Properties of polyurethanes SKU-10 under pulsed and static loads

Conclusion The investigations of the optical and mechanical properties of modifications of polyurethane SKU-10 under static and pulsed loads and the results of solving the model problem of the nonstationary stressed state permit concluding the possibility of using these materials for solving by the photoelasticity method engineering problems of the stressed state of structural elements and structures under static and pulsed loads?Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 121–128, January–February, 1981.     

Equilong-term strength surfaces of organic textolite in the plane stressed state

Conclusion Long-term strength tests of textolite were conducted for seven different particular cases of the plane stressed state. Maximum times to failure for which experimental data were obtained reach 2500 h. It is established from analysis of the test results that the experimental long-term strength curves for the types of stressed state under consideration are closely similar. The condition of long-term strength in the general case of the plane stressed state for constant levels of stresses is taken as the equation of the short-term strength surface in which the time factor is introduced parametrically; in this case, the apparent observance of similarity between equilong-term strength surfaces makes it possible to express the tensor components characterizing the long-term strength by tensor components of the short-term strength surface and a certain monotonically decreasing time function, which is independent of the form of stressed state.Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 51–56, January–February, 1979.     

Conditions of existence of univalently stressed contours in the first main problem of the theory of elasticity for a plane with cut

A definition of a univalently stressed contour in a compressible isotropic plane with a curvilinear cut is given, which extends the notion of an equiresistant contour. Conditions for elliptic and square contours to be univalently stressed are formulated and proved.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 47, No. 2, pp. 295–296, February, 1995.     

The stress—strain state of soft shells of arbitrary shape

A procedure is proposed for determining the stress—strain state of soft shells of arbitrary shape. The stressed state is analyzed for a hemispherical shell with a slot which is fixed along the contour. The stress concentration ratio is determined.Moscow. Translated from Dinamicheskie Sistemy, No. 10, pp. 34–41, 1992.     

Strength of honeycomb plastics in a flat stressed state

The strength of textile and paper honeycomb plastics in the flat stressed state is discussed, under the simultaneous action of compressing and shearing stresses. The application of a generalized strength criterion for anisotropic materials to honeycomb plastics is investigated.V. A. Kucherenko Central Scientific-Research Institute of Building Constructions, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 936–938, September–October, 1972.     

Optimal reinforcement of a glass-reinforced plastic plate

Relations are derived for the optimal arrangement of the reinforcement in a rectangular glass-reinforced plastic plate supported at the edges and stressed in uniaxial compression by a short-term or long-term, uniformly distributed load. (The optimal arrangement is understood to be that which maximizes the critical load.)All-Union Scientific-Research Institute of Railroad Transport, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 741–744, July–August, 1969.     

Formulation and solution of boundary value problems of polymer mechanics

Certain aspects of the formation of boundary value problems of polymer mechanics are stressed and effective methods of solution are discussed. Recent solutions of boundary value problems of polymer mechanics are reviewed.Lomonosov Moscow State University. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 54–62, January–February, 1969.     

Mechanical characteristics of oriented glass-reinforced plastics in shear

The mechanical characteristics of oriented glass-reinforced plastics stressed in shear are considered. Various methods of determining them are compared. The dispersion of the shear strength is characterized and the possibility of glass-reinforced plastics elements failing as a result of low interlaminar shear strength is discussed.Moscow Aviation Technological Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1008–1013, November–December, 1969.     

Long-term strength of rigid polyvinyl chloride in the flat stressed state

On the basis of experimental studies it has been established that the time to failure of rigid polyvinyl chloride depends basically on the magnitude of the largest stretching stress and at a long duration of testing deviates considerably from the exponential dependence. A refined formula is suggested for calculating the time to failure, which takes into account some characteristics of the stressed state.A. A. Zhdanov Leningrad State University. Translated from Mekhanika Polimerov, No. 3, pp. 453–457, May–June, 1970.     

Determination of fatigue life in bending with rotation

The fracture and stress redistribution processes in a specimen stressed in cyclic bending with rotation are considered. The calculations are based on the assumption of linear damage accumulation and a linear dependence of the modulus of elasticity on the damage; the fatigue strength curve for cyclic tension-compression is employed. The calculated damage accumulation and crack penetration times are compared. Specific calculations are made for the case of PMMA fatigue under isothermal conditions.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 875–880, September–October, 1971.     

Nonlinear physical stress - strain relationship of cellular polymers and glass plastics under conditions of attenuating creep

The coupling equations of hard cellular polymers and glass plastics based on these are analyzed. The material is considered as an elastically relaxing medium for the case of small deformations. The physical relationship between the rubber-elastic stresses and strains is derived in explicit form for the case of attenuating creep and a uniform three-dimensional stressed state. The total deformations are described by the one-dimensional rheological model of a "typical body" with a reduced stress and an instantaneous elastic modulus, having the appropriately chosen viscosity of a non-Newtonian liquid.Institute of Technical Mechanics, Bulgarian Academy of Sciences, Sofia. Translated from Mekhanika Polimerov, No. 2, pp. 231–235, March–April, 1972.     

Experimental determination of the displacement of the neutral surface in polymer specimens stressed in bending

The results of bending tests to determine the displacement of the neutral surface are presented for six different polymers. The specimens were both stressed in pure bending and bent by transverse loads. The values obtained for the displacements indicate that the effect should be taken into account in designing parts for bending. An attempt is made to explain the displacement of the neutral surface in terms of the textural characteristics of the chain molecules.Dnepropetrovsk Metallurgical Institute. Translated from Mekhanika Polimerov, No. 4, pp. 747–749, July–August, 1969.     

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     

Computation of anisotropic plates with curvilinear holes reinforced by prestressed rods

We consider the stressed state of an anisotropic plate with an elliptic hole whose boundary is reinforced by a prestressed curvilinear rod of arbitrary cross section symmetric with respect to the middle plane of the plate. The elastic equilibrium of the rod is described by the equations of the theory of curvilinear rods. The solution of the problem is reduced to a system of linear algebraic equations. We show the influence of prestressing on the stressed states of the bodies.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 36, 1992, pp. 76–80.     

Axially symmetrical deformation of an orthotropic layered cylindrical shell

An orthotropic layered cylindrical sheet subject to axially symmetrical loading is considered. A solution free from the hypothesis of the straight normal is presented; the material of the shell is regarded as incompressible in the radial direction. An attempt is made to allow for the real character of the rigid fixing at the edge of the shell. The stressed state in the neighborhood of the edge is analyzed.S. Ordzhonikidze Moscow Aviation Institute. Translated from Mekhanika Polimerov, No. 5, pp. 816–823, September–October, 1972.     

Temperature — Time dependence of the strength of polymers exposed to UV radiation

Experiments on several polymers have shown that the dependence of the radiation lifetime under load on the intensity of the ultraviolet radiation and test temperature is governed by general empirical laws. An analysis of the results yields important information on the photodegradation of stressed polymers.Ioffe Physico-Technical Institute, Academy of Sciences of the USSR. Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 442–448, May–June, 1969.     

Tensile strength of unidirectionally reinforced plates stretched at an angle to the direction of reinforcement

Conditions for the fracture of a unidirectionally reinforced plate under uniaxial tension at an arbitrary angle to the direction of reinforcement are proposed. The fracture conditions are applicable to the case where the adhesion strength between the bond and reinforcement is greater than the strength of the polymer bond. The strength of the polymer bond in the volume stressed state is determined by an energy criterion.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 9, No. 3, pp. 482–486 May–June, 1973.     

Stress state of freely supported multilayered elliptical plates of anisotropic materials

The problem of a stressed state in elliptic plates has been considered in general for a rigid contour fixation. It is much more difficult to obtain a solution for the freely supported plates, even for isotropic materials. In this paper we suggest an approach for defining the stressed state of thin elliptic plates with layered structure under the condition of a freely supported contour. The solution is obtained in a rectangular cartesian coordinate system. The displacements, which are the fundamental unknowns, are given in the form of polynomials with unknown coefficients defined by a system of algebraic equations. The resolving equations and three out of the four boundary conditions are satisfied precisely. One boundary condition, is satisfied by means of collocation method of separate points of the contour. Estimation of the accuracy of the suggested approach is carried out by comparing the obtained results with the known ones. The problem of deformation of a twolayered plate has been discussed, in which the principal direction of elasticity does not coincide with the coordinate directions.S. P. Timoshenko Institute of Mechanics, National Academy of Science of the Ukraine, Kiev. Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 4, pp. 496–504, July–August, 1997. Original article submitted March 19     

Thermally stressed state of solids of revolution with finite dimensions

The solution of the axisymmetric elasticity problem for an unparted hyperboloid of revolution is used to obtain the exact analytical solution of the reference problem of the thermally stressed state of an isotropic solid of revolution with finite dimensions and a transverse cross section of complex configuration.Kiev. Moscow. Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 21, pp. 3–9, 1990.     

Creep of reinforced plastics in uniaxial tension along the fibers

Relations are proposed for determining at any moment of time the strains in a reinforced plastic stressed in the resin and the reinforcement by a constant tensile load as a function of the reinforcement ratio and the rheological properties of the reinforcement and resin. The proposed relations agree quite well with the experimental data.Mekhanika Polimerov, Vol. 1, No. 6, pp. 69–77, 1965