is investigated with reference to polyurethane subjected to friction in various liquid media. It is shown that a definite relationship between these parameters does exist. The effect of various liquids on the elastic and high-elastic deformation of polyurethane is studied.Kiev Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, Vol. 5, No. 2. pp. 357–359, March–April, 1969.     

Temperature dependence of the deformation properties of compositions based on polyethylene and polyisobutylene

The temperature dependence of the deformation properties (deformability and recoverability) of compositions based on low-density polyethylene and polyisobutylene has been investigated. For two-component polyethylene—polyisobutylene systems this dependence varies with the component ratio. Introducing a filler (talc) reduces the recoverability of the compositions owing to increases in both the delayed high-elastic deformation and the flowability. The deformation properties of compositions plasticized with paraffin change abruptly at the melting point of the latter.Moldavian Scientific-Research Institute of the Food Industry, Kishinev. Translated from Mekhanika Polimerov, No. 4, pp. 758–760, July–August, 1971.     

Predicting the performance of extruded low-pressure polyethylene from rheological characterstics

Characteristic features of the high-elastic stalling of the melts of modern types of low-pressure polyethylene is investigated. The possibility of predicting the performance of polyethylene pipes from measurements of the following rheological characteristics is demonstrated: melt viscosity, shear-rate gradient at the outset of high-elastic stalling, swelling of the extrudate, and the amplitude of self-sustained fluctuations in shear stress.Kazan' State Technical University, Tatarstan, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 4, pp. 558–563, July–August, 1996.     

Deformation behavior of a filled nitrile vulcanizate in various states of stress

On the basis of experimental data obtained in uniaxial and symmetrical and nonsymmetrical biaxial tension and pure shear, the deformation behavior of unfilled and filled butadiene-nitrile rubbers is described by means of the Bartenev-Khazanovich one-parameter high-elastic potential.Leningrad Branch of the Scientific-Research Institute of the Rubber Industry. Translated from Mekhanika Polimerov, No. 2, pp. 363–366, March–April, 1972.     

A comparison of the elastomeric properties of inorganic glasses and high polymers

The high-elastic properties and structural-mechanical characteristics of inorganic glasses and high-polymer materials are compared. Points of similarity and also differences in the mechanical behavior of organic and inorganic polymers in the high-elastic state are noted. Comparative estimates of the molecular weights of the chains in organic and inorganic polymer networks are given.Mekhanika Polimerov, Vol. 1, No. 3, pp. 21–28, 1965     

Nature of the friction deformation of the surface layers of polymethyl methacrylate

The surface deformation of amorphous thermoplastics (polymethyl methacrylate) by a spherical steel indentor has been investigated at various sliding velocities. Small velocities correspond to elastic and forced-elastic deformation of the surface layers and asperities. At temperatures corresponding to the high-elastic state the deformed surface layer completely recovers its shape. As the sliding velocity increases, the forced-elastic deformation is localized in a thinner layer of plastic. Starting from a certain velocity, depending on the temperature and the activation energy for transition of the chain segments from one equilibrium position to another in the process of thermal motion, the deformation of the surface layers and asperities becomes purely elastic. In the event of elastic deformation at pressures above a certain value the surface layer of plastic suffers brittle fracture in the tensile zone behind the indentor.Mekhanika Polimerov, Vol. 4, No. 1, pp. 90–94, 1968.     

State of stress and strain of plates with two equal openings in the presence of high-elastic deformation

The apparatus of the nonlinear theory of elasticity [1–3] is used to investigate the high-elastic deformation of a plate with two equal circular openings and a massive block with two cylindrical channels. Computer-calculated stress concentration factors are given for compressible and incompressible materials.Translated from Mekhanika Polimerov, No. 4, pp. 687–692, July–August, 1969.     

Rheological properties of polymers in the fluid state

The possibilities and conditions of correlation are determined for the principal rheological characteristics of single-phase polymer systems measured for one-dimensional shear deformation in steady-state flow regimes, on transition from rest to steady-state flow, and in harmonic vibration regimes. Special significance attaches to the quantitative results of measuring the high-elastic properties of the polymer systems. It is shown that the Lodge theory, describing the flow behavior of high-elastic media, is well-founded in the linear region of deformation, i.e., for the limiting case of shear rates and shear stresses tending to zero, whereas the Mooney-Rivlin-Weissenberg theories are not in accord with the experimental data even in this limiting deformation regime.Topcheiv Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 164–181, January–February, 1969.     

A polymer film hardening effect

It is shown that a polyester film incapable of forced high-elastic deformation can be subjected to such deformation by stretching a film-substrate system. The resulting oriented structure is stable and on being measured from the substrate, the film exhibits a hardening effect. In this case contact with and adhesion to the substrate are a necessary condition for the development of the latent potential of the film.Lenin All-Union Electrical Engineering Institute, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 731–733, July–August, 1971.     

Effect of deformation on the supermolecular structure of PN-1 copolymer

It is shown that under the combined influence of temperature and tensile stresses the spherical structure of crosslinked PN-1 copolymer becomes ellipsoidal. The change of shape is associated with the zone of high-elastic deformation.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 6, pp. 1129–1131, November–December, 1969.     

Surface instability of high-elastic materials

The problem of the surface instability of a lower half-plane in compression is investigated for an arbitrary form of the potential within the framework of the plane problem of the deformational stability of incompressible elastic bodies at finite subcritical strains [1, 4]. Numerical examples are considered for high-elastic bodies with potentials of the Mooney and Treloar types.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 6, pp. 1107–1110, November–December, 1970.     

Effect of building structure on the distribution of random bending strength of multilaminate reinforced plastics

A probabilistic structural model has been constructed for predicting the bending strength distribution in multilaminate reinforced plastics. The number and random strength/elastic properties of the layers or repeating structural elements are parameters of the structure. The random properties of the repeating structural elements are characterized by the scheme and geometry of the unidirectional layers. Two failure conditions have been analyzed: multistep failure caused by successive failure of separate layers and failure caused by the failure of the weakest component. The effect of the number of layers and the instability of the strength and elastic properties on the basic statistical properties of the bending strength was analyzed numerically for typical structures and for both failure conditions. The quantitative significance of the size effect determined by the thickness of the plastic was investigated. The main theoretical results were checked experimentally for unidirectional reinforced carbon plastic under uniaxial bending. The experimental distribution agrees well with the predicted distribution.Translated from Mekhanika Kompozitnykh Materialov, Vol. 29, No. 3, pp. 336–344, May–June, 1993.     

Relaxation processes in oriented amorphous polymers

Values of the birefringence and high-elastic strain are presented for amorphous polystyrene subjected to stretching and annealing. The laws of the relaxation processes that occur in linear polymers under these conditions are discussed.Mekhanika Polimerov, Vol. 2, No. 3, pp. 323–329, 1966     

Maximum force of friction in rubber-metal friction pairs under conditions of constant compressive deformation of the rubber

The maximum force of friction at the initial moment of slip has been investigated on rubber-metal friction pairs under conditions of constant compressive deformation of the rubber during transition from the high-elastic to the glassy state. Filled butadiene-nitrile rubber compounds were studied in the temperature range from +20 to –50°C. The temperature dependence of the maximum force of friction has a sharply expressed maximum near the glass transition temperature. As the temperature falls, the force of friction at first increases, in accordance with the molecular-kinetic theory. As the temperature continues to fall, in the transition region the maximum force of friction begins to rise more sharply owing to a sharp increase in the volume-mechanical friction component. The fall in the maximum force of friction below the glass transition point associated with a decrease in the deformed volume of rubber due to shrinkage and with the reduced mechanical loss factor.Mekhanika Polimerov, Vol. 3, No. 3, pp. 533–538, 1967     

Effect of the physical state on tearing of amorphous polymers

On the assumption that the strength of linear amorphous polymers is determined by the efficiency of molecular interaction and the degree of orientation in a region adjacent to the tip of a tear, the temperature dependence of both indicated factors is described in the temperature range encompassing the rigid, high-elastic, and viscous flow states. On the basis of a comparison of the indicated temperature dependences, a -T curve for real polymers is proposed and confirmed by experiment. The dependence is characterized by a pronounced peak in the region of transition from the rigid state to the high-elastic state and is of exponential type in the temperature range encompassing this state.Mekhanika Polimerov, Vol. 1, No. 4, pp. 100–105, 1965     

Calculation of multilayer cylinders and disks composed of high-elastic polymer materials

The state of stress and strain of multilayer cylinders and disks composed of high-elastic materials is examined on the basis of the relations of the nonlinear theory of elasticity [2, 3].Mekhanika Polimerov, Vol. 3, No. 2, pp. 318–325, 1967