scholarly journals EVALUATION OF THE RESOURCE CHARACTERISTICS OF POLYCRYSTALLINE STRUCTURAL ALLOYS UNDER CYCLIC THERMOMECHANICAL LOADING

2021 ◽  
Vol 83 (4) ◽  
pp. 481-504
Author(s):  
I.A, Volkov ◽  
L.A. Igumnov ◽  
D.N. Shishulin ◽  
A.A. Belov
Keyword(s):  
Fatigue Damage ◽  
Damage Accumulation ◽  
Mechanical Characteristics ◽  
Stress Deviator ◽  
Thermomechanical Loading ◽  
Effective Stresses ◽  
Accumulation Of Damage ◽  
Resource Characteristics ◽  
Kinetics Of ◽  
Physical And Mechanical Characteristics

The main physical regularities of complex thermoviscoplastic deformation and accumulation of damage in structural materials (metals and their alloys) under various modes of cyclic combined thermomechanical loading and mathematical models of these processes are considered. A mathematical model of the mechanics of a damaged medium has been developed, which makes it possible to simulate the cyclic viscoelastoplastic behavior and determine the resource characteristics of polycrystalline structural alloys under the combined action of degradation mechanisms that combine material fatigue and creep. The model is based on the joint integration of equations describing the kinetics of the stress-strain state and damage accumulation processes. The final relation to the model is the strength criterion, the fulfillment of which corresponds to the formation of a macrocrack. The plasticity equations are based on the basic principles of the flow theory. To describe the creep process in the stress space, a family of equipotential creep surfaces of the corresponding radius and having a common center is introduced. The relationship between the creep equations and the thermoplasticity equations describing “instantaneous” plastic deformations is carried out at the loading stage through the stress deviator and the corresponding algorithm for determining and at the loading stage by means of certain relationships between “temporary” and “instantaneous” scalar and tensor quantities. At the stage of development of damage scattered throughout the volume, the effect of damage on the physical and mechanical characteristics of the material is observed. This influence can be taken into account by introducing effective stresses. In the general case, stresses, plastic strains, and creep strains are determined by integrating the thermal creep equations by the four-point Runge-Kutta method with correction of the stress deviator and subsequent determination of stresses according to the thermoplasticity equations, taking into account the average creep strain rate at a new time. The relationships that simulate the accumulation of damage are based on the energy approach to determining the resource characteristics. The kinetics of fatigue damage accumulation is based on the introduction of a scalar parameter of damage to a structural material and a unified model form for representing the degradation mechanism under fatigue and creep conditions. The influence of scattered damage on the physical and mechanical characteristics of the material is taken into account by introducing effective stresses. The results of numerical simulation of cyclic thermoplastic deformation and accumulation of fatigue damage in heat-resistant alloys (Haynes188) under combined thermomechanical loading are presented. Particular attention is paid to the issues of modeling the processes of cyclic thermoplastic deformation and the accumulation of fatigue damage for complex deformation processes accompanied by the rotation of the main areas of stress and strain tensors.

scholarly journals Kinetics of Damage of Materials under Various Regimes of Re-Changeable Loads

2021 ◽  
Vol 5 (3) ◽  
Author(s):  
Anatoliy Hrabovsʹkyy ◽  
Oleksandr Bondarets ◽  
Iryna Babiienko
Keyword(s):  
Structural Material ◽  
Service Life ◽  
Damage Accumulation ◽  
Load Force ◽  
Railway Transport ◽  
Damage Factor ◽  
Plastic Properties ◽  
Effective Stresses ◽  
Accumulation Of Damage ◽  
Kinetics Of

Kinetics of accumulation of damages in engineering objects, which work at repeated-alternating soft and hard modes of loading of details and elements of constructions of vehicles (cars, cars, railway transport, etc.). When changing the direction of the load force to the opposite in the structural material there is a phenomenon of changing the kinetics of accumulation of damage, ie the damage factor at separation and shear changes, which affects the effective stresses and service life of equipment. This effect of the factor of the influence of repeated variables on the redistribution of the kinetics of damage accumulation is considered experimentally for materials with different plastic properties

Local Viscoelastic Properties of a Thermoplastic/Carbon Laminate as an Indicator of Fatigue Damage

2014 ◽  
Vol 606 ◽  
pp. 237-240
Author(s):  
Jiří Minster ◽  
Martin Šperl ◽  
Jaroslav Lukeš
Keyword(s):  
Fatigue Damage ◽  
Viscoelastic Properties ◽  
Damage Accumulation ◽  
Mechanical Characteristics ◽  
Young Modulus ◽  
Time Dependent ◽  
Three Point Bending ◽  
Thermoplastic Matrix ◽  
Microindentation Testing ◽  
Cycling Loading

The paper is aimed at an assessment of influence of damage accumulation in a thermoplastic/carbon laminate during a tensile cycling loading on durability, Young modulus and both instant and time-dependent local mechanical characteristics of a thermoplastic matrix, analysed by means of instrumented microindentation. Standard mechanical data from three-point bending are compared with results of the local microindentation testing.

scholarly journals Adhesion strength of protective and decorative coatings depending on the porosity of the cement substrate

2020 ◽  
Vol 329 ◽  
pp. 04001
Author(s):  
Valentina Loganina ◽  
Bassam Shareef Denied Al Saedi
Keyword(s):  
Bonding Strength ◽  
Damage Accumulation ◽  
Operating Time ◽  
Adhesive Contact ◽  
Exponential Dependence ◽  
Surface Porosity ◽  
Hereditary Factor ◽  
Accumulation Of Damage ◽  
Kinetics Of

Information provided about long-term bonding strength protective decorative coatings. A method is proposed for assessing the long- term bonding strength of coatings. The method consists in determining the bonding strength before testing and after t hours of testing. The dependence of the long-term bonding strength on the porosity of the cement substrate has been established. With an increase in the surface porosity of the substrate, observed a decrease in the time of maintaining the adhesive contact “coating-substrate». The aging process of coatings is considered from the position accumulation of damage, taking into account the hereditary factor. The influence of the hereditary factor on the kinetics of damage accumulation was established. It is shown that the dependence of the operating time on the level of damage accumulation can be approximated by an exponential dependence. The values of the activation energy of adhesive destruction of coatings are calculated.

The Accumulation of Damage in Plates Subjected to Steady Mechanical Load and Cyclic Thermal Downshocks on One Surface

1982 ◽  
Vol 104 (3) ◽  
pp. 232-238 ◽  
Author(s):  
J. Phillips
Keyword(s):  
Fatigue Damage ◽  
Fast Reactor ◽  
Damage Accumulation ◽  
Mechanical Load ◽  
Computer Calculations ◽  
Accumulation Of Damage ◽  
Transient Thermal ◽  
Biot Numbers ◽  
Damage Summation ◽  
Dwell Period

Computer calculations, incorporating analysis of elastic, plastic and creep effects, are performed on a Bree plate subjected to steady mechanical load and cyclic thermal downshocks on one surface. Particular attention is given to the accumulation of creep and fatigue damage which is calculated from the stress-strain distributions using linear damage summation rules. The computations examine the dependence of the damage accumulation on such factors as the applied loads, the degree of hardening in the material, the length of the creep dwell period and the severity of the transient thermal loadings as measured by the Fourier and Biot numbers. This indicates which considerations are likely to be important in the design of fast reactor components which experience loadings of this type.

scholarly journals Problem of the degradation criteria for transportation construction elements

2020 ◽  
Vol 164 ◽  
pp. 03014
Author(s):  
Albert Lantukh-Lyashchenko ◽  
Artur Onishchenko ◽  
Oleksandr Davydenko
Keyword(s):  
Life Cycle ◽  
Theoretical Basis ◽  
Damage Accumulation ◽  
Control Parameter ◽  
Mechanical Characteristics ◽  
Prediction Models ◽  
Technical Condition ◽  
Building Structures ◽  
Advantages And Disadvantages ◽  
Physical And Mechanical Characteristics

The article is devoted to the pressing problem of managing the reliability and durability of transport constructions. Modern scientific approaches to assessing the technical condition of transport facilities based on an analysis of element degradation during the life cycle of operation considered. The article presents the advantages and disadvantages of the most common prediction models of the technical condition of building structures. Each model uses a characteristic criterion for degradation of building structures: load and unload cycles, rejection number of chlorides, intensity coefficient, a geometric parameter (parameters) of the crack in the material, reliability, etc. The problem of choosing the control parameter of the lifecycle model of the bridge elements is analyzed. The theoretical basis for the Markov phenomenological model of damage accumulation and the model of degradation based on the physical and mechanical characteristics of the material formulated. Depending on the stage of the life cycle, it is proposed to select the type of prediction model.

Chemical Vapor Crystallization of Hard Nanocomposite Tungsten Carbide Layers for Extreme Applications

2008 ◽  
Vol 59 ◽  
pp. 62-65 ◽  
Author(s):  
V.L. Goncharov ◽  
Y.V. Lakhotkin ◽  
V.P. Kuzmin ◽  
Vladimir K. Alimov ◽  
J. Roth
Keyword(s):  
Mechanical Characteristics ◽  
Crystallization Process ◽  
Extreme Environments ◽  
Gaseous Mixture ◽  
Chemical Vapor ◽  
Tungsten Carbides ◽  
Tungsten Hexafluoride ◽  
Physico Chemical ◽  
Kinetics Of ◽  
Physical And Mechanical Characteristics

The physico-chemical fundamentals (thermodynamics, kinetics) of tungsten carbides crystallization process are presented. Chemically vapor deposited coatings composed of tungsten carbides, metallic tungsten matrix with nanoparticles of tungsten carbides are synthesized from gaseous mixture of tungsten hexafluoride, hydrogen and propane at temperatures ranging from 623 to 923 K and can be used as materials for extreme environments. The physical and mechanical characteristics of these CVD coatings are discussed.

scholarly journals Damage to engineering objects during re-static alternating load modes

2021 ◽  
Author(s):  
Anatoliy Grabovskiy ◽  
Oleksandr Bondarets ◽  
Iryna Babiienko
Keyword(s):  
Structural Material ◽  
Service Life ◽  
Damage Accumulation ◽  
Load Force ◽  
Structural Elements ◽  
Plastic Properties ◽  
Effective Stresses ◽  
Defect Healing ◽  
Kinetics Of

The paper considers the kinetics of damage accumulation in engineering facilities that operate under repeated static alternating load modes - parts and structural elements of vehicles (cars, airplanes, railways). When changing the direction of the load force in the structural material there is a phenomenon of changing the shape of micro defects, which leads to their "healing", ie the factor of damage to separation and shear changes, which affects the effective stresses and service life of equipment. This effect of defect healing is considered experimentally for materials with different plastic properties.

BENCH DESIGN AND STUDY OF PHYSICAL AND MECHANICAL CHARACTERISTICS OF A TEAT CUP LINER WITH ANTIBACTERIAL FILLER

2020 ◽  
pp. 22-26
Author(s):  
YURY G. IVANOV ◽  
◽  
YELENA V. MASHOSHINA ◽  
LYUDMILA N. VERLIKOVA ◽  
DARIA G. GELETIY ◽  
...  
Keyword(s):  
Mechanical Characteristics ◽  
Physical And Mechanical Characteristics

Fatigue damage accumulation around notches

2004 ◽  
Vol 46 (6) ◽  
pp. 309-313
Author(s):  
Yutaka Iino ◽  
Hideo Yano
Keyword(s):  
Fatigue Damage ◽  
Damage Accumulation ◽  
Fatigue Damage Accumulation

Discharge-pulse Geotechnical Electro Discharge Technology of Bases Strengthening

2020 ◽  
Vol 787 (12) ◽  
pp. 63-65
Author(s):  
N.S. Sokolov
Keyword(s):  
Bearing Capacity ◽  
Mechanical Characteristics ◽  
Discharge Pulse ◽  
Zero Values ◽  
Traditional Technologies ◽  
Negative Friction ◽  
Geotechnical Problems ◽  
Physical And Mechanical Characteristics

The problem of increasing the bearing capacity of the base is an relevant problem in modern geotechnical construction. When significant loads are transmitted to the base, the use of traditional technologies is not always justified. Often there is an urgent need to use non-standard ways to strengthen the bases. In many cases, the geotechnical situation is aggravated by the presence of weak underlying layers with unstable physical and mechanical characteristics in engineering-geological sections. When strengthening such bases with the help of traditional piles, the latter can get negative friction, which significantly reduces their bearing capacity on the ground, sometimes reaching zero values. This may lead to additional precipitations of the objects being constructed and constructed in the zone of geotechnical influence. The use of ERT piles in most cases successfully solves many complex geotechnical problems.

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