Development of a method of accounting for the effect of stress concentration and residual stresses on the cyclic longevity of steel 10GN2MFA. Report 1. Analysis of material's stress?Strain state

1993 ◽  
Vol 25 (8) ◽  
pp. 547-555
Author(s):  
V. T. Troshchenko ◽  
G. V. Tsybanev ◽  
A. V. Stepura
Keyword(s):  
Stress Concentration ◽  
Residual Stresses ◽  
Strain State ◽  
Stress Strain ◽  
Stress Strain State

scholarly journals Stress strain state of elastic plate with elliptical cut-out

2020 ◽  
pp. 3-8
Author(s):  
E.E. Deryugin ◽  
Keyword(s):  
Plastic Deformation ◽  
Stress Concentration ◽  
Driving Force ◽  
Strain State ◽  
Mechanical State ◽  
Concentration Coefficient ◽  
Stress Strain ◽  
Crack Driving Force ◽  
Stress Strain State ◽  
Stress Concentration Coefficient

The article considers a crack in the form of a narrow cut with a certain cfn at the cut out in an unbounded plate. The characteristics of the mechanical state of this system under uniaxial loading are determined: the stress concentration coefficient, the crack-driving force, and the energy of a solid with a crack. The elastic energy expenditure during crack propagation is determined. The general regularities of the mechanical state of a solid with a crack, not necessary having the form of an ellipse, are revealed. An important parameter of a crack is the curvature at the tip. It is shown that the Griffiths crack does not actually have a singularity at the tip. The stress strain state of the plate with an elliptical crack is identical to the same of the plate with a focus of homogeneous plastic deformation.

Thermal-Fatigue Analysis of Turbine Discs under Complex Thermo-Mechanical Loading with Account of Plasticity and Creep Effects

2015 ◽  
Vol 725-726 ◽  
pp. 955-960 ◽  
Author(s):  
Igor Ignatovich ◽  
Artem S. Semenov ◽  
Sergey Semenov ◽  
Leonid Getsov
Keyword(s):  
Stress Concentration ◽  
Strain State ◽  
Local Strain ◽  
Complex Stress ◽  
Material Behavior ◽  
Stress Concentration Zone ◽  
Concentration Zone ◽  
Stress Strain ◽  
Thermomechanical Cycling ◽  
Stress Strain State

During operation of transport and maneuverable gas-turbine units, there are crack formation in turbine disc rims what exerted by thermomechanical cycling loads. For in-depth study of these problems we have to use theories of plasticity and creep which form the basis for determining the complex stress-strain state in the stress concentration zone for disc rims, and a modern failure criterion which can predict lifetime under conditions of simultaneous plastic and creep strain accumulation. There is a finite-element method (FEM) that allows us to evaluate the stress-strain state in a stress concentration zone for a non-elastic material behavior. With plasticity and creep theories, it is possible to determine local strain quiet reliable by FEM.

scholarly journals Modern systems for monitoring the stress-strain state of hazardous power generating facilities

2021 ◽  
Vol 263 ◽  
pp. 02008
Author(s):  
Anatoly Zemlyansky ◽  
Alexander Zhukov ◽  
Daria Bulavina
Keyword(s):  
Residual Stresses ◽  
Construction Industry ◽  
Strain State ◽  
State Level ◽  
Operational Reliability ◽  
Building Structures ◽  
Stress Strain ◽  
Factors Affecting ◽  
Stress Strain State ◽  
Dominant Direction

The paper considers the issue of effectively increasing the level of operational reliability of power generating nuclear and hydraulic facilities. Over the past 20 years, the number of accidents at these facilities has been growing. There are many factors affecting the collapse of structures, but, according to the authors, the lack of a monitoring system capable of fully assessing not only the stress-strain state, but also the so- called “residual” stresses of the material is the dominant direction of research. The same question is raised at the state level, as evidenced by the requirements of the STO, GOST and Federal laws, to which the authors refer below. The legislative prerequisites (requirements) for the creation of an improved system for monitoring critical structures, corresponding to the development trends of the construction industry, as well as the modernization of the existing fund are listed. The drawbacks and advantages of existing monitoring systems (strain gauge, string, fiber-optic sensors and acoustic emission systems) are analyzed in detail, and the general lack of the possibility of measuring, evaluating "residual" stresses in the material of structures is noted. A fundamentally new system for monitoring the stress-strain state of building structures and power equipment is proposed, which is based on the Foerster effect, a comparison is made with the existing systems described above. The main features and capabilities of the method are noted and options for use at highly important facilities are proposed.

scholarly journals The research of the stress-strain state with local thinning in pipelines and determination of allowable values of concentration stress and strain

2019 ◽  
Vol 15 (5) ◽  
pp. 384-391
Author(s):  
Dmitry A. Kuzmin ◽  
Anastasia V. Andreenkova
Keyword(s):  
Stress Concentration ◽  
Internal Pressure ◽  
Wall Thickness ◽  
Strain State ◽  
Stress Strain ◽  
Flow Acceleration ◽  
Stress Strain State ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Equipment And Pipelines

Relevance. The nuclear power plant contains a large number of equipment and pipelines subject to flow acceleration corrosion. As a result of a combination of various parameters - sizes (diameters, wall thickness), operational parameters (internal pressure, temperature), steels and elements types - the number of design cases is tens of thousands, without counting the possible forms of thinning. The process of maintenance and repair at the stations are doing an assessment of the accordance of actual and allowable values of wall thicknesses. The ensuring safe operations of equipment and pipelines have been introduced correction functions for regulatory functions, taking into account the forms of thinning, to determine the permissible thinning. The aim of the work. The task is to determine the influence of the forms and types of thinning on the stress-strain state and to determine the most critical thinning for straight sections of pipelines subject to flow acceleration corrosion taking into account emergency conditions. Methods. The allowable values of stress concentration factors (deformations) of pipelines subject without flow acceleration corrosion was determined taking into account allowable values, the requirements of the federal norms and rules for emergency operating conditions. For researches of the stress concentration coefficients were used the finite element method and analytical methods for various shapes, sizes and depths of thinning. Results. A method has been developed, that allows getting the maximum allowable values of stress concentration factors (deformations) for emergency operation, which afford to determine the maximum allowable depth of thinning in emergency conditions - an above criterion. The researches have been carried out definition of the stress concentration factors for local thinning with various types of these thinning. The functions of concentration coefficients depending on the geometric parameters of local thinning wall thickness were determined for a straight section of the pipeline. As a result of the research, the dependences of the sizes of thinning on the concentration coefficients for straight pipelines were created and a master-curve was obtained. The researches were carried out take into account the load from internal pressure and bending moment.

scholarly journals Analysis of the stress-strain state of the spine model with posterior fusion in the treatment of scoliotic deformities in children

TRAUMA ◽  
2021 ◽  
Vol 22 (6) ◽  
pp. 19-25
Author(s):  
A.F. Levitsky ◽  
V.O. Rogozinsky ◽  
M.M. Dolyanitsky ◽  
O.V. Yaresko ◽  
M.Yu. Karpinsky
Keyword(s):  
Stress Concentration ◽  
Bone Tissue ◽  
Ultimate Strength ◽  
Contact Area ◽  
Strain State ◽  
Stress Strain ◽  
Bone Contact ◽  
Stress Strain State ◽  
Scoliotic Deformity ◽  
Vertebral Bodies

Background. Mathematical modeling of the correction of scoliotic deformities of the spine makes it possible to analyze the effectiveness of various methods of treatment without surgical intervention. In the study of traction, mainly experimental methods were used. The purpose was to investigate the stress-strain state of the spine models with varying degrees of scoliotic deformity during posterior spinal fusion. Materials and methods. Deformities of the spine of 40, 70 and 100° were modeled, with posterior spondylodesis of the Th1-Th12 vertebrae. A load of 300 N was used. Results. With a deformity of 40°, the most stressed are the areas of frontal plane curve. For the upper vertebrae Th1-Th4, a more even distribution of stress over the vertebral body is observed. For Th5-Th10 vertebrae, the concave side of the vertebral bodies is more stressed. In the thoracic spine, the more stressed vertebrae are Th2 and Th5. The main load is borne by the fixing structure, in which the level of stress is significantly higher than in the bone structures of the vertebrae. In the posterior supporting complex of the vertebrae, the stress concentration areas are located at the points where fixing screws enter the bone. An increase in the magnitude of the scoliotic deformity of the spine up to 70° causes an increase in the level of stresses in all elements of the model, with the exception of Th9-Th10 vertebrae. With a deformity of 100° in the posterior supporting complex of the vertebrae, the stress concentration areas are located at the points where fixing screws enter the bone. The stress level of 116.0 MPa exceeds the ultimate strength of the cortical layer of the bone tissue of the spine, which can lead to microdamage of the bone tissue and loosening of the screws. Conclusions. For all values of scoliotic deformity of the spine, the most stressed are Th4 and Th5 vertebrae. A decrease in the degree of deformity has a significant effect on the stress-strain state of the spinal column. In the Th4 vertebral body, the level of stresses with a deformity of 100° is more than twice as high as with a deformity of 70°, and more than 4 times higher than with a deformity of 40°. In the body of the Th5 vertebra, the stress level with a deformity of 70° is 1.5 times less than with a deformity of 100°, and with a deformity of 40°, it is 3 times less. The level of stress in the Th1-Th5 vertebral bodies is higher than that of Th6-Th12. In the posterior supporting complex, at the points where screws enter the bone, the maximum stress value at a deformity of 40° is 34.0 MPa, which is not critical for the bone tissue. With a deformity of 70°, the stresses are 85.0 MPa, which can exceed the ultimate strength for the cortical bone and lead to microdestruction of the bone tissue in the screw-bone contact area. With a deformity of 100°, the stresses are equal to 116.0 MPa, which exceeds the ultimate strength for the cortical bone and can lead to microfracture in the screw-bone contact area.

scholarly journals Effect of the sector radius of a workpiece-deforming tool on the stress-strain state in the contact zone with a cylindrical surface

2022 ◽  
Vol 25 (6) ◽  
pp. 696-707
Author(s):  
S. A. Zaides ◽  
Quan Minh Ho ◽  
Nghia Duc Mai
Keyword(s):  
Surface Layer ◽  
Plastic Zone ◽  
Residual Stresses ◽  
Cylindrical Surface ◽  
Strain State ◽  
Stress Strain ◽  
Stress Strain State ◽  
Cylindrical Workpiece ◽  
Zone Depth ◽  
Depth Ranges

This paper aims to determine the effect of the sector radius of a workpiece-deforming tool on the stress-strain state in the center of elastoplastic deformation and residual stresses in the hardened zone of the surface layer of cylindrical workpieces. A mathematical model of local loading was constructed using the finite element method and AN-SYS software. This model was used to determine the values of temporary and residual stresses and deformations, as well as the depth of plastic zone, depending on the sector radius of the working tool. The simulation results showed that, under the same loading of a cylindrical surface, working tools with different sector radii create different maximum tempo-rary and residual stresses. An assessment of the stress state was carried out for situations when the surface layer of a product is treated by workpiece-deforming tools with a different shape of the working edge. It was shown that, compared to a flat tool, a decrease in the radius of the working sector from 125 to 25 mm leads to an increase in the maximum temporary and residual stresses by 1.2–1.5 times, while the plastic zone depth increases by 1.5–2.4 times. The use of a working tool with a flat surface for hardening a cylindrical workpiece ensures minimal temporary residual stresses, com-pared to those produced by a working tool with a curved surface. A decrease in the radius of the working sector leads to an increase in temporary residual stresses by 2–7%. The plastic zone depth ranges from 1.65 to 2.55 mm when chang-ing the sector radius of the working tool.

Analysis and assessment of the stress-strain state of large-sized metal structures

2021 ◽  
Author(s):  
N.E. Sadkovskaya ◽  
A.E. Tsykin
Keyword(s):  
Residual Stresses ◽  
Traffic Control ◽  
Strain State ◽  
Metal Structure ◽  
Stress Strain ◽  
Metal Structures ◽  
Stress Strain State ◽  
Calculated Stress ◽  
Residual Stresses And Strains ◽  
Non Destructive

The stress-strain state of large-sized metal structures is investigated. The causes and consequences of the formation of residual stresses and strains are shown. Methods for predicting residual stresses and strains by the calculation method are presented. Destructive and non-destructive methods for determining the stress-strain state of large-sized metal structures are presented. The influence of local deformations and clearances during assembly on the value of residual stresses and deformations is shown on the example of a typical curved large-sized metal structure, characteristic for the design of antenna devices of radar stations and air traffic control systems. Conclusions are made about the importance of analyzing and evaluating the stress-strain state of large-sized metal structures. Radar stations and air traffic control systems during operation experience extreme multi-parameter loads and thermal effects. To ensure the high reliability of their work, a thorough and accurate analysis is required, followed by an assessment of the stress-strain state of the bearing large-sized component parts of metal structures already manufactured and only being designed at the stage of experimental design work, in order to be able to choose the correct technological, constructive and organizational sequence for their manufacture. In modern production, metalworking methods are used, based on a sharp increase in the energy concentration on the treated surfaces of the elements, which contributes to the uneven distribution of thermodynamic potentials over their volume. The critical state is stress concentration in the metal structure, which can lead to its destruction. In zones of stress concentration, a complex stress state always arises, volumetric or flat. The type of local stress state significantly affects the level of loads that the metal structure can withstand without destruction. The most dangerous is a comprehensive uneven stretching. The conditional characteristics of the mechanical properties of a material such as tensile strength or elongation, determined in accordance with current standards, are not enough to calculate the loads that the structure can withstand without breaking. Also, the stress-strain state of the metal structure affects the dimensional stability in the metal structure, which leads to the need to use special technological solutions to relieve and relax existing residual stresses and strains. A sufficiently accurate assessment of predicting the stress-strain state of large-sized metal structures can be a model model, which analyzes and evaluates residual stresses and strains in-situ, and the level of breaking load when testing a model model under appropriate temperature conditions is taken as a criterion for assessing the health of a material. However, this method for large-sized metal structures is not always technically feasible and often unprofitable due to the large size of structures, the duration and cost of testing, the difficulty of creating full-scale operating conditions, etc. The problem of determining the calculated stress-strain state of a metal structure can be solved by separate solution of thermomechanical and deformation subtasks according to empirical formulas using the finite element method or the extended finite element method. Moreover, for the reliability of determining the calculated stress-strain state, it is necessary in the mathematical model to take into account many factors affecting the magnitude of the residual stresses and strains. The indicated assumptions, as well as the complexity of the proposed calculations, do not allow accurate prediction of the subsequent stress-strain state of large-sized metal structures having complex geometric and spatially oriented shapes. It is possible to use non-destructive and destructive methods to determine the actual stress-strain state of metal structures. For a more accurate assessment of the stress-strain state of metal structures, we must cut the object and subject the interior to the measurement of residual stresses. For this, it is possible to use two main methods: the stress relaxation method and the method of intrinsic deformation. As practice shows, it is necessary to predict residual stresses during welding of various types of joints without performing complex calculations of thermal elastoplastic analysis. In these cases, the following two simpler methods can be used: the use of experimental databases and the use of effective internal deformation, which is a source of residual stress. As an example, deformations of welded large-sized metal structures, typical for antenna systems of radar stations and made of sheet metal, are predicted. Thus, we can conclude that a preliminary and actual assessment of the stress-strain state of welded metal structures, especially large ones, is a difficult task, but its importance can hardly be underestimated. In this regard, new methods and techniques are constantly appearing that allow this to be done with the greatest accuracy and less computational complexity.

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