Home – Home – Jornals – Russian Geology and Geophysics 2014 number 1

Earlier reconstructions of climatic and environmental changes from data of deep-water drilling on the Akademichesky Ridge in Lake Baikal were based both on the content of biogenic silica or the abundance of diatom valves and on the results of X-ray diffraction (XRD) analysis of the sediment mineralogy. It was established that clay minerals are the main carrier of information about climatic variations in a drainage basin. The content of biogenic silica strictly correlates with two chrystallochemical parameters: the abundance of smectite beds in illite-smectite and the abundance of illite. However, detailed analysis of clay minerals calls for exclusive XRD techniques without mass determination of minerals in the sediments of long Baikal cores. We propose a new approach to determine the mineral composition of bottom sediments, based on their chemical composition. We compared the average chemical compositions of Pleistocene, Pliocene, and Miocene core sediments from the boreholes BDP-96 and BDP-98 and sediments of the Paleo-Barguzin River avandelta and recognized groups of chemical elements marking warm and cold climatic periods. However, the difference in the chemical compositions of sediments in warm and cold periods is insignificant. Since an XRD analysis of mineral composition is usually performed for short time intervals, it was necessary to identify cold and warm intervals by the mineral composition calculated from the chemical composition of sediments. The mineral contents were estimated using the Selektor software. Based on the average contents of chemical elements, we computed the mineral composition of the bottom sediments throughout the BDP-98 section and studied its warm and cold periods. We have established that feldspars weakly respond to climatic changes, their contents show minor variations in warm and cold epochs, whereas the contents of mica minerals change seriously. Thus, clay minerals, together with biogenic silica, are a good indicator of paleoclimatic environmental changes.

The Central Taimyr accretionary belt includes two granite-metamorphic terranes: Faddei and Mamont-Shrenk, which include the oldest igneous formations of the Taimyr folded area in the Arctic framing of the Siberian craton—granitoids and granite-gneisses with U–Pb zircon ages of 900–830 Ma. The [FeO^*/(FeO^* + MgO)] — enriched granitoids of these terranes are products of highly fractionated I -type magmas. This paper presents results of new petrographic, geochemical, geochronological, and paleomagnetic investigations of acid rocks fr om a volcanic-plutonic association (in the region of the Leningradskaya River) in the Faddei terrane in the northeastern Taimyr area. These rocks formed during the final stage of continent–island arc accretion and collision that occurred at approximately 870–820 Ma. We established that the studied rocks belong to a long granitoid belt extending from Mamont-Shrenk to Faddei terrane, wh ere all the igneous bodies are deformed and oriented uniformly. The paleomagnetic pole we calculated differs significantly from the apparent polar-wander path interval of corresponding age for Siberia. The 33.8° ± 5.4° angular distance between the poles indicates that the formation of this volcanic-plutonic association took place at a significant distance from the Taimyr margin of the Siberian paleocontinent.

At the Center of Isotope Studies of the A.P. Karpinsky Russian Geological Research Institute, the structure and isotope composition of zircons from two granitoid complexes, the age of their sequential growth zones, and the hosted inclusions have been studied using a SHRIMP-II ion mass spectrometer. The zircons consist of deformed cores with crystalline melt inclusions and of shells: inner, with glassy, partly devitrified inclusions, and outer metamorphogene, with fluid inclusions. Judging from the zircon zoning, crystallization of melts of both complexes proceeded in several stages: (1) The generation of melts and the beginning of zircon core growth (505 and 493 Ma) were synchronous with the overthrusting in the Ol’khon region; (2) The rapid ascent of melts (the inner shell, 479 and 475 Ma) together with the host rocks was caused by upthrust faulting and shear dislocations; (3) The metamorphogene shell (456 Ma) reflects the second stage of metamorphism. At the same time, the Shara-Nur migmatite–granite complex corresponds in composition, structures, and textures to syncollisional K-granites, whereas the differentiated Khaidai gabbro-diorite–diorite–granodiorite–granite complex is close in geochemical features (similar to those of the Anga sequence metavolcanics) and the mantle (juvenile) source of substance to the recent island-arc magmatism. It is suggested that the Caledonian island-arc magmatism was close in time to the accretion of the sediments of back-arc basin (Ol’khon Group) to the continental margin, on the one hand, and to the island-arc block, on the other.

The aim of the study is to detect deformations in the soft sediments in a tectonically active area (the Armenian Highland) and to examine the significance of the deformations as paleoseismicity indicators. Deformations in the form of pillows, pockets, sharp waves, and ovoids are exposed in the Sevan basin, within interbedded shallow lacustrine, beach, and fluvial sediments. Also, broken beds and low-amplitude thrusts are observed. Eight field criteria for assigning soft-sediment deformations to paleoseismic triggering provide strong evidence for the seismic origin of the deformations. According to the local relative stratigraphic scale, the Sevan seismites are of Pleistocene–Holocene age.

Study of Early Cambrian sedimentary-volcanogenic complexes hosting the Kyzyl–Tashtyg pyrite deposit in Eastern Tuva has revealed cyanobacteria and algae that existed in zones of ore-forming hydrothermal systems similar in characteristics to present-day “black smokers” at ocean bottoms. Along with archaeocyaths and Cyanophyta from the host sedimentary rocks and microfossils from basalt amygdules, various cyanobacteria, monocyatheans, and sponge spicules have been found in ferrosiliceous deposits and metasedimentary rocks. Scanning electron microscopic, mineralogical, and thermobarogeochemical studies helped to reconstruct their hydrothermal environment.

The paper presents new petrographic, geochemical, and petrological data from volcanic rocks of suprasubduction origin of the Char shear zone in eastern Kazakhstan. We discuss bulk rock composition (concentrations of major and trace elements), types of mantle sources and parameters of their melting, conditions of crystallization of mafic magma, and geodynamic settings of basalt eruption. According to the major element composition, the volcanic rocks are basalt, andesibasalt, and andesite of tholeiitic and transitional, from tholeiitic to calc-alkaline, series. They are characterized by low TiO ₂ (0.85 wt.% on average) and crystallization trends in MgO–major elements plots. In term of trace element composition, the volcanic rocks show moderately LREE-enriched rare-earth element patterns and are characterized by negative Nb anomalies present on the multi-element spectra (Nb/La _pm = 0.14–0.47; Nb/Th _pm = 0.7–1.6). The distribution of rare-earth elements (La/Sm _N = 0.8–2.3, Gd/Yb _N = 0.7–1.9) and the results of geochemical modeling in the Nb–Yb system suggest high degrees of melting of a depleted mantle source at spinel facies depths. Fractional crystallization of clinopyroxene, plagioclase, and opaque minerals also affected the final composition of the volcanic rocks. Clinopyroxene monomineral thermometry calculations suggest that the melts crystallized within the range of 1020–1180 °С. We think that this volcanic complex formed on the western active margin of the Paleo-Asian Ocean.

Phase compositions and microstructures of ore minerals in intrusive traps of the western part of the Siberian Platform have been studied using scanning electron microscopy. At the magmatic stage, oxide and sulfide solid solutions crystallize; their grain and aggregate shapes are determined by the cooling rate of magmatic bodies. We have revealed a gradual transition of oxides from fine-grained texture in the quenching zone, through skeleton, case, and frame forms, to isometric aggregates of mixed crystals in the holocrystalline silicate matrix. Sulfide spheroids (either conjugate with oxides or separated from them) are changed by dissemination and nests. The chemical compositions of both oxides and sulfides are correlated with the petrochemical types of rocks. Chrome-spinels or chrome-enriched ulvospinels crystallize first in the most magnesian dolerites. Iron and titanium oxides with Mn, V, Mg, and Al impurities prevail in the rest rock varieties. As temperature decreases, ilmenite, ulvospinel, and titanomagnetite crystallize after spinels. Exsolution structures are very intricate for titanium and iron oxides and depend on the oxidation regime and on the assemblage of impurities and their quantities. The first exsolution particles of ilmenite are more magnesian, while the following ones are more manganese. Subsolvus decomposition is accompanied by the release of impurities, grain stripping, and rearrangement and natural enrichment of ore material. Conjugate transformation of silicates and ore minerals results in aggregate pseudomorphs and minerals such as titanite, zircon, and baddeleyite. Nickel-containing sulfides formed at the magmatic stage prevail in more magnesian rocks. Copper minerals are more diverse. These are polymorphic modifications of chalcopyrite and cubanite in ore solid solutions formed at the magmatic stage, chalcopyrite in paragenesis with monoclinic pyrrhotite in zones of hydrothermal metasomatites, and chalcopyrite in solid solutions with bornite and chalcosine and in assemblage with low-temperature sulfides. The obtained data on mineral structures and assemblages can be used as indicators to classify the genesis and formation types of ores.

According to the data processing results, the basin is the deepest along its northern, southern, and eastern margins. The sedimentary fill comprises two resistivity units corresponding to two sequences deposited at different stages of the basin history. The lower, less resistive unit consists of Paleogene–Neogene lacustrine clay and the higher-resistivity upper unit represents coarser Quaternary deposits. In Paleogene–Neogene time, the basin formed by the left-lateral pull-apart mechanism. The earliest Quaternary strike-slip faulting in the setting of overall compression produced the Central Kurai basin within the northern Kurai basin, while the flanking ranges and fault blocks thrust upon the basin transforming it into a ramp. Thus, piedmont steps rose along the basin margins, and the marginal grabens became ramps and half-ramps.

Paleomagnetic studies of thick lava series are one of the most reliable sources of data on the ancient geomagnetic field. However, most of such data are younger than 5 Ma, with much fewer results on the rest of the Cenozoic and the Mesozoic. Two wholesome results are available for the Precambrian but none for the Paleozoic. Late Permian basalts and rhyolites from northeastern Kazakhstan were studied to obtain first estimates of the geomagnetic-field characteristics during that period. We present preliminary results on part of the collection (66 flows (sites)) from a section ~1600 m thick. The characteristic component of reversed polarity was isolated by stepwise demagnetization at all the sites with a slight error. This component is of prefolding age and, most likely, primary. No abnormal magnetization direction is observed in the data, and the average directions of the characteristic component at the sites are tightly clustered ( D = 243.3º; I = –57.0º, k = 79.1; α ₉₅ = 2.0º; 65 sites). As compared with the published data on Cenozoic and Mesozoic thick lava series, secular variation was much weaker in the Late Permian than in the Mesozoic or Cenozoic, and the geomagnetic field was less disturbed. Secular-variation models based on the Late Cenozoic data show even more dramatic differences.

A simultaneous use of artifical neural networks (ANN) and principal components has considered for remote sensing of temperature and composition profiles of the atmosphere. Some modification of ANN method has been offered based on minimisation of final product errors. An example of applications of the modification is adduced. An important advantage of the new approach has shown in speed of training of ANN and in profile precision.

At the end of winter and beginning of spring of 2011 significant negative anomalies of nitrogen dioxide were detected on the basis of results obtained from the ground-based spectrometric measurements of the stratospheric NO₂ content in Tomsk (West Siberia) and Zhigansk (East Siberia). Negative anomalies of NO₂ were observed in other years too, but in 2011 they were record. Negative anomalies of NO₂ were accompanied by anomalies of total ozone content (TOC), temperatures, and heights of the isobaric surfaces in stratosphere. The analysis of the transport atmospheric trajectories and horizontal TOC distribution demonstrated that the stratospheric NO₂ content decrease was caused by the transport of stratospheric air from low TOC area. Vertical NO₂ profiles in Tomsk show that, most probably, some contribution to the negative anomalies in the early spring of 2011 brought by denitrification of the polar stratosphere in ozone hole area.

Results of joint ground-based measurements of vertical structures of ozone and temperatures with the use microwave and lidar technical equipment during stratospheric warming are presented. During winter warming (December 2012 – January 2013) appreciable variations of ozone concentration and temperature in the middle atmosphere are registered. Changes of ozone concentration at height levels from 25 to 60 km increased by 1.5–2 times, the amplitude of their oscillations thus has considerably increased. The peak of a positive deviation of temperature from its monthly average value reached 70 K at a height of 30 km. Daily ozone oscillations at a height of 60 km, connected with sunset and sunrise, were about 30%.

The paper discusses the problem of reconstruction of long-term series of values of the Earth’s spherical albedo. The developed model reconstructs average values of albedo based on annual average surface air temperature and thermal inertia of the hydrosphere. Stability of the model to initial data variations is proved and confirmed by a practical example from 1880 series. The accuracy of reconstruction of the albedo is assessed over the interval since 1984.

A polarization spectronephelometer was used for measurements of spectral coefficients of angular aerosol scattering in mixed smokes during their 3-day evolution in the Large Aerosol Chamber of IAO SB RAS (1800 m³). The smokes were formed as a mixture of products of thermal decomposition of coniferous wood materials (pine) from sources of low-temperature pyrolysis (~ 400°C) and high-temperature open combustion with flame (~ 800°C). The inverse problem was solved to study peculiarities in formation of the disperse composition of smokes and the complex refractive index of smoke particles for three size ranges. It is shown that the dynamics of formation and evolution of mixed smokes is determined mostly by the contribution of the strongly absorbing ultra-fine fraction (particle radius of < 150 nm, the imaginary part of the refractive index of particulate matter of ~ 0.4–0.8 close to that of black carbon) to the optical properties. Medium and coarse particles (radius of > 200 nm) are moderately and weakly absorbing: the imaginary part of refractive index is ~ 0.03–0.15. The absorptivity of mixed smoke is high, and the single scattering albedo at the wavelength 525 nm achieves low values of ~ 0.60–0.45, decreasing during the smoke storage. At the smoke generation, bimodal particle size distributions with the medium of 350–400 nm and coarse of ~ 760 nm modes are formed. After long storage of the smoke, the particle size spectrum is characterized by a single mode of ~ 600 nm, and the effective radius of the particles increases from 160 nm to 330 nm. It is shown that the mutual dynamics between the volume backscattering and extinction coefficients, single scattering albedo and effective radius of particles are described by statistically significant linear correlations.

There are systematic temperature increases in stratosphere relative to long-term standard after major volcanic eruptions. The temperature anomalies in stratosphere of tropical belt cause the appearance of heat centers in the Arctic region, which in turn significant reduces ice cover boundaries in the Arctic Ocean. We analyzed the influence of the new temperature contrasts in the stratosphere of the Northern Hemisphere on the climate change in the Arctic regions using the atmospheric general circulation spectral model of intermediate complexity. We investigate the influence of major volcanic eruptions on the temperature changes in tropical stratosphere and surface temperature in the Chukotka Peninsula region. All major volcanogenic aerosol perturbations of stratosphere response within 10 years to surface temperature increases in the heat center on Chukotka Peninsula is showed.

Methods of calculating the emission of pollutants from forest fires, designed to adjust the input to the simulation of the propagation of atmospheric pollutants, applied to cases of fires in the center of the European Russia in August 2010. It is based on the type of vegetation and its biomass. It allows us to estimate the appropriate emission factor, and with the known (or assumed) fire area and duration, to model the spread of a fire plume taking into account the physical and chemical transformation of pollutants in the atmosphere. Numerical experiments are performed using the chemical transport model COSMO-Ru7-ART. Verification of the results demonstrates the ability of the model to calculate realistic plume shape and values for the concentration of pollutants in the surface layer.

In the paper we first considered the problems of the efficiency of the synchronous operation of sections of the two-sectional copper bromide vapor laser. A comparison with the “generator–amplifier” system was made. For the first time, on the basis of the sounding radiation absorption phenomenon before the amplification phase the role of residual electrons in the population of the metastable level is shown.

There are two types of photophoretic forces, the ΔT_S - (Crookes) and the Δα-force (Knudsen). This paper deals with the fundamental problem of distinguishing by experiment between both forces by using their different dependencies on pressure. We explored gravito-photophoresis of individual particles from three materials differing in their physical properties (carbon amorphous, crystalline, aluminium). On the grounds of available aerosol theory representation of the majority of cases is not feasible. Resolvable special cases and the data in their entirety, however, secure unambiguously earlier hypotheses that the force of gravito-photophoresis is normally caused by differences in the accommodation coefficient (Δα) over the surface. That conclusion is confirmed by a method for determining the size of particles from the force-pressure diagram which yields reasonable results. Hypothetical application of gravito-photophoresis to atmospheric aerosols now obtains empirical corroboration. Some aluminium particles surprisingly show changes in behaviour depending on pressure and irradiance. Here, the levitating force is determined not only (as usual) by the momentary irradiation, but also by the previous history of this factor. We assume that with some metals the irradiation can induce variations in the accommodation coefficient. Results of the investigations are applied to clarifying lasting problems of electro-photophoresis and apparent longitudinal photophoresis.

The Kelvin approach describing the structure of the generalized Hooke's law is used to analyze the potential model of anisotropic creep of materials. The creep equations of incompressible transversely isotropic, orthotropic materials and those with cubic symmetry are considered. The eigen coefficients of anisotropy and eigen tensors for the anisotropy tensors of these materials are determined.

The problem of elastoplastic deformation, buckling, and postcritical behavior of spherical shells is solved using a finite element method and a cross-type explicit scheme of time integration. Stability problems for hemispherical shells under external pressure and compression between rigid plates are considered. The influence of holes and boundary conditions on shell deformation is investigated. It is shown that the calculation results are in good agreement with experimental data.

Cracks arising in dilatant and multimodulus materials (different elasticity moduli for different types of the stress state) are under study. The stress and strain distributions in dilatant multimodulus bodies with cracks, which allow estimating the impact of damage on crack resistance characteristics, are investigated.

Antiplane strain in an incompressible cylindrical body is studied within the framework of a nonlinear model. The system of equations is reduced to a second-order nonlinear equation for the displacement. It is shown that the type of the equation is determined by the strain potential and can be mixed. An example of the strain in a hollow elliptic cylinder is considered, for which a displacement of the screw dislocation type is found and the corresponding stresses and load are studied.

The mechanism of obtaining high-strength mesocomposite materials with a cellular microstructure is studied. It is shown that the formation of the mesocomposite microstructure is determined by the method of pressing characterized by high strains and strain rates, and also by the mesocomposite composition; the high-plasticity matrix and nondeformable particles of the hardening phase, which are not bonded to the mesocomposite matrix, assist in the process of self-organization, i.e., formation of a cellular microstructure. The set of mesocomposite properties is studied to understand the general laws of mesocomposite formation and optimize the composition. A composite with an optimal composition is obtained, which retains high electrical conductivity of copper and sufficiently high plasticity necessary for its effective application; its strength is greater than the base strength by an order of magnitude; moreover, its strength and wear resistance are much higher than those of dispersion-hardened alloys obtained by the method of internal oxidation. The results obtained can be used for creating new composite materials.

The stress–strain state of axisymmetric multilayer shells is analyzed using kinematic and static hypotheses that allow for the transverse shear stresses satisfying the necessary equations of state, continuity conditions at the boundaries between the layers and given boundary conditions. A numerical solution of the problem of the stress–strain state for a multilayer bar is compared with the Lekhnitskii solution (for a cantilever beam loaded by a concentrated force and moment) to asses the applicability of the employed bending equations of multilayer shells. It is shown that these solutions are in good agreement. The problem of the initial fracture of the shells considered is formulated using phenomenological strength criteria for each layer. A coordinate-wise descent method in the unit interval is proposed to solve weight optimization problems for multilayer shells of composite materials under combined loading. Regions of safe operating loads and the optimal weight distribution of layer thicknesses are determined for a multilayer bar acted upon by a uniformly distributed load and concentrated force.

Buckling of a bar of an elastoplastic material is studied. It is shown that for any (σ–ε) diagram of the bar material, the limit load (the longitudinal external force) in dimensionless variables that the bar can withstand does not exceed the current bending stiffness of the most loaded (in terms of the bending moment) section.

Based on a single-domain model of myocardial conduction, isotropic and anisotropic finite element models of the myocardium are developed allowing excitation wave propagation to be studied. The Aliev–Panfilov phenomenological equations were used as the relations between the transmembrane current and the transmembrane potential. Interaction of an additional source of initial excitation with an excitation wave that passed and the spread of the excitation wave are studied using heart tomograms. A numerical solution is obtained using a splitting algorithm that allows the nonlinear boundary-value problem to be reduced to a sequence of simpler problems: ordinary differential equations and linear boundary-value problems in partial derivatives.

Based on approximations of solutions of elasticity theory equations by Legendre polynomial segments, differential equations for bending of orthotropic plates are constructed. In contrast to equations constructed with the use of kinematic and force hypotheses, the order of these differential equations is independent of the type of conditions on front surfaces. The matrices of the constructed equations depend on the type of boundary conditions. An analytical solution is given for the system of equations in the case with normal and shear stresses being specified on the upper and lower front surfaces.

A semi-analytical solution of the problem of compression of a tube by an outer pressure with subsequent unloading is obtained. The effect of the relationship between the shear modulus and plastic strain on the residual stress and strain was evaluated using experimental data, according to which at an accumulated plastic strain of 0.25, the shear modulus decreases by 20%. It is found that despite the significant decrease in the shear modulus, its dependence on the accumulated strain has no significant effect on the residual strain. The effect of this dependence is manifested mainly in the distribution of the residual radial stress, but, in this case, too, it is extremely weak. The obtained general solution can be used to evaluate the effect of the relationship between the shear modulus and the accumulated plastic strain on the residual stress and strain for other materials.

The problem of sliding of a spherical indenter on a viscoelastic foundation is solved in a quasistatic formulation taking account the forces of adhesive attraction which are considered different at the entrance to and exit from the contact region due to changes in the surface properties during the interaction. It is found that the contact characteristics and the frictional force due to the imperfect elasticity of the foundation depend on the surface and bulk properties of the materials of the interacting bodies and the interaction conditions (load, velocity, etc.).

This paper presents the results of mathematical and discrete modeling of linear dynamics problems for three-dimensional viscoelastic and porous elastic bodies. The employed methods and approaches are based on formulating boundary integral equations solved using boundary elements. The model of a standard viscoelastic body is employed as the viscoelastic model. The properties of porous elastic materials are described using the full Biot model with four basic functions. Examples of numerical solutions of the problems are compared with known results of solutions.

Experimental studies of deformation and fracture of rods made of Plexiglas (PMMA) under complex loading (quasi-static and cyclic torsion under axial compression) are performed. The existence of a range of critical values of axial stress, within which the rod is fractured by the torque, is established. The localization of “frozen” highly elastic strains in constrained cyclic torsion is revealed, and the conditions of its occurrence are determined. The effect of axial stress on strain localization and fracture and the influence of cyclic torsion on the loss of stability of a rod under axial compression are shown.

Experiments were performed to study the deformation and buckling of axially compressed circular cylindrical shells of Zr2.5Nb zirconium alloy under creep conditions. Computer simulation using the MSC.Marc 2012 software was conducted by step-by-step integration of the equations of quasistatic deformation of thin shells using Norton's law of steady creep. The results of the experiment and computer simulation show that the buckling modes are a combination of axisymmetric bulges located near one end or both ends of the shell and axisymmetric buckling modes with the formation of three or four waves in the circumferential direction. A comparison is made of the time dependences of the axial strain of the shells obtained in the experiment and by computer simulation. It is shown that for large axial compressive stresses, these dependences are in satisfactory agreement. For lower values of these stresses, the difference between the theoretical and experimental dependences is greater.

Basic results of experimental and theoretical research of creep processes and long-term strength of metals obtained by researchers of the Institute of Mechanics at the Lomonosov Moscow State University are presented. These results further develop and refine the kinetic theory of creep and long-duration strength proposed by Yu. N. Rabotnov. Some problems arising in formulating various types of kinetic equations and describing experimental data for materials that can be considered as statically homogeneous materials (in studying the process of deformation and rupture of such materials, there is no need to study the evolution of individual cracks) are considered. The main specific features of metal creep models at constant and variable stresses, in uniaxial and complex stress states, and with allowance for one or two damage parameters are described. Criterial and kinetic approaches used to determine long-term strength under conditions of a complex stress state are considered. Methods of modeling the metal behavior in an aggressive medium are described. A possibility of using these models for solving engineering problems is demonstrated.

This paper presents an overview of studies of creep–one of the most important characteristics of high-temperature materials. A structural model of creep and methods of accelerated creep tests are considered, and the effect of structural parameters on the creep resistance is studied. The problem of fracture toughness of metal matrix composites is analyzed. The possibility of designing composites with the necessary balance of high-temperature strength, fracture toughness, and oxidation resistance (heat resistance), in particular, composites operated at temperatures of 1400–1600 °C is demonstrated by the example of a molybdenum oxide composite.

Based on the ageing theory in Rabotnov's formulation, a unified approach to studying the creep of plates clamped over the contour and having different reinforcement structures is developed. A wide class of straightline and curvilinear reinforcement structures is considered in the Cartesian and polar coordinate systems. Equations of increasing deflections due to creep and equations for determining the ultimate admissible service times are derived for these structures.

Various models of subcritical fracture that make it possible to explain the significant decrease in the effective stress concentration factor compared with the theoretical value are described for fiber composites with a polymer matrix. The necessity of introducing a material parameter with the dimension of length to describe the scale effect of strength is substantiated. The biomechanical principle of stress concentration reduction by the use of curved fibers flowing around the hole is formulated.

The efficiency of algorithms for automatic control of forces prescribed in the test program is analyzed by an example of a large-aspect-ratio wing considered as a beam loaded by aerodynamic and inertial forces.

Energy-type kinetic equations of inelastic rheological deformation are proposed in which the elastic, plastic, and creep strains are the additive components of the total strain, and the damage parameter is taken into account. A model of viscoelastic material with a creep kernel of exponential type is considered. The Lyapunov stability of solutions under constant stress is studied. The stability range of the solutions of the differential equations of the mathematical model corresponding to asymptotically bounded creep is established. It is shown that the instability range of the solutions corresponds to the onset of the third stage of creep. The relationship is determined between the Lyapunov stability of the solutions and the stability of the computational algorithm for the numerical solution of the system of equations. The proposed model is experimentally verified. It is shown that the calculated and experimental data are in good agreement.

A theory of rolling of round bodies in the normal mode with adhesion conditions satisfied on the entire contact area is proposed. This theory refines the classical Coulomb's theory of rolling in which the rolling moment is directly proportional to the pressing force (e.g., the weight of the rolling body). The rolling moment of cylinders is found to be directly proportional to the pressing force raised to a power of 3/2, and the rolling moment of balls and tori is proportional to the pressing force raised to a power of 4/3. It is shown that the normal mode of uniform rolling can only be provided for a certain ratio of the elastic constants of the materials of the round body and the base forming an ideal pair. The Coulomb problem is solved for the cases of rolling of an elastic cylinder over an elastic half-space, of an elastic ball over an elastic half-space, of an elastic torus over an elastic half-space, and of a cylinder and ball over a tightly stretched membrane. The rolling law is derived for such cases. The rolling friction coefficients, the rolling moment, and the rolling friction force are calculated.