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.

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

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 Seismic Damage Accumulation in Highway Bridges in Earthquake-Prone Regions

2015 ◽  
Vol 31 (1) ◽  
pp. 115-135 ◽  
Author(s):  
Jayadipta Ghosh ◽  
Jamie E. Padgett ◽  
Mauricio Sánchez-Silva
Keyword(s):  
Service Life ◽  
Damage Accumulation ◽  
Main Shock ◽  
Prediction Models ◽  
Time Window ◽  
Damage Index ◽  
Active Regions ◽  
Highway Bridges ◽  
Main Shocks ◽  
Aftershock Sequences

Civil infrastructures, such as highway bridges, located in seismically active regions are often subjected to multiple earthquakes, including multiple main shocks during their service life or main shock–aftershock sequences. Repeated seismic events result in reduced structural capacity and may lead to bridge collapse, causing disruption in the normal functioning of transportation networks. This study proposes a framework to predict damage accumulation in structures subjected to multiple shock scenarios after developing damage index prediction models and accounting for the probabilistic nature of the hazard. The versatility of the proposed framework is demonstrated on a case-study highway bridge located in California for two distinct hazard scenarios: (1) multiple main shocks during the service life and (2) multiple aftershock earthquake occurrences following a single main shock. Results reveal that in both cases there is a significant increase in damage index exceedance probabilities due to repeated shocks within the time window of interest.

scholarly journals Early-Age Cracking in Concrete: Causes, Consequences, Remedial Measures, and Recommendations

2018 ◽  
Vol 8 (10) ◽  
pp. 1730 ◽  
Author(s):  
Md. Safiuddin ◽  
A. Kaish ◽  
Chin-Ong Woon ◽  
Sudharshan Raman
Keyword(s):  
Service Life ◽  
Concrete Structures ◽  
Real Life ◽  
Early Age ◽  
Structural Elements ◽  
Remedial Measures ◽  
Curing Conditions ◽  
Factors Affecting ◽  
Different Types ◽  
Service Conditions

Cracking is a common problem in concrete structures in real-life service conditions. In fact, crack-free concrete structures are very rare to find in real world. Concrete can undergo early-age cracking depending on the mix composition, exposure environment, hydration rate, and curing conditions. Understanding the causes and consequences of cracking thoroughly is essential for selecting proper measures to resolve the early-age cracking problem in concrete. This paper will help to identify the major causes and consequences of the early-age cracking in concrete. Also, this paper will be useful to adopt effective remedial measures for reducing or eliminating the early-age cracking problem in concrete. Different types of early-age crack, the factors affecting the initiation and growth of early-age cracks, the causes of early-age cracking, and the modeling of early-age cracking are discussed in this paper. A number of examples for various early-age cracking problems of concrete found in different structural elements are also shown. Above all, some recommendations are given for minimizing the early-age cracking in concrete. It is hoped that the information conveyed in this paper will be beneficial to improve the service life of concrete structures. Concrete researchers and practitioners may benefit from the contents of this paper.

Research of the kinetics of thickness of the boundary layers of lubricating materials applied to drilling technology

2021 ◽  
pp. 115-120
Author(s):  
R.A. Ismakov ◽  
◽  
V.G. Konesev ◽  
F.N. Yangirov ◽  
G.L. Gaymaletdinova ◽  
...  
Keyword(s):  
Service Life ◽  
Boundary Layers ◽  
Friction Pair ◽  
Roller Bearing ◽  
Equipment Safety ◽  
Efficiency And Effectiveness ◽  
Drilling Technology ◽  
Resource Characteristics ◽  
Friction Surfaces ◽  
Kinetics Of

Improving the operational properties of lubricants increases the service life of the mechanisms and increase the durability of rubbing joints, which has a positive effect on the indicators of technical and economic efficiency and equipment safety. Therefore, great attention in tribology is paid to the analysis of the state of friction units in technology and the assessment of their resource characteristics, which makes it possible to increase their service life. The research aim is to study the general provisions on lubricants and lubricants, as well as the features of the boundary layers formation on friction surfaces and the observed patterns. Calculations of the boundary layers thickness using lubricating reagents at different energetic loading of the friction pair were carried out as applied to the roller bearing of a roller cone bit in the medium of cylinder oil 52 and DPS grease. The proposed research methodology made it possible to in-crease the efficiency and effectiveness of the means development for improving the tribotech-nical properties of drilling lubricants.

Kinetics of damage accumulation in D16сh alloy specimens under static loading

2021 ◽  
pp. 18-26
Author(s):  
M.R. Tyutin ◽  
◽  
L.R. Botvina ◽  
V.P. Levin ◽  
E.N. Beletskii ◽  
...  
Keyword(s):  
Static Loading ◽  
Damage Accumulation ◽  
Kinetics Of
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