Consideration of friction between layers in determining the stress-strain state of structures with nonideal layer contact

A mathematical model for calculation of structures in a three-dimensional installation allowing for layer slippage with friction was constructed. The examples examined show that consideration of friction in problems of calculating laminated structures with nonideal layer contact can introduce an essential correction in the stress—strain state of the structure. In slabs with a freely sagging lower surface, friction is perceived for important friction coefficients and increases when the slippage surface approaches the loaded surface. In masses with a rigidly attached lower surface, even insignificant friction coefficients lead to essential redistribution of the stress—strain state.Ukraine Transportation University, Kiev, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 33, No. 2, pp. 192–199, March–April, 1997.     

Movement of low-molecular-weight polyisobutylene in capillaries at large rates of deformation

Conclusions 1. A decrease in flow rate is observed upon increase in the pressure drop between the ends of a capillary at large pressure drops in the unstable flow region.2. It has been ascertained that the radial distribution of mean lengthwise velocity has an inflection close to the capillary wall.3. Wall slippage of the polymer has been observed and measured.4. A correlation of velocity pulsations in the channel with disturbances in the jet has been established.Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow. Moscow Power Institute. Translated from Mekhanika Polimerov, No. 4, pp. 724–730, July–August, 1976.     

Optimal Design of Filament-Wound Composite Pressure Vessels

In this paper, the effect of the width of winding band on the stability of winding pattern is studied. Some key design variables are calculated to optimize the dome geometry. The influence of winding process parameters on the slippage tendency is also considered.__________Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 41, No. 4, pp. 489–498, July–August, 2005.     

Determination of contact stresses in problems on bending of a package of transversely isotropic bars

A mechanomathematical model for bending of packages of transversely isotropic bars of rectangular cross section is proposed. Adhesion, slippage, and separation zones between the bars are considered. The resolving equations for deflections and tangential displacements are supplemented with a system of linear differential equations for determining the normal and tangential contact stresses, and boundary conditions are formulated. A scheme for analytical solution of two contact problems—a package under the action of a distributed load and a round stamp—is considered. For these packages, a transition is performed from the initial system of differential equations for determining the contact stresses, where the unknown functions are interrelated by recurrent relationships, to one linear differential equation of fourth order and then to a system of linear algebraic equations. This transition allows us to integrate the initial system and get expressions for the contact stresses.Translated from Mekhanika Kompozitnykh Materialov, Vol. 40, No. 6, pp. 761–778, November–December, 2004.     

Failure of laminar fiberglass-plastics in compression

Conclusions 1. The most general form of failure of laminar fiberglass-plastics in compression, as revealed on the basis of experimental studies, is chipping along an inclined area.2. A numerical comparison of the theoretical and experimental values of the chip angles for the materials studied supports the suggestion of interpreting the chip bands as slippage bands in an ideal elastoplastic anisotropic body.3. On the basis of this suggestion, valuable equations (11)–(13) have been obtained for calculating the strength of fiberglass-plastics in compression as a function of the strength properties of the matrix and of the reinforcement, the percent reinforcement, and the cutting angle .M. V. Lomonosov Moscow State University. Translated from Mekhanika Polimerov, No. 2, pp. 240–243, March–April, 1978.     

Polymeric pairs having a low coefficient of friction

Results are given from studies on sets of pairs which have a coefficient of friction below 0.1 at medium specific loads and low rates of relative slippage. It is shown that this may be accomplished by using materials with different chemical structures in the pair, for example, Teflon and low-density polyethylene, or a self-lubricating material, for example oil-impregnated modified wood in a pair with a polymeric counterbody.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 933–935, September–October, 1973.     

Vibrational creep of polymeric materials

An experimental study of the effect of vibration on the creep process has been carried out in the case of the rigid porous polyurethane PPU-3, as a function of the magnitude of the vibrational loading and the level of basic static stresses. It has been shown that with increase in the velocity amplitude of the dynamic stresses, the creep process is accelerated, without being accompanied thereupon by vibrational heating of the material. The possibility has been established of approximating vibrational creep curves by the integral equation of Volterra, using a discrete series of relaxation times transformed by the vibro-time analogy method.For Communication No. 3, see [1].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 223–232, March–April, 1970.     

Effect of plasticization on the activation energy of failure of nitrocellulose

The authors investigate the temperature-force dependence of the service life of plasticized nitrocellulose under uniaxial tension. They show that when the plasticizer content of the polymer is sufficiently high, the activation energy U₀ of mechanical breakage is higher than the value for the same polymer without plasticizer. The authors propose the hypothesis that when the plasticizer content of the polymer is increased, an increasingly important part in the development of breakage is played by rupture of the intermolecular bonds and by mutual slippage of the segments of the macromolecules, while the part played by chemical bond rupture decreases.Presented at the Sixth Symposium on the Rheology of Polymers, Moscow, May 1971.D. I. Mendeleev Moscow Chemical Technology Institute. A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 355–358, March–April, 1974.     

Energy investigation of the softening of siloxane rubbers during deformation

The softening of filled siloxane rubbers in tension is investigated from the energy standpoint. It is shown that during extension the starting structure of the rubber is converted into a new, energetically equivalent one. It is concluded that the most probable softening mechanism for filled rubbers is a rearrangement of the macromolecular chains at the surface of the filler particles as a result of slippage. Softening anisotropy of the siloxane rubbers is observed.Institute of Hetero-Organic Compounds, Academy of Sciences of the USSR, Moscow. Synthetic Materials Council, Presidium of the Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 387–392, May–June, 1975.     

A new approach to the phenomenological interpretation of the concept of slippage

We propose a direct proof of the identity of the concepts of slippage and the Koiter version of the theory of plasticity based on parallel translation of planes enveloping the Tresk viscosity surface. One figure. Bibliography: 5 titles.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 30, 1989, pp. 55–57.     

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.     

Nonlinear shear response of fluid polymers during periodic deformation. Basic harmonics

Conclusions 1. A model with a relaxation spectrum independent of accumulated elastic strains describes the combination of data on the amplitude and frequency dependences of the components of the shear modulus in terms of basic harmonics for low-molecular-weight polyisobutylene and a filled-polyethylene melt.2. The greater the amplitude of the shear strain, the broader the region of invariance of the relaxation functions relative to the amplitude of the rate of oscillatory shear.3. The kinetic (s) function affects the amplitude dependences of the modulus in terms of basic harmonics. Its effect is significantly greater on the real component of the modulus than on the imaginary one.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1093–1100, November–December, 1977.     

Temperature-frequency reduction of the dynamic functions of black-filled rubbers in the nonlinear region

The possibility of using temperature-frequency reduction of the dynamic functions of black-filled rubbers in the nonlinear region is demonstrated and an additional applicability criterion — similar slopes of the isotherms of the amplitude dependences of the dynamic functions — is formulated. In the case of heavily filled rubbers it may be necessary to determine the constants of the Williams-Landel-Ferry equation and the reference temperature T_S from the experimental data — they may not coincide with the universal values. Master curves of the dynamic functions are obtained for a series of shock-absorbing rubbers at a shear strain amplitude =0.01.A. V. Topchiev Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow. Scientific-Research Institute of the Rubber Industry, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 751–754, July–August, 1973.     

Relation between deformation and rotational isomerism

In uniaxially oriented polyethylene and polyethylene terephthalate films conformational transitions were studied by the absorption IR-spectroscopy method during deformation of the specimens carried to rupture in a wide range of temperatures and with different loading methods. It is shown that upon elongation of the polymers the concentration of trans isomers increases and that of gauche isomers decreases. A linear unique relation is obtained between the number of rotational isomers and magnitude of deformation in the amorphous parts of the investigated polymers. It is hypothesized that the conformational transitions determine the magnitude of deformation of amorphous-crystal-line polymers.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 6, pp. 1077–1080, November–December, 1975.     

The influence of noise on a classical chaotic scatterer

A classical, chaotic scatterer consisting of three, equal-sized, equidistant hard discs, also known as the Gaspard–Rice system [Gaspard P, Rice SA. Scattering from a classically chaotic repellor. J Chem Phys 1989;90(4):2225–2241] is studied in the presence of white noise. The fractal dimension of the stable manifold is measured using the uncertainty fraction. The volume of the manifold, and thus of the invariant set, when considered in a possibilistic sense, is found to scale with the magnitude of the noise, thus extending the results of Ott et al. [Ott E, York ED, Yorke JA. A scaling law: How an attractors volume depends on noise level. Physica D 1985;16:62–78] from attracting to non-attracting sets.     

Mechanical properties of a carbon-fiber-reinforced plastic and the residual stresses in wound components made out of combined composites

A technique for calculating the residual stresses in wound components made out of mixed carbon-fiber-and glass-fiber-reinforced plastics and the results of the calculations are presented. The effect of the conditions under which the components are wound on the magnitude and nature of the residual stresses distribution in components made out of combined composites is investigated. The results of the calculations are compared with the experimental values.Translated from Mekhanika Polimerov, No. 6, pp. 996–1004, November–December, 1975.     

A new method of measuring the viscoelastic properties of polymer systems in fluid and highly elastic states using forced vibrations in the ultralow-frequency region

A method is considered for measuring the dynamic mechanical characteristics of polyer systems using forced vibrations in the ultralow-frequency region down to 10^–6 Hz. The essence of this method lies in the fact that during the measurement process the motion of the polymer sample is controlled with a set amplitude and frequency, and the dynamic characteristics of the polymer are determined from the controlling mechanical stress. The method is illustrated using the results of measurements of the components of the complex modulus for polybutadiene over a wide range of temperatures and frequencies without making use of superimposition.The Central Constructional Bureau for Prototype Instrument Construction, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 344–347, March–April, 1976.     

Experimental determination of the influence of periodic shear deformation and filling on the effective viscosity of solutions of synthetic rubber

The influence of periodic shear deformation on the effective viscosity of filled solutions of synthetic rubber has been studied. The study was carried out on an amplitude-frequency viscosimeter developed by the authors. It has been established that during periodic deformation a linear region exists in which the effective viscosity is independent of the vibration rate, and a nonlinear region where the effective viscosity of the solutions decreases with increase in amplitude of the speed of relative deformation.Presented at the IV Symposium on Rheology of Polymers at the A. V. Topchiev Institute for Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow, May 27–30, 1969.Institute for Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, 514–520, May–June, 1970.     

Strength of cylindrical shells of laminar composites under dynamic loading

Conclusion The methods described in the present review paper for the computation of cylindrical shells of laminar composites under various types of dynamic loads make it possible to calculate the stress-strain state at any point of the body of the shell at an arbitrary time and to determine the time of the first failure of a layer (including fatigue failure) using strength criterion of an anisotropic body for the case of a plane stressed state, and also the location of the first flaw in the shell. This makes it possible to determine the magnitude of the applied pulse (the amplitude of a pulsed loading), or the amplitude of a vibratory loading for which the first centers of failure appear in the design.Presented at the Second Soviet-American Symposium on the Problem Failure of Composite Materials (Bethlehem, Pa., USA, March, 1981).Translated from Mekhanika Kompozitnykh Materialov, No. 3, pp. 460–467, May–June, 1982.     

Localization of microfailure in fibrous composites

Conclusion When a fibrous composite is loaded, the process of microfailures becomes localized in consequence of the nonuiformity of internal stresses. The degree of localization can be quantitatively characterized by the magnitude of the parameter of localization whose determination was provided in the present work. The dependence of the parameter of localization on the stress applied to the specimen can be measured experimentally from the data on the location of the coordinates of the sources of AE, and it can be calculated theoretically on the basis of the model of failure of the composite. A comparison of the theoretical model with the experimental data makes it possible to determine the magnitude of the overstresses in the fibers of the composite material and the form of the distribution function of these overstresses.Translated from Mekhanika Kompozitnykh Materialov, No. 3, pp. 437–443, May–June, 1989.