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 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.

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 ANALYSIS OF THE EFFICIENCY OF APPLICATION OF BOMBINED ROLLERS TO REDUCE THE CONTACT TENSIONS IN THE ROLLER BEARING

2020 ◽  
pp. 96-104
Author(s):  
Diana Popova ◽  
◽  
Nikita Samoylenko ◽  
Sergey Semenov ◽  
Viacheslav Shisterov ◽  
...  
Keyword(s):  
Strain State ◽  
Roller Bearing ◽  
Calculation Model ◽  
Concentration Zone ◽  
Stress Strain ◽  
Roller Bearings ◽  
Stress Strain State ◽  
The Face ◽  
Rolling Elements ◽  
Highly Loaded

The main problem of using roller bearings with direct forming rolling elements in highly loaded units is the edge effect. A significant increase of stresses at the edges of the rolling elements is the cause of the fragility of highly loaded roller bearings, which is a significant problem, especially in such units as rotors of aircraft engines. The solution of this problem in aviation is the use of rolling elements with a modified contact - bombed rollers. This paper presents comparisons of the stress-strain state of contacts of pairs of bodies imitating bombarded rollers of various geometries. The calculation was performed by the finite element method in the ANSYS package. For the calculation, the contact of the roller with a flat plate was used. In the calculation, the stress-strain state of the roller with the direct forming, the roller with the rounding of the face and the bombed rollers with various shapes of the modified forming was evaluated. The calculation model is verified with respect to the classical Hertz formula. The dependence of stresses in the concentration zone on the relative dimensions of the bombarded part of the roller with a standard generator representing an arc of a circle is estimated. A form of the generatrix is proposed, which more effectively reduces stresses in the transition zone of the modified generatrix into the straight line. The proposed form of the generatrix eliminates the main drawback of the classical generatrix of the bombarded rollers - the appearance of a concentration zone in the transition region of the straight part of the roller to the bombed, thus providing a better stress distribution in the roller. The technique used to simulate the contact interaction of rolling elements in a roller bearing can be used to study the stress-strain state of roller bearings of a different geometry, including those used in modern gas turbine engines.

КОНСТРУКТИВНО-ТЕХНОЛОГІЧНІ ОСОБЛИВОСТІ ХВОСТО-ВИХ БАЛОК СІТЧАСТОГО ТИПУ З ПОЛІМЕРНИХ КОМПО-ЗИЦІЙНИХ МАТЕРІАЛІВ ВЕРТОЛЬОТІВ ТРАНСПОРТНОЇ КАТЕГОРІЇ

2020 ◽  
pp. 15-30
Author(s):  
А. Г. Гребеников ◽  
И. В. Малков ◽  
В. А. Урбанович ◽  
Н. И. Москаленко ◽  
Д. С. Колодийчик
Keyword(s):  
Finite Element ◽  
Strain State ◽  
Layer Structure ◽  
Metal Structure ◽  
Element Model ◽  
Stress Strain ◽  
Element Analysis ◽  
Mesh Structure ◽  
Stress Strain State ◽  
Mesh Structures

The analysis of the design and technological features of the tail boom (ТB) of a helicopter made of polymer composite materials (PCM) is carried out.Three structural and technological concepts are distinguished - semi-monocoque (reinforced metal structure), monocoque (three-layer structure) and mesh-type structure. The high weight and economic efficiency of mesh structures is shown, which allows them to be used in aerospace engineering. The physicomechanical characteristics of the network structures are estimated and their uniqueness is shown. The use of mesh structures can reduce the weight of the product by a factor of two or more.The stress-strain state (SSS) of the proposed tail boom design is determined. The analysis of methods for calculating the characteristics of the total SSS of conical mesh shells is carried out. The design of the tail boom is presented, the design diagram of the tail boom of the transport category rotorcraft is developed. A finite element model was created using the Siemens NX 7.5 system. The calculation of the stress-strain state (SSS) of the HC of the helicopter was carried out on the basis of the developed structural scheme using the Advanced Simulation module of the Siemens NX 7.5 system. The main zones of probable fatigue failure of tail booms are determined. Finite Element Analysis (FEA) provides a theoretical basis for design decisions.Shown is the effect of the type of technological process selected for the production of the tail boom on the strength of the HB structure. The stability of the characteristics of the PCM tail boom largely depends on the extent to which its design is suitable for the use of mechanized and automated production processes.A method for the manufacture of a helicopter tail boom from PCM by the automated winding method is proposed. A variant of computer modeling of the tail boom of a mesh structure made of PCM is shown.The automated winding technology can be recommended for implementation in the design of the composite tail boom of the Mi-2 and Mi-8 helicopters.

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