Problems of strenght and plasticity最新文献

{"title":"ABOUT SMOOTH INTERPOLATION OF A TRIANGULATED SURFACE","authors":"D. Chekmarev, M. Abuziarov, Cheng Wang","doi":"10.32326/1814-9146-2020-82-2-147-155","DOIUrl":"https://doi.org/10.32326/1814-9146-2020-82-2-147-155","url":null,"abstract":"A method and algorithm for rebuilding a surface triangulation in three-dimensional space defined by an STL file is proposed. An initial surface in 3D space (STL file) is represented as a polyhedron composed of triangular faces. The method is based on the analytical representation of the surface as a piecewise polynomial function. This function is built on a polyhedral surface composed of triangles and satisfies the following requirements: 1) within one face, the function is an algebraic polynomial of the third degree; 2) the function is continuous on the entire surface and preserves the continuity of the first partial derivatives; 3) the surface determined by the function passes through the vertices of the initial triangulated surface. The restructuring of computational meshes is required in cases of distortion of the shape of cells when solving problems of mathematical physics using mesh methods (finite-difference, FEM, etc.). Cell distortion can be due to various reasons. These can be large distortions of moving Lagrangian meshes in the calculations in the current configuration, with instability of the hourglass type, with distortion of the faces of the interface between interacting gaseous, liquid and elastoplastic bodies.\u0000\u0000The rebuilding of the mesh reduces to solving the problem of constructing a smooth surface passing through the nodes of an existing triangulated surface or part of it. Later the nodes of the new mesh are placed on the constructed smooth surface with existing requirements for the size and shape of the cells. The construction of a smooth piecewise polynomial surface is based on the ideas of spline approximation and reduces to the building of a cubic polynomial on each triangular face, taking into account the smooth conjugation of polynomial pieces of the surface constructed on adjacent faces.\u0000\u0000The proposed method for rebuilding surface triangulation can be useful for calculating the motion of deformable bodies when solving problems of the dynamics of continuous media on immovable Euler grids.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128759705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"TO THE ISSUE OF STRENGTH PROPERTIES OF THE COATING ZIRCONIUM DIOXIDE OF INCREASED THICKNESS","authors":"I. Tsareva, O. Berdnik, L. Krivina, S. Kirikov, Y. Tarasenko, V. Kuzmin, V. Mishakin, A. Gonchar, E. Razov","doi":"10.32326/1814-9146-2021-83-3-265-275","DOIUrl":"https://doi.org/10.32326/1814-9146-2021-83-3-265-275","url":null,"abstract":"With the use of special technological techniques (layer-by-layer spraying, air cooling and substrate temperature control), the technologically complex problem of applying plasma coatings of increased thickness with high adhesive strength has been solved. The difficulty of solving this problem is due to the occurrence of micro-stresses in the coating during spraying, the difference in the values of the coefficient of thermal expansion of the substrate and the coating, the accompanying heating during plasma treatment, as well as the warping of thin-walled parts during spraying. The regularities of the formation of a coating of zirconium dioxide with a thickness of ~1 mm during high-energy plasma spraying of a powder mixture ZrO2 +7% Y2O3 with a spherical morphology of particles have been studied. The structural-phase state of the coating is investigated. It is established that with this method of spraying, a layered hierarchy of the coating is formed with a columnar shape of zirconium dioxide grains in the interlayers. The effect of the plasma flow stimulates the partial phase transformation of the tetragonal phase T-ZrO2 into the cubic K-ZrO2. To study the adhesive strength of the coating, different methods were used: scratch test, Rockwell test and low-cycle fatigue tests. The high adhesive strength of the adhesion of the investigated coating to the substrate is shown since no detachment from the substrate occurred during any type of testing. In sclerometry, the cohesive mechanism of destruction due to microscopes prevails, affecting only the surface layers (5–10 microns thick) of the coating. The Rockwell test demonstrated the best crack resistance score and a sufficiently high plasticity of the coating. Cyclic vibration tests based on 250,000 cycles showed that microcracks are formed at the boundary with the sublayer. The coating of increased thickness can be used both for protection against high-temperature exposure and against mechanical wear of parts in power and aviation engineering.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124328777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"STUDY ACOUSTIC EMISSION SIGNALS AT TENSION STEEL 20","authors":"A. V. Ilyakhinskii, V. Rodyushkin, D. Ryabov, A. A. Khlybov, V. Erofeev","doi":"10.32326/1814-9146-2021-83-2-188-197","DOIUrl":"https://doi.org/10.32326/1814-9146-2021-83-2-188-197","url":null,"abstract":"An investigation was made of acoustic emission signals during uniaxial tensile testing of flat specimens of steel 20 used for parts of welded structures with a large volume of welding, as well as pipelines, collectors and other parts operating at temperatures from –40 to 450 °C under pressure. Tensile testing with simultaneous registration of acoustic emission was carried out on a universal testing machine manufactured by Tinius OIlsen Ltd, model H100KU, at a movement speed of the active gripper of 0.05 meters per minute. Registration of AE signals was carried out using wideband GT350 sensors from GlobalTest and an analog-to-digital converter NationalInstruments 6363X with subsequent storage of the registration results in the form of a time series in the computer memory. A comparative analysis of the amplitude distribution of the AE signal for the area of the yield area and the area of destruction was carried out according to the value of information entropy, fractal dimension, and self-organization parameter. It was found that the parameter of self-organization of the amplitude distribution of the signal is the most informative in describing the processes associated with acoustic emission. As additional information, it is advisable to use data on the structure of the self-organization parameter. The results obtained indicate the possibility of using the statistical model of the Dirichlet distribution as a model of processes associated with the appearance of acoustic emission signals from sources of incipient and developing defects during routine tests of products made of structural carbon high-quality steels with a pearlite-ferrite structure.\u0000\u0000The paper presents a version of the model and modeling algorithms for FE-modeling corrosion cracking processes in structural elements loaded by pressure and exposed to aggressive corrosion media. To assess the effectiveness of the present models and algorithms, the failure process of a thin-walled tubular specimen partly submerged into a chlorine-containing liquid and loaded by axial tension is numerically modeled.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114079485","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"COUPLED CALCULATIONS OF WEAKLY DEFORMABLE BODIES MOVING IN ELASTOPLASTIC ENVIRONMENT AND DEFINING ITS MODE OF DEFORMATION","authors":"A. А. Krayukhin, V. V. Borlyaev, M. V. Skobeeva, A. Stadnik","doi":"10.32326/1814-9146-2020-83-3-328-338","DOIUrl":"https://doi.org/10.32326/1814-9146-2020-83-3-328-338","url":null,"abstract":"This paper presents a technology of making coupled simulations of weakly deformable bodies moving in elastoplastic environment and defining its mode of deformation. Calculation of penetration of a projectile is made by EGAK methods on a fixed calculating mesh implying that the projectile is rigid and its inner structure is unimportant. Fluid flow is calculated in a noninertial base that is connected with the stationary projectile (using BODY-3D method). Mode of deformation of the projectile is calculated on a Lagrangian mesh using software package LOGOS. Finite-element model of the projectile with the required degree of detail is used with real elastoplastic material properties of its structural parts. Loading of the projectile is implemented with an assignment of force boundary condition on its outer surface. Methods of coupling calculations and test results are provided. In this paper, it is shown that test results obtained by this developed technology are in a good agreement with direct modeling on a fixed calculating mesh. As an example of using this technology, calculation results of a penetrator-probe MoonLITE intruding into a soft soil barrier are presented. This penetrator is developed within the scope of MoonLITE mission of studying the Moon and can deepen into moon soil. Results of numerical simulations are in a good agreement with the experimental data, maximum difference for average slow-down rate of the penetrator is 10–15%.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114047748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"THE EXACT SOLUTION FOR STRAINS AND STRESSES IN A HOLLOW CYLINDER OF NON-LINEAR VISCOELASTIC MATERIAL SUBJECT TO INTERNAL AND EXTERNAL PRESSURES IN THE CASE OF POWER MATERIAL FUNCTION GOVERNING NON-LINEARITY","authors":"Íàãðóæåíèè ÄÀÂËÅÍÈßÌÈ, Ïîëîãî Öèëèíäðà, ÈÇ Íåëèíåéíî, Íàñëåäñòâåííîãî Ìàòåðèàëà, ÑËÓ×ÀÅ Ñòåïåííûõ, Ôóíêöèé Íåëèíåéíîñòè","doi":"10.32326/1814-9146-2020-82-2-225-243","DOIUrl":"https://doi.org/10.32326/1814-9146-2020-82-2-225-243","url":null,"abstract":"We study analytically the exact solution of the quasi-static problem for a thick-walled tube of physically non-linear viscoelastic material obeying the Rabotnov constitutive equation with two arbitrary material functions (a creep compliance and a function which governs physical non-linearity). We suppose that a material is homogeneous, isotropic and incompressible and that a tube is loaded with time-dependent internal and external pressures (varying slowly enough to neglect inertia terms in the equilibrium equations) and that a plain strain state is realized, i.e. zero axial displacements are given on the edge cross sections of the tube. We previously have obtained the closed form expressions for displacement, strain and stress fields via the single unknown function of time and integral operators involving this function, two arbitrary material functions of the constitutive relation, preset pressure values and radii of the tube and derive functional equation to determine this unknown resolving function.\u0000\u0000Assuming creep complience is arbitrary and choosing the material function governing non-linearity to be power function with a positive exponent, we construct exact solution of the resolving non-linear functional equation, calculate all the convolution integrals involved in the general representation for strain and stress fields and reduce it to simple algebraic formulas convenient for analysis and use. Strains evolution in time is characterized by creep compliance function and loading history. The stresses in this case depend on the current magnitudes of pressures only, they don't depend on creep compliance (i.e. viscoelastic properties of a material) and on loading history. The stress field coincides with classical solution for non-linear elastic material or elastoplastic material with power hardening (for non-decreasing pressure difference). We obtain criteria for increase, decrease or constancy of stresses with respect to radial coordinate in form of inequalities for the exponent value and for difference of pressures. Assuming creep compliance is arbitrary, we study analytically properties of strain and stress fields in a tube under internal pressure growing with constant rate and properties of corresponding stress-strain curves implying measurement of strains at a surface point of a tubular specimen.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129121418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MODELING FATIGUE LIFE OF POLYCRYSTALLINE STRUCTURAL ALLOYS UNDER A COMBINED EFFECT OF LOW- AND HIGH-CYCLE FATIGUE MECHANISMS","authors":"I. Volkov, L. Igumnov, S. N. Sikaryov, D. N. Shishulin, A. Volkov","doi":"10.32326/1814-9146-2019-81-3-305-323","DOIUrl":"https://doi.org/10.32326/1814-9146-2019-81-3-305-323","url":null,"abstract":"Processes of fatigue life of polycrystalline structural alloys under a combined effect of low- and high-cycle fatigue are considered. In the framework of mechanics of damaged media (MDM), a mathematical model is developed, which describes processes of plastic deformation and fatigue damage accumulation. The MDM model consists of three interrelated parts: relations defining cyclic elastoplastic behavior of the material, accounting for its dependence on the failure process; equations describing fatigue damage accumulation kinetics; a strength criterion of the damaged material.\u0000\u0000The version of defining relations of elastoplasticity is based on the notion of yield surface and the principle of orthogonality of the plastic strain rate vector to the yield surface at the loading point. This version of equations of state reflects the main effects of the cyclic plastic deformation process of the material for arbitrarily complex loading trajectories.\u0000\u0000The version of kinetic equations of damage accumulation is based on introducing a scalar parameter of damage degree. The construction uses energy-based principles and accounts for the main effects of the process of nucleation, growth and merging of microdefects under arbitrarily complex multiaxial loading regimes. A combined form of the evolutionary equation of fatigue damage accumulation in the regions of low-cycle (LCF) and high-cycle (HCF) fatigue is proposed.\u0000\u0000It is shown that, under regular cyclic loading of the material, the stress amplitude of the cycle decreases by degrees during the transition from LCF to HCF and depends on the physical interaction of these mechanisms in the transition zone.\u0000\u0000The condition when the damage degree attains its critical value is taken as the strength criterion of the damaged material.\u0000\u0000A methodology of numerically determining parameters of the evolutionary equation of fatigue damage accumulation in the conditions of HCF is presented.\u0000\u0000To assess the reliability and the limits of applicability of the defining relations of MDM, processes of plastic deformation and fatigue damage accumulation in a number of structural alloys in cyclic tests have been numerically studied, and the obtained numerical results have been compared with the data of full-scale experiments.\u0000\u0000The results of comparison of the numerical and experimental data reveal that the developed model of mechanics of damaged media adequately describes durability of structures subjected to a combined effect of low- and high-cycle fatigue mechanisms. It is shown that the introduced MDM model qualitatively and, accurately enough for practical engineering purposes, quantitatively describes the main effects of the processes of plastic deformation and fatigue damage accumulation in structural alloys under cyclic loading.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"121 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115855029","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"MODELING PLASTIC DEFORMATION OF POLYCHRYSTALLINE STRUCTURAL ALLOYS UNDER BLOCK-TYPE NONSYMMETRICAL REGIMES OF SOFT LOW-CYCLE LOADING","authors":"I. Volkov, L. Igumnov, I. Tarasov, D. Shishulin, S. N. Pichkov, M. T. Markova","doi":"10.32326/1814-9146-2019-81-1-63-76","DOIUrl":"https://doi.org/10.32326/1814-9146-2019-81-1-63-76","url":null,"abstract":"Processes of plastic deformation of polycrystalline structural alloys under block-type nonstationary regimes of soft low-cycle loading are considered. Modified Korotkikh's thermal-plasticity model pertaining to the class of yield theories with translation-isotropic hardening is used as defining relations of plasticity. The modification of Korotkikh's model consists in using a different formulation of evolutionary equations for the displacement of the yield surface center (the micro-stress tensor), used for block-type nonstationary regimes of low-cycle loading for describing effects of setting under a hard loading regime (controlled strains) and ratcheting under a soft loading regime (controlled stresses) of the plastic hysteresis loop.\u0000Determining the material parameters and scalar functions of the plastic deformation model, assessing its adequacy and scope of application was done based on the experimental studies of the deformation process of laboratory specimens made of stainless steels of the austenite (SS316L, SS304) and ferrite (20MnMoNi5-5) classes in the conditions of uniaxial and multiaxial, proportional and non-proportional regimes of soft block-type cyclic loading.\u0000Comparison of the numerical results with the experimental data indicates that the developed plasticity model qualitatively and quantitatively, accurately enough for engineering purposes, describes the main effects of plastic deformation (displacements of the plastic hysteresis loops and decreasing strain amplitudes) under block-type nonstationary nonsymmetrical regimes of soft low-cycle loading.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126206884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"STABILITY OF A CYLINDER FROM MURNAGHAN MATERIAL UNDER STRETCHING, COMPRESSION AND INFLATION","authors":"M. Karyakin, L. Obrezkov","doi":"10.32326/1814-9146-2019-81-1-30-39","DOIUrl":"https://doi.org/10.32326/1814-9146-2019-81-1-30-39","url":null,"abstract":"The problem of equilibrium and stability of a hollow cylinder subjected to simultaneous uniaxial tension/compression and inflation is considered within the framework of the three-dimensional nonlinear theory of elasticity. To describe the mechanical properties of the material of the cylinder five-constant Murnaghan model is used. By the semi-inverse method the three-dimensional problem is reduced to the study of a nonlinear boundary value problem for an ordinary second-order differential equation. For most sets of material parameters known from the literature, the presence of a falling section in the stretching/inflation diagram, indicating the possible existence of instability zones even in the area of tensile stresses, has been found numerically. The stability analysis was carried out using a bifurcation approach based on linearization of the equilibrium equations in the neighborhood of the constructed solution by means of the method of imposing a small strain on a finite one. The value of a particular deformation characteristic, for which non-trivial solutions of a homogeneous boundary-value problem exist for the equations of neutral equilibrium obtained in the linearization process, was identified with the critical value of the loading parameter, i.e. value at which the system loses stability. As a rule, the coefficient of stretching/shortening of the cylinder and the coefficient of increase/decrease of its internal or external radius were chosen as such parameters. On the plane of the above-mentioned deformation characteristics the areas of stability under tension and compression, as well as under compression by external force and inflation by internal pressure, are constructed. The forms of possible of stability loss depending on the type of stress state are constructed, and the effect on the stability of material and geometric parameters is studied.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125499452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"EXPERIMENTAL STUDY ON PERFORATION OF BRITTLE LAYERED OBSTACLES","authors":"N. V. Baniсhuk, S.Yu. Ivanоva, K. Osipenko","doi":"10.32326/1814-9146-2021-83-2-137-150","DOIUrl":"https://doi.org/10.32326/1814-9146-2021-83-2-137-150","url":null,"abstract":"An experimental study of the process of perforation of plates made of brittle materials by rigid strikers has been carried out. The strikers were accelerated to the required speed with a pneumatic gun. Both homogeneous plates and obstacles from several plates glued together, put together without gluing, or spaced relative to each other were considered as targets. The results of experiments on the perforation of plexiglass plates by rigid spherical bodies at impact velocities of 100–200 m/s are presented. Qualitative features of the fracture at different velocities of impact are revealed. For the samples considered, it was found that spaced plates reduce the velocity of the striker during penetration more effectively than the same plates putted together. A set of experiments were also carried out on perforation of two combined plates made of various brittle materials: plexiglass, ceramics, artificial stone (polyacryl, quartz) by a rigid spherical striker for a velocity range of 200–350 m/s. For each considered combination of plates, a ballistic limit (ballistic limit velocity, BLV, at which the striker penetrates the obstacle with zero exit speed) was experimentally established, which characterizes the protective properties of the barrier. The effect on the ballistic limit of the order of the layers was studied. As a result, it was found that for all selected pairs of materials, a larger ballistic limit was achieved when a less dense and less brittle plexiglass layer was located behind a denser plate (made of ceramic or artificial polyacrylic or quartz stone). The reverse order of the layers led to a decrease in the ballistic limit in all cases. Photographs illustrating the nature of the destruction of the plates are presented.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129554709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DIFFUSION NUCLEATION OF CAVITIES IN GRAIN JUNCTIONS OF SUBMICROCRYSTALLINE MATERIALS","authors":"A. Pupynin, S. Kirikov, V. Perevezentsev","doi":"10.32326/1814-9146-2021-83-3-276-284","DOIUrl":"https://doi.org/10.32326/1814-9146-2021-83-3-276-284","url":null,"abstract":"The conditions of diffusional cavity nucleation in submicrocrystalline materials processed by the methods of intensive plastic deformation (equal-channel angular pressing, multiaxial forging, high pressure torsion, etc.) are analyzed. To date, the question of the mechanism of nucleation of cavities in such materials remains debatable due to the fact that the processing of materials by the methods of intensive plastic deformation is carried out at high hydrostatic pressures that prevent the appearance of pores. The possibility of diffusive nucleation of nanopores in the region of triple junctions of grains containing negative strain-induced wedge disclinations, generating high tensile stresses in the vicinity of triple junctions, comparable in magnitude to external hydrostatic pressure, is shown. Such junction disclinations inevitably occur at the grain junctions due to the heterogeneity of the plastic deformation through the ensemble of polycrystal grains. It is shown that an important condition for the nucleation of cavities is not only the presence of high internal tensile stresses from junction disclinations, but also an extremely high concentration of nonequilibrium strain-induced vacancies characteristic of submicrocrystalline metals, comparable in values to the vacancy concentration, at temperatures close to solidus. The influence of the strength of junction disclinations, the value of external hydrostatic pressure and the degree of supersaturation of the material by nonequilibriumstrain-induced vacancies on the rate of diffusional nucleation and the volume of critical pore nuclei is analyzed. It is established that in order to effectively suppress the process of pore formation in the grain boundary triple junctions, it is necessary to apply an external hydrostatic pressure that compensates for internal elastic fields from junction disclinations.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115152027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}