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The effect of wind on the wires of overhead transmission lines leads to their vibration, as well as oscillations of different amplitudes. At places where the wire is suspended, damage to the metal structure of the fatigue type occurs. This is an excessive number of vacancies, dislocations, grain boundaries and blocks compared to the equilibrium one. The defective structure degrades in the direction of the formation of micro-gaps and cracks. The generation and development of the damage zone occurs from the surface of the wire. To prevent a rupture, it is necessary to monitor the development of this zone during the operation of the line without dismantling the wire. To improve the accuracy of assessing the level of accumulation of fatigue damage, the limiting states of the wire, it is recommended to develop methods based on measuring the electrical resistance of the wire material during the development of fatigue damage. A method for monitoring the state of the surface layer by measuring electrical resistance at high frequencies is proposed. The thickness of the controlled layer is determined by the frequency of the measuring signal due to the presence of a surface effect. For effective control, the depth of penetration of the field into the conductor must be commensurate with the thickness of the defective layer. For experimental research, samples were taken of a new wire and wires after various periods of operation on existing lines. According to the results of static tests, the tensile strength and the degree of nonlinearity of the tensile curve were determined. The results of experimental studies of fatigue strength and surface electrical resistance of a separate aluminum wire of A50 conductor are presented. The samples were tested for fatigue under loads close to the conditional endurance limit. The surface resistance of the wires was measured before and after fatigue tests in the frequency range 200 Hz – 2 MHz. The studies have shown the dependence of surface resistance on the degree of development of fatigue damage, which can be used to diagnose the accumulation of fatigue damage.

The characteristic features of a change in the structure of samples of submicrocrystalline (SMC) technically pure titanium of VT1-0 brand after long-term annealing in a wide temperature range of 150–700°C with a duration of 0.5 to 1008 h, as well as after action by nanosecond laser pulses, are studied by transmission electron microscopy. It is found that the microstructure of the material under study remains stable during annealing for 1 h in the temperature range 150–400°C. Long-term (more than 1000 h) low-temperature annealing in the temperature range 150–190°C also does not lead to a significant change in the size of the structural elements. The action of nanosecond laser irradiation leads to additional grinding of the original SMC structure in the surface layers of the material to a depth of about 1 μm.

The features and generality of the effect of hydrostatic pressure and annealing on the surface relief of the contact and non-contact side of the Fe77Ni1Si9B13 metal glass ribbon are revealed. The relationship between transformation of the ribbon surface inhomogeneities under these effects and possible formation of nanocrystalline regions are analyzed. We found that the evolution of the surface inhomogeneities at the contact side of the ribbon after annealing procedure leads to appearing of discrete-sized fractions in these regions.

The paper analyzes how the elastic properties of titanium and its alloys vary as their structure is transformed from coarse- to ultrafine-grained under severe plastic deformation. The analysis includes acoustic measurements of the elastic modulus of Ti materials with a piezoelectric composite oscillator over a wide amplitude range, a detailed examination of their microstructure by electron microscopy and electron backscatter diffraction, and estimations of their nanoporosity by small-angle X-ray scattering and their density by precision weighing before and after applying a high hydrostatic pressure (1.5 GPa). The results of the analysis show that such structural transformations can cause a noticeable change in the elastic properties of Ti materials due to dislocations, nanoporosity, high internal stress, and initial grain structure.

The influence of dynamic preload on the fatigue endurance limit of AMg6 alloy has been experimentally studied in a range of 109 loading cycles. It is established that prestraining up to 10% deformation at 103 s–1 rate leads to a 22% decrease in the fatigue endurance limit. A mathematical model is proposed that can adequately predict fatigue fracture, including that after preload.

The structural factors that lead to a decrease in the mechanostability of ultrafine-grained (UFG) metals and alloys during creep tests at increased temperatures have been revealed using small-angle X-ray scattering, electron microscopy, and the measurements of the density. An important factor is found to be nanopores that form during severe plastic deformation. The development of these nanopores in grain boundaries, which form during the creep, occurs by a diffusion mechanism and leads to the fracture. The role of disperse inclusions and high-angle grain boundaries in the strength of UFG metals and alloys during their “short-time” and long-term loadings is considered.

Results of investigations of the influence of heat treatment at elevated temperatures on the elastic and microplastic properties of ultrafine-grained (UFG) titanium processed by severe plastic deformation are discussed. The samples were prepared from various batches of α-titanium (VT1-0, Grade 4, and PT3-V) with different initial polycrystalline structures and impurity compositions. Experiments showed that significant changes in the structure (grain size), elastic properties, and microplasticity characteristics only took place in the α-Ti grade of maximum purity (VT1-0). UFG titanium of Grade 4 and PT3-V showed much higher thermal stability of properties, which was probably related to the presence of large amounts of various impurities.

The effect of severe plastic deformation and the subsequent impact of high hydrostatic pressure on the elastic and microplastic properties of Cu–0.2 wt % Zr alloy has been studied and analyzed. The influence of nanoporosity, which is formed in the process of equal-channel angular pressing and is fixed by applying hydrostatic pressure, has been evaluated.

It was established that when loading ultrafine-grained metallic materials under creep conditions, the evolution of the “original” nanopores exerts a significant influence on the longevity. It is shown that in the process of creep the grains recrystallize, and the role of their boundaries in the transition from nano to microporosity is revealed.

Transmission electron microscopy data showed evidence of the formation of structural regions corresponding to deformation (dislocated) fragments and dynamically recrystallized grains in α-phase titanium upon torsion at high hydrostatic pressure at room and cryogenic temperatures. It is shown that the previously proposed “two-phase mixture” model is applicable to description of these defect structures.

This article considers the results of the study of the titanium VT1-0 surface degradation (Grade-4 equivalent) for recrystallized- and ultrafine-grained states after fatigue testing. Comparative analysis of peculiarities of the titanium samples degradation was performed after coating formation by Micro-Arc Oxidation. It was found, that the coating formed by Micro-Arc Oxidation shows different degradation behaviors for recrystallized and ultrafine-grained states

The variation of the internal friction, Young’s modulus, and electrical resistivity of two grades of polycrystalline titanium (VT1-0 and Grade 4) in the area of low temperatures (100–300 K) as depending on the initial structure and subsequent severe plastic deformation converting the material into the submicrocrystalline structural state in relation to the grain size is studied. The maximum of the internal friction is detected in submicrocrystalline titanium, which is interpreted as a Bordoni peak. All the studied characteristics are sensitive indicators for a nonequilibrium state of the grain boundaries after the deformation. The effect of the initial structure of the metal on its properties after the severe deformation is revealed.

The behavior of elastic (Young’s modulus) and microplastic properties of titanium depending on the initial structure and subsequent severe plastic deformation that transforms the material (concerning the grain size) into the submicrocrystalline structural state has been studied. It has been shown that, to a great extent, different initial structures of the metal predetermine its elastic properties after deformation.

The variation of interatomic interaction energy during allotropic transition in titanium is established by analyzing the stress and temperature dependences of durability. This energy is ≈458 kJ/mol in bodycentered β-Ti at a temperature of T > 1155 K, which agrees well with the titanium sublimation heat, and ≈305 kJ/mol in hexagonal close-packed α-Ti at T < 1155 K. Literature data confirming the conclusions drawn are discussed.

Mechanical stability under prolonged loading and thermostability under annealing have been studied for nano- and microcrystalline titanium obtained by different methods of intense plastic deformation. The effect of nanoporosity and the fraction of high angle boundaries formed due to intense plastic deformation has been revealed and analyzed. It has been established that, depending on the loading or the annealing temperature, thermomechanical stability of titanium can be affected, apart from the above structural characteristics, by either twin grain boundaries or titanium-carbide disperse particles.

The work is devoted to the study of evolution of dilatation and elastic properties in metals under deformation in the gigacycle fatigue regime. The deformation process was realized in the ultrasonic testing machine Shimadzy USF-2000. Two sets of samples at different loading times were investigated based on the hydrostatic weighing method and the acoustic resonance method. The proposed techniques were verified using Armco iron samples and then were applied to study the evolution of defects in sub-microcrystalline titanium Grade 4. The obtained results showed that fatigue loading leads to accumulation of porosity in the samples and a corresponding decrease of their elastic properties. This effect was simulated using a statistical model of defect accumulation, which revealed the influence of the sample surface on the fatigue crack initiation sites.

The publication describes the study of durability in tensile creep of VT1-0 commercial titanium in its two states-coarse-grained and ultrafine-grained. It is shown that the best temperature for log-term testing is 350°C. At this temperature, the ultrafine-grained titanium structure remains stable both during free annealing and durability testing. The obtained data enable retrieving the difference in fracture initiation energies for titanium in its coarse-grained and ultrafine-grained states.

The problem of application of physical acoustic methods to studying the mechanisms that control plastic deformation and fracture is considered using micro- and submicrocrystalline materials (Be, Al, Ti, Al–Sc alloy, Cu–Nb laminated material) as examples. The influence of grain boundaries on the acoustic (elastic, inelastic) properties of polycrystalline micro- and nanostructured metallic materials is analyzed. Experimental results are presented for a wide oscillating-stress amplitude range, from 0.2 to 50 MPa. The experimental data are discussed in terms of the theoretical concepts of oscillatory dislocation mobility, which depends on both the short-range stress fields around point defects and the long-range fields of internal stresses. It is shown that various types of discontinuities, such as pores and microcracks, noticeably influence the acoustic properties. The aspects of the relation, similarity, and difference between acoustic and mechanical (plasticity, strength) tests of polycrystalline materials with micro- and nanosized structural elements are discussed.

It is established that increases in nanoporosity and the proportion of high-angle grain boundaries in the process of equal-channel angular pressing are the main structural factors leading to reduction in mechanical stability (durability) of microcrystalline titanium during long-term tests under creeping conditions.

The effect of nanoporosity and the highly dispersed carbide particles that form during screw and lengthwise rolling of VT1-0 titanium on its mechanical and, partly, thermal stability characteristics is revealed and analyzed.

The effect of thermobaric treatment on the nanoporosity (excess free volume) and thus on the physical and mechanical properties of some amorphous alloys obtained by extra rapid quenching is studied.

A broad spectrum of physicomechanical properties of the VT1-0 nanocrystalline titanium produced by cryomechanical fragmentation of the grain structure using rolling at a temperature close to liquid-nitrogen temperature has been studied. It has been found that the mechanism of grain refinement is associated with grain fragmentation by twins. Exactly the twin nature of internal interfaces (crystallite boundaries) provides the thermal and structural stability of nanocrystalline titanium produced by cryomechanical grain fragmentation in the temperature range to ∼500 K. It has been assumed that the observed decrease in the titanium density due to cryorolling is associated with a number of factors (high density of introduced dislocations, nanopore formation, and changes in titanium lattice parameters).

Studies of elastic properties of titanium and its alloys processed by severe plastic deformation are presented. The evolution of the modulus of elasticity resulting from the transformation from a coarse-grained state to an ultrafine-grained one due to severe plastic deformation (SPD) was investigated. The acoustic composite oscillator technique was used to measure the elastic modulus in a wide strain amplitude range. The microstructure was studied in detail by scanning electron microscopy and electron backscatter diffraction methods. Parameters of nanoscale porosity were measured by small-angle X-ray scattering before and after treatment with a high hydrostatic pressure (1.5 GPa). In addition, densities of titanium and its alloys in various structural states were determined by the precision method of hydrostatic weighing. As experiments showed, noticeable changes in the elastic properties resulting from the change in the grain state can be attributed to several factors, such as dislocations, nanoporosity, high internal stresses, and the structure of the materials before SPD processing.

The elastoplastic properties (elastic modulus, amplitude-independent damping ratio, microplastic flow stress) of a Ti-26Nb-7Mo-12Zr titanium β alloy are determined using an acoustic resonance method. The effect of the strain during thermomechanical treatment on the structural features of the micro-crystalline alloy and, hence, its elastoplastic properties is analyzed.

Special features of formation and propagation of microscopic cracks and pores in metals and alloys are considered and analyzed depending on the conditions of their formation. The effect of curing of microscopic discontinuities on mechanical properties, and especially on the endurance, is studied in tests performed under conditions of creep or cyclic loading.

Multiscale mechanisms of failure of metals (Armco iron, titanium, aluminum) are studied for high cycle and very high cycle fatigue. By correlating with the results of structural studies, a theoretical approach is developed to describe fatigue crack kinetics in damaged material under high cycle and very high cycle fatigue loading conditions. Stages of crack nucleation and propagation are analyzed using the profilometry data from the fracture surface. The scale invariance of fracture surface roughness is established, which allows an explanation of the self-similar nature of fatigue crack kinetics under high cycle and very high cycle fatigue. Variation of elastic-plastic properties of Armco iron under very high cycle fatigue is studied using an acoustic resonance method. It is found that the material density decreases during fatigue damage accumulation, with the minimum of the material density in the bulk of the specimen. This work was supported by the Skolkovo Institute of Science and Technology (contract MRA-319) and the Russian Science Houndation (in terms of the analysis of characteristics of titanium fracture, project No. 15-12-30010)

The regularities of the influence of the number of passes under equal-channel angular pressing on the mechanical properties and defect structure of an aluminum alloy have been elucidated. It has been established that the degradation of the mechanical properties (a decrease in the durability) is associated with the formation of nanoregions of an excess free volume in the course of severe plastic deformation under equalchannel angular pressing. A correlation between the nucleation of excess free volume regions and the formation of high-angle grain boundaries under equal-channel angular pressing has been revealed. The nature of the influence of severe plastic deformation on the elastic modulus, the vibration decrement, and the microplastic flow stress has been analyzed.

The Young’s modulus, internal friction, and microplastic flow stress in Cu-Nb nanolaminate has been determined by an acoustic technique. The influence of high hydrostatic compression (1 GPa) on these elasto-plastic properties of the nanolaminate has been studied.

The work is devoted to the study of the metal structure evolution under gigacyclic fatigue (VHCF) regime. The study of the mechanical properties of the samples (Armco iron) with different state of life time existing was carried out on the base of the acoustic resonance method. The damage accumulation (porosity of the samples) was studied by the hydrostatic weighing method. A statistical model of damage accumulation was proposed in order to describe the damage accumulation process. The model describes the influence of the sample surface on the location of fatigue crack initiation.

The influence of hydrostatic pressure on the structure and durability of ultrafine-grained aluminum obtained equal-channel angular pressing (ECAP) has been studied. It is established that the experimentally observed initial growth in the durability of ECAP-processed metal is due to the healing of nanopores, whereas a decrease in this growth with increasing number of passes is caused by the related increase in the fraction of large-angle grain boundaries.

Results of small-angle X-ray scattering and high-precision density measurements showed that the application of counterpressure during the equal-channel angular pressing (ECAP) of ultrafine-grained copper leads to a decrease in nanoporosity and an increase in mechanical properties of the ECAP-processed metal.

The dissipation properties, evolution of the dilatation and elastic properties in sub-microcrystalline titanium Grade 4 samples loaded in HCF and VHCF regime were investigated. The dissipation properties were studied based on self-heating (Risitano) test. The mechanical properties (elastic modulus, amplitude-independent damping) and dilatation for a set of samples with different degrees of the life time exhaustion were studied based on the acoustic resonance method. The dilatation was studied by the method of hydrostatic weighing. The experimental results show the increasing of energy dissipation in submicrocrystalline titanium and absence the characteristic knee point on the graph of dependence of temperature rise versus stress amplitude for this material in self-heating test. The structural investigation shows the decreasing of elastic properties during fatigue loading and increasing of dilatation.