Lateral strain coefficients of human compact bone tissue

The values of all the lateral strain coefficients of the compact bone tissue of the human tibia have been experimentally determined. The variation of these coefficients in six zones of the cross section have been studied at various stress levels, including the ultimate strengths in the corresponding directions. It has been established that the bone tissue possesses orthotropy of the elastic properties. The change in the volume of the bone tissue during deformation has been studied. The bulk moduli for both uniaxial and hydrostatic loading have been determined. A bulk deformation parameter characterizing the strain energy expended in producing a volume change of 100% is introduced. The coefficients of the rank correlation between the lateral strain coefficients and bulk moduli, on the one hand, and the concentrations of a number of biochemical substances found in bone tissue, on the other, are analyzed.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1089–1100, November–December, 1973.     

Effect of the rate of deformation on the mechanical properties of compact bone tissue

Conclusions The results of this study show that the ultimate stress increases with increasing deformation rate from 10^–5 to 1 sec^–1 but the initial elasticity modulus remains virtually constant. A characteristic feature of bone tissue is the significant increase or even maximum in specific deformation energy for destruction in the range of deformation rates corresponding to normal physiological conditions for bone function. The deformation diagrams of human bone tissue for the same values of moisture content and deformation rate in tensile testing do not differ from the analogous curves for the bone tissue of cattle. Quantitatively, the ultimate stress ₁₁ and the initial elasticity modulus E₁ are 5–10% and 15–25% greater, respectively, than for cattle bone tissue, while the ultimate deformation eu is virtually the same. An increase in the moisture content of bone tissue leads to a more pronounced dependence of the mechanical parameters on the deformation rate.Translated from Mekhanika Kompozitnykh Materialov, No. 3, pp. 512–517, May–June, 1982.     

Degree of deformation and strength of compact bone tissue during torsion

This paper discusses the variation in the deformation and strength properties of compact bone tissue during torsion in various zones of the cross section of human tibia. A correlation has been found between the specific energy of deformation consumed during the loading process and the level of stress attained. The degree of correlation between the deformation and strength properties of the bone tissue has been studied as a function of the concentration of certain biochemical substances in its composition.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No.5, pp. 911–918, September–October, 1973.     

Durability of polymers as a function of loading regime during repeated loading with a small number of cycles

Specimens of oriented polycaproamide and unoriented polymethyl methacrylate subjected to uniaxial extension were used to study durability as a function of the number of loading cycles and the intervals between them in different segments of the creep curve. It was shown that the deformation hardening during the initial segment of the creep curve governs the ability of the specimen to withstand subsequent loading cycles. With a relatively low loading rate, deloading-loading cycles during the initial segment of the creep curve lead primarily to an increase in local stresses. During the second stage, repeated loading causes principally an increase in local heating. The interval between loading cycles has only a weak influence on durability.A. F. Ioffe Physicotechnical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 2, pp. 252–256, March–April, 1972.     

Modeling the influence of mineral content and porosity on ultrasound parameters in bone by using synthetic phantoms

Model composite media – 10×15×80 mm³ bone tissue phantoms based on an epoxy resin with fillers—were made to study the influence of porosity and mineral content on ultrasound velocity and attenuation. The pores were simulated by 1 mm³ particles of a soft rubber, while the mineral content was imitated by a mineral residue of natural bone obtained by burning and grinding. The porosity and mineral content were varied in the range of 0–70% by volume with a step of 10%. The velocity, attenuation, and prevalent frequency of ultrasound were measured by the pulse transition method, using transducers with nominal frequencies 0.1, 0.2, 0.5, and 1.0 MHz. It was experimentally found that the ultrasound velocity decreased nearly exponentially with growth in porosity, while the velocity dispersion was negligible at frequencies >0.2 MHz; the ultrasound attenuation increased linearly with growth in porosity and strongly depended on the frequency; the velocity increased nonlinearly with growth in mineral content above 40%; the attenuation did not exhibit a distinct dependence on the mineral content; the porosity provoked a shift in the prevalent frequency of transducers, tending to the common value of 0.2 MHz, while the mineral content did not excite similar changes. The complex measurement of velocity, frequency-dependent attenvation, and prevenlent frequency of ultrasound is proposed in ultrasonic diagnostics of bone for more precise determination of the influence of the porosity and the degree of mineralization on the bone condition.Published in Mekhanika Kompozitnykh Materialov, Vol. 35, No. 2, pp. 211–220, March–April, 1999.     

Deformation of elastic polyurethanes with a bimodal cellular structure

This article examines the cellular structure and mechanical properties of elastic foamed polyurethanes with a bimodal cellular structure (BFPUs). It is shown that the sizes of the oval cells (3–12 mm) in the elastic foamed polyurethenes that are studied are a tenth of an order greater than the sizes of the polyhedral cells (0.1–0.6 mm). Conversely, for rigid foamed polyurethanes, the polyhedral cells are more than a tenth of an order larger than the oval cells (microcells). The equations of the compression curve of BFFUs are found, and it is established that the deformation of BFPUs is determined by the deformation function of the cellular structure and the viscoelastic properties of the polymer matrix. The deformation functions of the cellular structure and the relaxation properties of BFPUs are determined. It is shown that choosing BFPUs with a cellular structure improves the comfort properties of the foamed material: the softness coefficient increased by 8–19% in the investigated case, while the support coefficient increased by 15–35%.Paper presented at the IX International Conference on the Mechanics of Composite Materials (Riga, 1995).Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 3, pp. 330–339, May–June, 1996.     

Investigation of the relations between the various mechanical properties and the biochemical composition of human bone tissue

Nondestructive and destructive methods have been used to establish a series of elastic and strength characteristics of the compact bone tissue in six zones of the cross section of the diaphysis of the human tibia. The quantity of five characteristic biochemical substances present in each zone has been determined. The experiments show that, from the standpoint of continuum mechanics, the compact bone tissue is an orthotropic material and that the bone is nonhomogeneous with respect to biochemical composition. The rank correlation coefficients between the mechanical characteristics and the biochemical concentrations are subjected to a detailed analysis. The important effect of the common glycoproteins on the elastic and strength properties of bone tissue in tension is established.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 138–145, January–February, 1973.     

Effect of compression on bone tissue crystals

The effect of compressive forces on the mineral components of bone tissue was studied. On the basis of x-ray diffraction analysis and the observed electrical and recrystallization effects, it is proposed that compression has a direct effect on the formation of callus through a definite means of compression osteosynthesis.Paper presented at the First All-Union Conference on Engineering and Medical Biomechanics, Riga, October, 1975.Orthopedic Clinic, Semmelweis Medical School, Budapest, Hungary. Translated from Mekhanika Polimerov, No. 4, pp. 664–668, July–August, 1975.     

Investigation of the nonuniform distribution of the elastic and strength characteristics over the cross section of the diaphysis of the human tibia

The elastic, deformation, and strength properties of six different zones of the cross section of the diaphysis of the human tibia have been experimentally investigated. It is shown that when the compact bone tissue is stressed in tension all these properties differ significantly from zone to zone. The greatest values of the initial modulus of elasticity and the tensile strength correspond to the frontal-outer zones of the bone. The nonlinear stress-strain curves are analytically approximated. The secant and tangent moduli are shown to depend on the stress intensity.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 940–946, September–October, 1971.     

Deformation properties of demineralized human compact bone tissue upon stretching

Conclusions 1. Demineralized human compact bone is a physically nonlinear material with a nonuniform distribution of deformation parameters over the bone cross section.2. At the initial moment of stressing (₁₁=0), the modulus of elasticity of demineralized tissue is 380 times less than that of normal tissue. The minimum value of this parameter is in zone 6 (3.32 kgf/mm²) and the maximum value is in zone 1 (7.12 kgf/mm²). With increasing stress, the tangential modulus of elasticity increases.3. The specific energy of deformation under the same stressing conditions ₁₁/*₁₁ expended is greater for demineralized bone than for normal bone.4. The parameter of cross-sectional deformation ₁₂ upon stressing (at ₁₁/*₁₁ from 0.1 to 0.3) increases for demineralized tissue by a factor of 1.56, while for normal tissue this increase is only by a factor of 1.01. The average values of ₁₂ ^0·1 and ₁₂ ^0·3 for demineralized tissue are 3.3 and 2.2 times, respectively, higher than for normal tissue.5. The greatest correlations for the deformation parameters were found between the internal and external layers of the cross-sectional zones for E ₁ ⁰ (0.94) and ₁₂ ^0·3 (0.87), though the discrepancies in the zones between the internal and external layers are insignificant (p>0.05).6. The changes in the deformation parameters over the cross section have a positive correlation (with the exception of U ₁ ^0.3 ) with the amount of ground substance in normal tissue (determined relative to hexosamine).7. The deformation parameters of demineralized tissue may be described by a multi-dimensional linear equation using quantitative indices of the major biochemical components (hydroxyproline, phosphorus, and hexosamine) of normal tissue, which characterize the amounts of collagen, mineral substance, and ground substance, respectively.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 1, pp. 101–108, January–February, 1978.     

Technology and Some Mechanical Properties of Biocomposites Based on Mineral Components

Two types of new composite implant materials are investigated. Their mechanical characteristics, biocompatibility, and the dynamics of bond strength between the biocomposites and a live bone tissue are determined. The first type of the biomaterials is based on silicate glass and hydroxyapatite. Both the natural and a synthetic hydroxyapatite were used. The second type of the biomaterials was made of an ultrahigh-molecular polyethylene and the synthetic hydroxyapatite. Composite materials of both the types were implanted in the rabbit femur. The bond strength between the bone tissue and the implants was determined in 2, 4, 10, and 25 weeks.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 2, pp. 273–282, March–April, 2005.     

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.     

Behavior in the transient regime of vibrating systems incorporating nonlinear spring-plastic shock absorbers

Combined spring-plastic shock absorbers, in which the part of load-bearing elements is played by springs while the plastic components with high internal friction provide for the intense absorption of vibration energy on passage through resonance, are subjected to a theoretical analysis. The model of the plastic component incorporates elastic and high-elastic elements connected in series, the high-elastic component of the total deformation being expressed by a fractional integration operator (see [5]).V. A. Kucherenko Central Scientific Research Institute of Building Structures, Moscow. Translated from Mekhanika Polimerov, No. 6, pp. 1082–1088, November–December, 1973.     

Effect of liquid media on the deformation of the surface layers of a polymer-metal pair in sliding friction

The relation between the high-elastic component of polyurethane deformation and the deformation of the surface layers of metals has been investigated for sliding friction in various media. The surface layers of polymer and metal are plastically deformed. There is a certain correlation between the coefficient of friction and the amount of deformation.Kiev Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 1, pp. 147–149, January–February, 1970.     

Investigation of the state of water sorbed by an organic polymer by high-resolution1H nuclear magnetic resonance and differential thermal analysis

Conclusions The results of the experimental investigation of a moist organic composite by high-resolution NMR and DTA indicate a change in the structure of water, due to an interaction between the water molecules and the macromolecules when water is sorbed by the organic polymer. A part of the sorbed water molecules is strongly bound to the macromolecules; their mobility is very low and is not recorded by high-resolution NMR. As the moisture content of the composite increases, molecules of water appear, the mobility of which is intermediate between the strongly bound and free water molecules in the macrospace. This part of the molecules is represented in the NMR spectrum by a broadened and shifted line and a shift of the endothermic peak towards lower temperatures is observed on the thermal analysis diagrams. The weakly bound water can be detected in the composite starting at a moisture content of 5–8%.Translated from Mekhanika Kompozitnykh Materialov, No. 2, pp. 317–320, March–April, 1990.     

Structural deformation properties of organic fibers based on para-polyamides

Conclusion On the basis of x-ray analytical data it has been established that the studied material has a liquid crystal type structure. In the direction along the fiber axis there is a further degree of ordering; in the radial direction further order is not observed. The dependence of the microdeformation on the deformation of the sample and external loading was studied from the change in the diffraction picture during loading. It was established that is directly proportional to . The closeness of and indicates a uniformity of the material in the structure relationship. It is suggested that the deformation mechanism of the given material is similar to the deformation mechanism of some materials of similar chemical structure which have been considered in the literature. It has been established that after loading the material retains a residual deformation both at the macro- and the microlevels. After thermal treatment the residual microdeformation disappears. It is assumed that ^resid arises due to a partial fixation of the stretched state of the chains by strong intermolecular interaction. Small-angle diffraction provides little information with respect to studying the fracture and structure of the material. The experiments carried out may be lacking in some undetermined regimen of loading — in which during recording of the reflection (10 min) relaxation of the stress on the sample and creep occurs. However, qualitatively this cannot influence the results obtained.Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 10–14, January–February, 1979.     

Periodic simple shear deformation of polymers in the visco-fluid state

Research on the periodic deformation of polymers in the linear and nonlinear regions is reviewed. Special attention is given to the boundary of the region of linear deformation and to deformation in the nonlinear region. It is shown that deformation in the nonlinear region leads to a reversible fall in the viscosity and elasticity of the system due to the selective destruction of certain types of structural bonds. The effect of mineral fillers and the nature of their surfaces on the mechanical characteristics of polymers in the visco-fluid state is stressed. Use of the theory of thixotropy makes it possible to describe the mechanical characteristics of melts in the regions of nonlinear periodic deformation and combined periodic and steady-state deformation on the basis of the results of trivial rheological measurements.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, Vol. 5, No. 1, pp. 182–188, January–February, 1969.     

Modified method of constructing the thermomechanical curves of polymer films

It is shown that because of its sharply expressed dependence on time in the region of the glass-transition point, deformation is not a sufficiently convenient criterion for evaluating the glass-transition temperature of polymers. A modified method of constructing the thermomechanical curve that takes this factor into account is proposed. It is shown that this method can be used to investigate the plasticization effect in cellulose triacetate films.Mekhanika Polimerov, Vol. 3, No. 5, pp. 940–943, 1967     

Effect of the physical state on tearing of amorphous polymers

The temperature dependence of the basic tear characteristics of deformation and failure of SKS-85 copolymer in the range from Tg to T>T_f is examined. It is established that the total work done in tearing the polymer in the brittle state is determined by the work of deformation up to separation of the specimen into two parts. In contrast to this, the total work done in tearing the polymer in the high-elastic state is determined mainly by the work of formation of the tear surface.Mekhanika Polimerov, Vol. 1, No. 5, pp. 71–77, 1965     

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.