Hereditary theory of creep and low-cycle fatigue of polymeric materials

The results of an investigation of the creep of polymethyl methacrylate under alternating loading and recovery are presented. The experiments ended in the failure of the specimen. The creep data obtained are described on the basis of the nonlinear Boltzmann-Persoz theory and Bryzgalin's theory of hereditary recovery. Korabel'nikov's result, according to which for alternating loading and recovery the total time under load up to failure is less than the static life of the polymer, is confirmed.Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow; Scientific-Research Institute of Mechanics, Lomonosov Moscow State University. Translated from Mekhanika Polimerov, No. 4, pp. 615–621, July–August, 1970.     

Creep of a thermoplastic cylindrical shell under axisymmetric loading

The solution of the problem of creep of an axisymmetrically loaded thermoplastic cylindrical shell is considered. The strains and stresses for the zero-moment zone and with allowance for the edge effect are predicted on the basis of Kachanov's variational method using a computer. An algorithm is constructed for polyethylene and PVC shells at various values of the load. The analysis of the results obtained is illustrated by the calculation data for individual variants of the program.Leningrad Mozhaiskii Military Engineering Academy. Translated from Mekhanika Polimerov, No. 3, pp. 512–518, May–June, 1969.     

Simulation of thermo-mechanical loading processes on amorphous thermoplastic polymers

A constitutive model for the thermo-mechanical behavior of amorphous thermoplastic polymers is presented that accounts for the dependence of the macromolecular network and entropic hardening on large temperature changes. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Deformation of polymers under friction loading

A study has been made of the laws of distribution of elastic and residual deformations in the surface layers of polymers subjected to friction. The dependence of these deformations on normal pressure, sliding velocity, and duration of loading has been determined. A relation between deformation and antifriction characteristics has been established, and the relative effect of normal and tangential loads on surface-layer deformation determined.Mekhanika Polimerov, Vol. 3, No. 3, pp. 539–543, 1967     

Dynamic loading of polymeric materials

Published material dealing with the dynamic behavior of ductile elastic materials is reviewed. The methods used up unitl now for the investigation of the mechanical characteristics of materials under the conditions of uniaxial stretching and wave propagation are evaluated. There are also presented the basic results of the experimental studies carried out in order to elucidate the effect of rate on the mechanical properties of elastomers, vitrified polymers, glass-reinforced plastics, and crystalline polymers. A review is presented of the experimental and theoretical studies dealing with wave propagation in ductileelastic rods.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 326–338, March–April, 1970.     

Friction and wear of certain thermoplastic materials in physiological solution

The wear resistance of certain thermoplastics has been subjected to comparative investigation together with the velocity dependence of the coefficients of friction at various pressures and after various periods of contact with a model physiological solution.Priorov Central Scientific-Research Institute of Traumatology and Orthopedics. Moscow Technological Institute of the Food Industry. Second Moscow Pirogov State Medical Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1116–1119, November–December, 1971.     

Deformation of cylindrical composite shells under combined dynamic loading

Conclusions A procedure has been shown for calculating the stress-strain state of cylindrical multilayer shells made from composite materials under the combined action of dynamic axial compression and dynamic external pressure, as well as with different variants of combined loading with static and dynamic forces. An investigation has been made of the effect on the mode of the buckled shell surface of the ratio of the application rate of dynamic loads; ranges of loading rates have been established in which stresses predominate caused either by axial compression or external pressure. It has been shown that, as a result of preliminary static loading, a marked change occurs in the initial imperfections of the shell mode which affects subsequent dynamic buckling. To calculate the time when the first defect occurs and its location in the shell body, a procedure has been devised for layer-by-layer strength analysis employing a tensor-polynomial criterion. It was demonstrated that the level of preliminary static loading noticeably affects the time until the first failure of the layer, not only a reduction of this time being possible with an increase in the static loads, but also an increase in it.We should also point out the work in [10] where it is shown that it is possible to weaken the susceptibility of the shell to initial imperfections when internal pressure is applied.Translated from Mekhanika Kompozitnykh Materialov, No. 3, pp. 461–473, May–June, 1981.     

A constitutive model for thermoplastic materials subjected to high strain rates

Reliable prediction of the behaviour of structures made from polymers is a topic under considerable investigation in engineering practice. Especially, if the structure is subjected to dynamic loading, constitutive models considering the mechanical behaviour properly are not available in commercial finite element codes yet. A constitutive model is derived including important phenomena like necking, strain rate dependency, unloading behaviour and damage. In particular, different yield surfaces in compression and tension and strain rate dependent failure, the latter with damage induced erosion, is taken into account. With the present formulation, standard verification tests can be simulated successfully. Also, an elastic damage model can be used to approximate the unloading behaviour of thermoplastics adequately. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Deformation theory for gas-impregnated transversely isotropic materials

A mathematical model is constructed for a gas-impregnated transversely isotropic material. The material is modeled by a three-phase solid at each point of which there is a solid phase, and free and sorbed gas. Gas movement proceeds in two ways: by a crack and macropores system (filtration flow), and through microcracks (diffusion flow).Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 20, pp. 93–97, 1989.     

Deformation of polymer materials in nonuniform omnidirectional compression

The author presents the results of experiments to determine the nature of the deformation of 12 polymer materials compressed in thick-walled metal tubes. It is shown that there is a considerable increase in the plasticity of the materials. Moreover, it has been found that all the materials are capable of adhesion when two specimens are deformed together. However, for most of the materials tested the strength declines with increase in strain owing to cracking.Mekhanika Polimerov, Vol. 2, No. 2, pp. 229–233, 1966     

Microstructural changes of filled rubber-like materials under cyclic loading

The concept of network decomposition has vastly been used in many micro-mechanical models describing stress-softening of rubber-like materials in the first loading cycle as for example the Mullins-effect. Nevertheless, this concept highly simplifies the rubber matrix by decomposing it into two parallel networks that have no interactions with each other. In order to take into account the interactions between these networks some further extensions to the network decomposition concept seem necessary. To this end, a third network is introduced and the concept of rubber cell is proposed and developed. Using this concept, the influence of the filler network on elasticity of the two networks can be predicted by considering the cell as a RVE. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)