Accumulation of defects during nonstationary loading of Plexiglass

The fatigue resistance is studied in programmed tests on Plexiglass samples. The effect of the nonstationary character of loading and, in partcular, that of the shape of the load spectrum on durability of Plexiglass is estimated.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 1, pp. 169–171, January–February, 1972.     

Comparative analysis of two algorithms for numerical solution of nonlinearstatic problems for multilayered anisotropic shells of revolution 2. Account of transverse compression

Two algorithms for numerical solution of static problems for multilayer anisotropic shells of revolution are discussed. The first algorithm is based on a differential approach using the method of discrete orthogonalization, and the second one—on the finite element method with linear local approximation in the meridional direction. It is assumed that the layers of the shell are made of linearly elastic, anisotropic materials. As the unknown functions, six displacements of the shell are chosen, which often simplifies the definition of static problems for multilayer shells. The calculation of a cross-ply cylindrical shell stretched in the axial direction is considered. It is shown that taking account of the transverse compression, anisotropy, and geometrical nonlinearity is important for the given class of problems.Tambov State Technical University, Tambov, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 4, pp. 435–446, May–June, 1999.     

Long-term strength of thermoplastics in air and a physiological solution

The effect was examined of a physiological fluid on the long-term strength of P-12 polyamide CTD copolymer, fluorinated polymethylmethacrylate PMMAF and cast polyethylene terephthalate (PETP). It has been found that the durability curves for the thermoplastics in air and the physiological fluid are described by an exponential function which has an aberration in the region of low stresses.N. N. Priorov Central Scientific-Research Institute of Traumatology and Orthopedics, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1044–1047, November–December, 1972.     

Comparative analysis of two algorithms for numerical solution of nonlinear static problems for multilayer anisotropic shells of revolution. 1. Account of transverse shear

The discussion focuses on two numerical algorithms for solving the nonlinear static problems of multilayer composite shells of revolution, namely the algorithm based on the discrete orthogonalization method and the algorithm based on the finite element method with a local linear approximation in the meridian direction. The material of each layer of the shell is assumed to be linearly elastic and anisotropic (nonorthotropic). A feature of this approach is that the displacements of the face surfaces of the shell are chosen as unknown functions, i.e., the functions which allows us to formulate the kinematic boundary conditions on these surfaces. As an example, a cross-ply cylindrical shell subjected to uniform axisymmetric tension is considered. It is shown that the algorithms elaborated correctly describe the local distribution of the stress tensor over the shell thickness without an expensive software based on the 3D anisotropic theory of elasticity.Tambov State Technical University, Tambov, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 3, pp. 347–358, May–June, 1999.     

Anisotropy of the mechanical properties of cross-linked poly(n-butyl methacrylate)

Mechanical properties of cross-linked poly(n-butyl methacrylate) synthesized under shear stress are reviewed. The effect of shear stress rate and of the cross-linking agent concentration on the resulting polymer properties was demonstrated.Kiev Branch, All-Union Scientific-Research Institute of Complex Polygraphy Problems in Special Types of Printing. Institute of the Chemistry of High-Molecular-Weight Compounds, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 1, pp. 150–152, January–February, 1972.     

Effect of long-term storage of polycarbonates on stress relaxation

The effect of long-term storage (three-five years) on the mechanical properties of polycarbonates and Makrolon has been experimentally investigated under conditions of stress relaxation at normal and elevated temperatures.Scientific-Research Institute of Mechanics, Lomonosov Moscow State University. Translated from Mekhanika Polimerov, No. 1, pp. 149–151, January–February, 1973.     

Diagnostics of the physicomechanical properties of glass textolites in articles of three-layer construction

Possibilities are examined for the diagnostics of some indicators of durability and stiffness of glass textolites in articles of three-layer construction (cemented three-layer combined construction, the two outer layers of which are of glass textolite and the inner layer of which is a foam layer) from a complex of structural parameters and physical characteristics measured directly in the article by nondestructive methods.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 362–364, March–April, 1976.     

Accelerated testing of polymeric materials operating in a vacuum in the presence of ionizing radiations

The effect of ionizing radiations on polymeric materials is considered and an accelerated method of determining the wear rate under these conditions is proposed.All-Union Scientific Research Institute of Optico-Physical Measurements, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1105–1107, November–December, 1969.     

Durability of polymers as a function of loading regime during repeated loading with a small number of cycles

Specimens of oriented polycaproamide and unoriented polymethyl methacrylate subjected to uniaxial extension were used to study durability as a function of the number of loading cycles and the intervals between them in different segments of the creep curve. It was shown that the deformation hardening during the initial segment of the creep curve governs the ability of the specimen to withstand subsequent loading cycles. With a relatively low loading rate, deloading-loading cycles during the initial segment of the creep curve lead primarily to an increase in local stresses. During the second stage, repeated loading causes principally an increase in local heating. The interval between loading cycles has only a weak influence on durability.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 252–256, March–April, 1972.     

Structural susceptibility of strength characteristics of polystyrene under uniaxial stretching

The structural susceptibility of the strength characteristics of polystyrene under uniaxial stretching and under test conditions with = const and v_elong = const was studied at 20–100°C. The low structural susceptibility of the durability and durability-equation parameters is due to a change in the elementary fracture volume at different test conditions. It was proposed to characterize the degree of participation of chemical and intermolecular forces by the value U₀/.Moscow Technological Institute of Meat and Milk Industry. Translated from Mekhanika Polimerov, No. 6, pp. 979–984, November–December, 1974.     

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 gaseous oxygen pressure on the kinetics of accumulation of residual deformation in resins

The authors studied changes in the properties of resins in the static deformed state under the effect of gaseous oxygen pressures of up to 200 atm at 25, 50, and 70° C for 20–500 days, depending on the experimental conditions. It was shown that an increase in gaseous oxygen pressure significantly affects the process of accumulation of residual deformation up to 30–40 atm while a further pressure rise has practically no effect on changes in the accumulation rate of residual deformation.Scientific-Research Institute of the Resin Industry, Moscow. Translated from Mekhanika Polimerov, Vol. 9, No. 3, pp. 552–554, May–June, 1973.     

Influence of hydrostatic pressure on the lifetimes of polymers

Under uniaxial tension, the lifetimes of polymers under hydrostatic pressure are longer than under atmospheric pressure. This effect is attributed to a change in the failure mechanism under pressure owing to retardation of the free-radical chain reaction of breakage of the macromolecules under omnidirectional compression.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 207–213, March–April, 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.     

Endurance limit of polyethylene during cyclic loading under conditions of a plane stressed state

Conclusions The effect of the asymmetry of the loading cycle on the fatigue strength of HDPE subjected to biaxial tension has been studied. An increase in the acuteness of the cycle leads to an increase in the durability of the material. Under conditions of cyclic loading, the material became embrittled as the duration of the experiment was extended. The effect of various different ratios between the principal stresses on the fatigue strength of HDPE has been investigated. It has been shown that the form of the isochronous boundary curves depends on the duration of the experiment. It was established that the mechanism of HDPE fracture changes depended on the duration of the loading. The accumulation of defects, when an experiment was of average or longer duration, built up at a greater rate than would have been predicted by a linear rule for summation.M. I. Kalinin Leningrad Polytechnic Institute. The "Plastpolimer" Okhtinsk Scientific Manufacturing Association, Leningrad. Translated from Mekhanika Polimerov, No. 1, pp. 35–40, January–February, 1977.     

Winding glass-reinforced plastic rings under programmed tension

The strength, stiffness, and initial stresses of glass-reinforced plastic rings wound under variable tension in accordance with five different programs are considered. The relative thickness of the rings was 0.15–0.20. It is shown that the law of variation of the tension on the tape during winding has an important effect on the investigated parameter.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 361–364, March–April, 1971.     

Effect of structural-chemical modification of a polycaprolactam block on the retention of strength during thermo-oxidation

The structure and strength of a block of polycaprolactam (PC) have been investigated in relation to diffusion stabilization and thermo-oxidation. It is shown that structural modification of the surface layers of the PC block with zinc iodide has an important effect on the retention of strength during prolonged thermo-oxidation.Kaunas Polytechnic Institute; Institute of Physicotechnical Problems of Energetics, Academy of Sciences of the Lithuanian SSR, Kaunas. Translated from Mekhanika Polimerov, No. 1, pp. 10–14, January–February, 1970.     

Effect of material properties on the stability of transversely isotropic shells with an elastic filler subjected to the action of mechanical loads and temperature

The effect of the low shear strength of the material (glass-reinforced plastic) on the stability of cylindrical shells with an elastic filler is investigated in relation to axial compression, external pressure, and heating. The equations of the thermoelastic problem of the theory of monotropic shells, constructed with allowance for the effect of tangential shearing stresses, are used in the calculations.Physicomechanical Institute, Academy of Sciences of the Ukrainian SSR, L'vov. L'vov Polytechnic Institute. Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 903–907, September–October, 1970.     

Stability of shear-compliant cylindrical shells connected with an elastic foundation in a geometrically nonlinear formulation

The effect of transverse shear strains on the stability "in the large" of a cylindrical transversal-isotropic shell with an elastic filler under the effect of axial compression is investigated. The length of the cylindrical shell is assumed to be greater than the diameter. The approximate solution is obtained by the Bubnov-Galerkin method. Such a problem for an isotropic shell was considered earlier in [2, 4] on the basis of the equations of the classical Kirchhoff-Love theory.L'vov Physicomechanical Institute, Academy of Sciences of the Ukrainian SSR. Ternopol Branch, L'vov Polytechnic Institute. Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 113–117, January–February, 1972.     

Effect of lubricating greases on rubber-metal sliding friction at high temperatures

The effect of sliding velocity and temperature on the lubricating action of greases has been investigated under constant and variable temperature conditions. The most important factor is the friction temperature. Two different temperature regions, separated by a change in the type of friction, have been detected. A method has been developed for evaluating the lubricating effect of greases.Scientific-Research Institute of the Rubber Industry, Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 876–880, September–October, 1968.