Predicting the Deformability of Expanded Polystyrene in Short-Term Compression

A regressive model is presented for the relationship between the compressive stress and strain of expanded polystyrene (EPS) on a 0–35% strain range. On the whole, the model agrees well with experimental data. A practical way is suggested for determining the coefficients of the model from the known density of EPS plates and their compressive stress at a 10% strain. The model allows one to predict the critical compressive stress and the elastic modulus of EPS.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 2, pp. 157–162, March–April, 2005.     

Analitical Description of the Creep of Expanded Polystyrene under Compressive Loading

Data obtained in testing the creep of expanded polystyrene plates in compression are discussed. Power-type and exponential regression equations are used for describing the compression creep curves. Within the limits of data spread, both these equations represent experimental results equally well. A correlation between the creep strain and density, the compressive stress at a 10% strain, and the elastic modulus in compression is revealed for the material investigated.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 4, pp. 525–534, July–August, 2005     

Density changes in stretched polymers

Data are presented on the relation between the density of polystyrene and polyvinyl alcohol specimens and the relative elongation. The change in density observed during the stretching of polyvinyl alcohol specimens is associated with changes in the optical density of the 1146 cm^–1 band and the crystalline phase content of the polymer.Mekhanika Polimerov, Vol. 3, No. 5, pp. 777–781, 1967     

Quasistatic anti-plane motion in the simplest theory of nonlinear viscoelasticity

We consider a very simple model in the framework of differential viscoelastic materials which are isotropic and incompressible. In this model the Cauchy stress tensor is split in an elastic part and a dissipative part. The elastic part is derived from a strain-energy density function only of the first invariant of the Cauchy–Green strain tensor. The dissipative part is like the Navier–Stokes equations: linear in the stretching tensor with a constant viscosity parameter. For this model we provide some time and spatial estimates in the quasistatic approximations for the equations governing anti-plane shear motions. Several explicit examples for specific form of the strain energy are produced. Our results impose analytical restrictions on the mathematical properties of the strain energy to ensure a physical behavior in the creep and recovery experiments. Moreover, we show polynomial decay for the spatial behavior in the class of stress-hardening (or strain-stiffening) materials. For stress-softening materials a Phragmen–Lindelof alternative is proved.     

Determination of the optical density of human coronary arterial walls

Conclusions 1. The greatest thickness is found for the segment of a coronary artery adjacent to the myocardium; this effect is observed even in a neonate.2. At a young age, the greatest thickness is found for the middle and outer wall layers of both coronary arteries.3. In individuals reaching age 40 and having atherosclerosis of the major branches of the cardiac arteries, the walls of both coronary arteries become thicker due to the inner and middle layers, but the thickening of the individual layers is most pronounced in the wall of the left coronary artery.4. The method of optical densitometry relative to stained histological sections of the vascular wall may be used for the relative determination of the densities of tissues and their distributions over the individual wall layers.5. The optical density of elastic tissue of the walls of the coronary arteries reaches a maximum in the third decade of life in the human and decreases after age 40 (especially in the distal segment of the left coronary artery).6. The optical density of the total connective tissue in the walls of the left coronary artery increases with increasing age, especially in the distal segment of this artery. In youth, the optical density of connective tissue is greater in the wall of the right coronary artery, but with increasing age this density decreases markedly.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 312–318, March–April, 1978.     

Effect of the incompressibility condition on the stability of the solutions of ill-posed problems of the theory of elasticity

One considers the energy functional with density depending only on the first invariant of the strain tensor. Under natural constraints on the density and in the absence of exterior actions, the zero displacements yield a minimum to the energy functional both for the compressible and the incompressible media. In the paper one proves the isolation of this minimum for incompressible media and its nonisolation for compressible media.Translated from Problemy Matemticheskogo Analiza, No. 10, pp. 62–71, 1986.     

Effect of hydrostatic pressure on the density of various plastics

It is shown that application of hydrostatic pressure causes an increase in the density of ebonite but practically no change in the density of polyethylene, kapron (nylon-6), PVC, plexiglas, and FKP-1. Uniaxial compression of some materials first increases their mean density, then, at fairly high strain, causes the density to decrease. For the majority of the materials examined, the rate of this reduction in density decreases in the simultaneous presence of hydrostatic pressure.Mekhanika Polimerov, Vol. 2, No. 3, pp. 355–358, 1966     

Periodic axial and shear deformation of polymers in the viscous-flow state

Results are given of an experimental investigation of the combined periodic axial and shear deformation of polymers in the viscous-flow state. Specimens in the form of right cylinders were disposed between two parallel plates to which the material adhered completely. The experimental data are compared with those obtained under simple shear. The results indicate that, with combined periodic axial and shear deformation, nonlinear shear deformations affect the axial viscoelastic properties and nonlinear axial deformations affect the shear properties of the material.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 880–885, September–October, 1972.     

Crosslinked polychlorostyrene as an optically sensitive material for photoelastic stress analysis

The photoelastic properties of chlorostyrene-ethylene glycol dimethacrylate copolymers have been investigated. Thanks to the high segmental polarizability anisotropy of chlorostyrene and the possibility of regulating the crosslink density in the crosslinked polymer, these materials possess high optical sensitivity combined with a broad range of moduli of elasticity at the "freezing" temperature.Institute of High-Molecular Compounds, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 554–556, May–June, 1969.     

Study of the role of intermolecular interactions (hydrogen bonds) in the initial stage of orientation of polyvinyl alcohol and vinyl alcohol copolymers

The effect of hydrogen bond rupture on the process of destruction of the starting crystallite structure of polyvinyl alcohol and copolymers of vinyl alcohol and N-vinylpyrrolidone and -vinylcaprolactam has been investigated. The differential spectrum method is used to establish the frequency (3200 cm^–1) of the band corresponding to the vibrations of the bound hydroxyl groups; the temperature dependence of the optical density of the 3200 cm^–1 band has been recorded. The strength of the starting structure is calculated from the stress-strain diagram and its temperature dependence is plotted. It is concluded that the strength of the starting structure is chiefly determined by the presence of hydrogen bonds between the polymer macromolecules.Leningrad Kirov Institute of Textile and Light Industry. Translated from Mekhanika Polimerov, No. 2, pp. 327–329, March–April, 1971.     

Generalizations of the Nikodym boundedness and Vitali–Hahn–Saks theorems

Generalizations of the Nikodym boundedness and Vitali–Hahn–Saks theorems for scalar-valued measures on rings of sets that are in general not σ-rings are presented. As a consequence, the rings of subsets of N with density zero and uniform density zero are shown to have the Nikodym property. In addition, vector measure generalizations of the Vitali–Hahn–Saks theorem are given.     

Optimization of the axial stability of equal-strength reinforced cylindrical pressure vessels

The class of reinforced cylindrical shells obtained by spiral winding with reinforcing ring or longitudinal layers is considered. The structure of the shells is optimal with respect to internal pressure. The reinforcement angle is selected so as to maximize the critical axial load.Translated from Mekhanika Polimerov, No. 6, pp. 1123–1126, November–December, 1973.     

Melting of Two-Dimensional Systems: Dependence of the Type of Transition on the Radius of the Potential

In the framework of the two-dimensional melting theory based on the density functional approach, we use a Monte Carlo computer simulation to study melting of a two-dimensional hard disk system with a rectangular-well attraction potential. We show that depending on the attraction radius, the melting can occur via a single first-order transition as well as continuously in accordance with the Kosterlitz–Thouless–Halperin–Nelson–Young theory.     

Relaxation and optical properties of cured epoxy resin

Epoxy resin cured with methyltetrahydrophthalic and maleic anhydrides has been tested in relaxation, creep, and compression at constant strain rate. The constants characterizing the relaxation properties and the approximate limits of the spectrum of most probable relaxation times have been determined; it is shown that the mechanical properties can be described by means of equations with two relaxation times. The residual optical effect has also been investigated. A linear relationship between the high-elastic strains and the path difference in the birefringent state is preserved at temperatures below the glass transition region.Read at Moscow State University polymer mechanics seminar.Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 15–23, January–February, 1970.     

The dynamic properties of polyethylene and an acrylonitrile — Butadiene — Styrene material in a broad range of temperature and strain-rate variation

Conclusions The mechanical properties of an acrylonitrile-butadiene-styrene material and polyethylenes of densities =0.92 and 0.96 g/cm³ are studied within the temperature range of from 100 to –196°C and at strain rates of from 10^–3 to 1.3 · 10³ sec^–1. It is observed that under low-temperature and high-strain-rate conditions, the laws governing the mechanical properties of the acrylonitrile-butadiene-styrene material and polyethylenes are similar. Regions of strain rates and temperatures are found for which the behavior of the test materials is in good agreement with the Ree-Eyring equation, and, consequently, conforms to a temperature-time analogy. No embrittlement of the polyethylene is observed during tests at strain rates to 1.3 · 10³ sec^–1 and temperatures down to –196°C. In approximating these values of and T, the mechanical properties of polyethylenes will cease to be dependent on initial density.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, 1027–1033, November–December, 1978.     

Effect of deformation rate on the vector properties of polyethylene

On the basis of experiments with strain trajectories in the form of two-segment broken lines it is shown that the vector properties of low-density polyethylene do not depend on the strain rate.M. V. Lomonosov Moscow State University. Translated from Mekhanika Polimerov, No. 4, pp. 739–741, July–August, 1973.     

Experimental study of the effect of friction and bending on the strain distribution around the perimeter of a glass-reinforced plastic ring with unidirectional structure

The effect of friction and bending on the circumferential strain distribution in glass-reinforced plastic rings with unidirectional structure, stretched by two rigid half-disks, has been experimentally investigated. Strain distribution curves for rings of various thicknesses are given. The strain distribution at different levels over the thickness of the ring and the change in compressive strain along the radius have been studied.Institute of Chemical Physics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 947–949, September–October, 1971.     

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.     

Static strength and failure mechanism of CFRP under biaxial loadings

Tests of cross-ply composite tubes were performed under combined axial and torsional loading up to failure. Strength properties and failure mechanisms were evaluated with reference to the biaxiality ratio of the loading. The scattering of the biaxial strength data was analyzed using the Weibull distribution. The axial contraction of carbon fiber-reinforced plastic (CFRP) tubes under biaxial loading was investigated theoretically and experimentally. Artificial neural networks were introduced to predict the failure strength using the algorithm of the error back-propagation. The prediction was also made by the Tsai-Wu theory using the experimental data and by the combined optimized tensor-polynomial theory. A comparison shows that the artificial neural network has the smallest root-mean square (RMS) error of the three prediction methods. The prediction of the axial contraction of the tubes correlates well with the results of a linear variable differential transformer (LVDT) of the testing machine. From the phenomenological analysis of the failure and the fractographic observations of the fracture surface, three types of failure modes and microscopic failure were investigated, depending on the biaxiality ratio, and the corresponding failure mechanisms are suggested.Submitted to the Tenth International Conference on Mechanics of Composite Materials, Riga, April 20–23, 1998.Department of Mechanical Engineering, Pohang University of Science and Technology, Pohang 790–784, Korea. Published in Mekhanika Kompozitnykh Materialov, Vol. 34, No. 1, pp. 38–56, January–February, 1998.     

An experimental study of the deformation of multilayer cylindrical shells

Experimental results are presented on the deformation of two-layer and four-layer reinforced shells subject to static loading. The strains on the outside and inside surfaces are unequal at points remote from the region of the edge effect when the shell is subject to an internal pressure and an axial force.P. I. Baranov Central Institute for Aviation Engine Design. Translated from Mekhanika Polimerov, No. 5, pp. 943–944, September–October, 1973.