Temperature stresses in a long hollow viscoelastic cylinder with variable inner boundary

As distinct from existing solutions for the state of stress and strain, in addition to the stresses created by internal pressure acting on the moving inner surface, the thermal stresses created by a temperature field are also taken into account. A solution is obtained using tabulated singular kernels of the hereditary theory of viscoelasticity.Moscow Lomonosov State University. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 219–226, March–April, 1969.     

State of stress of a hollow viscoelastic cylinder whose material properties depend on temperature

The state of stress of a long thick viscoelastic cylinder enclosed in an elastic shell is examined. The inner boundary recedes; body forces, internal pressure, and a uniform nonstationary temperature field are considered. The material properties depend on temperature; time-temperature superposition does not hold. A singular kernel is taken as the influence function. An approximate solution is found in displacements and stresses. A numerical example is presented.M. V. Lomonosov, Moscow State University. Translated from Mekhanika Polimerov, No. 1, pp. 86–94, January–February, 1970.     

Theory of spherofibrous composites. 1. Input relationships: Hypotheses and models

A theory is proposed for fibrous composites with a matrix reinforced with spherical hollow and solid inclusions based on an internal stress field and structural models. The problem solutions are obtained for the fiber-averaged matrix level. The matrix properties are determined assuming a regular distribution of the matrix inclusions. The problem of accounting for the scatter of inclusion properties on the effective composite parameters is examined.Presented at the Ninth International Conference on the Mechanics of Composite Materials, Riga, Latvia (October, 1995).A. A. Blagonravov Mechanical Engineering Institute. Russian Academy of Sciences. Moscow, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 3, pp. 291–305. May–June, 1996.     

Mechanical properties and internal shear stress field in reinforced media as a function of the type of microstructure

The effect of type of microstructure and volume content of filler and binder on the internal stress field and shear modulus has been analyzed for various composite materials. There is an "optimum" filler content at which the maximum stresses in the structure are lowest. A quantitative estimate is obtained for the error of the approximate formulas for the shear modulus of various types of structure.Mekhanika Polimerov, Vol. 3, No. 4, pp. 667–670, 1967     

Investigation of the mechanical properties and internal stress field of directionally reinforced materials in transverse tension

The dependence of the transverse Young's modulus and Poisson's ration on the reinforcement ratio, type of structure, and internal fiber radius has been investigated. The microstress field in the structure of a composite in transverse tension is analyzed. Simple approximate expressions, which can be used to determine the corresponding mechanical characteristics without analyzing the state of stress, are obtained from the exact equations. A medium reinforced with doubly periodic groups is taken as a model. The exact solutions of the problem are obtained by means of elliptic functions.Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 5, pp. 812–817, September–October, 1970.     

Calculation of the long-term strength of thin-walled polymeric tubes under biaxial loading

The problem on calculating the failure time of thin-walled polymer tubes in creep under internal pressure, internal pressure with tension, pure torsion, and torsion with tension is solved. The solution is constructed based on the concept of equivalent stresses. A mixed long-term failure criterion taking into account the sings of principal stresses is used as the equivalent stress. The calculation results are in a satisfactory agreement with experimental data.Translated from Mekhanika Kompozitnykh Materialov, Vol. 40, No. 6, pp. 811–826, November–December, 2004.     

On the statistical mechanics of deformable media

Random stress and strain fields are examined in relation to machine parts made of materials of the randomly reinforced fiberglass type subjected to random external loads. The conditions of existence of the principal axes of the fourth-order tensor representing the second-order central moments of a plane random stress or strain field are determined. A method of determining the principal axes and principal values is described. A numerical example is worked.V. A. Steklov Mathematical Institute, Sverdlovsk Branch, Academy of Sciences of the USSR. S. M. Kirov Ural Polytechnic Institute, Sverdlovsk. Translated from Mechanika Polimerov, Vol. 4, No. 4, pp. 618–623, July–August, 1968.     

Determination of the stresses in polymeric coatings with allowance for "frozen" strains

The state of stress and strain of polymeric coatings is determined in the case of a time varying temperature field that includes the range on which the coating goes over into the glassy state.Leningrad Mechanical Institute. Translated from Mekhanika Polimerov, No. 1, pp. 66–71, January–February, 1973.     

Flexure of transversely isotropic plates with a low resistance to transverse deformation

This study is concerned with the stress field around holes in plates of a transversely isotropic material, such as a reinforced plastic, with a low resistance to transverse, normal, and tangential deformation. The problem is solved on the basis of the general theory according to I. N. Vekua. It is shown that in the case of a strongly anisotropic material disregarding the transverse deformation will lead to a large error in the determination of the stress field.Institute of Metallurgy, Dnepropetrovsk. Institute of Mechanics, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 1, pp. 89–92, January–February, 1974.     

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.     

Modeling the mechanical behavior of metal-reinforced plastic pipes under internal pressure

Numerical nonlinear models for the mechanical behavior of the metal-reinforced plastic pipes (MRP) in destructive tests are developed to analyze the stress-strain state (SSS) in such pipes during loading. The influence of contact conditions at the polyethylene-steel boundary on the SSS of the metal-reinforced plastic pipes at normal temperatures is considered. A criterion of ultimate state of MRP is suggested to predict the load-carrying capacity of the pipes under internal pressure. The behavior of a welded butt joint of the MRP is studied, a stress redistribution phenomenon in the reinforcing skeleton is revealed, and the results obtained in destructive tests of butt joints are explained.Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 1, pp. 57–70, January–February, 2005.     

Strength of reinforced plastics under static loading

The question of the static fatigue of reinforced plastics is considered for plane stress. Relations that predict the static fatigue are given for very simple types of loading. Experimental data are presented for thin-walled tubes of SVAM (5:1) glass-reinforced plastic subjected to long-time tests at constant internal pressure.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 265–273, March–April, 1969.     

Effect of temperature on the dynamic properties of polyethylene

When the temperature is reduced and the loading rate increased, parts made of low-density polyethylene exhibit brittle fracture. The brittle point depends on the nature of the supermolecular structure formed during processing. A method is proposed for determining brittleness by means of impact tests that also gives qualitative information about the internal stress relaxation kinetics.Mekhanika Polimerov, Vol. 4, No. 2, pp. 263–270, 1968Part 1 of a series on the dynamic properties of crystalline polymers.     

Effect of tensile stresses on the strength of heat-treated glass fibers

Possibilities of controlling the internal stresses developing during production of glass reinforced plastics were investigated. A favorable effect can be obtained by prestressing the glass fiber reinforcement during molding. Prestressing during heat treatment was found to increase the strength of the fibers. The strengthening is due to a reduction in stress concentration around microcracks as a result of forced elastic and plastic deformation.Mekhanika polimerov, Vol. 1, No. 1, pp. 89–92, 1965     

Thermodynamic determination of the shift factor

The determination of the shift factor is examined on the basis of the thermodynamics of irreversible processes assuming a closed homogeneous system. It is shown that for any internal state the shift factor is equal to the product of the temperature and stress shift factors. An equation in which the nonequilibrium character of the processes is taken into account is obtained for the temperature shift factor.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1001–1010, November–December, 1973.     

Low-frequency internal friction in complex composite strands

Conclusion A method was proposed which makes it possible to study the low-frequency internal friction of complex fibers. This method was used to study the internal friction of complex composite fibers based on PCA and PE. We observed a relaxation process which is typical of the composite and is absent in the pure materials.Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 11–15, January–February, 1989.     

Macromolecular mechanics

The fundamentals of "macromolecular" mechanics are outlined and approximate quantitative relations are established between the parameters of the mechanical properties of elastically stretched macromolecules and the characteristics of the mechanical properties of polymers determined at significant uniaxial deformations. This new scientific approach is based on the assumption of "framework connectivity." The conditions of internally compensated mechanical equilibrium at the molecular level are investigated. Several variants of simple geometric models of the "framework" reinforcing the stretched polymer are proposed. A system of quantities characterizing the mechanical properties of the polymer and the "framework" is developed. According to the theory, the stress in the "framework" macromolecules, considered as a molecular elastic continuum, substantially exceeds the stress in the stretched polymer. The nature of the internal stresses and elastic aftereffect in glassy crystalline polymers subjected to significant deformation is reinterpreted.Moscow. Translated from Mekhanika Polimerov, No. 2, pp. 221–231, March–April, 1971.     

Mechanical characteristics of medium-sized human blood vessels

Conclusions 1. The authors have developed a method of mechanically testing medium-sized vessels that takes into account their structural characteristics and the properties of the walls. The method is based on obtaining the mechanical characteristics by extending annular and cylindrical specimens and comparing the radial displacements calculated from the mechanical characteristics obtained with the radial displacements obtained by subjecting the vessels to internal pressure and axial tension. A comparison of the experimental and calculated data indicates good agreement.2. As a result of the experiments and calculations, relations are obtained for the moduli of elasticity and Poisson's ratios as functions of the stress level.3. The experimental procedure developed makes it possible not only to take into account the structure of the vessel but also to obtain the stress levels in the vessel walls, using the equilibrium equation.N. É. Bauman Moscow Higher Technical School. Translated from Mekhanika Polimerov, No. 4, pp. 708–711, July–August, 1978.     

Stressed state of a rock mass around a working with a relief cavity

The stressed state of a rock mass in the vicinity of a preparatory working protected by a relief cavity is studied. A numerical study is made of the stress field and the relief zone, and the effect of length and slope of a slot on formation of the relief zone is clarified.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 20, pp. 31–36, 1989.     

Effect of the conditions of formation of glued joints on their thermophysical properties

A correlation has been experimentally established between the thermal resistance of adhesive films and the internal stresses that develop during the curing process. During cure the thermal resistance varies in parallel with the internal stresses. It is assumed that the development of thermal resistance is determined by the tension produced in the film by the development of the internal stresses.Voronezh Forest Engineering Institute. Translated from Mekhanika Polimerov, No. 4, pp. 754–756, July–August, 1973.