Investigation of fatigue damage in polymer films by the method of light scattering

Conclusions In cyclic loading of the investigated polyurethane there originates a polydisperse system of microdefects with nonspherical shape, in consequence of which the light scattering increases irreversibly. The method of light scattering is sufficiently sensitive for determining the relative concentrations and dimensions of microdefects that are smaller than the wavelength of light. It was shown that the predominant mechanism of failure of polyurethane is the increased concentration of microdefects whereas their dimensions change only imperceptibly.Translated from Mekhanika Kompozitnykh Materialov, No. 5, pp. 910–917, September–October, 1984.     

Investigation of the dynamic fatigue of composite polymer materials

The dynamic fatigue of composite film materials has been studied as a function of the frequency and amplitude of deformation. The tests were carried out on a vibration apparatus with a frequency range from 10 to 600 cps. The test objects consisted of foil packaging with a polyethylene backing (foil-film).The dependence of the dynamic fatigue of foil-film on amplitude, frequency, and acceleration was studied. It has been shown that in all cases failure of the material is preceded by cracking of the foil and peeling of the foil from the polyethylene backing at the site of the cracks. The material fails as a result of puncture of the polyethylene backing by the broken edge of the cracked foil.Mekhanika Polimerov, Vol. 1, No. 5, pp. 90–94, 1965     

Investigation of the anisotropy of the properties of glass-reinforced plastic shells

The load-carrying capacity and deformation of cylindrical and conical glass-reinforced plastic (ÉDT-10 resin) shells loaded in axial compression have been investigated experimentally in relation to the orientation of the fabric reinforcement. The results of the tests are compared with the relations of the theory of elasticity of an orthotropic body.Zhukovskii Central Aerohydrodynamics Institute, Moscow Region; Scientific Research Institute of Production Technology and Organization, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 814–818, September–October, 1969.     

Identification of inverse problems of deformation of thin-walled shells by the decomposition method

We have developed a decomposition approach for the solution of inverse problem of deformation of a thin-walled system. Decomposition of the vector of parameters leads to the necessity of solution of parallel problems of substantially lower dimension. As a result of decomposition, the problem is regularized, and the conditioning of matrices, which are to be inverted, becomes better.     

Acoustic fatigue of polymer materials

An experimental investigation of the fatigue properties of filled rubber under acoustic loading is briefly discussed. It is shown that two processes take place in the material—hardening and softening. A corresponding mathematical model is proposed. The form of the Wöhler fatigue curve in logarithmic coordinates is almost linear for high-frequency cyclic loading and may be assumed linear in the calculations with a risk of not more than 1%.Mekhanika Polimerov, Vol. 3, No. 3, pp. 467–475, 1967     

Acoustic fatigue of polymer materials

Methods are proposed for experimentally estimating the temperature-time aging of a filled rubber and the degree of damage accumulation in high-frequency fatigue tests. A procedure for experimentally determining the energy dissipation function of a material from the specimen temperature kinetics is described. The results of an investigation of the fatigue properties of two series of filled rubbers at a vibration frequency of 20 kHz are presented. It is shown that the fatigue failure of the materials tested is thermal in character. No accumulation of mechanical damage in the material in the course of intense vibration could be detected.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 662–668, July–August, 1969.     

Acoustic fatigue of polymer materials

Work on the development of experimental techniques and methods of testing materials under high-frequency cyclic loading are briefly reviewed. Certain aspects of the acoustic fatigue of polymer materials are examined. Future research trends are discussed.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 108–126, January–February, 1969.     

Investigation of the mechanical properties of polymer surface layers using surface waves

It is possible to excite ultrasonic surface waves at the surface of polymer materials and to determine the dependence of the wave parameters on the mechanical properties of the surface. The nature of the variation of the surface wave characteristics with material, temperature, and the frequency of the exciting vibrations has been established.Mekhanika Polimerov, Vol. 3, No. 5, pp. 933–939, 1967     

Investigation of the fatigue properties of rigid polymers used in making harmonic drives

The fatigue properties of rigid polymers used for making harmonic drive components have been investigated. Certain data on the fatigue of flexible shells under complex loading conditions have been obtained. The effect of the polymer structure on the fatigue properties of a series of compounds with various antifriction fillers and plasticizing additives is evaluated.Translated from Mekhanika Polimerov, No. 6, pp. 1014–1019, November–December, 1970.     

An evaluation of the activators of static polymer fatigue

In conformity with the kinetic theory [1, 2] a generalized temperature-time dependence of the brittle strength of isotropic polymers is obtained on the basis of a phenomenological model [7]. A quantitative relation between mechanical and thermal degradation is established.Special Design Office for Automation in Petroleum Refining and Petrochemistry, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 654–667, July–August, 1970.     

The possibility of a theoretical confirmation of the experimental values of the external critical pressure of thin-walled cylindrical shells

The problem of the buckling of elastic, isotropic, thin-walled cylindrical shells with small initial shape defects that are under the action of an external pressure is solved in a geometrically non-linear formulation. Equations that are identical to Marguerre's equations for a shallow cylindrical shell are used in formulating the problem. The solution is constructed by the Rayleigh–Ritz method with the points of the middle surface of the shell approximated by double functional sums over trigonometric and beam functions. The system of non-linear equations obtained is solved by arc-length methods. Cases of the clamped and supported shells when loading with a lateral and uniform hydrostatic pressure are considered. Its deflections from the limit points of the postbuckling branches of its loading trajectory are used as the initial imperfections. An inspection of the different forms of the initial imperfections when they have maximum values of up to 30% of the shell thickness made it possible to obtain practically the whole range of experimentally found critical pressures.