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.     

Some properties of the polypropylene - aluminum system

The effect of composition on the properties (bulk resistivity, hardness, compressive deformation, density, and microstructure) of polypropylene-aluminum specimens has been investigated. The changes are not additively related with the composition. An explanation of the observations is proposed.Riga Lenin Komsomol Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 2, pp. 323–326, March–April, 1971.     

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.     

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.     

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.     

Changes in the structure of polymeric materials in a magnetic field

It is shown that the action of a magnetic field leads to a change in the supermolecular structure of crystalline polymers. The creation of an oriented state in amorphous thermoplastics and thermosets is accompanied by an increase in their hardness and the homogeneity of the structural state.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 737–739, July–August, 1973.     

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.     

Investigation of the wedge pressure (Ludwik) method of testing certain plastics

The feasibility of Ludwik's method, which consists in squeezing a test piece between two wedges, as a means of determining the tensile strength of polymeric materials is demonstrated.Riga Polytechnic Institute. Riga Lenin Komsomol Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, No. 2, pp. 366–369, March–April, 1971.     

Multifactor investigation of the process of polymer wear in the thermally stressed state

Conclusions 1. The temperature regime and stress in the surface layers of polymers exert the most significant effect on wear intensity.2. The effect of these factors is displayed via a change in contacting conditions and the complex of mechanical properties of the polymeric materials.3. The effectiveness of using statistical methods of experiment planning has been revealed in studying the wear process, and also in studying the change in mechanical properties from the action of temperature factors: Reliable mathematical models have been obtained which connect up hardness and wear intensity with temperature regimes.A report presented at the Third All-Union Conference on Polymer Mechanics, Riga, 1976.Rostov-on-Don Institute of Railroad Transport Engineers. Rostov Agricultural Engineering Institute. Translated from Mekhanika Polimerov, No. 1, pp. 67–72, January–February, 1978.     

Age aspects of the torsional strength of compact bone tissue

The variation of the strength of specimens of human tibial compact bone tissue with age has been investigated. It is shown that the torsional strength _i ^* increases sharply in childhood, reaches a maximum at age 25–35, and then gradually falls. There is a correlation between _i ^* and the porosity of the bone tissue. The mode of fracture of the bone tissue has been studied in relation to its orientation with respect to the principal axes of anisotropy.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 493–503, May–June, 1975.     

Supermolecular structure and properties of polymers

Questions relating to methods of obtaining supermolecular structures and their effect on the properties of polymers are considered.Presented at 2nd All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1971.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 409–415, May–June, 1972.     

Connection between the mechanical characteristics of the human abdominal aorta and its biochemical composition

The basic characteristics of the mechanical properties of the subrenal portion of the abdominal aorta have been determined experimentally for biaxial stretching, and their change with increase in size has been established. Amounts of the five main biochemical components of the aorta wall have been determined and a correlational analysis between the mechanical characteristics and biochemical composition has been carried out.Paper presented at the First All-Union Conference on Engineering and Medical Biomechanics, Riga, October, 1975.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Riga Scientific-Research Institute of Traumatology and Orthopedics. Translated from Mekhanika Polimerov, No. 4, pp. 722–729, July–August, 1975.     

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.     

Influence of a plasticizer on the viscoelastic properties of polyvinyl chloride and the time-concentration analogy

Conclusions 1. The addition of plasticizer shifts the generalized pliability curves in the direction of shorter times. However, for corresponding states, the more highly plasticized composition has smaller values of pliability.Paper presented at the Third All-Union Conference on Polymer Mechanics in Riga, 1976.All-Union Scientific-Research Institute for the Use of Polymeric Materials in Reclamation and Water Management, Elgava. Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 861–865, September–October, 1977.     

Numerical identification of properties of particle-reinforced composite materials

The paper deals with numerical identification of the average elastic properties of particle-reinforced composite materials. The finite element method for the determination of deformation energy of the characteristic volume element was used. In earlier analytical investigations, an approximation function of the averaged elastic properties of the composite was derived. An identification procedure allows the estimation of the unknown approximation parameters from numerical experiments. The obtained functions describe precisely the numerical data for any relationships between constituents of the material.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Institute of Computer Analysis of Structures, Riga Technical University, Riga PDP-1658, Latvia. Institute of Materials Science, Department of Materials Science, Martin-Luther-University Halle-Wittenberg, D-06099 Halle, Germany. Published in Mekhanika Kompozitnykh Materialov, Vol. 34, No. 3, pp. 383–390, May–June, 1998.     

Problems of the theory of deformation of polymeric materials under complex loading

Research on problems of the theory of deformation of polymeric materials under complex loading based on a synthesis of creep theories and the local strains theory is reviewed.Presented at the 2nd All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1971.M. V. Lomonosov Moscow State University. Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 434–443, May–June, 1972.     

Resistance of bony tissue to tensile fracture

The tensile fracture resistance of compact bony tissue is considered. The relation between specific strain energy and stress level is established. A strength criterion characterizing the degree of deformation is proposed on the basis of a model, according to which compact bony tissue may be regarded as a composite material. The mode of variation of the proposed resistance parameter over the various zones of the cross section of the diaphysis of a human tibia has been experimentally established.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1084–1091, November–December, 1971.     

Hardness of textolites and its relationship to strength

It is shown that the regularities previously obtained for a series of homogeneous polymer materials also apply to a heterogeneous material: 1) the Brinell hardness ata/R>0.7 can be used to calculate the compressive strength; 2) a quantity proportional to the tensile strength can be obtained from the experimentally determined HM =f(a/R) curve. Various Textolites based on phenol-formaldehyde resin were investigated.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 616–620, July–August, 1969.     

Investigation of the relation between the depth of penetration and indentation diameter in polymer hardness measurements

It has been experimentally demonstrated that for polymeric materials the area of the indentation should not be calculated from the depth of penetration of the spherical indenter, since this gives hardness values that are too low. It is shown that when the surface of a polymeric specimen is indented by a rigid ball, the effect of the spherical stress tensor on the yield point is important; the average stress on the contact area at the beginning for forced high-elastic deformation is close to the compressive yield stress of the polymeric material and considerably higher than its tensile yield stress.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 995–998, November–December, 1971.     

Polymer breakdown and fatigue

Problems of the mechanical breakdown of polymer materials are discussed on the basis of kinetic considerations on such breakdown, viewed as a thermofluctuation-induced process of an accumulation of breaks in interatomic bonds (either break or damage). The present state of this problem is analyzed, both for static and for cyclic loads (fatigue). Some approaches for developing a theory of breakdown are reviewed. Theories related to the accumulation of damage in the volume of the sample receive particular attention. Recent studies on fatigue in polymer materials are listed.Paper presented at the 2nd All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1971.A. I. Ioffe Physicotechnical Institute, Academy of Sciences of the SSSR, Leningrad. Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 597–611, July–August, 1972.