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Papers by Олексій Куценко
22nd International Scientific Conference Engineering for Rural Development Proceedings
In the present work the stress-strain state of a reinforced concrete slab with a transverse edge ... more In the present work the stress-strain state of a reinforced concrete slab with a transverse edge crack of constant depth is considered. There is investigated the effect of reinforcement upon the distribution of the fracture mechanics along the crack front. The uniformly or linearly distributed stresses at the slab ends are described as an external load. These loads correspond to pure tension and pure bending of the slab, respectively. For a case when the depth of the crack is less than the depth of the reinforcement rod, an analytical approach for an assessment of the crack state is proposed. As a characteristic of the crack state, the stress intensity factor (SIF) is used. Using the finite-element CalculiX package, the numerical results have been obtained, and adequacy of the analytical solution justified. The calculations have been performed for a wide range of variations in the geometrical parameters of the slab and the crack. For this purpose, a principle of replacing the extern...
Naukovij žurnal «Tehnìka ta energetika»
A preliminary analysis of the available publications devoted to the study of crack resistance of ... more A preliminary analysis of the available publications devoted to the study of crack resistance of reinforced concrete structures showed the absence of established general patterns of influence of important geometric parameters inherent in reinforced concrete elements on the distribution of the characteristics of fracture mechanics along the crack front. Based on the analysis, the purpose of the study was formulated: to establish these regularities for a concrete slab reinforced with a system of longitudinal steel rods. When conducting the research, a linear and elastic model of concrete was used, and the stress intensity factor was considered as a characteristic of the fracture mechanics. A surface crack of constant depth located in the cross-section of the slab was postulated. It was assumed that its faces completely cover the cross-section of reinforcing rods. The crack depth, the depth of reinforcing rods, their diameter, and the distance between adjacent rods were chosen as dimen...
Bulletin of Taras Shevchenko National University of Kyiv. Series: Physics and Mathematics, 2021
The problem of axial stretching of a plate with a double-periodic system of round holes arranged ... more The problem of axial stretching of a plate with a double-periodic system of round holes arranged in a checkerboard pattern is considered. The specified problem is reduced to elasticity second problem for one period of plate, which was solved by the finite element method. As a result, the reduced elastic characteristics of the equivalent homogeneous orthotropic plate are found. The analysis of their behavior depending on dimensionless geometrical parameters is carried out. The area of variation of the geometric parameters was divided into two subareas. The behavior of the equivalent elastic characteristics in these areas is significantly different. It turned out that the double-periodic perforated plate shows significantly anisotropic behavior. The limit values of the Poisson's ratios can reach unity and, on the other hand, may be less than the original value. Dependences of the stress concentration coefficient on dimensionless geometrical parameters are obtained too. Performed c...
Bulletin of Taras Shevchenko National University of Kyiv. Series: Physics and Mathematics, 2019
The rings torsion theory that is based on the assumption about flat rigid cross-section was sugge... more The rings torsion theory that is based on the assumption about flat rigid cross-section was suggested by the authors in the previous papers. The analytical expressions of torsional stiffness have been derived for different kind of loads: pure moment, shear force and surface pressure. In the present paper the analytical model of flange with attached cylindrical shell deforming under internal pressure is suggested. The mechanical system is split into two parts (flange and shell) with the help of imaginary section method. An unknown shear force and bending moments are applied to both parts according to this method. Therefore flange is loaded under internal pressure, shear force and bending moments. As mentioned above, for all these loads the angle of flange cross-section rotation can be presented in analytical form based on the rings torsion theory. Full rotation angle is presented as a sum of these angles. The radial displacement of imaginary section was determined on the basis of the...
Bulletin of Taras Shevchenko National University of Kyiv. Series: Physics and Mathematics, 2021
The nonstationary axisymmetric thermoelasticity problem for a two-layer cylinder at the inner sur... more The nonstationary axisymmetric thermoelasticity problem for a two-layer cylinder at the inner surface of which convective heat transfer with an environment takes place is considered. The solution of this problem is derived for the case of inhomogeneous initial temperature field. The solution is presented in the form of development by the system of eigenfunctions of the boundary value problem for a two-component beam and expressed in terms of the elementary functions. Based on this solution, an incremental algorithm of solving thermoelasticity problems for a two-layer cylinder is proposed for the case that the heat transfer coefficient between the inner surface of the cylinder and environment is time-varied. The idea of the algorithm is to divide the entire transient time interval into a sequence of subintervals, the heat transfer coefficient is considered constant on each. Once the temperature field is determined, the axisymmetric stress field can be founded on the basis of analytic...
In this work, we propose a procedure that allows us to quickly, without involving finite-element ... more In this work, we propose a procedure that allows us to quickly, without involving finite-element packages at the execution stage, evaluate the state of postulated cracks in cylindrical structural elements with internal anticorrosion cladding under pressure and unsteady temperature loading. The procedure contains three components. The first component of the procedure is based on the analytical solution of the unsteady thermal conductivity problem. The second component of the procedure is also analytical relations specifying circumferential and longitudinal stresses in a two-layer cylinder as a function of internal pressure and temperature distribution along the depth of the wall. In the third stage of the procedure, the coefficients of stress intensity along the crack front are determined by the method of influence functions using the known distribution of stresses. To implement this part of the procedure, the influence functions must first be calculated by the finite element method....
International Journal of Pressure Vessels and Piping, 2019
This paper discusses the assessment of the WWER-1000 reactor pressure vessel integrity and the an... more This paper discusses the assessment of the WWER-1000 reactor pressure vessel integrity and the analyses performed to protect the irradiated vessel against brittle failure. The paper focuses on studies assessing the effects of base metal hardening on fast fracture evaluation results. It is shown that the results depend significantly on the material model used (elastic or elastic-plastic) as well as on the base metal mechanical properties (including or not the hardening produced by irradiation). Considering the change in tensile properties of the base material under irradiation may change the identification of the limiting combination of the pressurised thermal shock scenario, the limiting crack front point, and the crack aspect ratio. To demonstrate these effects, the results of the calculations performed for the South Ukrainian Nuclear Power Plant Unit 2 reactor pressure vessel residual lifetime are presented.
20th International Scientific Conference Engineering for Rural Development Proceedings, 2021
The previously obtained solution of a nonstationary heat conduction problem for a two-piece rod, ... more The previously obtained solution of a nonstationary heat conduction problem for a two-piece rod, one end of which is in convective heat exchange with the environment, is generalized to the case of an inhomogeneous initial temperature field. The solution is presented as an eigenform expansion of the corresponding boundary problem and is expressed in terms of elementary functions. The obtained generalization makes it possible to propose an algorithm for solving a general problem with arbitrarily varying ambient temperature and heat exchange coefficient. The relations are presented, which allow to find axisymmetric stress fields in a two-layer cylinder by the calculated temperature field in a two-layer rod also in an analytical form. A comparative analysis has been made of the results obtained on the basis of the proposed analytical algorithm and the results of numerical calculations by the finite-element method. The aim of this comparison was to determine the influence of different simplifying assumptions used in constructing the algorithm on the accuracy of the results. These assumptions include: disregard of the cylinder curvature in the heat conductivity problem, disregard of the temperature dependence of material properties, change in the heat transfer coefficient. The comparison was performed using the example of a cylindrical body part under the thermal shock scenario. For these conditions, in general, the deviation of temperature and stresses calculated from the proposed approach from numerical results did not exceed 3%. In this case, the main part of the error-1.7% was introduced by a change in the dependence of physical properties on temperature. The second largest factor introduced into the calculation of the error was the failure to take into account the curvature of the cylinder when solving the problem of heat conduction. It corresponds to an error of about 1.1%. Considering that the thermoshock scenario is boundary in terms of temperature change rate, it can be stated that the obtained analytical solution is sufficient for practical assessment of the axisymmetric stressstrain state of the corresponding equipment and pipelines.
22nd International Scientific Conference Engineering for Rural Development Proceedings
In the present work the stress-strain state of a reinforced concrete slab with a transverse edge ... more In the present work the stress-strain state of a reinforced concrete slab with a transverse edge crack of constant depth is considered. There is investigated the effect of reinforcement upon the distribution of the fracture mechanics along the crack front. The uniformly or linearly distributed stresses at the slab ends are described as an external load. These loads correspond to pure tension and pure bending of the slab, respectively. For a case when the depth of the crack is less than the depth of the reinforcement rod, an analytical approach for an assessment of the crack state is proposed. As a characteristic of the crack state, the stress intensity factor (SIF) is used. Using the finite-element CalculiX package, the numerical results have been obtained, and adequacy of the analytical solution justified. The calculations have been performed for a wide range of variations in the geometrical parameters of the slab and the crack. For this purpose, a principle of replacing the extern...
Naukovij žurnal «Tehnìka ta energetika»
A preliminary analysis of the available publications devoted to the study of crack resistance of ... more A preliminary analysis of the available publications devoted to the study of crack resistance of reinforced concrete structures showed the absence of established general patterns of influence of important geometric parameters inherent in reinforced concrete elements on the distribution of the characteristics of fracture mechanics along the crack front. Based on the analysis, the purpose of the study was formulated: to establish these regularities for a concrete slab reinforced with a system of longitudinal steel rods. When conducting the research, a linear and elastic model of concrete was used, and the stress intensity factor was considered as a characteristic of the fracture mechanics. A surface crack of constant depth located in the cross-section of the slab was postulated. It was assumed that its faces completely cover the cross-section of reinforcing rods. The crack depth, the depth of reinforcing rods, their diameter, and the distance between adjacent rods were chosen as dimen...
Bulletin of Taras Shevchenko National University of Kyiv. Series: Physics and Mathematics, 2021
The problem of axial stretching of a plate with a double-periodic system of round holes arranged ... more The problem of axial stretching of a plate with a double-periodic system of round holes arranged in a checkerboard pattern is considered. The specified problem is reduced to elasticity second problem for one period of plate, which was solved by the finite element method. As a result, the reduced elastic characteristics of the equivalent homogeneous orthotropic plate are found. The analysis of their behavior depending on dimensionless geometrical parameters is carried out. The area of variation of the geometric parameters was divided into two subareas. The behavior of the equivalent elastic characteristics in these areas is significantly different. It turned out that the double-periodic perforated plate shows significantly anisotropic behavior. The limit values of the Poisson's ratios can reach unity and, on the other hand, may be less than the original value. Dependences of the stress concentration coefficient on dimensionless geometrical parameters are obtained too. Performed c...
Bulletin of Taras Shevchenko National University of Kyiv. Series: Physics and Mathematics, 2019
The rings torsion theory that is based on the assumption about flat rigid cross-section was sugge... more The rings torsion theory that is based on the assumption about flat rigid cross-section was suggested by the authors in the previous papers. The analytical expressions of torsional stiffness have been derived for different kind of loads: pure moment, shear force and surface pressure. In the present paper the analytical model of flange with attached cylindrical shell deforming under internal pressure is suggested. The mechanical system is split into two parts (flange and shell) with the help of imaginary section method. An unknown shear force and bending moments are applied to both parts according to this method. Therefore flange is loaded under internal pressure, shear force and bending moments. As mentioned above, for all these loads the angle of flange cross-section rotation can be presented in analytical form based on the rings torsion theory. Full rotation angle is presented as a sum of these angles. The radial displacement of imaginary section was determined on the basis of the...
Bulletin of Taras Shevchenko National University of Kyiv. Series: Physics and Mathematics, 2021
The nonstationary axisymmetric thermoelasticity problem for a two-layer cylinder at the inner sur... more The nonstationary axisymmetric thermoelasticity problem for a two-layer cylinder at the inner surface of which convective heat transfer with an environment takes place is considered. The solution of this problem is derived for the case of inhomogeneous initial temperature field. The solution is presented in the form of development by the system of eigenfunctions of the boundary value problem for a two-component beam and expressed in terms of the elementary functions. Based on this solution, an incremental algorithm of solving thermoelasticity problems for a two-layer cylinder is proposed for the case that the heat transfer coefficient between the inner surface of the cylinder and environment is time-varied. The idea of the algorithm is to divide the entire transient time interval into a sequence of subintervals, the heat transfer coefficient is considered constant on each. Once the temperature field is determined, the axisymmetric stress field can be founded on the basis of analytic...
In this work, we propose a procedure that allows us to quickly, without involving finite-element ... more In this work, we propose a procedure that allows us to quickly, without involving finite-element packages at the execution stage, evaluate the state of postulated cracks in cylindrical structural elements with internal anticorrosion cladding under pressure and unsteady temperature loading. The procedure contains three components. The first component of the procedure is based on the analytical solution of the unsteady thermal conductivity problem. The second component of the procedure is also analytical relations specifying circumferential and longitudinal stresses in a two-layer cylinder as a function of internal pressure and temperature distribution along the depth of the wall. In the third stage of the procedure, the coefficients of stress intensity along the crack front are determined by the method of influence functions using the known distribution of stresses. To implement this part of the procedure, the influence functions must first be calculated by the finite element method....
International Journal of Pressure Vessels and Piping, 2019
This paper discusses the assessment of the WWER-1000 reactor pressure vessel integrity and the an... more This paper discusses the assessment of the WWER-1000 reactor pressure vessel integrity and the analyses performed to protect the irradiated vessel against brittle failure. The paper focuses on studies assessing the effects of base metal hardening on fast fracture evaluation results. It is shown that the results depend significantly on the material model used (elastic or elastic-plastic) as well as on the base metal mechanical properties (including or not the hardening produced by irradiation). Considering the change in tensile properties of the base material under irradiation may change the identification of the limiting combination of the pressurised thermal shock scenario, the limiting crack front point, and the crack aspect ratio. To demonstrate these effects, the results of the calculations performed for the South Ukrainian Nuclear Power Plant Unit 2 reactor pressure vessel residual lifetime are presented.
20th International Scientific Conference Engineering for Rural Development Proceedings, 2021
The previously obtained solution of a nonstationary heat conduction problem for a two-piece rod, ... more The previously obtained solution of a nonstationary heat conduction problem for a two-piece rod, one end of which is in convective heat exchange with the environment, is generalized to the case of an inhomogeneous initial temperature field. The solution is presented as an eigenform expansion of the corresponding boundary problem and is expressed in terms of elementary functions. The obtained generalization makes it possible to propose an algorithm for solving a general problem with arbitrarily varying ambient temperature and heat exchange coefficient. The relations are presented, which allow to find axisymmetric stress fields in a two-layer cylinder by the calculated temperature field in a two-layer rod also in an analytical form. A comparative analysis has been made of the results obtained on the basis of the proposed analytical algorithm and the results of numerical calculations by the finite-element method. The aim of this comparison was to determine the influence of different simplifying assumptions used in constructing the algorithm on the accuracy of the results. These assumptions include: disregard of the cylinder curvature in the heat conductivity problem, disregard of the temperature dependence of material properties, change in the heat transfer coefficient. The comparison was performed using the example of a cylindrical body part under the thermal shock scenario. For these conditions, in general, the deviation of temperature and stresses calculated from the proposed approach from numerical results did not exceed 3%. In this case, the main part of the error-1.7% was introduced by a change in the dependence of physical properties on temperature. The second largest factor introduced into the calculation of the error was the failure to take into account the curvature of the cylinder when solving the problem of heat conduction. It corresponds to an error of about 1.1%. Considering that the thermoshock scenario is boundary in terms of temperature change rate, it can be stated that the obtained analytical solution is sufficient for practical assessment of the axisymmetric stressstrain state of the corresponding equipment and pipelines.