Determination of the physicomechanical characteristics of viscoelastic materials in orthotropic and isotropic layers from the propagation velocities and damping constants of longitudinal and shear vibrations

The author examines the propagation of longitudinal and shear waves in viscoelastic orthotropic and isotropic layers. Relations are obtained for determining the elastic constants and the real and imaginary parts of the complex moduli and Poisson's ratios in orthotropic and isotropic layers from the propagation velocities and damping constants of longitudinal and shear vibrations.Mekhanika Polimerov, Vol. 3, No. 1, pp. 161–166, 1967     

On bending vibrations of a periodically inhomogeneous orthotropic plate

The matrix technique which has been developed by the author in connection with solving the problem of elastic wave propagation in an unbounded medium with periodic inhomogeneities is applied. The formalism is extended to the case of bending vibrations of inhomogeneous and periodically inhomogeneous orthotropic plates.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova, Vol. 179, pp. 179–181, 1989.     

Ultrasonic determination of the stiffness characteristics of an orthotropic material with imperfect elasticity

The propagation parameters of ultrasonic vibrations in an orthotropic material with imperfect elasticity have been measured. The results of the measurements are used to calculate the complex stiffness characteristics, and the correspondence between the nature of the anisotropy and the adopted model is examined. The anisotropy of the inelastic properties is investigated.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 195–206, March–April, 1973.     

Creep and long-time strength of unidirectional reinforced plastics in compression

An attempt is made to predict the creep and long-time strength of unidirectional reinforced plastics in compression in the direction of the reinforcement from the properties of the components. The reinforcement is assumed to be elastic, while the resin is described by a Boltzmann-Volterraintegral equation with fractional-exponential Rabotnov kernel. Experimentally obtained creep and long-time strength curves are presented for unidirectional reinforced plastics.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 830–835, September–October, 1970.     

Elastic and strength characteristics of a glass-reinforced plastic in compression

The elastic constant and strength characteristics in compression have been experimentally determined for a cold-cured glass-reinforced plastic in the direction of all three principal axes of anisotropy. It is shown that the elastic constants obtained satisfy the constraints imposed on orthotropic materials by the thermodynamic relations.Translated from Mekhanika Polimerov, No. 5, pp. 866–869, September–October, 1970.     

Solution of some dynamic problems of viscoelasticity theory by the averaging method

Damping of longitudinal vibrations of a viscoelastic bar and transverse vibrations of a freely supported orthotropic plate is investigated by the averaging method. The problem of the forced movement of a viscoelastic cylinder enclosed in a thin elastic shell under the effect of an arbitrarily time-varying internal pressure is studied.Institute of Cybernetics at the Computer Center Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Mekhanika Polimerov, No. 2, pp. 246–252, March–April, 1970.     

Polarization-spectral anomalies of surface waves in an almost layered elastic half space

The propagation of Love and Rayleigh waves in an isotropic elastic half space whose properties vary little in a horizontal direction is considered. Expressions are obtained for the admixed components of the displacements.Translated from Zapiski Naukchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 165, pp. 102–114.     

Structural approach to calculation of the effect of moisture on elastic characteristics of organoplastics

Data have been obtained for the structural calculation of the effect of moisture on the elastic characteristics of organoplastics from the properties of components. The distribution of moisture between the fiber and matrix — the components of a unidirectional composite — is considered. The elastic properties of the fiber are determined by an inverse calculation using the experimental dependences of the composite and matrix on moisture. The moisture effect on the properties of the materials is taken into account with influence functions, which differ by more than 25% for various characteristics. The results can be used for calculating the elastic properties of composites with various reinforcement schemes and at the nonequilibrium distribution of the moisture concentration in an actual environment.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Institute of Polymer Mechanics, Riga, LV-1006, Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 4, pp. 525–530, July–August, 1998.     

Wave propagation through a high-velocity elastic layer

We consider theoretical seismographs of a wave field passing through an elastic layer with high propagation velocity. We note the presence of a low-frequency part of the seismogram for longitudinal waves. It is shown that the propagation time of low-frequency vibrations is equal to that of longitudinal disturbances screened by the layer.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova, AN SSSR, Vol. 173, pp. 134–141, 1988.     

Vibrations of a viscoelastic cylinder with an elastic shell

The nonlinear vibrations of a viscoelastic cylinder with an elastic shell subjected to two harmonic forces are investigated using the averaging scheme described in [3, 4]. Nonresonance, resonance, and subharmonic vibrations are examined. It is shown that the presence of viscosity in the system leads to a single stationary equilibrium position for which the stability conditions are given.V. I. Lenin Tashkent State University. Translated from Mekhanika Polimerov, No. 4, pp. 691–697, July–August, 1973.     

Stability with the axial compression of an axisymmetrically heated orthotropic cylindrical shell fastened to an elastic cylinder which is pliable with respect to shear

The article gives a solution to the problem of stability with the axial compression of an axisymmetrically heated orthotropic cylindrical shell fastened to an elastic thin-walled cylinder through an intermediate layer. It is assumed that the parameters of the elasticity of the orthotropic shell depend on the temperature, and vary over the thickness of the wall. The intermediate layer is assumed to be isotropic and absolutely rigid in a radial direction, but pliable with respect to axial shear. The thin-walled cylinder is considered to be elastic, isotropic, and unheated.Scientific-Research Institute for Chemical Engineering, Moscow Region. Translated from Mekhanika Polimerov, No. 3, pp. 546–550, May–June, 1970.     

Deformation and strength properties of carbon-reinforced plastics in compression

The deformation and strength properties of unidirectionally reinforced carbon plastics have been experimentally investigated for uniaxial compression in the longitudinal and transverse directions and at 45° to the direction of reinforcement in both short-time and long-time tests. On the basis of the deformation properties of the components an attempt is made to describe the creep curve of the plastic in all three loading directions. The Mohr theory is used to predict the compressive strengths in the direction of reinforcement and at right angles to the reinforcement.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 29–35, January–February, 1973.     

Numerical model of one possibility of determining the tensor of elastic constants of an anisotropic body

An algorithm for a digital computer is presented which permits calculating the tensor of the elastic constants of a material with any given symmetry on the basis of experimentally measured Young moduli and Poisson ratios for several specimens oriented in unequivalent crystallographic directions. The results of determining the components of the tensor of elastic constants by means of it for a modification of orthotropic reinforced plastic are also given.Translated from Mekhanika Polimerov, Vol. 9, No. 3, pp. 436–442, May–June, 1973.     

Elastic characteristics of ferrocement reinforced by hexagonal grids

The methods of the structural mechanics of composite materials are used to develop a method for predicting the elastic modulus and shear modulus of ferrocement reinforced with hexagonal woven and stamped grids. The method takes into account the elastic properties of the components and the geometry of the reinforcement.Riga Technical University, LV-1047 Latvia. Translated from Mekhanika Kompozitnykh Materialov, No. 2, pp. 182–186, March–April, 1997.     

The method of averaging in nonlinear dynamical problems occurring in the theory of viscoelasticity

The degenerate vibrations of an oscillator with slightly nonlinear elastic properties and a memory characteristic have been investigated with the aid of the averaging technique proposed in [2]. The vibrations have been studied in the case of fractional resonance and the principal resonance. A basis for the principle of averaging a nonlinear multidimensional system over an infinite time interval has been given.V. I. Lenin Tashkent State University. Translated from Mekhanika Polimerov, No. 1, pp. 39–44, January–February, 1972.     

Optimal rigidity of a thin-walled orthotropic cylinder in combined tension and torsion

The problem of optimizing the reinforcement of an orthotropic cylinder in combined torsion and tension is considered in relation to the condition of minimum displacement. A numerical example is given. It is shown that the stiffness depends on the ratio of the normal and shear stresses, the elastic moduli, and the parameters.Moscow Aviation Technological Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1121–1123, November–December, 1973.     

Dependence of elastic and strength characteristics of high-modulus composites on schemes of reinforcement

The elastic and strength characteristics of high-modulus composites with 12 different reinforcement schemes have been studied thoroughly. The effect of reinforcement schemes on change in elastic and strength characteristics of composites has been evaluated. A calculation of the elastic characteristics of high-modulus composites has been performed from the properties of the reinforcement and binder, and a comparison of the results with experimental data is given. Diagrams of deformation upon extension of the composites studied are given.All-Union Scientific-Research Institute of Aviation Materials, Moscow. Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1019–1027, November–December, 1974.     

Physical relations for an orthotropic material in the local strains theory

Compressible and incompressible orthotropic materials are investigated. A method of constructing variants of the local strains theory describing the deformation properties of an orthotropic material is developed on the basis of the concept of an elastic potential.Institute of Polymer Mechanics, AS LatSSR, Riga. Translated from Mekhanika Polimerov, Vol. 4. No. 6, pp. 970–975, November–December, 1968.     

Composites reinforced with a system of three straight mutually orthogonal fibers

The effectiveness of reinforcement in direction 3 has been estimated by investigating the mechanical characteristics of two types of three-dimensionally reinforced materials differing with respect to the arrangement of the reinforcement and the fiber content in each direction. The superior transverse stiffness, shear strength, and transverse tensile strength of three-dimensionally reinforced composites based on a system of three mutually orthogonal fibers, as compared with laminated materials, is demonstrated. The theoretical values of the elastic constants, calculated from the relations of [5], are compared with the experimental data.For communication 1 see [5].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1011–1018, November–December, 1973.