Comparative performance of living and dead bony tissue under static and dynamic loading

The dependence of the mechanical properties of bony tissue on different conditions of storing the samples has been studied. As the performance characteristic under static loading we used the ultimate compressive strength of the bony tissue, and under dynamic loading we used the specific impact strength.Paper presented at the First All-Union Conference on Engineering and Medical Biomechanics, Riga, October, 1975.I. M. Sechenov First Moscow Medical Institute. Translated from Mekhanika Polimerov, No. 4, pp. 647–649, July–August, 1975.     

Effect of porosity on the strength of a glass laminate

The results of a microstructural analysis of glass laminates based on various resins are presented; the pore-size distribution is shown to depend on the total porosity. The effect of porosity on the static bending strength of glass laminate specimens in the starting state, after boiling in water, and after drying is established. The effect of the testing procedure on the strength-porosity dependence is considered.Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 585–593, July–August, 1970.     

Mathematical model of muscular contraction with a ccount of excitability

A model of muscular contraetion has been developed which establishes the relationship between normal stresses and longitudinal deformations of the muscle tissue and takes into account its excitability. A transfer function has been proposed for the equation describing the behavior of the muscle as a dynamic system which is controlled by synegisms. The validity of the model has been tested experimentally. The model has been used to develop type-II Lagrange equations for the solution of the basic task of biomechanics for some movements of the human body.Paper presented at the FirstAll-Union Conference on Engineering and Medical Biomechanics, Riga, October, 1975.P. F. Lesgaft State Institute of Physical Culture, Leningrad. Translated from Mekhanika Polimerov, No. 4, pp. 608–612, July–August, 1975.     

Rate of resorption of polymeric implants in relation to biological fluid hydrodynamics

The dissociation of water-insoluble macromolecular complexes dissociating with the formation of soluble macromolecules is theoretically examined. The dissociation dynamics in static and open systems are compared (model media and the living organism, respectively). The effect of the rate of metabolic processes and the water-salt balance on the dissociation-association equilibrium in the organism is predicted. The effect of the tension in thread formed from a polycomplex on its life is analyzed for constant and relaxing stress. The use of the theory for predicting the resorption times of polymeric implants (sutures) in the living organism is demonstrated.Paper presented at the First All-Union Conference on Engineering and Medical Biomechanics, Riga, October, 1975.All-Union Scientific-Research Institute of Medical Polymers, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 740–743, July–August, 1975.     

Validation of a Structural Optimization Algorithm Transforming Dynamic Loads into Equivalent Static Loads

Generally, structural optimization is carried out based on external static loads. However, all forces have dynamic characteristics in the real world. Mathematical optimization with dynamic loads is almost impossible in a large-scale problem. Therefore, in engineering practice, dynamic loads are often transformed into static loads via dynamic factors, design codes, and so on. Recently, a systematic transformation of dynamic loads into equivalent static loads has been proposed in Refs. 1–3. Equivalent static loads are made to generate at each time step the same displacement field as the one generated by the dynamic loads. In this research, it is verified that the solution obtained via the algorithm of Refs. 1–3 satisfies the Karush–Kuhn–Tucker necessary conditions. Application of the algorithm is discussed.     

Experimental evaluation of the strength of one-piece Kapron nuts

The strength of one-piece Kapron nuts has been investigated in static loading tests. Graphs of the load versus the number of turns, which reflect the distribution of the load over the turns, are presented. The types of failure of threads of five standard sizes with different profiles are analyzed. It is concluded that there is an important difference between the usual thread calculation model based on the strength of the turns in shear, bearing and bending and the actual loading of the turns of polyamide nuts cooperating with steel screws.Dnepropetrovsk Metallurgical Institute. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 752–754, July–August, 1968.     

Effect of shear compliance in bending and torsion on the stress concentration in a transversely isotropic plate with a hole whose edge is supported

The stress concentration in shear-compliant, transversely isotropic plates with a hole whose edge is supported has been investigated in bending and torsion. Two variants of the boundary conditions are examined. It is shown that the use of the classical Kirchhoff model may lead to a number of qualitative discrepancies.Mathematical Physics Branch, Institute of Mathematics, Academy of Sciences of the Ukrainian SSR. Translated from Mekhanika Polimerov, No. 3, pp. 458–463, May–June, 1975.     

Dynamic Robust Output Min–Max Control for Discrete Uncertain Systems

Min–max control is a robust control, which guarantees stability in the presence of matched uncertainties. The basic min–max control is a static state feedback law. Recently, the applicability conditions of discrete static min–max control through the output have been derived. In this paper, the results for output static min–max control are further extended to a class of output dynamic min–max controllers, and a general parametrization of all such controllers is derived. The dynamic output min–max control is shown to exist in many circumstances under which the output static min–max control does not exist, and usually allows for broader bounds on uncertainties. Another family of robust output min–max controllers, constructed from an asymptotic observer which is insensitive to uncertainties and a state min–max control, is derived. The latter is shown to be a particular case of the dynamic min–max control when the nominal system has no zeros at the origin. In the case where the insensitive observer exists, it is shown that the observer-controller has the same stability properties as those of the full state feedback min–max control.     

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.     

Deformability of thermoplastics in physiological salt solution

Conclusions 1. The creep of thermoplastics in physiological salt solution is characterized by change in the rate of creep deformation relative to the creep in air. The bending creep deformations of HMWPE and phenylone and the compressive creep deformation of HMWPE are described by a binomial equation [Eq. (5)] and the compressive creep deformation of phenylone is described by Eq. (6).2. The lifetime of the thermoplastics studied under static compression and bending determined relative to limiting deformations is described by Eq. (7). Under the same stresses and limiting deformations, the lifetime of phenylone in physiological salt solution is greater than the lifetime of HMWPE.3. After the simultaneous action of physiological salt solution and static stress over one month, most of the characteristics of short-term strength in phenylone are significantly reduced due to swelling in the model medium.Paper presented at the Third All-Union Conference on Polymer Mechanics, Riga, 1976.N. N. Priorov Central Scientific-Research Institute of Traumatology and Orthopedics, Moscow. Kazan Construction Engineering Institute. Translated from Mekhanika Polimerov, No. 2, pp. 325–331, March–April, 1978.     

Seismoacoustic prediction of the fracture processes in glass-reinforced plastics

A technique and equipment for investigating the seismoacoustic emission associated with the fracture of a loaded glass-reinforced plastic are described. It is shown that the emission is present from the beginning of loading and increases regularly up to failure. Glass strands consisting of 100 plain elementary fibers of varying diameter and resin-impregnated strands have been investigated in tension and specimens of glass-reinforced plastic and unreinforced epoxy resin in tension and bending. Experimental data on short-time, static and repeat loading are presented for the glass-reinforced plastic. It is shown how the integral pulse distribution and the pulse amplitude frequency function depend on the applied load level.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 421–429, May–June, 1971.     

Flow of a viscous fluid in a deformable valved tube in the presence of gravity

The problem of the flow of a viscous incompressible fluid in a tube of finite length with valves at the ends is solved numerically with allowance for gravity and elastic wall properties that vary periodically with time.Paper presented at the First All-Union Conference on Engineering and Medical Biomechanics, Riga, October, 1975.M. V. Lomonosov Moscow State University. Translated from Mekhanika Polimerov, No. 4, pp. 756–760, July–August, 1975.     

Nonlinear parametric vibrations of cylindrical shells made from composite materials

The dynamic properties of a hinged shell made from a composite material and subjected to combined loads are investigated by means of an orthotropic model. The problem is solved by means of the geometrically nonlinear dynamic equations of the theory of sloping shells, set up on the basis of the Kirchhoff-Love hypothesis. Various cases of loading are considered, i.e., the combined action of a longitudinal pulsating load and an external static pressure and also of a pulsating external pressure and a static axial compression. The wave processes at the middle surface are not taken into account. The system of resolvents is obtained by consecutive application of the variation and averaging methods. The results of the calculations are presented graphically and are analyzed in detail.Moscow. Translated from Mekhanika Polimerov, Vol. 9, No. 3, pp. 531–539, May–June, 1973.     

Acoustic creep of glass-fiber-reinforced plastic

A method of investigating acoustic creep of polymer composites developing under the effect of static tensile forces and small amplitudes of dynamic stresses with a frequency of 20 kHz acting coaxially with the static loads is considered. Results of investigating acoustic creep of glass-fabric-reinforced plastic are presented. It is shown that the presence of a high-frequency stress component regularly accelerates relaxation processes and reduces considerably the deformation resistance of the material. Generalized curves simulating the long-time static creep of reinforced plastic are constructed by the method of temperature-time, stress-time, and vibration-time analogies. The results of prediction are compared with the control experiment.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 9, No. 3, pp. 397–404, May–June, 1973.     

Experimental determination of the displacement of the neutral surface in polymer specimens stressed in bending

The results of bending tests to determine the displacement of the neutral surface are presented for six different polymers. The specimens were both stressed in pure bending and bent by transverse loads. The values obtained for the displacements indicate that the effect should be taken into account in designing parts for bending. An attempt is made to explain the displacement of the neutral surface in terms of the textural characteristics of the chain molecules.Dnepropetrovsk Metallurgical Institute. Translated from Mekhanika Polimerov, No. 4, pp. 747–749, July–August, 1969.     

Applicability of influence functions determined from quasi-static experiments for solving dynamic problems of vibration protection

Creep of shock-absorbing foamed materials and a vibration-protecting structure is investigated. The parameters of the influence functions, whose numerical realization is conducted in solving the dynamic problem of vibration protection, are determined from the creep curves by the method of logarithmic matches. The conclusions agree with the experimental.Moscow Institute of Electronic Machinery. Translated from Mekhanika Polimerov, No. 3, pp. 537–540, May–June, 1975.     

Investigation of the dynamic behavior of optically active polymer materials

In view of the importance of the dynamic behavior of optically active plastics in connection with their use in model studies of the earthquake resistance of hydraulic engineering structures by the photoelastic method, the static and dynamic characteristics of the commonest types of photoelastic plastics are presented using published data and measurements made in the Photoelasticity Laboratory of the Vedeneev All-Union Scientific Research Institute of Hydroengineering, Leningrad.Mekhanika Polimerov, Vol. 3, No. 6, pp. 1117–1124, 1967     

Experimental study of young's modulus of glass-plastics

The results of study of Young's modulus of glass-plastics in the 10^–1–10⁵-Hz frequency range are presented. A stepwise variation in the modulus, which governs the relaxation process corresponding to a low-temperature internal-friction peak in the filler, is obtained.Rybinsk Institute of Aircraft Technology. Translated from Mekhanika Polimerov, No. 6, pp. 1089–1091, November–December, 1975.     

Viscous-elastic properties of amorphous polymers used in the polarization-optical method for investigation of stresses

The present article gives the results of an investigation of the mechanical properties of certain optically sensitive polymers under static and dynamic loading. It is shown that the Kelvin-Voight model can be used to describe the behavior of the materials investigated over limited time intervals corresponding to the duration of static or dynamic experiments.B. E. Vedeneev All-Union Scientific-Research Institute of Hydraulic Engineering, Leningrad. Translated from Mekhanika Polimerov, No. 4, pp. 585–596, July–August, 1972.     

Dispersion of the mechanical characteristics of plastics at various temperatures

The results of an investigation of the dispersion (standard deviation s and coefficient of variation V) of the static and dynamic strengths of plastics are described. The effect of temperature, state of stress, and type of plastic on the dispersion characteristics is considered.Moscow. Translated from Mekhanika Polimerov, No. 1, pp. 29–34, January–February, 1970.