The mechanical properties of human blood vessels relative to their location

The major characteristics of the mechanical properties of strips of the common and internal carotid arteries, anterior and posterior segments of the abdominal aorta wall, the common iliac and femoral arteries, and a large subcutaneous vein in man were experimentally determined. A comparison was carried out of the strength and deformative properties of these vessels, and a correlational analysis of the major indices of the mechanical properties was undertaken.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2, pp. 320–325, March–April, 1975.     

Features of biomechanical properties of human coronary arteries

The mechanical properties, biochemical composition, and structure of proximal and distal parts of the right and anterior descending branch of the left coronary arteries were studied experimentally. The vessels were removed during an autopsy of 121 males and 84 females aged from one day to 80 years. The material was divided into six age groups. From the proximal and distal parts, branchless segments of 15–20 mm long vessels were cut out. The mechanical properties of the coronary arteries were determined by passing a fluid at a pressure ranging from 0 to 240 mm Hg. It was found that the part of the wall of the coronary artery adjacent to the myocardium was thicker than the other part of the arterial wall. With increasing age, the mean thickness of the wall of both coronary arteries increased, but the wall thickening process was nonuniform in character in the proximal and distal parts, and individual layers. The changes of the stretch ratio and tangential modulus in the circumferential direction with age and sex were also investigated. The greatest changes in the wall thickness and mechanical parameters were found in the left coronary artery wall for mean over 40 years and in the right coronary artery wall for females over 50 years. The results of the biochemical and densitometric investigations agree well.Published in Mekhanika Kompozitnykh Materialov, Vol. 35, No. 2, pp. 221–238, March–April, 1999.     

Effect of the chemical structure of the polymer matrix on the properties of foam polyurethanes at low temperatures

The dependence of physical and mechanical properties of oligoether-based foam polyurethanes on the molecular mass (M_c) of polymer chains between the nodes of the polymer network and on the content of rigid segments in the polymer is investigated at 293 and 98K. The values of M_c at which the foam plastics have the best mechanical properties at low temperatures are determined. The content of rigid segments in the polymer at which foam polyurethanes have the best combination of the linear thermal expansion coefficient and mechanical properties in tension at a temperature of 98K is found.Latvian State Institute of Wood Chemistry, Riga, LV-1006, Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 4, pp. 517–526, July–August, 1999.     

Effect of structural changes in amorphous polymer films on the mechanical properties of coatings

The effect of structure formation on the mechanical properties of amorphous paint films has been investigated. It is shown that the organization of the supermolecular formations affects the internal stresses and adhesion of the film and, moreover, their tensile and impact strengths over a broad temperature interval. Fibrillar and "reticulate" structures give the best mechanical properties.State Scientific-Research and Planning Institute of the Paint Industry, Moscow. L. Ya. Karpov Physicochemical Institute, Moscow. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 771–775, September–October, 1968.     

Hygrothermomechanical behavior of composites under nonsymmetric environmental effects

The paper discusses analytical methods for the stimation of mechanical properties and the behavior of composite materials under unilateral environmental exposure. An advanced graphite/epoxy composite plate and a densified wooden strand board of different configurations were examined. It was found that midplane strains, curvatures, and warping at nonsymmetric moisture (or temperature) distribution depended on the moisture content profile, composite type, and configuration as well as stacking sequence of layers. The optimum configuration for hygrothermal response may not coincide with that of mechanical properties.Institute of Structural Engineering and Reconstruction, Riga Technical University, Riga, Latvia, LV-1048. Published in Mekhanika Kompozitnykh Materialov, Vol. 34, No. 4, pp. 507–518, July–August, 1997.     

Effect of age on the mechanical properties and biochemical composition of human cardiac arteries

Conclusions 1. The human left coronary arterial wall in subjects from age 15 to 28 has better deformative properties than the right artery.2. With increasing age, a worsening of mechanical properties of the walls is observed specifically for the left coronary artery in comparison with the right coronary artery.3. Quantitative biochemical analysis of the major components of the connective tissue of the human coronary arteries (fibrillar and nonfibrillar proteins and glycoproteins) also disclosed differences among the age groups and the position of the artery (left or right).4. As a result of a dispersion analysis carried out by computer, it was found that both age and position of the artery have a significant effect on the elastin content in the arterial wall and only the age of the subject has a significant effect on the contents of collagen, tyrosine, and hexuronic acids.5. Neither age nor type of artery have a significant effect on the contents of arginine, hexosamines, and hexoses in the arterial wall.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. 3, pp. 502–506, May–June, 1978.     

Biaxial orientation of amorphous linear polymers

The mechanical properties of biaxially oriented polymethyl methacrylate, obtained on a broad range of stretch ratios and under a variety of orientation conditions, have been investigated. There is a fundamental difference between the variation of the forced elastic limit with increase in stretch ratio, which is monotone increasing, and the variation of such properties as the brittle strength, brittle temperature, true strength and elongation at break, which have an optimum at a certain stretch ratio. It is shown that the presence of an optimum is associated with the transformation of the supermolecular structures in the process of biaxial high-elastic deformation. A relation is established between the mechanical properties of biaxially oriented polymethyl methacrylate (orientation hardening) and the density of the molecular network.For communication 1 see [3].Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 586–593, July–August, 1971.     

Regulation of the mechanical properties of thermoplastic carbon fiber-reinforced plastics by changing their production conditions and surface treatment of the fibers

The effect of technological parameters of processing and surface treatment of carbon fibers on the mechanical properties of carbon fiber-reinforced plastics (CFRPs) was investigated. The copolymer of 1,3,5-trioxane with 1,3-dioxolane was used as the polymer matrix, and medium-modulus hydrated cellulose Ural LO-24 carbon fibers served as the reinforcing filler. The polymer matrix was mixed with the carbon fibers by the method of combined extrusion. The dependence of the mechanical properties of CFRPs on the technological parameters of screw-disk extrusion was studied. It was found that the properties of the composites were greatly affected by the size of the working disk gap, the disk rotation rate, and the temperature in the zone of normal stresses. The surface of the carbon fibers was activated with atmospheric oxygen in the temperature range of 450–600°C, with mass loss of the fibers no greater than 3–4%. A 30–40% increase in the mechanical properties of the CFRPs was achieved. A decrease in the melt index of the 1,3,5-trioxane copolymer with 1,3-dioxolane reinforced with oxidized carbon fibers was observed, which should be taken into account in processing the composites into products. Introduction of carbon fibers in the 1,3,5-trioxane copolymer with 1,3-dioxolane allows us to increase the wear resistance and decrease the friction coefficient, which makes it possibile to use these materials in the friction units of machines and mechanisms, such as plain bearings, gears, and flange packings.Presented at the 10th International Conference on the Mechanics of Composite Materials (Riga, April 20–23, 1998).Ukrainian State University of Chemical Technology, Dnepropetrovsk, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 34, No. 5, pp. 673–682, September–October, 1998.     

Problem of evaluation of activation energy from the temperature-rate dependences of strength

Conclusions 1. A method has been developed for treating the experimental data on strength, obtained under conditions of uniaxial extension at v_e = const.2. It has been proposed that the deformation-strength properties of polymers of different structures be characterized by the value of coefficient L, i.e., by the relative lowering of the potential barrier of degradation under the action of mechanical stress.3. A high structure sensitivity of the proposed strength characteristics has been shown using vulcanized rubbers with different structure of the vulcanized lattice point as examples.Moscow Technological Institute of the Meat and Milk Industry. Translated from Mekhanika Polimerov, No. 4, pp. 591–596, July–August, 1976.     

Effect of cellular structure on the mechanical properties of plastic foams

A generalized equation for the compressive stress-strain diagrams of plastic foams is derived on the basis of a 14-faced model of the cell. The results obtained make it possible to predict the polymer base and type of cellular structure required to obtain a foam with predetermined mechanical properties in compression. The calculated values are shown to be in satisfactory agreement with the experimental data.Vladimir Scientific-Research Institute of Synthetic Resins. Translated from Mekhanika Polimerov, No. 4, pp. 594–602, July–August, 1970.     

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.     

Physicomechanical properties of elastomers in binary and ternary systems

A study was made of the physicomechanical and thermophysical properties of elastomers in binary and ternary systems consisting of polyamide, polyvinyl chloride, and rubber in various proportions. Binary and ternary systems with optimal physical and mechanical properties were selected from the composition-property diagrams for engineering applications. It was found that at a given ratio of polyvinyl chloride and SKN-40 rubber there is a nonmonotonic change in the physicochemical properties of films caused, apparently, by chemical interaction. It was shown that the mechanical properties of polyamide can be stabilized against thermal aging by blending with binary systems.Mekhanika Polimerov, Vol. 1, No. 5, pp. 3–12, 1965     

Changes in the mechanical properties of human coronary arteries with age

Conclusions We were the first to experimentally find that the greatest changes in E₂, E_2(K) ^tan, _2(K), and W_(K) of the human cardial coronary arteries are observed in people who have reached the age of 40 years. To compare the experimental data, all the parameters of the mechanical properties of the coronary arteries were determined at one and the same stress level — 0.01 kgf/mm², which on an average corresponds to an increased intravascular pressure of within 200 to 240 mm Hg. Under elinical conditions, this pressure is considered critical for arterial vessels affected by atherosclerosis. The most marked shifts in the changes of the mechanical properties were found in the superior part of the left coronary artery. At the age of 40, a considerable decrease in the deformability of the arterial walls in the circular direction is observed, and the walls become more rigid. At the same time, the vessel wall becomes thicker, especially because of increase in its internal layer — the intima. All this facilitates the development of intravascular thrombosis in people suffering from coronary sclerosis and leads to the development of acute stenosis, frequently exceeding 75% of the clearance area of the vessel, or to a complete obstruction of the superior part of the left coronary artery. If the inferior part of this vessel still retains a fair deformability, it is possible to perform a reconstructive operation, by means of which normal blood circulation is restored from the initial part of the ascending aorta to the inferior section of the corresponding coronary artery. From the experimentally found characteristics of the mechanical properties of the inferior parts of coronary vessels, we can select the best autoplastic material — a vessel segment derived from the patient himself — with properties similar to those of the affected vessel, which ensures the successful performance of such an operation, namely, the reconstruction of the human coronary vessels.Lecture delivered at the Third All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1976.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 2,, pp. 277–282, March–April, 1977.     

Use of acoustic emission to study the breakdown of explosive products

Acoustic emission (AE) was used to investigate the breakdown of products formed from fiber-reinforced explosives under mechanical loading. Acoustic emission was measured during the tensile and compressive testing of the explosives, and with hollow products loaded under internal pressure. Specimens were tested prior to and after being subjected to thermal effects. It was established that breakdown of crystals in the explosive filler provides the basic contribution to the AE effect. It is demonstrated that as for many other materials exhibiting acoustic activity, the Kaiser effect and the effect of a sudden change in AE during crack formation is characteristic of the explosive under investigation. It is also established that the breakdown of hollow products is discontinuous in nature under internal pressure. The results of the investigation suggest the potential of the AE method for investigation of changes in the structure of explosives subsequent to various external effects.Russian Federal Nuclear Center, All-Union Scientific-Research Institute of Experimental Physics, Sarov, Russia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 6, pp. 818–823, November–December, 1996.     

Dynamic mechanical spectroscopy of polyethylenes with aggregating disperse and hybrid granular-fibrous fillers

Conclusion Based on the results of dynamic experimental studies, it was shown that addition of mineral fillers to polyethylenes does not result in a significant change in the relaxation properties of the polymer matrix of CM. It was found that aggregation of the particles of the granular filler causes a significant increase in the real part of the modulus and a decrease in the mechanical loss tangent of the CM. The possibility of using a modified elastic solution for predicting the effective characteristics of the dynamic viscoelasticity of composites was demonstrated.Translated from Mekhanika Kompozitnykh Materialov, No. 4. pp. 579–586, July–August, 1989.     

Features of rheological and electrophysical properties of compositions based on polyvinyl alcohol and carboxymethylcellulose

A study has been made of the rheological and electrophysical properties (conductivity and dielectric loss angle) of aqueous solutions of polyvinyl alcohol (PVA), water-soluble carboxymethylcelluloses (Na-CMC), and compositions based on PVA and Na-CMC or methylcellulose, with PVA solution concentration 1% to 10% by weight and cellulose ether content in the polymer mixture up to 50% by weight. It was found that anisotropic structures can be formed in solutions based on PVA compositions under the influence of an orienting mechanical field; this is related to the formation of structure-sensitive associates in solution in the form of complexes.Paper presented at the 9th International Conference on the Mechanics of Composite Materials, Riga, October 1995.Translated from Mekhanika Kompozitnykh Materialov, Vol. 31, No. 6, pp. 742–753, November–December, 1995.     

Experimental investigation of a series of mechanical properties of the lumbar disks

A series of mechanical properties of the lumbar disks under longitudinal loading have been experimentally investigated. The parameters of the principal mechanical properties of the third, fourth, and fifth lumbar disks are compared in relation to the age and degree of osteochondrosis of the spine.Riga Medical Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1090–1095, November–December, 1974.     

Mechanical characteristics of autopericardium and indications for its application in surgery

We compare the mechanical characteristics under uniaxial tension of human pericardium in native form and stabilized by glutaraldehyde solution. We assess the effect of the media (water, hypertonic and physiological solutions) on the change in the mechanical properties of the stabilized autopericardium. We determine the optimal concentration of the stabilizing solution and the treatment time ensuring the required properties of the autopericardium. We present data from analysis of the morphological changes occurring in the transplant and the results of the operations.Report presented at the Ninth International Conference on the Mechanics of Composite Materials, Riga, October, 1995.Translated from Mekhanika Kompozitnikh Materialov, Vol. 32, No. 2, pp. 219–225, March–April 1996.     

Temperature dependence of the mechanical properties of polymers of different chemical structure in the temperature range from 4.2 to 300°K

Conclusions 1. The temperature dependences obtained for the ultimate alongation, tensile strength, and elastic modulus of various polymers showed that the relationship between the mechanical properties and chemical structure of macromolecules found in our earlier work at 4.2°K is retained at 78°K and, possibly, up to 90°K.2. It was shown that the passage of the tensile strength through a maximum upon warming from 4.2°K results from a corresponding increase in deformability, which is accompanied by a decrease in the elastic modulus and deviation of the polymer bodies from Hooke's law progressively with increasing temperature.3. It was shown that the amorphization of crystallizing polymers, for example, by quenching, gives a marked change in the deformability, tensile strength, and elasticity of the polymer body over the entire range from 300 down to 4.2°K.4. Study of the mechanical properties of polymers at 78°K in a helium medium and liquid nitrogen showed a marked effect of contact of the polymer with liquid nitrogen on these properties. This effect is different for polymers of varying chemical structure as well as for the same polymer in different physical states.Report presented at the Third All-Union Conference on Polymer Mechanics, Riga, November 10–12, 1976.L. Ya. Karpov Scientific-Research Institute of Physical Chemistry, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 387–391, May–June, 1977.     

Effect of the biochemical composition of the wall of the vessels of the human thigh on its mechanical properties

The principal characteristics of the mechanical properties of the walls of the human femoral artery and great saphenous vein and their variation with age have been experimentally determined. Macroscopic and microscopic analyses have revealed characteristic age-related changes in the artery and vein walls. The concentrations of six principal biochemical components of the vessel walls have been determined for each age group and the rank correlation coefficients for the principal mechanical properties and biochemical components have been analyzed.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga; Riga Institute of Traumatology and Orthopedics. Translated from Mekhanika Polimerov, No. 2, pp. 316–327, March–April, 1974.