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.

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 Conceptual Approaches to Solving the Issue of Reinforcing the Rock - Cut Structures of Geghard Monastery Complex

2021 ◽  
Vol 1 (2) ◽  
pp. 3-9
Author(s):  
† Artavazd Avetik Arzumanyan ◽  
Avetik Artavazd Arzumanyan ◽  
Hasmik Hamle Qaramyan ◽  
Nelli Gagik Muradyan
Keyword(s):  
Mechanical Characteristics ◽  
Technical Condition ◽  
Laboratory Studies ◽  
Underground Structures ◽  
Rock Samples ◽  
Sandstone Rock ◽  
Comprehensive Development ◽  
Strength And Deformation ◽  
Physical And Mechanical Characteristics

The article presents a visual and instrumental research of the technical condition of the main rock-cut structures and their masonry additions, the documentation of their damages (cracks, crevices, destructions and erosions) and deformations, thorough complete laboratory studies of rock samples and their physical and mechanical characteristics, conceptual approaches to preventive and reinforcing measures necessary for the further safe survival of structures, as well as the comprehensive development and implementation of measures to prevent further damages (elimination of causes) and ensure the long-term existence of structures. Based on the analyses carried out, it is recommended to use a ready-made dry mixture mortar of the “Mapegrout'' brand produced by the Italian company “Mapei” to fill cracks if necessary. It is available in the market of the country and is successfully used in the reconstruction of tunnels and other underground structures. The issues of compatibility of reinforcing materials with sandstone rock are also considered on the basis of some averaged data of the main decisive physical and mechanical characteristics of the strength and deformation of sandstone.

Experimental Study on Self-Made Similar Material of Soft Rock

2016 ◽  
Vol 717 ◽  
pp. 140-146 ◽  
Author(s):  
Jian Guang Li ◽  
Yang Wu ◽  
Yong Yan Wang ◽  
Nan Qin ◽  
Wei Xing Wang
Keyword(s):  
Model Experiment ◽  
Mechanical Characteristics ◽  
Soft Rock ◽  
Material Model ◽  
Similar Material ◽  
Advantages And Disadvantages ◽  
Mixed Mortar ◽  
Cementing Agent ◽  
Physical And Mechanical Characteristics ◽  
The Ideal

Similar material of soft rock used at domestic and abroad are analyzed and compared and researched the advantages and disadvantages of them. Self-made similar material of soft rock mixed with cement, plaster mixed mortar as a cementing agent and sand, rubber powder as aggregate were analyzed and compared. After analyzed multi physical and mechanical characteristics, different ratios of specimens were verified by adjusting the ratio of different materials in similar material to obtain the ideal similar material of soft rock. It was provided reference for similar material model experiment of soft rock.

Development of Dry Sand-Lime New Multicomponent Mortars into the Historical Cultural Monuments Applied on Local Raw Basis

2022 ◽  
Vol 906 ◽  
pp. 53-58
Author(s):  
Hasmik Qaramyan
Keyword(s):  
Mechanical Characteristics ◽  
Detailed Examination ◽  
Technical Condition ◽  
Rehabilitation Work ◽  
Complex Development ◽  
Dry Sand ◽  
Basic Characteristics ◽  
Cultural Constructions ◽  
Cultural Monuments ◽  
Physical And Mechanical Characteristics

The visual and instrumental research of the technical condition of historical cultural constructions and their stone additions, documentation of their existing damages, as well as complex development and implementation of further collapse preventing measures and construction durability ensuring measures are presented. Application of processed sand-lime complex mortars based on local raw is offered for blockage of composition cracks during the rehabilitation work taking into consideration some averaged indices of Mape Antique I, Italian “Mapey” firm, similar injection mortar orientation basic characteristics (physical and mechanical characteristics, leakage, viability) and complete laboratory detailed examination results of the component mineralogical and physical and mechanical characteristics of the substances originally used in the construction. The data on local based raw processed sand-lime construction complex mortars (blockage mortar, injection mortar) physical and mechanical characteristics, thermographic dilatometric properties dependence on composition and fastening conditions of mortars are presented

scholarly journals DEVELOPMENT OF RADIATION-PROOF CONCRETE COMPOSITIONS

2020 ◽  
Vol 3 (5) ◽  
pp. 24-33
Author(s):  
M. Sopin ◽  
Sergey Klyuev ◽  
Marina Ageeva ◽  
R. Lesovik ◽  
G. Bogusevich
Keyword(s):  
Water Consumption ◽  
Nuclear Power ◽  
Power Plants ◽  
Mechanical Characteristics ◽  
Nuclear Reactor ◽  
Coefficient Of Thermal Expansion ◽  
Raw Materials ◽  
Raw Material ◽  
Advantages And Disadvantages ◽  
Physical And Mechanical Characteristics

The article considers the possibility of using composite binders and magnetite as components of concrete with radiation-proof properties. The use of the developed concrete is possible not only when it is necessary to build nuclear power plants, but also to create bunkers or anti-radiation shelters. A special feature of concretes used for the protection and design of nuclear reactor cranes is their properties, which they must have. These properties include: low thermal conductivity, increased density, high temperature resistance, reduced values of the coefficient of thermal expansion, shrinkage and creep. Technogenic raw materials for the production of very heavy concrete are studied, the main physical and mechanical characteristics, the requirements that need to be considered in the selection of raw mix composition for protective concrete are analyzed. The paper presents a comparison of physical and mechanical characteristics, the advantages and disadvantages of introducing a binder of various types: cement, cement with a superlasticizer and a binder of low water consumption. It was found that the use of a low-water-consumption binder increases the physical and mechanical characteristics while reducing the consumption of cement in the raw material mix compared to traditional heavy concrete with cement.

scholarly journals FORECASTING CHARACTERISTICS OF COMPOSITE STRENGTH ON THE BASIS OF PREFORMS IN ELEMENTS OF BUILDING STRUCTURES

2020 ◽  
Vol 6 (159) ◽  
pp. 2-9
Author(s):  
A. Kondratiev ◽  
O. Andrieiev
Keyword(s):  
Composite Material ◽  
Composite Materials ◽  
Composite Structures ◽  
High Speed ◽  
Mechanical Characteristics ◽  
Unidirectional Composite ◽  
Test Material ◽  
Practical Implementation ◽  
Building Structures ◽  
Physical And Mechanical Characteristics

Currently, wicker composite structures for various purposes are widely used in many industries. The use of such preforms allows to provide the possibility of automation of production, high speed and efficiency of the process of manufacturing polymeric composite materials and structures based on them. Knowledge of their properties allows you to optimize the production of structures with the necessary parameters during design. In the article the model of composite material on the basis of wicker reinforcement was further developed. For the practical implementation of this model, it is sufficient to test material samples with three different angles between the harnesses, for example, ± 30º, ± 45º and ± 60º. A mathematical description of the model is given. The model made it possible to predict the physical and mechanical characteristics of the composite material when it is laid out on curved surfaces. At the same time some fictitious limits of durability of a composite are defined. This is due to the fact that each value of the angle between the harnesses corresponds to its physical and mechanical characteristics of the unidirectional composite material. In this case, the ultimate strength curves necessarily pass through the points corresponding to the experimental data. The article shows that the possible deviations of the strength limits in the range of angles between the harnesses will lie within the range of characteristics obtained by testing. The article shows that in the realized interval of angles between the harnesses, almost any polynomial criterion of strength will accurately describe the strength of the composite reinforced with a braided sleeve. The obtained parameters, in contrast to the existing ones, allow to predict the strength characteristics of the composite on the basis of braided sleeves depending on the positioning and location of the material on the forming surface. The obtained results are the basis for solving the problems of calculating the strength of building structures from composite materials based on wicker preforms.

scholarly journals RESEARCH AND IMPLEMENTATION OF INTELLIGENT INFORMATION TECHNOLOGY FOR TESTING THE NEURAL NETWORK OF THE DIAGNOSTIC SYSTEM OF TECHNICAL CONDITION OF BUILDINGS

2021 ◽  
pp. 76-83
Author(s):  
Alexander Terentyev ◽  
Yevhenii Gorbatyuk ◽  
Olena Dolya ◽  
Olha Serpinska ◽  
Mariia Liashchenko
Keyword(s):  
Information Technology ◽  
Life Cycle ◽  
Diagnostic System ◽  
Technical Condition ◽  
Automated System ◽  
Building Structures ◽  
Measurement Systems ◽  
Determination Of Parameters ◽  
The Impact

The methodological bases of construction of information system of diagnostics of technical condition of constructions of buildings and constructions and substantiation of efficiency of technologies of instrumental definition of parameters of buildings, constructions at all stages of their life cycle which are considered from a position of strategic information management are offered; carried out, from the standpoint of a systematic approach, the formalization of the processes of wear of building structures, which allows the creation of an effective and reliable analytical apparatus for monitoring the technical condition and diagnosis of future conditions in the process of their reliable and safe operation; built, using the apparatus of fuzzy sets, models and methods of monitoring a certain technical condition of buildings; The information technology of the decision support system, which is based on powerful intellectualizing analytical tools that allow experts to make more plausible assessments and management decisions, has been further developed. Based on the results of studying scientific sources, conclusions were made about the absence or need to deepen the solutions to the following problems: establishing general principles for the formation of a system for diagnosing the technical condition of buildings at all stages of their life cycle; lack of methodology to substantiate the effectiveness of technologies and tools for instrumental determination of parameters of buildings, structures and building areas at all stages of the life cycle; adaptation of methods for determining organizational and technological indicators to calculate the effectiveness of measurement systems and technology of their application; determining the impact of organizational and technical indicators on the efficiency of measurement systems and technology of their application; determination of the duration and periodicity of instrumental inspections as part of the operating costs of measuring systems; establishment of necessary volumes of instrumental observations at operation of buildings and constructions of substantiation of expenses of time for performance of measuring works at all stages of a life cycle of construction objects; lack of a single methodology for creating an automated system for diagnosing the technical condition of buildings; lack of integrated models and methods of modeling diagnostic processes that would ensure the effective functioning of information technology diagnostics of technical condition of buildings and high accuracy of expert decisions on their condition and forecasting the main technical characteristics of their operation under external and internal environments; the lack of a single information database that would make it possible to compare the results of surveys, to observe the dynamics of aging of buildings, to systematize conclusions about their condition.

Efficiency of application of the phase-chronometric method and neurodiagnostics for monitoring the degradation of rolling bearings during operation

2020 ◽  
pp. 43-50
Author(s):  
A.S. Komshin ◽  
K.G. Potapov ◽  
V.I. Pronyakin ◽  
A.B. Syritskii
Keyword(s):  
Life Cycle ◽  
Wavelet Analysis ◽  
Metrological Support ◽  
Rolling Bearing ◽  
Technical Condition ◽  
Measurement Information ◽  
Rolling Bearings ◽  
Vibration Diagnostics ◽  
Bearing Life ◽  
Alternative Approach

The paper presents an alternative approach to metrological support and assessment of the technical condition of rolling bearings in operation. The analysis of existing approaches, including methods of vibration diagnostics, envelope analysis, wavelet analysis, etc. Considers the possibility of applying a phase-chronometric method for support on the basis of neurodiagnostics bearing life cycle on the basis of the unified format of measurement information. The possibility of diagnosing a rolling bearing when analyzing measurement information from the shaft and separator was evaluated.

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