Possible flow mechanisms of polymer solutions and melts

The experimental results on combined parallel stationary flow and linear periodic deformation are analyzed. The correlation limits of the frequency viscoelastic functions and the stationary flow characteristics, determined by the flow mechanisms at different shear rates, are established.Presented at the 5th Symposium on Rheology, Moscow, May, 1970.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 546–549, May–June, 1971.     

Resolvents of the theory of orthotropic shells with low shear stiffness in force-moments and stress functions

The problem of the theory of orthotropic layered shells with low shear stiffness is reformulated in force-moments and stress functions on the basis of new strain continuity relations constructed with allowance for transverse shears.Physicomechanical Institute, Academy of Sciences of the Ukrainian SSR, L'vov. Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 950–952, September–October, 1970.     

Flow characteristics of a metasilicate-filled low-density polyethylene melt

Certain of the flow characteristics of a filled low-density polyethylene melt have been investigated. The results obtained are compared with the results of measurements in the single-frequency vibrational shear regime.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 693–697, July–August, 1969.     

Thermal-fluctuation model of a thixotropic rubbery liquid

The isothermal deformation of a viscoelastic liquid, whose structural elements are simulated by the Maxwell elements of the relaxation spectrum, is considered. It is assumed that in the presence of temperature fluctuations the elements of the spectrum can be destroyed and restored. A comparison is made with experiment. A procedure for calculating the relaxation spectrum from the results of shear and normal stress measurements in the steady-state shear flow regime is proposed.Presented at the Symposium on Polymer Rheology, Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow, May, 1970.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 307–317, March–April, 1971.     

Periodic deformation and viscous flow of polymer solutions and melts

The transition from the start of deformation to the establishing of a stationary state of nonlinear, periodic shear deformation and the kinetics of the change in the mechanical characteristics after deformation at finite amplitudes has ceased have been investigated. The calculated values have been compared with those obtained experimentally.For Communication 2 see [3].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Institute of Mechanics Problems, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 521–529, May–June, 1970.     

On the applicability of two-dimensional applied theories to problems of the stability of axially loaded cylindrical shells made of materials with low shear stiffness

The applicability of two-dimensional applied theories of the Kirchhoff-Love, Timoshenko, and Ambartsumyan types to problems of the stability of shells with low shear stiffness [1] is discussed. The critical loads given by these theories are compared with those recently obtained [6–8] by solving the problem of the stability of a cylindrical shell on the basis of general solutions [3, 4] of the three-dimensional linearized equations of the theory of elasticity [5].Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. L'vov Polytechnic Institute. Translated from Mekhanika Polimerov, No. 1, pp. 141–143, January–February, 1970.     

Periodic shear deformation of a curing epoxy composition

The curing of an epoxy resin with amines is investigated in relation to the changes in the viscoelastic shear characteristics. The effect of the shear deformation amplitude on the curing kinetics is considered.Presented at the Symposium on Polymer Rheology, Institute of Petrochemical Synthesis, Academy of Sciences of the USSR, Moscow, May, 1970.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 301–306, March–April, 1971.     

Viscoelastic characteristics of the interaction between structures and soils

The shear coefficients of a body relative to the soil and the shear creep and relaxation kernels are determined from the data of creep and relaxation tests.Urazbaev Institute of Mechanics and Earthquake Resistance of Structures, Academy of Sciences of the SSR, Tashkent. Translated from Mekhanika Polimerov, No. 2, pp. 207–211, March–April, 1973.     

Effect of steady-state flow of a polyisobutylene solution on its dynamic characteristics measured in the direction of flow

The effect of steady-state flow on the linear dynamic characteristics of a 10% solution of polyisobutylene in cetane, measured in the direction of flow, is investigated. The material characteristics in steady-state flow quantitatively describe the dynamic viscosity and elasticity at deformation frequencies small as compared with the steady-state shear rate.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 913–919, September–October, 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.     

Some negative characteristics of fiber-reinforced materials

The effect of low resistance to shear and tension-compression at right angles to the layers of reinforcement on the state of stress and strain of elements composed of fiber-reinforced materials is analyzed. It is shown that to take these characteristics into account the calculations must be refined. In certain cases this leads to the appearance of qualitatively new effects. Typical problems in which the negative characteristics of the material must be allowed for are examined.Review of research conducted in the Polymer Structures Laboratory of the Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 140–149, January–February, 1969.     

Variation of the deformation resistance of phenol-formaldehyde thermosets during cure

The dependence of the viscosity of phenol-formaldehyde thermosets on the previous thermal history has been investigated at a fixed shear rate.Moscow Institute of Chemical Machine Building. Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 619–623, July–August, 1971.     

Experimental investigation of the deflection of beams made of fiberglass plastics,resting on an elastic base

Results obtained in the testing of beams made of LSB-F fiberglass plastic are compared with those calculated on the basis of shear between layers.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 946–949, September–October, 1972.     

Analysis of certain methods of determining shear moduli 1. Testing composites uniform over the thickness

Four methods of determining shear moduli on flat specimens are discussed. For each method the effect of the geometric parameters and the load range on the values of the shear moduli determined is estimated. Experimental values of the shear moduli obtained by each of these methods for the same materials are compared with the calculated values.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 133–140, January–February, 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.     

Thixotropy of filled-polyethylene melts subjected to periodic shear deformation

As a result of the action of periodic finite-amplitude shear deformations filled high-pressure polyethylene melts exhibit thixotropic properties. The effect of the previous deformation history on the frequency dependence of the complex dynamic shear modulus is investigated.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR Riga. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 927–931, September–October, 1968.     

Periodic deformation and viscous flow of polymer solutions and melts

The effect of nonlinear periodic deformation on the relaxation spectra and viscous-elastic characteristics of polymer melts and solutions is considered. The experimental and calculated relationships between the dynamic characteristics and effective viscosity and the amplitude of the rate of periodic deformation were compared.For Communication 1, see [6].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Institute of Mechanics Problems, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 357–366, March–April, 1970.     

Rheological characteristics of a low-molecular branched polyethylene melt near the melting point

Data are presented on the rheological characteristics of low-density polyethylene with near-critical molecular weight at 110°C. A comparison of the shear rate dependence of the viscosity in repeat measurements indicates that the material has a kinetic memory for isothermal, shear flow-initiated crystallization from the melt.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga; Plastpolimer Research and Production Association, Leningrad. Translated from Mekhanika Polimerov, No. 6, pp. 1129–1132, November–December, 1973.     

Effect of nature of metallic subs trate on adhesion strength of polyvinylbutyral - metal joints

The effect of the physicomechanical properties of the substrates on the adhesion strength of the metal—polymer system was investigated.Institute of the Mechanics of Polymers, Academy of Sciences of the Latvian SSR, Riga. Institute of Chemistry and Chemical Technology, Academy of Sciences of the Lithuanian SSR, Vil'nyus. Translated from Mekhanika Polimerov, No. 1, pp. 81–86, January–February, 1972.     

Static and vibrational creep of a fabric-reinforced plastic in shear in the plane of the reinforcement

The results of a comparative experimental investigation of the short-term static and vibrational creep of a fabric-reinforced plastic in shear in the plane of the reinforcement are presented. The experimental procedure is described in detail. It is shown that on the investigated ranges of temperature, stress, and amplitude-frequency parameters the effect of an additional vibrational load on the creep process is unimportant.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 605–610, July–August, 1971.