Table of contents

The XXII-th Winter School on Continuous Media Mechanics, a scientific event traditionally organized by the Institute of Continuous Media Mechanics Ural Branch of the Russian Academy of Sciences. It is a biennial meeting, which attracts researchers in the field of mechanics. The School was approved the Russian National Committee for Theoretical and Applied Mechanics, the Scientific Council of the Russian Academy of Sciences on mechanics of deformable solids of the Urals Branch of the Russian Academy of Sciences, the Technical Committee 17 (Non-Destructive Assessment) of the European Society for Structural Integrity (ESIS), and the Russian Committee of ESIS.

The Schools are also attended by our foreign colleagues, who are involved in active collaboration with the scientists of the Institute. About 370 people from 9 countries (Russia, Germany, France, Israel, Italy, USA, China, UK, Azerbaijan) took part in the XXII Winter School on Continuum Mechanics. Russian participants represented 50 organizations in 15 cities (Perm, St. Petersburg, Moscow, Yekaterinburg, Krasnoyarsk, Novosibirsk, Kazan, Samara, Rostov-on-Don, etc.). Most participants are regular attendees of this scientific event. The Scope of the Conference traditionally covers the following topics:

– physics and mechanics of meso- and nano-structured systems

– convection, hydrodynamic stability and turbulence

– hydrodynamics of multiphase media

– hydrodynamics of non-Newtonian liquids and liquids with special characteristics

– computational continuum mechanics

– coupled problems of solid mechanics

– interdisciplinary studies

– mining mechanics.

During the conference reports were made on fundamental and applied problems of physics and continuum mechanics, including 20 invited reports (45 minutes) of well-known experts in the relevant branches of physics and mechanics (academicians, corresponding members of the Russian Academy of Sciences, doctors of science).

All the participants had 15 minutes to present their latest academic research findings one by one. Besides, there was a Q&A discussion after every of 342 presentation.

Due to the severe impact of the COVID-19 outbreak and travel restrictions, it has been difficult for authors to attend the offline meeting. Therefore, the XXII-th Winter School on Continuous Media Mechanics virtual conference is a better way to achieve the goal of ensuring the safety and health of all participants. The conference was conducted virtually through the platform "Big Blue Button". Before the official meeting, the organizing committee has opened a test room for all keynote speakers and authors to test the platform whether the operation is normal or not. The plenary reports were broadcast simultaneously on YouTube. 5-6 sections were working at the same time. The total number of views of the plenary lectures on Youtube during the School's work reached 954, and on Big Blue Button-726. On average, 100 to 175 people were connected to the Big Blue Button platform during the breakout sessions. The participants of the School note the high scientific level, the good organization and intensity of the work, the relevance of the plenary and oral reports, the possibility of a broad and in-depth discussion of the issues presented in the program by specialists in various areas of physics and continuum mechanics. This issue contains articles on the part of the reports presented at the School. After the detailed reviewing, we have accepted 73 submissions.

List of Program Committee, Organizing Committee are available in this pdf.

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

• Type of peer review: Single-blind

• Conference submission management system:

E-mail address used for the submission of papers (ws@icmm.ru) and the person in charge is Iurlova N.A.

• Number of submissions received: 84

• Number of submissions sent for review: 84

• Number of submissions accepted: 73

• Acceptance Rate (Number of Submissions Accepted / Number of Submissions Received X 100): 87

• Average number of reviews per paper: 2

• Total number of reviewers involved: 21

• Any additional info on review process: antiplagiat.ru system

• Contact person for queries:

Dr. N.A. Iurlova, Institute of Continuous Media Mechanics Ural Branch of Russian Academy of Sciences, yurlova@icmm.ru, ws@icmm.ru

The natural oscillations of a cylindrical gas bubble surrounded by an incompressible fluid with free interface are considered. The bubble has an equilibrium cylindrical shape and is bounded axially by two parallel solid surfaces. Dynamics of contact lines is taken into account by an effective boundary condition: velocity of the contact line is assumed to be proportional to contact angle deviation from the equilibrium value. The equilibrium contact angle is right. Different Hocking parameters determine individual damping rates, but dissipation in the integral system is determined by their total contribution. The frequency of the volume (breathing) harmonic of free oscillations can vanish in a certain interval of the values of the Hocking parameter for homogeneous plate surface. However, Surface inhomogeneity destroys this monotonic damping effect.

One of the classical problems of hydrodynamics is the problem of droplet deformation in the state of neutral buoyancy under the action of an external force. It is assumed that if the droplet size is initially equal to or less than the capillary diameter, it takes the shape of a regular sphere, regardless of the density gradient in the environment and the droplet, the degree of their mutual solubility, the possibility of Marangoni convection, and the time elapsed since the creation of the system of liquids. To elucidate the influence of these unaccounted factors as well as that of initial deformation of the droplet, we experimentally studied the evolution of the shape of large-diameter droplets in the solution with density stratification. The droplet behaviour was studied in the case when it took the form of a spheroid flattened vertically under the action of gravity. The interferometer was used to visualize the distribution of solution concentration near the drop. The dependence of the ratio of the vertical to horizontal diameter of the droplet on time and the average concentration gradient in the surrounding medium was determined.

The study focuses on the rheological behavior of a fluid based on a viscoelastic surfactant (Surfogel grade D, type 70-100, produced by JSC "Polyex") in wide range of strain rates. This fluid is used for hydraulic fracturing technology as a proppant-carrying and proppant-retaining fluid in order to enhance oil recovery, including those with hard-to-recover oil and gas reserves. Quasi-static experiments to determine the values of the dynamic viscosity of the fluids under study were carried out using a falling ball viscometer (according to the Stokes method). The viscoelastic properties of fluids were studied using a Physica MCR501 rheometer with a cone-plane measuring system and an original rheometer with coaxial cylinders measuring system. The rheological properties of the fluid with the addition of proppant were studied using a Rheolab QS rheometer with a measuring system of the type of coaxial cylinders. The analysis of the rheological properties of fluids based on a viscoelastic surfactant has been carried out, and it has been established that fluids based on a viscoelastic surfactant has stable rheological properties over the entire range of strain rates, including fluid with proppant concentration up to 20%.

An experimental study of the activity of cavitation processes and the intensity of coalescence of vapor-gas bubbles arising in the volume of a liquid in the presence of ultrasonic (US) exposure in a NaCl salt solution and at various concentrations of sodium dodecyl sulfate (SDS) as a surfactant has been carried out. The process of bubble formation and drift was recorded using a highspeed camera in the plane of the cuvette illuminated by a laser knife. It is shown that the addition of a surfactant to an aqueous solution of NaCl salt leads to a partial inhibition of the coalescence of the observed bubbles and a change in the degassing mode of the liquid in the presence of ultrasonic treatment. The maximum activity of cavitation processes and the formation of vapor-gas bubbles was observed in the presence of salt and a low concentration of SDS. Thus, the presence of a surfactant in an aqueous solution of 0.1 M NaCl salt leads to a change in the growth dynamics of the bubble ensemble, since small bubbles are not able to float to the surface, due to the prevalence of viscous and vibrational forces over buoyancy force.

In this work, by the method of mechanical processing in a high-energy planetary mill of titanium powder (PTS – 1) and ceramic powder of titanium nitride, composite particles with a size of 10 to 100 μm were obtained, in the volume of which ultrafine particles of titanium nitride are distributed. It is assumed that the use of such particles in powder spraying by cold or thermal spray will increase the homogeneity of the distribution of refractory elements in the coating volume. Depending on the time of mechanical treatment of the powder mixture containing three weight fractions of ultrafine particles of titanium nitride, agglomerated composite particles were obtained. Their granulometric composition and surface morphology were studied; a map of the distribution of elements over the surface and volume of the particle material is obtained. It is noted that during mechanical processing of materials in a planetary mill, the behavior of titanium nitride particles is similar to the role of a surfactant. It is shown that the time of mechanical processing of the powder mixture for three minutes is optimal: composite particles have an average size of 38 microns; mass fraction of particles of fraction 20 – 90 μm more than 60 %.

Computer simulation of blade and annular samples made of polymer viscoelastic materials testing has been carried out. Calculations have shown that the rate of material deformation in the working part of the blade specimen can differ significantly from that calculated by the movement of tensile testing machine grips. This is due to the unevenness of the cross-section of blade sample: in the middle (working part) it is constant, and at the ends its area increases. As a result, inhomogeneous stress fields arise in the material, which leads to a variable deformation rate of the specimen working part, even in case when grips move at a constant speed. This effect is not significant at small deformations and a low strain rate and can be ignored in principle. However, in the case of large extensions high speeds, it can seriously distort the test results. According to the authors, the way out of this situation is that, in experiments with viscoelastic polymers, it is better to use annular specimens with the same cross-section along the entire length, rather than blade ones. As shown by computer calculations, in this case, this problem almost completely ceases to exist.

The research carried out a comparative assessment of the physical and mechanical properties of tooth enamel: healthy; demineralized; demineralized and subsequently infiltrated with a flowable composite according to a standard or modified technique. An original in vitro model of artificial caries of human tooth enamel was used for the study, the clinical-topographic, color-textural and physical-mechanical properties of which correspond to the characteristics of enamel caries in vivo. Comparative analysis of the results of kinetic microindentation of enamel samples allows to characterize the biomaterial from the standpoint of physical materials science, to determine the advantages and disadvantages of different regimens of resin infiltration. The advantages of the modified infiltration technique are illustrated by significantly greater, as compare with classic method, increase in microhardness and elasticity against background of a decrease in a creep index of the infiltrated enamel in itsdeep zones. The results reflect the fact of incomplete obturation of microporous in the deep layers of enamel after classical treatment.

The paper uses mathematical modeling to calculate loads on interchamber pillars under incomplete undermined conditions by using the room and pillar system at great depths and by retaining rigid barrier pillars. The approaches are based on the method of the fictitious pillars, as well as the method of forming a rock pressure arch in the incompletely undermined area. The unloading effect of the barrier pillars on the interchamber pillars is shown, the distribution of vertical loads is obtained, and the height of the rock pressure arch is calculated.

The paper presents a block diagram of an automated inclinometer-based system for monitoring the inclination of a high-rise metal structure of the shaft headframe. The stress-strain state of this structure is defined by the loads associated with the operation of shaft skip and the impact of the environmental factors on the structure. The data obtained by 6 inclinometers located at different height were used to determine the inclination of the headframe and distortion of its shape. Analysis of long-term observation data revealed the existence of deformation processes having different time scales (long-term, seasonal and daily). A correlation between changes in the tilt angle of the structure and ambient temperature was established. Long-term monitoring of tilt angle showed that the displacements of the structure were within the permissible limiting values. The developed monitoring system is of great theoretical importance for understanding the deformation processes arising during the operation of such structures.

When analyzing the structural integrity of a material or structural part, the mechanics of continuous media is traditionally used with the concept of the homogeneity and isotropy of material properties; with this approach, the fracture criteria are related to the integral characteristics of the material and are described by the invariants of the stress tensor. However, this approach does not consider the physical aspects of the occurrence of local areas of plastic deformation, which ultimately means the impossibility of predicting the fracture, and, consequently, the resource of the structure. This is especially evident in the conditions of cyclic loading, when the material can fail at stresses well below the traditional «fatigue limit». In the current work, an approach is proposed that allows to save traditional methods of design and resource forecasting by expanding the scale of modeling. The paper introduces the concept of inherent stress concentration in any structurally heterogeneous medium as its inherent attribute. A universal algorithm for determining this characteristic is presented.

Experimental and numerical investigations of a magnetic ponderomotive force acting on non-magnetic body immersed in ferrofluid were carried out. The study was performed on a nonmagnetic sphere in a cylindrical container filled with the magnetic fluid and magnetized by a uniform magnetic field. The symmetry of the experimental setup allowed the simplification of the problem: 2D axisymmetric numerical simulation corresponded to the 1D experimental measurements. The magnetic ponderomotive force turned out to be non-monotonic: it has two extrema and one or three zero values depending on the geometrical parameters of the container and magnitude of the applied field intensity. It was shown that wall effects are crucial for this problem, because the ponderomotive force in the vicinity of the container's bottom (or top) may change its sign (direction). This behaviour can be described only in the framework of the inductive approach, which takes into account all demagnetizing fields generated by the ferrofluid container. On the contrary, the simplified non-inductive approach is unable to explain the magnetic force behaviour, especially the wall effects.

Granitic rock is considered one of the most important economic materials used as building materials, ornamental stones, and other purposes. According to previous radiological studies conducted on these granites, it was found that the activity concentrations of ²³⁸U, ²³² Th and ⁴⁰ K of these granitic rocks are natural as well as the radiation effects are not harmful due to the natural radioactivity of the examined granites so that it can be exploited economically in the future.The current study aims to determine some of the physical and mechanical properties of granites in the Um Taghir area to detect these rocks' suitability for ornamental stones. The samples of the granitic rocks were cut according to the American Society for Testing and Materials specifications (cubic shape) for the detection of uniaxial compressive strength in addition to some of the physical properties were determined for each sample. Granite rock samples showed good results according to mechanical and physical tests. So that it can be extracted, transported and later used for various economic purposes.

Using atomic force microscopy in the semicontact AFM mode, we examined the surface of the filled elastomer obtained by the rupture method. A feature of the material is that it consists of a soft binder and hard nanofiller particles. Filler particles are usually hidden by a binder layer. In our work, we have shown that the information on the phase shift obtained during scanning makes it possible to look into the subsurface layer and obtain more information about the geometry of the filler particles and their location in the nanocomposite. It is possible to make visible the fragments of particles immersed in the binder, which are almost invisible on the surface relief. This does not require the use of special modes of the atomic force microscope for analysis. It is enough to use the reliable and fast scanning method in semicontact mode.

We consider free oscillations of a clamped liquid drop. An incompressible fluid of different density surrounds the drop. In equilibrium, the drop has the form of a circular cylinder bounded axially by the parallel solid planes, the contact angle is right. These plates have different surface (wetting etc.) properties. The solution is represented as a Fourier series in eigenfunctions of the Laplace operator. The resulting system of complex equations for unknown amplitudes was solved numerically. The fundamental frequency of free oscillations can vanish in a certain interval of values of the Hocking parameter. The length of this interval depends on the ratio of the drop dimensions. Frequencies of other drop eigenmodes decrease monotonically with increasing Hocking parameter.

Cyclic creep, also known as ratcheting, is a progressive accumulation of inelastic strain under cyclic stress-controlled loading. This mechanical effect is of great importance for numerous applications. In engineering practice, phenomenological models of cyclic creep are calibrated against a limited set of macroscopic test data. Since the testing results are prone to systematic and non-systematic experimental errors, the impact of experimental errors on the quality of simulation has to be analysed. A simple inspection procedure is demonstrated and tested. Based on the Monte Carlo computations, it allows for analysis of error propagation through the simulation cycle. The focus of the paper is on the independence of the procedure from the chosen model parametrization. For demonstration purposes, cyclic creep of VT6 alloy is simulated. The corresponding macroscopic constitutive equations are based on the second Ohno-Wang model, combined with refined rule of isotropic hardening. Two different parametrizations are introduced to show that the procedure predicts the same results for both of them.

Waves on the free surface of a magnetic fluid located on a liquid substrate were studied experimentally. The wave motion of the surface was induced by a homogeneous oscillating magnetic field orthogonal to the layer. In this case two types of waves can be formed on the surface of a magnetic fluid: a standing wave of the same frequency as the alternating magnetic field, and a standing wave, independent of the field frequency. The paper reviews the main theoretical and experimental studies of wave instability of such systems. The stability of a two-layered liquid system in an alternating vertical magnetic field is investigated. For efficient processing of the experimental results, the optical part of the experimental setup was modified. An algorithm has been developed for processing the profiles of the magnetic fluid surface obtained during the experiment, which helps to determine the length of the generated waves.

The paper describes the technique and results of experiments on the introduction of SiC and BN nanoparticles into an aluminum melt contained in a cylindrical crucible with a water-cooled bottom and heated walls. The crucible was placed in an MHD stirrer, which generated a travelling and rotating magnetic fields ensuring in such a way bidirectional stirring of the liquid metal in the crucible. After introducing the reinforcing particles, aluminum was stirred and directionally crystallized. Reinforcing particles were introduced into molten aluminum as a component of pressed pellets. Pellets with diameter of 20 mm and thickness of 15 mm were made from a mixture of aluminum powder (100-156 µm) and reinforcing nanoparticles (100-200 nm) by pressing in a special pellet die. The concentration of reinforcing particles in the pellets was selected using preliminary experiments and was 5% of their total weight. In some experiments, the aluminum was reinforced with SiC nanoparticles introduced into the melt in the amount of 0.59%, 1.04%, 1.77%, while in other experiments the concentration of hexagonal BN nanoparticles introduced into aluminum was 7%, 1%, 1.8% of the ingot weight. As the experiment showed, the reinforcing particles formulated into tablets can be introduced into aluminum by means of MHD stirring. The dependence of the ultimate strength and electrical resistance of aluminum on the concentration of the reinforcing nanoparticles introduced into it has been obtained experimentally. It has been found that with an increase in the concentration of nanoparticles in aluminum, its ultimate strength and specific electrical resistance increase. The dependences of the ultimate strength and electrical resistance of aluminum on the concentration of SiC and BN nanoparticles are very similar and close to linear (in the investigated range of concentrations of introduced particles. With an increase in the concentration of introduced nanoparticles the mechanical strength of the resulting material grows faster than the electrical resistivity. In the experiments, the ultimate strength of the samples increased by 22%, while the electrical resistance increased by 5-6%. This opens up new possibilities for industrial applications of such materials, for example, in manufacture of self-supporting wires in power lines.

Constitutive equations of finite strain elasto-plasticity are coupled to continuum damage mechanics to simulate the initiation and propagation of cracks in ductile materials. The diffuse deterioration of material's strength is modelled using porosity as a damage parameter. We show that the local damage model yields simulation results, pathologically dependent on the FEM mesh upon mesh refinement: (i) the structural behaviour becomes unrealistically brittle; (ii) the FEM mesh determines the crack path. To solve these problems, an integral-based approach to nonlocal damage is implemented. It enables physically sound results by introducing the linear size of the microstructure into the model's formulation. To prevent the effect of unrealistic diffusion of damage, the averaging operator is applied not to the porosity, but to its dual parameter, material's continuity. Solutions of test problems for crack propagation in a compact tension specimen are presented. The convergence of FEM solutions is demonstrated for different slopes of the mesh with fine and coarse discretizations.

This study demonstrates that the equations for a two-dimensional steady flow of a viscous fluid contain an integral of motion, i.e., they have some function whose gradient is zero in the solutions of hydrodynamic equations A system of partial differential equations has been derived to calculate this function. It has been established that, at a certain integral of motion, the calculation of hydrodynamic fields is reduced to the solution of a system consisting of three first-order partial differential equations with a characteristic manifold.

The experimental study of heat and mass transfer in the atmosphere of a skip shaft of a Gypsum mine was carried out during the summer and winter seasons. The air flow overturning was observed in the winter season due to the ingress of cold heavy air from the surface into the shaft space. To analyze this phenomenon, a computational fluid dynamics (CFD) model of heat and mass transfer processes in a mine shaft was developed, considering the vertical temperature gradient, roughness of the shaft walls, heat exchange with the shaft lining. Based on numerical simulation, it was found that at relatively low air velocities in the shaft and with a relatively large difference between warm air in the shaft and cold air on the surface, the latter begins to penetrate the shaft and descend down it, gradually filling its space. The interaction of cold air from the surface with the warm air rising up the shaft, as well as with warm walls of the shaft leads to the formation of an unsteady convective vortex cellular structure along the shaft. The depth of the vortex depends on the velocity of the air in the shaft, as well as the difference between the temperatures of the warm and cold air. Based on the obtained numerical simulation data, it was possible to calculate the minimum allowable air velocity at which partial return air flows appear in the shaft cross-section.

The application of embedded into material fiber-optic sensors based on Bragg gratings for strain measurement on the example of a cement sample during the manufacturing stage, under operational loads and upon the appearance and development of a defect is studied in the paper. The integrity and performance of fiber-optic sensors at all stages of the study, as well as the efficiency of strain measurement, have been demonstrated. An approach is implemented to register the appearance and development of defects based on information received from embedded fiber-optic sensors. The approach considered in the study is based on the location of sensors in the vicinity of the expected damage. The results obtained indicate the possibility of using embedded fiber-optic sensors to assess the mechanical state of civil structures.

This paper presents an experimental study of thermal convection of ferrofluid inside a closed hydrodynamic loop heated from the side in the presence of a magnetic field applied to the loop section nearby the heater. The pipes of the circuit are blown with a stream of thermostatic air, which ensures a constant heat transfer coefficient on the outer surface of the pipes and an exponential temperature distribution along the circuit. The value of the exponent measured provide information on the integral axial heat flux (Nusselt number). The experiments were conducted with undecane under natural gravitational convection and with a colloidal solution of magnetite in kerosene of moderate concentration under mixed (gravitational and thermomagnetic) convection at the Rayleigh numbers varied in the range 10³ – 10⁴. It is shown that thermomagnetic convection causes a 4 – 6 – fold increase in heat transfer.

The paper deals with modeling the stress state experienced by rocks in a loaded around-borehole volume to justify a promising method of in-situ stress measurements based on the Kaiser effect. Mathematical modeling of loading the horizontal borehole walls with a NX-borehole jack in a direction of principal components σ₁ or σ₃ of the natural stress field was performed for conditions of the unperturbed salt rock mass of the Verkhnekamskoe potassium salt deposit. As a result of the numerical calculation of stresses, it was determined that recovery of radial component σ_r in compression regions of the rock volume around the borehole occurs when the jack's pressure reaches the initial value of the principal stress. At the same time, the concentration of tangential component σ_θ in these regions is retained. The rock salt specimens were tested under modes similar to the stress states of the rocks in the around-borehole volume to study the Kaiser effect under these conditions using a triaxial compression vessel. It was found that in the second loading cycle, the recovery of the initial values of axial component σ_axial of the specimen stress field, unloaded after the first cycle, stimulates acoustic emission. This regularity is true for the case when there is no increase in confining pressure σ_conf on the specimen between the cycles. In the conditions with an increase in confining pressure σ_conf between the first and second cycles, the Kaiser effect is found at higher values of σ_axial component than the initial ones. It is shown that the nature of the effect depends on a type of a specimen's initial stress state and is caused by the growth resumption of longitudinal microcracks, if σ_axial > σ_conf in the first loading cycle, or by a closure of lateral microcracks when σ_axial < σ_conf in the first loading cycle.

The paper presents an experimental study of steady streaming generated by harmonic oscillations of the boundaries of a deformable spherical container. The container is filled with a viscous fluid and its oscillations are produced by means of two linear servo motors, installed symmetrically. The shape of the boundary during deformation is studied by processing images recorded with a high speed camera. The flows are investigated using the particle image velocimetry. In the analysis of results, the focus is made on the relation between the shape of the oscillating boundary, the dimensionless frequency and the streaming velocity. The possibility of controlling the steady streaming pattern in order to affect the convective mass transfer is discussed.

According to the latest research, cancer is a complex biological system that evolves over time and space. This means that cancer cells differ from each other in their functions in the tumor. They engage in various interactions with the microenvironment and compete for available nutrients to survive. The main problem of mathematical modeling in oncology today is the heterogeneity of a typical malignant neoplasm. In this work, we propose a chemomechanical model of the pattern formation of small groups of cancer cells of invasive carcinoma of a non-special type (IC NST). The model assumes that carcinoma is a heterogeneous formation, which consists of cells of different phenotypes performing different tasks to maintain the existence of the tumor. In the model, each cell is represented as a deformable polygon that changes its shape and size as the tissue develops. Numerical modeling implements various subtypes of IC NST structures. These patterns are compared with morphological structures identified in clinical studies.

The work is devoted to an experimental study of the main parameters of the acoustic flow that occurs in a liquid under the influence of an ultrasound source (US) with a frequency of 1.7 MHz. To study the type of emerging currents, the method of tracer and fluorescence imaging was used; the distribution of relative acoustic pressure was found using a vibration sensor; to measure the intensity of cavitation events, thermocouple measurements were used. Experiments have shown that an increase in the concentration of the NaCl salt in the water solution reduces the intensity of vibrations when the sensor is removed from the ultrasonic source. The maximum intensity of cavitation events also changes its position, moving to the area near the ultrasonic source. Thus, the effect of an increase in the salt concentration on the type of flow in a sonochemical reactor was noted, which was also experimentally recorded in the work using light-reflecting particles.

Currently, many researchers pay attention to studying the influence of process variables on the quality of metal products after manufacture. The most common methods of metalworking are forming processes, in which a high degree of deformation, uneven plastic deformation, and elevated temperatures are utilized. In most cases of manufacturing using these methods, a self-balanced system of residual stresses is formed that significantly affects the accuracy, strength, durability, reliability, corrosion resistance, and fatigue strength of machine parts after manufacture and processing. At the same time, the level of technological residual stresses depends on the main process variables. And in this regard, the analysis of the residual stress calculation for the deformation of rods will identify the effect of process variables, mechanical properties of the material, the geometry of the workpiece on the level and distribution of formed residual stresses. The object of the study is distributions of residual stresses formed after plastic deformation in rods and wire. In the work, experimental data on the distribution of residual stresses in rods after drawing were investigated. The residual stress calculation method takes into account parameters of technology, geometry and mechanical constants of material. Dependencies of axial and circumferential residual stresses in steel rods and wires after drawing were found.

This paper describes the results of experiments on the magnetization of barium hexaferrite particles embedded in lyotropic liquid crystals. The carrier liquid crystal medium was an aqueous solution of a mixture of sodium lauryl sulfate and lauric acid in a ratio 2/1. Barium hexaferrite particles were stabilized with two layers of surfactant. The first layer consisted of oleic acid molecules. Second layer was a mix of sodium lauryl sulfate and lauric acid in a ratio 1/1. The process of particle magnetization was investigated by observing the effect of birefringence. The intensity of light passing through the system of crossed polaroids and the time of its establishment were measured depending on the magnitude of the magnetic field and the concentration of the components of the liquid crystal. It was found that the field dependence of the birefringence effect changes significantly depending on the concentration of the liquid crystal. In a concentrated solution in the liquid-crystalline phase, a significant enhancement of the birefringence effect is observed in weak fields. As the concentration of the solution decreases, the field dependence of the birefringence effect smoothly transforms into the curve for particles dispersed in water.

The stability of water supply systems is one of the main factors that determine the reliability of the functioning of large industrial complexes. This problem is considered on the example of the "Azot" branch of URALCHEM JSC in the city of Berezniki, which takes fresh industrial water from the Kama river (Kama reservoir). A specific feature of this water body is the significant variability of its hydrological regime. During the summer dry season, it is characterized by low flow velocities. In winter, with a decrease in the water level in the reservoir, a typical river regime is observed. In addition, there is a strong technogenic impact on the water body. The impact is formed largely due to non-declared dispersed (diffuse) sources. Their characteristic feature is high mineralization and, accordingly, the density of the formed wastewater. Their behavior is fundamentally different from the processes of dilution and migration of effluents with neutral buoyancy. A two-layer structure is formed, when the content of the main ions in the surface horizon is more than an order of magnitude less than in the bottom layer. This circumstance must be taken into account when assessing the reliability of the functioning of water intakes. The most effective tool for solving such problems is the conjugation of a complex of field monitoring observations with computational experiments using hydrodynamic models in one-, two- and three-dimensional formulations.

The behaviour of the ternary hydrocarbon mixture of toluene-methanol-cyclohexane in mass proportion 0.62/0.31/0.07 is studied. The direct numerical simulation is carried out for the two-dimensional closed cavity heated from above. The mixture is supposed to be in the gravity field. The behavior of the mixture is predominantly caused by the Soret effect (thermal diffusion). An important parameter, responsible for the Soret effect, is the net separation ratio, Ψ. For the mixture under consideration, the two sets of values of Ψ are known. In both cases, the values of Ψ turn out to be close to zero, but in one case Ψ is slightly positive, and it is slightly negative in the second one. This results in qualitative difference in the evolution of the mixture under consideration. If Ψ > 0, the mixture comes to the mechanical equilibrium. If Ψ < 0, we observe the system to be at the border of stability, under small perturbation there is no instability, but for the perturbation amplitude higher than a threshold value of the convective single-vortex flow arises.

The paper is devoted to the numerical study of two-dimensional convective motion of a viscoplastic fluid in a closed region under lateral heating. The problem is solved numerically using the ANSYS Fluent software. The Bulkeley-Herschel model describing viscoplastic behavior was chosen as a non-Newtonian fluid model. Under certain rheological parameters, this model is reduced to a Newtonian fluid model, the behavior of which is also investigated as a limit case. Based on the results of the calculations, the dependence of the maximum value of the stream function in the cavity on the Rayleigh number is plotted and the evolution of the unyielded zones with an increase in the Rayleigh number is traced. The threshold value of the Rayleigh number, at which a sharp growth of the flow intensity is observed, has been determined. The calculated threshold value of the Rayleigh number for the Bulkley-Herschel liquid was found to be very close to the threshold value of the Rayleigh number at which the flow of the Bingham liquid arises, which was obtained analytically.

In this paper we present the results of numerical simulation of nonlinear regimes of a NaCl aqueous solution in a square cavity with rigid and impermeable for substance boundaries. The vertical boundaries are thermally insulated, there are different constant temperatures on horizontal ones, it corresponds to the heat from below. The calculations are carried out within the non-stationary approach, with using of Boussinesq approximation and taking into account the polynomial dependence of the thermal diffusion coefficient on temperature. According to experimental data, the sign of thermal diffusion coefficient of the mixture under study changes at a temperature 285.4 K. In this work we consider a temperature range such that the sign of the thermal diffusion coefficient changes inside the simulated region. Other transport coefficients factors are considered as constant. The calculations were carried out for the cases of Earth and reduced gravity. A comparison is made with the case of the thermal diffusion coefficient constant value, which is negative at the considered average temperature.

In the work, when ball milling of mixture of aluminum powder (ASD – 1) and boron carbide (F 500) powder in a high-energy planetary mill, composite particles sized from 10 to 100 microns were produced, in the volume of which ultrafine boron carbide particles were distributed in the size range from 0.1 to 20 microns. It is assumed that the use of such particles in the production of coatings by cold gas-dynamic spraying will increase the deposition efficiency and the weight fraction of boron carbide in the coating. An increase in the concentration of carbide particles in the processed powder mixture, under all other conditions being equal, leads to a decrease in the average volume size of the particles. It is noted that in this case, the boron carbide particles behave as a surfactant. The X-ray phase analysis has shown diffraction peaks corresponding only to aluminum and boron carbide, therefore, under the selected milling conditions, the phase composition remain the same as in the original powders.

A semi-analytical finite element method is used to analyze the stability of composite cylindrical shells interacting with a rotating fluid inside them. A mathematical formulation of the problem of deformable structure dynamics is based on the variational principle of virtual displacements and classical shell theory. The behavior of an ideal compressible fluid is described within the framework of the potential theory. The validity of the obtained results is supported by comparing them with the known solutions. Numerical experiments were performed for two- and three-layer cross-ply shells made of boron-epoxy resin with different boundary conditions and geometrical dimensions. It is demonstrated that, for the examined configurations, an increase in the fibre angles leads to a significant increase in the critical rotation velocities of the fluid, regardless of the conditions for fixing the edges of a thin-walled structure.

The development of efficient methods for non-invasive collection of alveolar lining fluid (ALF) samples containing pulmonary surfactant (PS) components and the study of the surface activity of the obtained native material is relevant for the diagnosis of inflammatory pneumopathies of the lungs. The paper presents an electrostatic aerosol trapping (ESAT) mobile complex for capturing droplets of ALF contained in an exhaled air. Passing the exhaled air through the corona discharge area results in the aerosol droplets charging and their further transferring by electrostatic force into a water surface, where they accumulate forming an adsorbed layer. Additionally, ALF samples were collected using a bronchoalveolar lavage (BAL). The surface properties of the PS obtained by both methods have been examined using the capillary wave method, which was previously modified by the authors specifically for biomedical applications. Significant difference was found in the results obtained with ESAT and BAL in the group of healthy subjects, which can be explained by different origin of the samples obtained by these techniques. Furthermore, significant difference in surface properties was established in the samples collected from healthy volunteers and patient with disseminated tuberculosis, while we did not find significant differences in the limited inflammatory process. The results presented in the paper demonstrate high potential of the proposed non-invasive technique for clinical usage.

In this paper, the mixing process of two solutions of inorganic salts in a continuous flow channel with Y-type micromixer is investigated. Due to different diffusivity rates of solutes the double-diffusion convection develops in the channel. To visualize convective flows and the distribution of mixing substances the shear interferometer technique and a fluorescent dye are used. The latter makes it possible to quantify the mixing degree. The mixing extent for different volume flow rates is calculated. The comparison of convection and pure diffusion mechanisms of mixing is provided.

In multiphase systems the thermodynamic and rheological properties of the interfacial layer have influences on the overall system behavior. The geometrical properties of capillary waves are extremely useful in the characterization of surface parameters. In Shmyrov et al 2019, the modified capillary wave technique was successfully used to perform experiments, to register surface profiles and to realize data processing, yet the algorithm for semi-manual data processing proposed by the authors is labor-intensive and time-consuming. It appears that the analysis of the data is compex because of specific geometry problems, presence of noise at different scales, and data gaps. In this study, the algorithm for analysis of a surface instantaneous profiles formed due to capillary waves propogating is proposed. It was found that the noise and the useful signal have different scales. Moreover, the structure of the useful signal is defined, and therefore it becomes possible to study the noise part of the signal and the patterns of the useful signals. On the basis of the preliminary knowledge about the signal structure, the algorithm has been developed to overcome the above mentioned problems. The proposed method has been tested on the set of semi-synthetic data and provides a reliable result.

In the work the influence of thermal limiters on the formation of a dendritic structure of the stainless steel AISI 304L layer deposited by electric arc welding in argon medium was investigated. The structure of the billets was investigated in the mode of differential interference contrast. The analysis of the obtained structures showed that the use of thermal limiters in the form of graphite skids allows to obtain a uniform structure in billets without sharp transitions between the deposited layers.

The results of numerical modeling (in ANSYS) are presented, concerning the effect of the local residual stress field in the vicinity of the crack tip on the fatigue crack growth rate and change of the crack trajectory. Static indentation by a spherical indenter is considered as a method for creating a residual stress field. In this case, the point (or points) of indentation can be located both symmetrically relative to the line of initial crack orientation and with an offset. It is shown that the fatigue crack can grow in the direction opposite to its initial orientation. This effect can be employed to control the fatigue crack growth trajectory.

It is necessary to achieve high fatigue strength in order to apply carbon reinforced fiber plastics (CRFP) for critical elements subjected to vibration. Gradual accumulation of fatigue damage is accompanied by changes in the material stiffness and natural frequencies. The purpose of this work is to found experimental data on the change of the elastic characteristics of layered CRFP as fatigue damage accumulates. The object of the study is standard samples made of unidirectional carbon/epoxy fiber with different layering schemes. The samples were subjected to fatigue tests under cyclic tension with constant amplitude. The test of each sample was stopped several times at different loading stages to execute experimental modal analysis and non-destructive inspection of the appeared defects. The found natural frequencies were used to solve the inverse problem of identifying the elastic parameters of the laminate monolayer: two Young's modulus, shear modulus and Poisson's ratio. As a result, the dependences of these parameters on the relative fatigue life were obtained. These dependences, together with the results of non-destructive testing, can be used to describe the process of fatigue damage accumulation and for the subsequent development of methods for the fatigue life prediction.

Modern VHCF testing regimes are studied. A new loading scheme applicable to a piezoelectric fatigue testing machine is proposed. The scheme is studied analytically and numerically. The analytical part comprises the calculation of the specimen's geometry to operate correctly on the VHCF testing machine, as well as the specimen's stress-strain state calculation during an experiment in order to determine the one's durability. A model based on a kinetic damage equation is introduced. This model is used in the numerical experiment. The behavior of a finite-element specimen in a fatigue experiment is calculated from the beginning up to the stage of active crack growth.

A two-criterion kinetic damage model is proposed to describe the development of the fatigue fracture process under cyclic loading. On this basis, a procedure is proposed for calculating the coefficients of the kinetic equation for various modes of fatigue fracture from low-cycle to very-high-cycle fatigue. A uniform numerical method has been developed based on an implicit approximation of the differential equation for damage. This method makes it possible to carry out an end-to-end calculation of the evolution of crack-like zones of fatigue fracture in the material without considering cracks in their classical sense, as well as to estimate the durability of samples from the first nucleation to macrofracture. Calculations were made of the fatigue fracture of specimens under long-term cyclic loading according to the three-point bending scheme with the development of crack-like fracture zones in the modes from HCF to VHCF. Comparison of numerical and experimental results for specimens of titanium alloys is carried out.

The problem of cyclic loading under pure torsion is an important problem for numerous different industrial applications, such as shafts, springs, blades, and others. The loading conditions for aircraft, railway, automobile industries are often corresponding to long fatigue life. The rough estimation shows that the number of cycles for springs in car engine is exceeds 10⁸ cycle while blades for aircraft turbine may undergo more than 10¹⁰ loading cycles. Such, to provide a safety in service life for such elements a multiaxial fatigue failure criterion is needed to predict damage zone location and fatigue life. This paper is aimed to introduce the multi regime approach to predict fatigue damage zone evaluation and number of cycles to crack initiation and total fatigue life. The presented approach is based on damage theory supplemented by multiaxial failure criterion. The proposed model includes the algorithm for automatic determination the fatigue loading range (low-, high- or very-high cycle fatigue) and allows different crack opening modes. To show how to apply the proposed approach and verify the results of calculation the series of numerical simulation on hourglass specimen subjected to VHCF pure torsion is performed. The results of numerical simulation are compared to VHCF torsion tests.

This article presents the results of a simulation of conjugate heat transfer between cold air and warm shaft lining during airflow reverse at a hard rock mine. A comparison of the numerical results with collected experimental data was carried out. A significant discrepancy between the two was revealed, indicating that not all heat sources and additional air heating mechanisms were taken into account in the simulation. Possible reasons for the discrepancy are discussed and the most probable reasons are identified for further study. A quantitative assessment of the possible factors considered is carried out. Further tasks for research are determined.

The article is devoted to the study of the mechanical response of an electro-viscoelastic structure if an electric voltage with given characteristics supplied to a piezoelectric element attached to the surface of the structure. A cantilever plate made of a viscoelastic material is considered as a structure under study. The amplitude of displacements of the free end of the plate in resonance modes occurring at forced steady-state vibrations is considered as the mechanical response. Excitation of vibrations is realized by a harmonic movement applied to the clamped end of the plate. The control of the mechanical response within the framework of this work is supposed to be performed by supplying an electric signal to the piezoelectric element. This signal changes harmonically and has the form of a potential difference which changes according to a harmonic law. The magnitude of the vibration amplitude of the structure is determined numerically by the finite element method implemented in the ANSYS software package. The viscoelastic properties of the plate material are described according to the relations of hereditary theory of viscoelasticity in terms of complex dynamic moduli. Within the framework of this work, the relations between the mechanical response of the structure and the magnitude and polarity of the electric voltage applied to the piezoelectric element were obtained. It is shown that by a proper selection of the characteristics of the electric voltage, it is possible to control the magnitude of the amplitude of forced steady-state vibrations.

Protein fields synthesized by genes play a principal role in the functioning of living systems. The processes of gene regulation determine the properties of these fields. Since the number of nucleotides usually is not large, a deterministic description of the field dynamics is insufficient. In this work, we consider a special kind of protein field, the dynamic behavior of which is described by the non-Markov process. Generally, the dynamics of complex organic compounds is time-dependent and spatially extended, and it may depend on all the previous evolution of the system. We consider a time-delayed repressilator as a model system. We study this system numerically using a modified Gillespie algorithm. New dynamic phenomena, which are visible only within a stochastic description, are reported. We show that synchronization in a gene expression occurs much faster due to the non-linear interaction of noise and delay. It results in almost regular oscillations even below the neutral curve derived within the deterministic analysis. We apply a hybrid approach to study the spatial dynamics of the repressilator proteins. This approach includes a deterministic calculation of the diffusion fluxes between cells and the stochastic simulation of gene regulation processes. We found that the combined action of time-delay, noise, and spatial signaling can lead to pattern formation even when the deterministic description predicts the absolute stability of the system.

The impact on the molten metal with electromagnetic forces makes it possible to create specific flows in the metal, which, in turn, are able to concentrate particles of inclusions in a given area, from where they can be removed mechanically. In this case, it is important to determine the shape of the inclusions, which will provide the best efficiency of impact on them with electromagnetic forces. The use of such an effect is possible in the process of crystallization (transfer of partially crystallized small regions of the metal), as well as during the separation of impurities from liquid metals using electromagnetic forces.

The work is devoted to a numerical study of the features of the effect of electromagnetic forces on inclusions (in shape that differs from spherical) in an electrically conductive medium.

The deformation behavior of capillary porous (CP) Ni and CP Ti is examined under uniaxial compression in air, water, and ethanol. CP metals contained inert liquids such as H₂0 and C₂H₅OH are used as the heat pipes' active elements in space applications. The samples for mechanical testing were isostatic compacting and vacuum annealing (porosity of 60%). Uniaxial compression tests were carried out in the air, water, and ethanol in Shimadzu AG-50K XD (traverse rate 0.1 mm/min). It was shown that CP Ni and CP Ti exhibit the ductile deformation behavior in all cases, which is inherent to Ni and Ti. The ethanol environment induces the increase of the compression strength and the total deformation in both materials compared to deformation behavior in air and water. Therefore, a heat pipe's failure containing CP Ni and CP Ti matrixes and ethanol as the working body is caused rather by manufacturing defects, but not the structural materials' intrinsic properties.

The problem of the malleability of rhenium at room temperature is discussed. It has shown that rhenium manufactured by the mean of the electron beam melting is able to the mechanical treatment by rolling at room temperature. The primary condition for mechanical treatment is the minor share of the tensile stress in the processing scheme. It suppresses the grain boundary sliding in a coarse-grained workpiece of this refractory HCP-metal.

We analyse for approaches to elimination of a fast variable, which are applicable for systems like passive Brownian particles: (i) moment formalism, (ii) corresponding cumulant formalism, (iii) Hermite function basis, (iv) formal 'cumulants' for the Hermit function basis. The accuracy and its strong order are assessed. The applicability and performance of two first approaches are also demonstrated for active Brownian particles.

One of the promising methods for increasing the resistance of polymer composite materials to high-speed impact is the use of protective shockproof coatings. At the same time, over the past two decades, polyurea have been gaining noticeable popularity among such coatings. This work is devoted to study the effect of polyurea coating of 1.2 mm thickness on ballistic resistance characteristics of glass-fibre reinforced layered polymer of 8.5 mm thickness. During the experiments thirteen composite targets was affected by high-speed impact loading in the range of 80...150 m/s by spherical steel projectile of 23.8 mm diameter. It was shown that using the polyurea coating can increase the ballistic limit by 19% increasing the mass of the target only by 7%. Dynamic strain and displacement fields on the back surface of the target was obtained using digital image correlation method for 81.2 m/s collision process.

The dynamics of some magnetic fluid (MF) samples of various concentrations filling the tube horizontally and held by a field of a magnetic axial system made based on unipolar permanent rare-earth ring magnets were studied. The magnetic field of an "axial" magnetic system of MSO was studied, as well as the dependence of the system oscillation frequency on the length of the MF cylinder. An original method for determining MF magnetization is proposed and applied to the obtained data. Magnetization was determined for three magnetic fluid samples. The results obtained by the developed method are comparable to the magnetization values obtained by the ballistic method. The developed and presented technique of a dynamic experiment with measuring oscillations frequency of the "MF column suspended in a strong and inhomogeneous magnetic field" system involves the creation of a new absolute method for determining saturation magnetization and can be useful for studying magnetophoresis and aggregation processes of magnetic nanoparticles. This technique is used to study the degree of elastomagnetic consistency parameters over time.

The results of the flow structure visualization experiments conducted on the surface of a single bubble streamlined by uniform flow are presented. It is shown that, at certain critical values for bubble size, flow velocity, and contamination level, the axial symmetry of the surface flow loses its stability in a threshold manner, and the first instability mode in the form of two vortices appears. Below the threshold, the stationary flow on the bubble surface is impossible. The experimental results indicate that the assumption about the axial symmetry of the motion on the bubble surface containing surfactants, which is used in most theoretical and numerical studies, is invalid. Analysis of the results has revealed the most likely reason for the spiral form of the trajectory in the problem of a small rising bubble in the surrounding fluid. For the surfactant-free surface realized in the experiments with isopropyl alcohol, the rising trajectory was a straight line, and no vortex structures were observed on the bubble surface. In the experiments with water, a spiral rising trajectory was observed, and the first instability mode was formed on the bubble surface.

Acquired defects of the maxillofacial region require orthopedic treatment. When choosing a structural material for the manufacture of a jaw prosthesis, it is necessary to provide for functional loads on the prosthesis during operation. Defects in the jaw bones require a structural material with high strength characteristics. The article deals with the method of increasing the strength of polyamide dental material with nanoscale titanium dioxide. Objective: to improve the strength characteristics of orthopedic structures made of polyamide. The study of the polyamide material was carried out on control and experimental samples, in which a modifying component was introduced by the method of dispersion reinforcement-nanoscale titanium dioxide in an amount of up to 1 wt.%. The three-point bending strength (σmax, MPa) and Young's modulus (E, MPa) were experimentally studied. These criteria are indicative when assessing the strength of the basic structural materials from which removable dentures are made. These parameters take into account both vertical and horizontal functional loads, similar to the forces that arise when using removable dentures. The results of the study showed an increase in the maximum voltage by 8.4%, and the Jung module by 7.2% in samples with nanoscale titanium dioxide introduced into their composition to 1 wt. %. This study is of practical importance for orthopedic dentistry in cases where it is necessary to strengthen the structural base material in the manufacture of jaw prostheses for patients with acquired defects of the jaw bones, which reduces the risk of fracture of the base structures under the influence of functional loads.

Thermal convection of dehumidified air is studied experimentally under conditions close to normal (atmospheric pressure ≍ 740 mm Hg, temperature range T = 0...50 C). The study is based on fundamental experiment, which is focused on the physical aspects of thermoconcentration convection in fluids, undergoing first-order phase transitions of the "gas-liquid" type. The peculiar features of convection, caused by concentration changes of water vapor (as a result of its evaporation or condensation), are discussed in terms of dimensionless parameters. The couple of standard complementary experimental methods are used: holographic interferometry for visualization of convective flows and thermocouple method for heat flux measurements. Test experiments demonstrate and approve the design characteristics of the setup. The observations of convective flows in dehumidified air are demonstrated. Experimental setup is described in all details, including the original design of the cold heat exchanger (resembling a heat tube), proposed for next experiments with humid air.

Magnetostriction effect of a spherical sample of a magnetoactive elastomer (MAE) is analyzed. In comparison with the preceding study, the consideration is done on a more realistic basis: taking into account saturation of the MAE magnetization in contrast to the former model where the magnetization was supposed to be linear whatever the field strength. This more thorough investigation has revealed that the striction-induced elongation effect, depending on the material parameters, may occur in two forms. One scenario manifests itself as tapering of the polar zones of the former sphere, where 'beaks' are formed, so that the shape of the object drastically deviates from a spheroidal one. The mechanism the underlies the occurrence of beaks is the surface instability of a magnetizable elastic continuum, and the beak nucleation follows the second-order transition pattern; the resulting overall elongation of the body does not display any hysteresis. Another scenario—it is related to MAEs with higher magnetic properties and softer matrices—implies that the beak formation happens simultaneously with a jump-like overall elongation of the former sphere, and this transformation resembles the first-order transition pattern. Upon assessing the chances to observe the predicted effects on the samples of now existing MAEs, one comes to a conclusion that the second scenario is hardly possible, whereas the first one, i.e., beak formation without hysteretic stretching, is much more realizable.

Experimental verification of the applicability of self-similar hierarchical mechanics model for calculation of the mechanical properties of human dentin was carried out. A comparison of the deformation behavior of human dentin with the several polymer based dental composites under compression and bending was performed. It was shown that the deformation behavior of some highly filled composites was close to human dentin in the elastic regime whereas they cannot be deformed plastically under compression. Low filled composites possess higher plasticity, but a lower Young's modulus than dentin under compression. Mechanical properties of a highly filled composite (∼60%, by volume) with smaller size of fillers are closer to the properties of human dentin under bending whereas other tested dental materials have a lower Young's modulus and flexural strength in comparison with dentin. Therefore, we concluded that it was impossible to achieve complete combination of the mechanical properties of human dentin such as high elasticity and plasticity at high strength by means of varying the amount and size of solid filler in polymer matrix. Self-similar hierarchical mechanics model can be used for describing of the deformation behavior of human dentin in elastic regime and one level is sufficient for these calculations.

The effect of non-axisymmetric inertial waves on the zonal flow structure in a rotating spherical shell is studied experimentally. The wave source is the inner core, which performs circular oscillations in the equatorial plane. The case of positive frequencies that corresponds to the advanced core motion is considered. As a result of non-linear effects, a quasi-two-dimensional axisymmetric steady flow with a complex distribution of angular velocity is generated. The extrema in the velocity profile are equivalent to the nested liquid geostrophic cylinders, which appearance is due to the interaction of the inertial waves within a viscous boundary layer. One of the extrema is associated with the critical latitude at the core boundary, where the inertial waves are excited. With an increase in the oscillation frequency, the position of this extremum gradually shifts to the rotation axis. Additional geostrophic circulation occurs close to the points where the inertial wave reflects from the cavity boundary.

Residual stresses are common in metal structures, essentially influencing their mechanical behaviour. We consider a combined experimental/theoretical approach to residual stresses. The theoretical basis of analysis is provided by the recently developed F0-approach, operating with explicit relation between load-free and stress-free configurations. The titanium alloy Ti-6Al-4V is modelled with the multiplicative decomposition of the deformation gradient into the elastic and the plastic parts. Isotropic hyperelastic relations between stresses and elastic strains are assumed. The weak invariance of the material model allows for incorporation of residual stresses without additional numerical costs. In order to demonstrate the new experimental/theoretical approach to residual stresses, experimentally measured stresses are extrapolated from the surface inside the welded T-joint. The robustness of the stress extrapolation procedure is confirmed on synthetic experimental data.

This paper presents the results of long-term monitoring of ground subsidence above flooded mining. To assess the change in the shape of ground surface, the data obtained by monitoring the settlement of the foundation of a large group of buildings were used. The control of the slope was carried out using automated hydrostatic level systems mounted on the foundations of 40 buildings located in this area. The accumulated data on the long-term evolution of the tilt were processed using the methods of statistical analysis of non-stationary time series. Choice of forecast model was made based on a comparison of forecast and real monitoring data. A forecast based on 5-year monitoring data predicts that the observed deformation processes in the rock massif will not change over the next 2 years.

Thermal convection of a liquid in a simply connected horizontal cylindrical layer rotating at a variable velocity is investigated experimentally. The inner boundary of the layer has a higher temperature. The cavity rotates rapidly and the liquid is stably stratified in a centrifugal force field. The parameters of the experiment correspond to the conditions when inertial waves are not excited (the modulation frequency is more than twice the cavity rotation frequency). The excitation thresholds of thermal convection and the structure of convective flows are studied depending on the rotation velocity and the parameters of the rotational vibrations of the cavity. It is found that the thermal convection is excited in a threshold way and its excitation is not associated with the manifestation of the mechanism of pendulum vibrational convection. A system of toroidal rolls with a spatial period commensurate with the layer thickness is observed in the cavity.

The steady time-averaged flows in a rotating system of immiscible fluids are studied experimentally. The fluids fill a horizontal cylindrical container and are brought into a centrifuged state, when a less dense fluid forms a cylindrical core, and a denser fluid is distributed in the form of a coaxial layer. Under the action of the gravity field, the core is steadily displaced along the radius in such a way that its axis is oriented parallel to the container axis and remains stationary in the laboratory frame of reference. In the frame rotating with the container, the core and the fluid surrounding it oscillate. This leads to the generation of a steady flow in the form of differential rotation of the fluid with respect to the container. To study the structure of the flow, light-scattering tracers of neutral buoyancy are added to the liquid. The flow rate is calculated from their displacement. Measurements show that at the interface, from the side of the external fluid, a Stokes boundary layer is formed, at the boundaries of which a tangential discontinuity of the averaged velocity is formed.

The experimental and theoretical analysis of thermodynamical peculiarities of heat flux at the fatigue crack tip during its propagation was made in presented work. The goal is to elucidate the relation between heat flow at the crack tip and kinetic of fatigue crack propagation for different loading conditions. The plane specimens with notch made from stainless steel (AISI 304) were studied. There were two types of specimens for uniaxial loading and one type for biaxial loading. A heat dissipation during fatigue crack propagation was measured by simultaneous use of contact and noncontact techniques. The samples were subject to cyclic loading with constant stress amplitude and different biaxial coefficients. The functional dependence between crack propagation and heat flow at the crack tip was received by experiment measurement and analytical calculation. This relation depends on only type of material and righty for all fracture mode.

A practical method of studying the dynamics of respiratory function associated with the registration of the electrical impedance of conductive biological fluids exhaled by the patient is described. In the model measuring cell, the physical causes and relationships in the conductivity of the air flow, saturated with an electrolytic fluid aerosol created by an ultrasonic nebulizer have been investigated experimentally. The design of a new electrical impedance spirometer in the form of a mouthpiece with electrical sensors, filled with a porous medium impregnated with electrolyte, through which the patient breathes, is developed and tested. To register fluctuations in the magnitude of the impedance modulus, an original hardware and software complex is used, made on the basis of a high-speed analog-to-digital converter. Based on electrical impedance analysis data, the methods are proposed for quantitative assessment of the basic spirometric medical indicators characterizing the state and functioning of the patient's breathing apparatus, such as respiration rate, entry and expiration rate, exhaled air volume, amount and concentration of exhaled lung fluid.

The paper presents the results of studies directed toward the determination of physical mechanisms and causal factors responsible for variations in the electrical impedance of the cardiovascular system. Experiments were carried out using the original hydrodynamic apparatus modelling different hemodynamic conditions, i.e., a pulsatile flow in a blood vessel of variable diameter, ramified pulmonary blood flows and the function of a cardiac valve. Computer-assisted signal processing techniques provided measurements of the active and capacitive components of the electrical conductivity with an error not exceeding 0.1%. Impedance values were analyzed for different vessel size and geometry, flow rate, temperature, concentration of ionic and dielectric components in some model biological fluids at different frequencies of the probing alternating current. It has been found that bioimpedance oscillations can be mainly attributed to the local modulations of the diameter of blood vessels such as the function of cardiac valves.

Contemporary medicine applies the analysis of molecular composition and physicochemical properties of biological fluids as one of the main tools for diagnostics and control over body state and behaviour of pathological processes. However, most laboratory diagnostics methods (such as biochemical, enzyme-linked immunosorbent assay, etc.) are too expensive and time-consuming. They demand the availability of well-equipped laboratories, complex equipment, scarce and expensive reactants and materials and the highly skilled medical staff. Compared to them, bioimpedansometry is an incomparably simpler and cheaper method of laboratory research, becoming increasingly popular for diagnosing internal diseases. In the current research the main physical factors responsible for bioelectrical impedance variations in some conductive intracellular and extracellular biological fluids with different protein molecules, cell components and microbes were studied experimentally. The original laboratory impedance meter was developed for investigation of blood or interstitial biological fluids as well as condensates composition in orderto determine the concentration of organic substances in them and the rate of biochemical and immune reactions.

The study of the electromagnetic force acting on a medium with inhomogeneous electrical conductivity has been carried out. The electrical conductivity changes abruptly which simulates the liquid–solid interface during the crystallization of a pure metal. The electromagnetic force is created by a traveling field inductor with one of the most demanded in metallurgy construction. The results showed a significant dependence of the electromagnetic force on the position of the interface with respect to the inductor. Consequently in the mathematical modeling of the directional crystallization process under the influence of an electromagnetic force created by an inductor of this type it is necessary during the movement of the interface, either to do the calculation of the electrodynamic part of the problem anew or to use the method of canonical domains.

In this work, we studied the effect of a carbon coating created on the surface of a polyvinyl chloride blood storage bags on protein adsorption, cell culture proliferation, and on whole blood leukocytes. Based on the results obtained, it can be assumed that the preservation of leukocytes is more effective in the blood storage bags treated by the ion-plasma method, in comparison with the untreated one. The adhesion of blood cells occurs on the carbon coating of the plasma-treated surface of the blood storage bags. This can be eliminated by preliminary application of proteins that prevent cell adhesion on the walls of the blood storage bags.

In this work, we propose the finite-element-based mathematical model of the metal-inducer system. This system consists of a coil with put-on C-shaped ferromagnets. We study how the measurands of the inducer, such as the coil voltage and the uncompensated force acting on metal, depend on the system parameters. We variate the geometry of the system to estimate the boundary effect impact. Also, we study how the coil voltage depends on the ferromagnets' spacing and their number. The inhomogeneity of electric conductivity is modeled via holes in the metal volume. To estimate their impact, we defined the dependences of the measurands on the number and the size of inhomogeneities.

This paper examines a carbon layer on a blood vessel implant. The carbon layer is created by high energy ions bombarding an inner surface of the polyurethane implant. An analysis of the molecular structure of the layer was carried out, demonstrating the appearance of free radicals stabilized by aromatic clusters, as well as new carbon-carbon, oxygen-containing and nitrogen-containing groups in the inner surface of the blood vessel implant. The covalent adsorption of the protein on the carbon layer inside the implant has been proven. The antithrombogenicity of the carbon layer with a covalently bound protein on polyurethane implant of blood vessels in an experiment on rabbits has been shown.

The structure of a steady radial thermocapillary flow from the local heat source in cylindrical geometry has been studied numerically. The up boundary of the liquid was partially covered by the stationary film of an insoluble surfactant, pushed to the wall of the cavity. The calculations are fulfilled on the base of interfacial hydrodynamics equations by using mathematical package "Comsol Multiphysics". It is shown that the effect of a radial flow symmetry breakdown appears as a result of convective instability, so that the initial poloidal rotation of the liquid transforms into the azimuthal plane. The system of inclined steady volumetric vortices is formed under the film of surfactant. The inclination angle of the plane of rotation in dependence on the intensity of radial thermocapillary flow is studied. It is shown that the azimuthal vorticity can be regulated by the power of point-heat source and by free surface area. The increase of heating intensity leads to the growth of the azimuthal vorticity. Thus, the initially radially symmetric toroidal flow is divided into two parts with the origination of vortices in the azimuthal plane under the film.

In the first part of the paper, the effect of mechanical treatment of particles of reacting Ti + C + Me (Me = NiCr or Co) mixtures on the process of self-propagating high-temperature synthesis (SHS) is investigated. It is shown that as a result of SH-synthesis in the free burning mode, a metal-ceramic sinter of high porosity is formed, which is easily destroyed by mechanical action. An increase in the volume fraction of the metal binder (NiCr or Co) leads to a redistribution of the sizes of carbides towards smaller values.

In the second part of the paper, the results of cold spraying nickel-chromium alloy particles and cermet particles of the TiC – NiCr composition on an aluminum substrate are presented. Produced NiCr coatings have a high porosity (up to 10 %) and a layered structure with clearly defined contours of individual deformed particles (splats). Due to the high hardness and low plasticity of metal – ceramic particles of the TiC – NiCr composition, during their interaction with the surface of aluminum substrate, continuous coating cannot be produced, only individual adhered particles are observed. With prolonged exposure to the flow of such particles, erosion of the substrate takes place.

The propagation of plane longitudinal waves in a fluid-saturated porous medium with cavities is considered in linear elastic approximation. It has been shown that as distinct from the classical porous medium (Biot's medium) where two longitudinal dispersionless waves can propagate (a fast wave and a slow wave), in the porous-cavity media three dispersive longitudinal waves propagate and one of them is solely induced due to cavities in the material. The study of waves is carried out by obtaining and analyzing the dispersion equation, phase velocity and group velocity. The frequency spectrum density is considered, which enables to identify the degree of dispersion expressiveness. At certain values of the system parameters some regions of strong and weak dispersion, regions of normal and anomalous dispersion have been identified.