Variation of certain mechanical properties of human compact bone tissue with age

The nature of the variation of the moduli of elasticity, shear moduli, and flexural and torsional decrements of human compact bone tissue during biological aging has been investigated. It has been found that the moduli of elasticity and shear moduli increase sharply up to age 20–25 and then progressively fall; the distribution of the modulus of elasticity over the individual zones of the cross section of the tibia changes significantly with age. By investigating the changes in the logarithmic decrements by nondestructive methods it is possible to estimate the changes in the mechanical and structural properties of the bone.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 885–891, September–October, 1974.     

Relaxation phenomena in rubber-like polymers with small deformation above the glass transition temperature

In the temperature region in which rubber-like polymers have a high elasticity, a high-temperature subregion has been observed which is characterized by the presence on the extension curve of a critical strain at a small deformation (1–2%). The rigidity of the polymer below and above the critical value is different. The relaxation character of this phenomenon is considered.V. I. Lenin Moscow State Pedagogical Institute. Laboratory of Polymer Physics Problems. Translated from Mekhanika Polimerov, No. 3, pp. 544–546, May–June, 1970.     

Wear resistance of cured epoxy-novolac compositions

It has been established that changing the elasticity of rigid crosslinked epoxy-novolac block copolymers changes the friction mechanism and wear characteristics. The optimal conditions for obtaining block copolymers with the greatest wear resistance have been determined. The results of testing epoxy novolacs in neutral and alkaline media are presented.Leningrad Lensovet Technological Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1107–1109, November–December, 1969.     

Elastic unbalance of composite rim flywheels

Elastic unbalance of a composite flywheel is considered to be caused by different strain character of the rotating rim due to the distributed material density homogeneity or the corrective mass balancing it in the static state. An analysis has been carried out on the effect of elasticity of the rim flywheel on the linear elastic unbalance and its magnitude for an actual composite flywheel has been calculated. A procedure has been developed for the elimination of unbalance using two corrective masses. The problem of angular unbalance of a rim flywheel has also been considered. The finite element method has been used for computation.Translated from Mekhanika Kompozitnykh Materialov, Vol. 30, No. 4, pp. 552–561, July–August, 1994.     

Effect of fiber curvature on the modulus of elasticity for unidirectional glass-reinforced plastics in tension

The effect of curvature of the fibers on the modulus of elasticity of unidirectional glass-reinforced plastics (GRP) in tension has been investigated on the basis of the theory of layered reinforced media with random initial irregularities [1,2]. It is shown experimentally that relatively minor distortion of the fibers during manufacture may result in important changes in the modulus of elasticity. A model is proposed for determining the effect of fiber curvature on Young's modulus; experiments on specimens with a given regular fiber curvature indicate good agreement with the theory. The effect of prestressing the fibers on the modulus of elasticity has been studied using commercial AG-4S material and the optimum prestress has been established.Mekhanika Polimerov, Vol. 3, No. 2, pp. 243–249, 1967     

Higher-order elasticity and strength surface tensors in the two-dimensional case

The number of independent components of the higher-order elasticity and strength surface tensors has been calculated for the two-dimensional case. Media with different symmetry classes are considered.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 372–374, March–April, 1974.     

Determination of the static strength of plastics from the elasticity and internal friction characteristics

It has been shown experimentally that the tensile or compressive strengths of various plastics on a broad temperature range can be estimated from the values of the dynamic modulus of elasticity and logarithmic decrement measured by a vibration method.All-Union Scientific-Research Institute of Aviation Materials, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 551–554, May–June, 1976.     

Zero-moment laminated cylindrical shells with variable elasticity parameters obtained by the continuous winding method

Conclusions The general solution in the displacements of the problem of thermal-force loading of a zero-moment laminated cylindrical shell with variable elasticity parameters has been obtained in analytic form. Boundary-value problems for the practically important and often realized boundary conditions which arise in tests of samples, models, and natural structures have been discussed.Presented at the Fifth All-Union Conference on the Mechanics of Polymer and Composite Materials (Riga, October, 1983).Translated from Mekhanika Kompozitnykh Materialov, No. 3, pp. 493–502, May–June, 1984.     

Structural changes in a cotton fiber under load

Mechanical tests and x-ray studies have shown that a shift of the meridional reflection towards smaller angles signifies the stretching of the crystallite lattice in the meridional direction. The shift has been used to determine the modulus of elasticity of the crystal lattice of cotton. The microdeformation (of the crystal lattice) and the macrodeformation (extension of the specimen as a whole) are compared. The modulus of elasticity of the crystal lattice is an order greater than that of the fiber itself.V. I. Lenin Tadzhik State University, Dushanbe. Translated from Mekhanika Polimerov, No. 4, pp. 594–598, July–August, 1973.     

Effect of the molecular weight of monodisperse specimens of high-density polyethylene on the dynamic modulus of elasticity

The effect of the molecular weight on the instantaneous dynamic modulus of elasticity of monodisperse specimens of linear polyethylene has been studied. It is shown that above a critical value of the molecular weight the modulus of elasticity is constant and equal to 4·10⁹ N/m², while below that value it increases to 7.28·10⁹ N/m².M. Azizbekov Azerbaidzhan Institute of Petroleum and Chemistry, Baku. Translated from Mekhanika Polimerov, No. 3, pp. 531–533, May–June, 1976.     

Determination of the elastic characteristics of compact bone tissue by investigation of the natural vibration frequency

The dynamic elastic H and shear G_dyn moduli of compact bone tissue have been determined by investigating the natural vibration frequency of specimens obtained from long tubular human bones. The modulus of elasticity E has also been determined by conducting mechanical bending tests. The value of the H modulus is found to change in the course of storage.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 167–172, January–February, 1971.     

Multicritical phenomena in flow of viscoelastic liquids. 1. Zaremba-Fromm-De Witt liquid

It has been shown that multicritical phenomena caused by nonlinearity of viscosity and high elasticity, and forced anisotropy at finite shear rates take place during flow of viscoelastic polymer melts which are isotropic in the resting state. The sign of the low-frequency asymptotic values of the dynamic viscosity and elasticity measured during steady flow is a criterion of the appearance of instability. These arguments are illustrated by the solution and analysis of the complex reaction to low-amplitude, periodic shear of a steady-flowing, very simple viscoelastic liquid — ZFD liquid. It was shown that the instability of viscoelastic liquids for a given steady shear rate is due to the effect of perturbations lasting for no less than some limiting value and its manifestations are caused by superposition of different types of instability — multicritical phenomena.Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 4, pp. 555–572, July–August, 1995.The study was conducted based on Topic 93,177 of the Latvian Science Council.     

The theory of transverse bending of plates with asymmetric elasticity

The problems of bending plates made of various types of composites can be solved efficiently using Cosserat's theory. An approximate theory, reducing three-dimensional equations of the asymmetric theory of elasticity of solids to two-dimensional equations of plate theory has been formulated.Institute of Mechanics, Academy of Sciences, Erevan, Armenia. Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 42–52, January–February, 1996.     

Some properties of rigid polyurethane foam obtained from oligoglycerooxalate

The dependence of the modulus of elasticity and compressive strength on the apparent density has been found for polyurethane foam based on oligoglycerooxalate.Institute of Wood Chemistry, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, p. 739, July–August, 1973.     

Correlation between the equilibrium modulus of high elasticity and the number of crosslinks in rigid crosslinked polymers

A study has been made of the temperature dependence of the equilibrium modulus of high elasticity of dimethacrylate-poly(butanediol-1,4-phthalates).Mekhanika Polimerov, Vol. 2, No. 1, pp. 3–6, 1966     

Investigation of the thermophysical and antifriction properties of polyethylene compositions

The coefficient of linear expansion of polyethylene compositions has been determined. Metals, oxides, and silicates were used as fillers. The coefficient depends significantly on the geometry of the filler particles. Powdered fillers reduce the coefficient by 10–20% (an amount somewhat greater than their volume concentration). Fillers consisting of material with a low coefficient of linear expansion and a high modulus of elasticity in chopped-fiber form may reduce the coefficient of linear expansion by one order as compared with pure polyethylene.Mekhanika Polimerov, Vol. 3, No. 5, pp. 873–880, 1967     

The effect of interphase on residual thermal stresses. 1. Single fiber composite materials

Conclusions The residual thermal stresses in the constituents of a fiber-reinforced epoxy have been predicted using a concentric three-cylindrical (fiber-interphase-matrix) assemblage analysis. The interphase has been treated as a region with a variable Young's modulus — a direct consequence of the changes in the microstructure of the matrix near the fiber surface. The Navier equations of elasticity have been solved in series form solutions for each type of property variation.A parametric study is used to demonstrate the fact that changes in the interphase properties can drastically affect the residual stresses in the interphase.Published in Mekhanika Kompozitnykh Materialov, Vol. 30, No. 5, pp. 579–589, September–October, 1994.     

Relationship between internal stresses and rheological properties

It is shown that, under practically identical viscous-shear conditions, the correlation between orientation and relaxation processes taking place in an extruder die is different for different brands and batches of shock-resistant polystyrene. It has been found that the material with the the higher orientation tendency in the viscous-fluid state in the die is oriented more strongly at the same conditions in the Mackian elasticity state in the reception and pulling of the extruded polymer. It is shown that the thermal shrinkage of the sheets correlates reasonably well with the degree of swelling and the Mackian elasticity deformation of the polymer."Plastpolimer" Scientific-Industrical Association, Leningrad. Translated from Mekhanika Polimerov, No. 5, pp. 952–955, September–October, 1972.     

Determination of the modulus of elasticity of the amorphous regions of chemical fibers

A method of calculating the orientation index and modulus of elasticity of the elements of a two-phase fiber model is presented. The effect of orientational drawing on the variation of these characteristics has been investigated for nylon [capron] fibers.Mekhanika Polimerov, Vol. 3, No. 3, pp. 409–412, 1967     

Viscoelastic equilibrium in a thick plate having a circular cavity

The small-parameter method has been used with Volterra's principle to consider the axisymmetric equilibrium in a viscoelastic plate by the sequential solution of analogous topics in elasticity theory and in the expansion of elementary time functions. A study has been made of how the viscoelasticity affects the state of strain.Donetsk. Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 21, pp. 116–120, 1190.