Pub Date : 2019-06-16DOI: 10.32326/1814-9146-2019-81-2-222-232
A. I. Аbakumov, Y. B. Bazarov, E. A. Veselova, A. Vyalykh, A. V. Gubachev, S. Lobastov, I. Safronov, V. I. Tsypkin, A. Smirnov
A design of a rapidly erected temporary structure reducing adverse factors of a powerful explosion to the levels safe both for people and building structures is proposed. The protective structure consists of three separate metal frames with the open upper part, welded or bolted to each other and covered with metal profile. Each frame houses reservoirs of watertight cloth filled with water. Damping of an air shockwave has been numerically modeled, and a full-scale rapidly erected temporary protective structure has been tested with an explosion of a home-made 100kg-trotil equivalent explosive device installed in a car. The explosion process and its impact on the protective structure were numerically modeled in a hydrodynamic formulation, where the structure prior to the beginning of failure was regarded as a rigid non-deformable body. According to the computational results, a rectangular geometry of the frame is more effective than a trapezoidal one. The parameters of the air shockwave were measured with SPK-sensors according to the certified and registered in the State Register methodology “SVР20-VUV” providing measurement of pressure amplitudes to the accuracy of not more than ±11 %. The numerical results are compared with the results of tests of the proposed design of a protective structure. The numerical and experimental data on the peak value of pressure without the protective structure satisfactorily agree Sadovskiy's formula for a ground explosion. Times of arrival of the air shockwave and maximal pressures along its front in the control points in front of and behind the protective structure obtained numerically and experimentally agree within measuring accuracy.
{"title":"A RAPIDLY ERECTED TEMPORARY STRUCTURE PROTECTING FROM POWERFUL EXPLOSIONS","authors":"A. I. Аbakumov, Y. B. Bazarov, E. A. Veselova, A. Vyalykh, A. V. Gubachev, S. Lobastov, I. Safronov, V. I. Tsypkin, A. Smirnov","doi":"10.32326/1814-9146-2019-81-2-222-232","DOIUrl":"https://doi.org/10.32326/1814-9146-2019-81-2-222-232","url":null,"abstract":"A design of a rapidly erected temporary structure reducing adverse factors of a powerful explosion to the levels safe both for people and building structures is proposed. The protective structure consists of three separate metal frames with the open upper part, welded or bolted to each other and covered with metal profile. Each frame houses reservoirs of watertight cloth filled with water.\u0000Damping of an air shockwave has been numerically modeled, and a full-scale rapidly erected temporary protective structure has been tested with an explosion of a home-made 100kg-trotil equivalent explosive device installed in a car. \u0000The explosion process and its impact on the protective structure were numerically modeled in a hydrodynamic formulation, where the structure prior to the beginning of failure was regarded as a rigid non-deformable body. According to the computational results, a rectangular geometry of the frame is more effective than a trapezoidal one.\u0000The parameters of the air shockwave were measured with SPK-sensors according to the certified and registered in the State Register methodology “SVР20-VUV” providing measurement of pressure amplitudes to the accuracy of not more than ±11 %. \u0000The numerical results are compared with the results of tests of the proposed design of a protective structure. The numerical and experimental data on the peak value of pressure without the protective structure satisfactorily agree Sadovskiy's formula for a ground explosion. Times of arrival of the air shockwave and maximal pressures along its front in the control points in front of and behind the protective structure obtained numerically and experimentally agree within measuring accuracy.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114762400","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}
Pub Date : 2019-06-16DOI: 10.32326/1814-9146-2019-81-2-240-248
R. Chmielewski, L. Kruszka, L. Muzolf
The paper presents problems related to the load-bearing capacity analysis of the building partitions of the cold storage facility. The subject of the case study are two different buildings built in the early fifties of the last century. Despite the similar cubature and the construction period, the structures of these buildings are different. The analysed cold store in Warsaw (Poland) is a steel and brick structure, while the second example concerns a reinforced concrete slab-pillar structure located in Wloclawek (Poland). In both cases, the issue related to the assessment of the current technical condition of the structural elements, including the safety of the load-bearing structure and the safety of its use was considered. Moreover, the permissible load for inter-storey slabs in both cases was determined. In order to properly determine the current load-bearing capacity of inter-story slabs, the archival technical and operational documentation of buildings was firstly analysed. Their technical condition was also taken into account in the assessment process. In-situ inspections of both buildings had been carried out. This allowed the determination of the scope of necessary tests and the selection of test and check points for each structural element. Such actions allowed to identify cross-sections of the structural elements and the parameters of built-in materials. The performed diagnostics also allowed to properly determine the technical condition of each structural element, the degree of degradation of the structure and to correctly determine its current load-bearing capacity while simultaneously satisfying both limit states - the Ultimate Limit State (ULS) and the Serviceability Limit State (SLS).
{"title":"LOAD-BEARING CAPACITY ANALYSIS OF BUILDING PARTITIONS OF THE COLD STORAGE CHAMBERS","authors":"R. Chmielewski, L. Kruszka, L. Muzolf","doi":"10.32326/1814-9146-2019-81-2-240-248","DOIUrl":"https://doi.org/10.32326/1814-9146-2019-81-2-240-248","url":null,"abstract":"The paper presents problems related to the load-bearing capacity analysis of the building partitions of the cold storage facility. The subject of the case study are two different buildings built in the early fifties of the last century. Despite the similar cubature and the construction period, the structures of these buildings are different. The analysed cold store in Warsaw (Poland) is a steel and brick structure, while the second example concerns a reinforced concrete slab-pillar structure located in Wloclawek (Poland). In both cases, the issue related to the assessment of the current technical condition of the structural elements, including the safety of the load-bearing structure and the safety of its use was considered. Moreover, the permissible load for inter-storey slabs in both cases was determined. In order to properly determine the current load-bearing capacity of inter-story slabs, the archival technical and operational documentation of buildings was firstly analysed. Their technical condition was also taken into account in the assessment process. In-situ inspections of both buildings had been carried out. This allowed the determination of the scope of necessary tests and the selection of test and check points for each structural element. Such actions allowed to identify cross-sections of the structural elements and the parameters of built-in materials. The performed diagnostics also allowed to properly determine the technical condition of each structural element, the degree of degradation of the structure and to correctly determine its current load-bearing capacity while simultaneously satisfying both limit states - the Ultimate Limit State (ULS) and the Serviceability Limit State (SLS).","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"119 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133314386","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}
The Rabotnov physically non-linear (quasi-linear) constitutive equation for non-aging elasto-viscoplastic materials with four material functions is studied analytically in order to outline the set of basic rheological phenomena which it can simulate, to clarify the material functions governing abilities, to indicate application field of the relation and to develop identification and verification techniques. General properties of the theoretic creep curves for volumetric, longitudinal and lateral strain generated by the model under uni-axial loading are investigated assuming material functions of the relation are arbitrary. Intervals of creep curves monotonicity and conditions for existence of extrema and sign changes are considered and the influence of minimal qualitative restrictions imposed on its material functions is analyzed. It is proved that the Rabotnov relation is able to simulate non-monotone behavior and sign changes of lateral strain and Poisson's ratio (lateral contraction ratio in creep). The expressions for Poisson's ratio via the strain state parameter (equal to volumetric strain divided by deviatoric strain) and via four material functions of the model are derived. The Poisso'n ratio dependence on time, stress level and material functions is examined. Assuming material functions are arbitrary, general two-sided bound for the Poisson's ratio range is obtained. Additional restrictions on material functions providing negative Poisson's ratio values are found and the criterion for its non-dependence on time is formulated. Taking into account volumetric creep (governed by two material functions of the model) is proved to affect strongly the qualitative behavior and characteristic features of longitudinal creep curves and the Poisso'n ratio evolution.
{"title":"GENERAL PROPERTIES OF THE CREEP CURVES FOR VOLUMETRIC, AXIAL AND LATERAL STRAIN GENERATED BY THE RABOTNOV NON-LINEAR VISCOELASTICITY RELATION UNDER UNI-AXIAL LOADINGS","authors":"Êðèâûõ Îáúåìíîé, Îñåâîé È ÏÎÏÅÐÅ×ÍÎÉ, ÏÎËÇÓ×ÅÑÒÈ Ïðè, Îäíîîñíîì ÐÀÑÒßÆÅÍÈÈ, ÂßÇÊÎÓÏÐÓÃÎÑÒÈ Ðàáîòíîâà","doi":"10.32326/1814-9146-2019-81-2-146-164","DOIUrl":"https://doi.org/10.32326/1814-9146-2019-81-2-146-164","url":null,"abstract":"The Rabotnov physically non-linear (quasi-linear) constitutive equation for non-aging elasto-viscoplastic materials with four material functions is studied analytically in order to outline the set of basic rheological phenomena which it can simulate, to clarify the material functions governing abilities, to indicate application field of the relation and to develop identification and verification techniques. General properties of the theoretic creep curves for volumetric, longitudinal and lateral strain generated by the model under uni-axial loading are investigated assuming material functions of the relation are arbitrary. Intervals of creep curves monotonicity and conditions for existence of extrema and sign changes are considered and the influence of minimal qualitative restrictions imposed on its material functions is analyzed. It is proved that the Rabotnov relation is able to simulate non-monotone behavior and sign changes of lateral strain and Poisson's ratio (lateral contraction ratio in creep). The expressions for Poisson's ratio via the strain state parameter (equal to volumetric strain divided by deviatoric strain) and via four material functions of the model are derived. The Poisso'n ratio dependence on time, stress level and material functions is examined. Assuming material functions are arbitrary, general two-sided bound for the Poisson's ratio range is obtained. Additional restrictions on material functions providing negative Poisson's ratio values are found and the criterion for its non-dependence on time is formulated. Taking into account volumetric creep (governed by two material functions of the model) is proved to affect strongly the qualitative behavior and characteristic features of longitudinal creep curves and the Poisso'n ratio evolution.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131640187","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}
Pub Date : 2019-06-16DOI: 10.32326/1814-9146-2019-81-2-249-259
V. Eremeev
The paper presents constitutive equations of deformed solids, the state parameters of which, apart from the displacement vector, include concentrations of photochromic compounds. Equilibrium equations are completed with chemical kinetic equations, which are a system of, in a general case, nonlinear ordinary differential equations or parabolic-type equations accounting for the diffusion of products of photochromic reactions. Coefficients of such equations (for example, quantum reaction yield, reaction rate) can be assumed to depend on the stressed state. Several versions of the dependence of coefficients of chemical kinetic equations on the stressed-strained state are introduced. Also, in the assumption of electrostatics, possible effects of electric fields are taken into account. In analogy with mechanics of semiconductors and conductors, related equations of state are proposed. The introduced model of a coupled photo-electro-mechanical effect is a strongly nonlinear boundary-value problem, the equations of which contain a large number of material constants that must be determined experimentally. For conducting potential mechanical experiments, a simplified one-dimensional model is proposed, which is analogous to problems of tension-compression and bending in mechanics of bars and beams. In the framework thereof, solutions of related one-dimensional problems are constructed, which make it principally possible to define dimensionless complexes containing unknown material constants.
{"title":"ON AN APPROACH TO THE DERIVATION OF CONSTITUTIVE EQUATIONS OF PHOTOCHROMIC MATERIALS","authors":"V. Eremeev","doi":"10.32326/1814-9146-2019-81-2-249-259","DOIUrl":"https://doi.org/10.32326/1814-9146-2019-81-2-249-259","url":null,"abstract":"The paper presents constitutive equations of deformed solids, the state parameters of which, apart from the displacement vector, include concentrations of photochromic compounds. Equilibrium equations are completed with chemical kinetic equations, which are a system of, in a general case, nonlinear ordinary differential equations or parabolic-type equations accounting for the diffusion of products of photochromic reactions. Coefficients of such equations (for example, quantum reaction yield, reaction rate) can be assumed to depend on the stressed state. Several versions of the dependence of coefficients of chemical kinetic equations on the stressed-strained state are introduced. Also, in the assumption of electrostatics, possible effects of electric fields are taken into account. In analogy with mechanics of semiconductors and conductors, related equations of state are proposed. \u0000The introduced model of a coupled photo-electro-mechanical effect is a strongly nonlinear boundary-value problem, the equations of which contain a large number of material constants that must be determined experimentally. For conducting potential mechanical experiments, a simplified one-dimensional model is proposed, which is analogous to problems of tension-compression and bending in mechanics of bars and beams. In the framework thereof, solutions of related one-dimensional problems are constructed, which make it principally possible to define dimensionless complexes containing unknown material constants.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"67 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127528266","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}
Pub Date : 2019-06-16DOI: 10.32326/1814-9146-2019-81-2-191-201
V. A. Ivanov, A. I. Kibets, Yu. I. Kibets
Nonstationary deformation of spatial structures made of piecewise-homogeneous isotropic materials (matrices), stiffened by a discrete system of curvilinear rods sustaining effects of tension-compression, is considered. It is assumed that the number of reinforcing rods is not large and their arrangement in the main material can be irregular. In analyzing such structures, the averaging methods used in mechanics of composite materials may become inapplicable. The defining equation set is formulated in Lagrange variables. Equations of motion are derived from the virtual work power balance. Kinematic relations are defined in the metrics of a current state. Relations of Beton's yield theory are used as equations of state for metals and alloys, and masonry is considered as a hetero-modular medium, the equations of state of which depend on the type of stressed-strained state and damage degree. The problem is analyzed using a momentary scheme of the finite element method and a cross-type explicit finite-difference time integration scheme. The analyzed region is discretized using 8-node finite elements with a poly-linear approximation of displacement velocities. The curvilinear, in a general case, reinforcing rods are discretized into straight sections, the spatial location of which is defined by the coordinates of the points of their intersection with the sides of the finite elements of the mesh of the main material. Slipping between the reinforcement and the binding material is not considered. Stresses in the rod are substituted for by statically equivalent forces of the nodes of the finite element of the matrix, which are projected onto a common coordinate system and summed with node forces from stresses in the main material and external loading. To verify the developed finite-element methodology, a number of benchmark problems have been analyzed.
{"title":"A FINITE-ELEMENT METHODOLOGY OF ANALYZING A 3D PROBLEM OF DYNAMICS OF STRUCTURES STIFFENED BY A SYSTEM OF REINFORCING RODS","authors":"V. A. Ivanov, A. I. Kibets, Yu. I. Kibets","doi":"10.32326/1814-9146-2019-81-2-191-201","DOIUrl":"https://doi.org/10.32326/1814-9146-2019-81-2-191-201","url":null,"abstract":"Nonstationary deformation of spatial structures made of piecewise-homogeneous isotropic materials (matrices), stiffened by a discrete system of curvilinear rods sustaining effects of tension-compression, is considered. It is assumed that the number of reinforcing rods is not large and their arrangement in the main material can be irregular.\u0000In analyzing such structures, the averaging methods used in mechanics of composite materials may become inapplicable. The defining equation set is formulated in Lagrange variables. Equations of motion are derived from the virtual work power balance. Kinematic relations are defined in the metrics of a current state. Relations of Beton's yield theory are used as equations of state for metals and alloys, and masonry is considered as a hetero-modular medium, the equations of state of which depend on the type of stressed-strained state and damage degree. The problem is analyzed using a momentary scheme of the finite element method and a cross-type explicit finite-difference time integration scheme. The analyzed region is discretized using 8-node finite elements with a poly-linear approximation of displacement velocities. The curvilinear, in a general case, reinforcing rods are discretized into straight sections, the spatial location of which is defined by the coordinates of the points of their intersection with the sides of the finite elements of the mesh of the main material. Slipping between the reinforcement and the binding material is not considered. Stresses in the rod are substituted for by statically equivalent forces of the nodes of the finite element of the matrix, which are projected onto a common coordinate system and summed with node forces from stresses in the main material and external loading. To verify the developed finite-element methodology, a number of benchmark problems have been analyzed.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122390071","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}
Pub Date : 2019-06-16DOI: 10.32326/1814-9146-2019-81-2-233-239
A. Dubinsky
Calculations related to pile driving play an important role in construction. Therefore, corresponding processes are controlled by regulatory documents, including the necessary formulas, which are accompanied by numerous tables and graphs, allowing the use of techniques in specific conditions of construction. The basis of such applied methods are the results of research in mechanics; the results of such studies are widely presented in the literature. This article is made within the framework of such studies. The article presents an approximate approach based on the evaluation of the real values of the parameters that determine the process of driving the pile. The proposed approach allowed to obtain an approximate formula to calculate the motion of the pile in soil by successive blows of the hammer falling freely. The following ways to analyze and improve models within this approach are outlined: (1) analysis of the accuracy of the proposed model by its presentation with the results of experiments and calculations using other models as well as with recommendations of normative instruments; (2) generalization of the model for the case when the mechanical properties of the soil vary depending on the depth of immersion into the soil.
{"title":"A MODEL OF PILE DRIVING BY MULTIPLE IMPACTS OF FALLING HAMMER","authors":"A. Dubinsky","doi":"10.32326/1814-9146-2019-81-2-233-239","DOIUrl":"https://doi.org/10.32326/1814-9146-2019-81-2-233-239","url":null,"abstract":"Calculations related to pile driving play an important role in construction. Therefore, corresponding processes are controlled by regulatory documents, including the necessary formulas, which are accompanied by numerous tables and graphs, allowing the use of techniques in specific conditions of construction. The basis of such applied methods are the results of research in mechanics; the results of such studies are widely presented in the literature. This article is made within the framework of such studies.\u0000The article presents an approximate approach based on the evaluation of the real values of the parameters that determine the process of driving the pile. The proposed approach allowed to obtain an approximate formula to calculate the motion of the pile in soil by successive blows of the hammer falling freely. The following ways to analyze and improve models within this approach are outlined: (1) analysis of the accuracy of the proposed model by its presentation with the results of experiments and calculations using other models as well as with recommendations of normative instruments; (2) generalization of the model for the case when the mechanical properties of the soil vary depending on the depth of immersion into the soil.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129817630","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}
Pub Date : 2019-03-15DOI: 10.32326/1814-9146-2019-81-1-118-128
V. Balandin, V. Parkhachev
Investigating impact interaction of solid and deformed bodies with obstacles of various physical natures requires developing experimental methodologies of registering the parameters of the interaction process. In experimental investigations of impact interaction of solids, it is common practice to measure displacement of strikers as a function of time, as well as their velocity and deceleration. To determine the displacement and velocity of a striker, a radio-interferometric methodology of registering the displacement of its rear end is proposed. In contrast with the registration methods based on high-speed filming and pulsed X-ray photography, the method using a millimeter-range radio-interferometer provides continuous high-accuracy registering of the displacement of the rear end of a striker in a wide range of displacement values. To test the effectiveness of the methodology, a series of experiments have been conducted on registering the motion of a cylindrical striker of an aluminum alloy, fired from a 20mm-dia gas gun. The displacement of the striker was also monitored using high-speed filming. The results of measuring using the two methodologies differ within the limits of the error of measurement. Based on the results of the above experiments, it has been concluded that the methodology of determining the displacement and velocity of strikers in a ballistic experiment using a mm-range radio-interferometer makes it possible to measure practically continuously large displacements (100 mm and larger) to a safe accuracy. The present methodology can be used for measuring the displacement and velocity of the rear end of a striker interacting with obstacles of various physical natures (metals, ceramics, soils, concretes, etc.).
{"title":"MEASURING DISPLACEMENT AND VELOCITY OF A STRIKER USING A RADIO-INTERFEROMETER","authors":"V. Balandin, V. Parkhachev","doi":"10.32326/1814-9146-2019-81-1-118-128","DOIUrl":"https://doi.org/10.32326/1814-9146-2019-81-1-118-128","url":null,"abstract":"Investigating impact interaction of solid and deformed bodies with obstacles of various physical natures requires developing experimental methodologies of registering the parameters of the interaction process. In experimental investigations of impact interaction of solids, it is common practice to measure displacement of strikers as a function of time, as well as their velocity and deceleration. To determine the displacement and velocity of a striker, a radio-interferometric methodology of registering the displacement of its rear end is proposed. In contrast with the registration methods based on high-speed filming and pulsed X-ray photography, the method using a millimeter-range radio-interferometer provides continuous high-accuracy registering of the displacement of the rear end of a striker in a wide range of displacement values. To test the effectiveness of the methodology, a series of experiments have been conducted on registering the motion of a cylindrical striker of an aluminum alloy, fired from a 20mm-dia gas gun. The displacement of the striker was also monitored using high-speed filming. The results of measuring using the two methodologies differ within the limits of the error of measurement. Based on the results of the above experiments, it has been concluded that the methodology of determining the displacement and velocity of strikers in a ballistic experiment using a mm-range radio-interferometer makes it possible to measure practically continuously large displacements (100 mm and larger) to a safe accuracy. The present methodology can be used for measuring the displacement and velocity of the rear end of a striker interacting with obstacles of various physical natures (metals, ceramics, soils, concretes, etc.).","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129064239","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}
Pub Date : 1900-01-01DOI: 10.32326/1814-9146-2020-82-4-399-412
Yuriy N Radayev, E. Murashkin
The possibility of applications of relative tensors concepts to the mechanics of micropolar continuum and, in particular, for the hemitropic micropolar continua is considered. The fundamental tensors and orienting relative scalars in three-dimensional space are introduced. Permutation symbols and absolute Levi-Civita tensors are investigated in further details. Algebraic and differential properties of the relative tensors are discussed. The weights of the fundamental kinematic tensors are determined. The wryness tensor and the asymmetric strain tensor are constructed in terms of the vectors of micro-rotation and displacements. Notions of force and couple traction vectors, associated force and associated couple stress vector, force and couple stresses tensors are discussed in the frameworks of relative tensors algebra. The weights of the basic micropolar elasticity tensors are determined and discussed. The constitutive form of the micropolar elastic potential is introduced as an absolute scalar in order to obtain micropolar constitutive equations. In the linear case, the elastic potential is a quadratic form whose coefficients are pseudoscalars. The weights of the constitutive pseudoscalars are calculated. The dimensionless constitutive micropolar constants and constitutive constants with physical dimensions are discriminated. Statics and dynamics of micropolar elastic continua are developed in terms of relative tensors. Dynamic equations involving displacements and microrotations in the case of semi-isotropic (hemitropic) symmetry are derived and represented by the pseudotensor technique. The paper can be considered as a script of fundamental formulas and concepts related to the algebra and differentiation of relative tensors of arbitrary rank.
{"title":"PSEUDOTENSOR FORMULATION OF THE MECHANICS OF HEMITROPIC MICROPOLAR MEDIA","authors":"Yuriy N Radayev, E. Murashkin","doi":"10.32326/1814-9146-2020-82-4-399-412","DOIUrl":"https://doi.org/10.32326/1814-9146-2020-82-4-399-412","url":null,"abstract":"The possibility of applications of relative tensors concepts to the mechanics of micropolar continuum and, in particular, for the hemitropic micropolar continua is considered. The fundamental tensors and orienting relative scalars in three-dimensional space are introduced. Permutation symbols and absolute Levi-Civita tensors are investigated in further details. Algebraic and differential properties of the relative tensors are discussed. The weights of the fundamental kinematic tensors are determined. The wryness tensor and the asymmetric strain tensor are constructed in terms of the vectors of micro-rotation and displacements. Notions of force and couple traction vectors, associated force and associated couple stress vector, force and couple stresses tensors are discussed in the frameworks of relative tensors algebra. The weights of the basic micropolar elasticity tensors are determined and discussed. The constitutive form of the micropolar elastic potential is introduced as an absolute scalar in order to obtain micropolar constitutive equations. In the linear case, the elastic potential is a quadratic form whose coefficients are pseudoscalars. The weights of the constitutive pseudoscalars are calculated. The dimensionless constitutive micropolar constants and constitutive constants with physical dimensions are discriminated. Statics and dynamics of micropolar elastic continua are developed in terms of relative tensors. Dynamic equations involving displacements and microrotations in the case of semi-isotropic (hemitropic) symmetry are derived and represented by the pseudotensor technique. The paper can be considered as a script of fundamental formulas and concepts related to the algebra and differentiation of relative tensors of arbitrary rank.","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"18 2 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":"125016446","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}
Pub Date : 1900-01-01DOI: 10.32326/1814-9146-2021-83-2-207-219
O. Berdnik, I. Tsareva, L. Krivina, S. Kirikov, Y. Tarasenko, M. Chegurov
Intensively operated modern technology requires the use of high-strength fasteners. The article presents the results of studies of the structure and physical and mechanical properties of the material of fastening elements (threaded hardware) in order to determine the causes of their destruction during operation. The fractographic analysis of fractures of fractured bolts revealed pronounced centers of crack initiation with traces of delayed brittle fracture, which is typical for high-strength hardware that are under high load for a long time, close to the yield point. Mechanical tests of the studied fastening elements showed increased values of ultimate strength. The performed relaxation tests of the material of broken bolts also revealed an increased value of the microplasticity limit, which is responsible for the onset of plastic deformation processes in microvolumes of the material, and for the material of whole hardware, the value of the limit is included in the permissible interval. At the same time, the average hardness of the material of all products meets the regulatory requirements. The maximum spread of hardness 70 HB is fixed on the destroyed bolt. Using the experimental values of microhardness, theoretical estimates of the coefficient of plasticity, which characterize the ability of a material to perceive elastic and plastic deformations, were carried out. To ensure a sufficient level of ductility of a long-term working metal material, the ductility coefficient must be at least 0.8. The average value of the hardness of the material of the fastening elements satisfies this criterion for assessing ductility. According to the results of a step-by-step analysis of the microstructure of the samples, the inhomogeneity of the distribution of the carbide phase over the cross-section of the bolts was established. The two-phase composition (a-Fe + Fe3C) of steel was established by X-ray structural analysis, which confirms the results of microstructural studies. It should be noted that the phase composition of all studied samples is identical. Based on the results of the studies carried out, it was found that the destruction occurred due to the reduced strength and increased fragility of the material due to the presence of microdefects. The material of the whole bolts in terms of structure and mechanical properties comply with regulatory requirements.
{"title":"DETERMINATION OF THE CAUSES OF DESTRUCTION OF HIGH-STRENGTH FASTENING ELEMENTS","authors":"O. Berdnik, I. Tsareva, L. Krivina, S. Kirikov, Y. Tarasenko, M. Chegurov","doi":"10.32326/1814-9146-2021-83-2-207-219","DOIUrl":"https://doi.org/10.32326/1814-9146-2021-83-2-207-219","url":null,"abstract":"Intensively operated modern technology requires the use of high-strength fasteners. The article presents the results of studies of the structure and physical and mechanical properties of the material of fastening elements (threaded hardware) in order to determine the causes of their destruction during operation. The fractographic analysis of fractures of fractured bolts revealed pronounced centers of crack initiation with traces of delayed brittle fracture, which is typical for high-strength hardware that are under high load for a long time, close to the yield point. Mechanical tests of the studied fastening elements showed increased values of ultimate strength. The performed relaxation tests of the material of broken bolts also revealed an increased value of the microplasticity limit, which is responsible for the onset of plastic deformation processes in microvolumes of the material, and for the material of whole hardware, the value of the limit is included in the permissible interval. At the same time, the average hardness of the material of all products meets the regulatory requirements. The maximum spread of hardness 70 HB is fixed on the destroyed bolt. Using the experimental values of microhardness, theoretical estimates of the coefficient of plasticity, which characterize the ability of a material to perceive elastic and plastic deformations, were carried out. To ensure a sufficient level of ductility of a long-term working metal material, the ductility coefficient must be at least 0.8. The average value of the hardness of the material of the fastening elements satisfies this criterion for assessing ductility. According to the results of a step-by-step analysis of the microstructure of the samples, the inhomogeneity of the distribution of the carbide phase over the cross-section of the bolts was established. The two-phase composition (a-Fe + Fe3C) of steel was established by X-ray structural analysis, which confirms the results of microstructural studies. It should be noted that the phase composition of all studied samples is identical. Based on the results of the studies carried out, it was found that the destruction occurred due to the reduced strength and increased fragility of the material due to the presence of microdefects. The material of the whole bolts in terms of structure and mechanical properties comply with regulatory requirements.","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":"128250851","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}
Pub Date : 1900-01-01DOI: 10.32326/1814-9146-2021-83-3-294-310
I. V. Smetanin
The main regularities of deformation processes are consideredand degradation of the initial strength properties of structural materials (metals and their alloys) by the mechanism of long-term strength. To describe the processes of high-temperature creep and long-term strength of polycrystalline structural alloys, an approach based on the concept of “hidden” or “internal” parameters is used, which can give a qualitative and quantitative description of experimental data. This approach has two important advantages: it allows you to cover a wide range of behavior of structural materials and at the same time it is very convenient for analyzing the stress-strain state. The mathematical model of the mechanics of a damaged medium used in this work, describing the processes of inelastic deformation and damage accumulation during creep, consists of three interrelated components: evolutionary relations that determine the inelastic behavior of the material, considering the dependence on the destruction process; kinetic equations describing the process of damage accumulation; criteria for the strength of the damaged material. The variant of the determining relations of viscoplastic deformationof polycrystalline structural alloys is based on the idea of the existence of a family of equipotential creep surfaces in the stress space and the principle of gradiency of the creep strain rate vector to the corresponding surface at the loading point.This version of the equations of state reflects the main regularitiesthe process of viscoplastic deformation of the material under proportional and disproportionate modes of combined thermomechanical loading. The variant of the kinetic equations of damage accumulation is based on theintroduction of a scalar damage parameter, is based on energy principles, and considers the main effects of the formation, growth and fusion of microdefects for arbitrary complex modes of thermomechanical loading. As a criterion of the strength of the damaged material, the condition for reaching the critical value of the damage value is used. The results of experimental studies of short-term high-temperature creep of several structural alloys (copper, stainless steel X18H10T) at constant temperature values and various levels of forces set in the samples are presented. To assess the degree of reliability and determine the limits of applicabilitymodels of the mechanics of the damaged medium numerical studies of the process of high-temperature creep and long-term strength of these structural alloys are carried out and the numerical results obtained are compared with the data of field experiments. The results of comparing the calculated and experimental data allow us to conclude that the proposed determining relationships are reliable when the initial strength properties of structural materials are degraded by the mechanism of long-termstrength. It is shown that the model used qualitatively and with the accuracy necessary for practical calculati
{"title":"NUMERICAL STUDY OF THE PROCESS OF HIGH-TEMPERATURE CREEP AND LONG-TERM STRENGTH OF STRUCTURAL ALLOYS UNDER UNIAXIAL TENSION","authors":"I. V. Smetanin","doi":"10.32326/1814-9146-2021-83-3-294-310","DOIUrl":"https://doi.org/10.32326/1814-9146-2021-83-3-294-310","url":null,"abstract":"The main regularities of deformation processes are consideredand degradation of the initial strength properties of structural materials (metals and their alloys) by the mechanism of long-term strength. To describe the processes of high-temperature creep and long-term strength of polycrystalline structural alloys, an approach based on the concept of “hidden” or “internal” parameters is used, which can give a qualitative and quantitative description of experimental data. This approach has two important advantages: it allows you to cover a wide range of behavior of structural materials and at the same time it is very convenient for analyzing the stress-strain state. The mathematical model of the mechanics of a damaged medium used in this work, describing the processes of inelastic deformation and damage accumulation during creep, consists of three interrelated components: evolutionary relations that determine the inelastic behavior of the material, considering the dependence on the destruction process; kinetic equations describing the process of damage accumulation; criteria for the strength of the damaged material.\u0000\u0000The variant of the determining relations of viscoplastic deformationof polycrystalline structural alloys is based on the idea of the existence of a family of equipotential creep surfaces in the stress space and the principle of gradiency of the creep strain rate vector to the corresponding surface at the loading point.This version of the equations of state reflects the main regularitiesthe process of viscoplastic deformation of the material under proportional and disproportionate modes of combined thermomechanical loading.\u0000\u0000The variant of the kinetic equations of damage accumulation is based on theintroduction of a scalar damage parameter, is based on energy principles, and considers the main effects of the formation, growth and fusion of microdefects for arbitrary complex modes of thermomechanical loading. As a criterion of the strength of the damaged material, the condition for reaching the critical value of the damage value is used.\u0000\u0000The results of experimental studies of short-term high-temperature creep of several structural alloys (copper, stainless steel X18H10T) at constant temperature values and various levels of forces set in the samples are presented.\u0000\u0000To assess the degree of reliability and determine the limits of applicabilitymodels of the mechanics of the damaged medium numerical studies of the process of high-temperature creep and long-term strength of these structural alloys are carried out and the numerical results obtained are compared with the data of field experiments. The results of comparing the calculated and experimental data allow us to conclude that the proposed determining relationships are reliable when the initial strength properties of structural materials are degraded by the mechanism of long-termstrength. It is shown that the model used qualitatively and with the accuracy necessary for practical calculati","PeriodicalId":340995,"journal":{"name":"Problems of strenght and plasticity","volume":"123 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":"133902217","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}
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