scholarly journals On extending the life of nuclear reactors

2021 ◽  
Vol 2131 (2) ◽  
pp. 022030
Author(s):  
A V Kramskoi ◽  
Y G Lyudmirsky ◽  
M E Zhidkov ◽  
M I Kramskaia
Keyword(s):  
Service Life ◽  
Base Metal ◽  
Strain State ◽  
Mutual Influence ◽  
Nuclear Reactors ◽  
Test Procedure ◽  
Reactor Vessel ◽  
Stress Strain ◽  
Stress Strain State ◽  
Additional Service

Abstract To extend the service life of nuclear reactors, witness samples from the shells of the core of the reactor vessel are placed in their core. According to the requirements in force in the industry, the reference samples are loaded into the reactor plant unloaded up to the design stresses. This can lead to a biased assessment of the possible extension of the reactor’s life. In connection with the above, in order to assess the mutual influence of operating factors and the stress-strain state of the base metal and welded joints on embrittlement, the reference specimens must be loaded with a force that causes the maximum possible stresses in the specimens during the operation of the reactor. On the basis of domestic and international experience, a test procedure, design and loading scheme for compact witness samples are proposed for modeling and assessing the mutual influence of operating factors and stress-strain state on the object under study (VVER power reactor vessel). For VVER RPVs, the duration of the additional service life should be confirmed by the justification that by the end of the additional service life, the fracture toughness values of the base metal and metal of the welded seams located in the irradiation zone will allow without destruction to withstand all operational and emergency loads, as well as loads at hydraulic tests.

scholarly journals Assessment of the mutual influence of deformation-strength characteristics of the fastening system elements

2019 ◽  
Vol 123 ◽  
pp. 01006 ◽  
Author(s):  
Iryna Kovalevska ◽  
Zenon Pilecki ◽  
Oleksandr Husiev ◽  
Vasyl Snihur
Keyword(s):  
Mine Working ◽  
Strain State ◽  
Mutual Influence ◽  
Strength Characteristics ◽  
Stress Strain ◽  
Load Bearing ◽  
Stress Strain State ◽  
Operation Modes ◽  
Mine Workings ◽  
Rigid Element

The degree of influence has been determined of diversified deformation-strength characteristics of load-bearing elements in the fastening system of the preparatory mine workings, while maintaining them in a laminal massif of soft rocks. The analysis has been performed of multivariate computational experiments of the stress-strain state of the load-bearing elements of the fastening system in the preparatory mine workings from the position of the mutual influence of their deformation-strength characteristics and the support loading as a whole. An analysis is represented of the mutual influence of the operation modes of the mine working support elements between themselves and the fastening system as a whole; it has been studied the stress-strain state of the mine working fastening system with a central hydraulic prop stay, as well as a significant increase in reliability of the support performance has been analysed and determined. The tendency has been substantiated of minimizing the load on the mine working fastening system – increasing the coherence of the diversified operation modes of fastening elements by enhancing preferentially the yielding property of the rigid element. The application has been substantiated of the central yielding prop stays of the strengthening support of a frame in case of intensive rock pressure manifestation in the zone of the stope works active influence.

Ensuring the strength and stability of the tank wall during repairs by installing rigid frames

2021 ◽  
pp. 152-165
Author(s):  
Артем Николаевич Задумин ◽  
Евгений Григорьевич Ильин ◽  
Михаил Владимирович Лиховцев ◽  
Алексей Александрович Катанов
Keyword(s):  
Computer Modeling ◽  
Strain State ◽  
Mutual Influence ◽  
Tank Wall ◽  
Stress Strain ◽  
Stability Calculation ◽  
Actual Structure ◽  
Repair Work ◽  
Stress Strain State ◽  
Cutting Out

Устранение дефектов металла и сварных швов стенок вертикальных цилиндрических резервуаров возможно методом вырезки и замены удаленных фрагментов ремонтными вставками с использованием рам жесткости. При этом в нормативных документах отсутствуют методики расчета таких усиливающих элементов и собственно конструкции стенки резервуара с данными элементами. С целью оценки прочности и устойчивости стенки резервуара и рамы жесткости во время проведения ремонтных работ выполнено компьютерное моделирование и проведены расчеты напряженно-деформированного состояния указанных металлоконструкций. В рамках исследования рассмотрены основные российские и зарубежные нормативные документы, регламентирующие нагрузки и методики расчета устойчивости стенки резервуара, проанализированы публикации, посвященные расчету устойчивости стенки резервуара с применением компьютерного моделирования. Приведены результаты компьютерного моделирования и расчетов на прочность и устойчивость в зависимости от снеговой и ветровой нагрузок. По итогам выполненных работ сделаны следующие выводы: 1) расчеты должны учитывать ветровую нагрузку, действующую под углом 40° к вырезаемому фрагменту; 2) допустимые размеры одной вставки не должны превышать габариты одного листа пояса резервуара; 3) не рекомендуется одновременная вырезка и замена более чем одного фрагмента; 4) при необходимости возможность одновременной вырезки проемов в двух и более местах должна определяться расчетом, учитывающим взаимное влияние количества, расположения и размеров проемов на напряженно-деформированное состояние стенки резервуара и рам жесткости. Elimination of metal defects and welds in the walls of vertical cylindrical tanks is possible by cutting out and replacing the removed fragments with repair inserts using stiffening frames. At the same time, there are no methods for calculating such reinforcing elements and the actual structure of the tank wall with these elements in the regulatory documents. In order to assess the strength and stability of the tank wall and the stiffening frame during the repair work, computer modeling was performed and the stress-strain state of these metal structures was calculated. Within the framework of the research the main Russian and foreign normative documents regulating the loads and methods of tank wall stability calculation are considered; the publications devoted to the tank wall stability calculation by means of computer modeling are analyzed. The results of computer modeling and calculations for strength and stability depending on snow and wind loads are presented. Results of the research performed were used to make the following conclusions: 1) calculations should take into account the wind load, acting at an angle of 40° to the section to be cut out; 2) the allowable dimensions of one insert should not exceed the dimensions of one sheet of the tank ring; 3) simultaneous cutting out and replacement of more than one section is not recommended; 4) if necessary simultaneous cutting of openings in two or more places should be determined by calculation, taking into account the mutual influence of the number, location and sizes of openings on the stress-strain state of the tank wall and stiffening frames.

scholarly journals Influence of the choice of the base model on the stress-strain state of the vertical load-bearing elements of a monolithic-frame house

2020 ◽  
pp. 45-54
Author(s):  
Viktor Nosenko ◽  
Ostap Kashoida
Keyword(s):  
Finite Element ◽  
Finite Elements ◽  
Strain State ◽  
Mutual Influence ◽  
Vertical Load ◽  
Soil Environment ◽  
Stress Strain ◽  
Single Node ◽  
Load Bearing ◽  
Stress Strain State

Comparison of the stress-strain state of vertical elements of the frame of a monolithic house (basement, first and fourth floors), depending on the method of modeling the soil environment and piles, is carried out. The use of pile foundations is due to the fact that they provide the transfer of loads to deeper soil layers and, as a rule, a greater bearing capacity compared to shallow foundations. In the design of foundations, engineers face the question of how to model the soil environment and piles? This paper presents the influence of the decision taken (the selected soil model and the method of modeling piles) on the stress-strain state of the vertical load-bearing elements of the house frame. Comparison of the stress-strain state of vertical elements of the frame (basement, first and fourth floors), which were obtained using the following models of the system «base - pile foundation - overhead supporting structures»: 1) the piles are modeled by single-node finite elements, have only vertical stiffness according to the results of testing the piles for vertical static pressing loads, the mutual influence of piles and soil characteristics are not taken into account (FE-56 hereinafter, this is the number of the finite element in the library of elements of the PС «Lira -SAPR») 2) the piles are modeled by single-node finite elements, are located with a given step along the length of the pile and have rigidity in different directions and approximately take into account the surrounding soil around the pile and under its tip (FE-57); 3) the soil environment is modeled by volumetric elastic finite elements; piles - rod finite elements. It is shown that the choice of the foundation model carries stress-strain state not only for the foundation structures, but also for the vertical bearing elements of the house. When using various options for modeling the base: using a single-node finite element that simulates a smoke like elastic ligature (FE-56), using a chain of single-node skinned elements (FE-57), or a volumetric soil massif, it is possible to obtain quantitative differences in stresses from 2 to 20%, and a qualitative change, which is observed in a change in the sign of bending moments.  

scholarly journals Experimental studies of the various soils bedding influence on the stress-strain state of a layered subsoil base of the slab foundation

2021 ◽  
Vol 274 ◽  
pp. 03021
Author(s):  
Lenar Siraziev ◽  
Danil Sergeev
Keyword(s):  
Strain State ◽  
Mutual Influence ◽  
Experimental Studies ◽  
Contact Layer ◽  
Deformation Pattern ◽  
Stress Strain ◽  
Stress Strain State ◽  
Compressive Stresses ◽  
The Individual ◽  
Slab Foundation

The purpose of the study is to reveal the effect of the stress-strain state of the three-layer soil base of the slab foundation with a rigid underlying layer, which is heterogeneous along the depth of the ground. The main results of the study are obtaining relative deformations in the soil massif and the settlement of ground values of each layer. The results of experimental studies are obtained in the form of a deformation pattern of a layered base, distribution graphs of compressive stresses in the soil in depth and in a horizontal plane. The significance of the results achieved for the construction area is to establish the mutual influence of various soils on the stress-strain state of the laminate basement of the slab foundation. The presence of a dense top layer in a laminate base significantly increases its distribution ability. The stress distribution is proportional to the load-carrying capacity of the individual base layers. On the boundary between the layers, a jump in the compressive stresses may occur, which indicates the presence of shear deformations in the contact layer.

Impact Estimation of a Transient Temperature Field on the Service Life of the High Pressure Rotor of K-1000-60/3000 Turbine

2021 ◽  
Vol 23 ◽  
pp. 408-419
Author(s):  
Olga Chernousenko ◽  
Tetyana Nikulenkova ◽  
Anatolii Nikulenkov
Keyword(s):  
High Pressure ◽  
Service Life ◽  
Steam Turbine ◽  
Strain State ◽  
Life Assessment ◽  
Single Type ◽  
Stress Strain ◽  
Stress Strain State ◽  
Operation Modes ◽  
Numerical Examination

The one of purposes of this paper is to estimation some impact on the service life of the high-pressure cylinder rotor of a typical high-speed turbine K-1000-60/3000. The residual life assessment of power equipment would require determining viability and damage of its base metal. Typical degradation mechanisms of steam turbine equipment include long-term strength reduction and low cycle fatigue accumulation. Intensity of their impact is determined by a numerical examination of equipment thermal (TS) and stress strain states (SSS) for standard operation modes. To perform a numerical examination of the stress strain state would require solving a thermal conductivity boundary problem in quasi-stationary (for nomal operation modes) and nonstationary models (for transients). It is convenient to solve such problems of mathematical physics through discretization of the calculation object using the finite element method (Chernousenko et al. 2018). The service life of steam turbine is determined as an individual one and is assigned based on the results of individual an inspection of a separate element or the largest group of single-type equipment elements of the considered plant. The fleet service life being reached is followed by diagnostics of specific units of power installations and analysis of their operation, measurement of actual dimensions of components, examination of structure, properties and damage accumulation in the metal, non-destructive testing and estimate of stress strain state and residual service life of the component. The results of performed studies are used to determine an individual service life of each element of energy equipment (Nikulenkov et al. 2018).

Prediction of contact-fatigue damage to rails using computational-experimental methods

2020 ◽  
Vol 86 (4) ◽  
pp. 46-55
Author(s):  
N. A. Makhutov ◽  
V. S. Kossov ◽  
E. S. Oganyan ◽  
G. M. Volokhov ◽  
M. N. Ovechnikov ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Service Life ◽  
Software Package ◽  
Strain State ◽  
Contact Fatigue ◽  
Cumulative Distribution ◽  
Stress Strain ◽  
Stress Strain State ◽  
Contact Fatigue Life ◽  
The Impact

Analysis of the operational data related to rails failure showed that contact-fatigue defects consistently hold a prominent place. The goal of the study is to show the possibilities of using modern numerical methods in calculation assessment of the service life of rails before the onset of contact fatigue crack formation on a running surface depending on the values of axial load. To calculate a stress-strain state in the area of contact interaction between the wheel and rail a detailed finite-element model implemented in the MSC. Marc software package is used. The analysis revealed complex multiaxial and non-proportional nature of the stress-strain state. The Brown – Miller multiaxial fatigue model implemented in the MSC. Fatigue software package was taken to determine accumulation of the contact fatigue damages on a rail running surface. The model is based on the assumption that maximum fatigue damages in the metal occur in the area with the maximum shear stress. The impact of normal stresses in this area is also taken into account. The results of a comparative computational analysis of the rail life time confirm that the service life decreases with increasing axial loads, all other conditions being the same. With a share of 20% of freight trains with axle loads of 25 tonf in a daily pattern one should expect a decrease in the contact fatigue life of rails by 3 – 4 %. It is possible to improve the method for prediction of the contact fatigue life of rails in terms of experimental definition of the fatigue and strength characteristics of the rail steel depending on the degree of hardening of the running surface, their probabilistic properties and the use of a cumulative distribution of vertical forces taking into account the structure of the freight traffic passing through the section.

Application of micropolar theory to the description of the skin effect due to hydrogen saturation

2021 ◽  
pp. 108128652110592
Author(s):  
Ksenia Frolova ◽  
Elena Vilchevskaya ◽  
Nikolay Bessonov ◽  
Wolfgang Müller ◽  
Vladimir Polyanskiy ◽  
...  
Keyword(s):  
Strain State ◽  
Skin Effect ◽  
Mutual Influence ◽  
Average Concentration ◽  
Stress Strain ◽  
Hydrogen Saturation ◽  
Stress Strain State ◽  
Metal Specimen ◽  
Cylindrical Metal ◽  
Stress Induced Diffusion

A model is proposed for the description of a highly inhomogeneous distribution of hydrogen within a saturated metal specimen (the so-called skin effect due to hydrogen saturation). The model is based on the micropolar continuum approach and results in a nonuniform stress–strain state of a cylindrical metal specimen due to distributed couples or microrotations. The dependence of the diffusion coefficient on the strain energy is considered in order to model stress-induced diffusion. Accumulation of hydrogen within a thin boundary layer results in a highly nonuniform distribution of hydrogen across the specimen. The mutual influence of the stress–strain state and hydrogen accumulation is taken into account. The estimated thickness of the surface layer containing hydrogen is comparable to the thickness observed in experiments. The predicted average concentration coincides with experimental data.

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