scholarly journals Kinetics of damages accumulation and criterion of the limit state of construction materials

2018 ◽  
Vol 82 (1) ◽  
pp. 131-138
Author(s):  
D. Pham ◽  
A. Babak ◽  
V. Koval
Keyword(s):  
Limit State ◽  
Construction Materials ◽  
Kinetics Of

scholarly journals Justification of risk-based approach of operation of mobile agricultural equipment on example of details of separate units of tractors

2020 ◽  
Vol 11 (3) ◽  
pp. 173-179
Author(s):  
O. V. Voynalovich ◽  
◽  
S. M. Holopura ◽  
Keyword(s):  
Service Life ◽  
High Reliability ◽  
Limit State ◽  
Construction Materials ◽  
Flaw Detector ◽  
Agricultural Machinery ◽  
Acceptable Risk ◽  
Agricultural Equipment ◽  
Power Load ◽  
Kinetics Of

It is shown that in order to justify the extension of the service life of the machine beyond the resource set by the developers, it is necessary to focus on the allowable risks of accidents that can lead to accidents. After all, today for mobile agricultural machinery, the operation of which is associated with high-risk work, the concept of acceptable (acceptable) risk is not used, which does not allow to assess the danger of being on fields, farms and roads without machinery, with exhaustion of installed resources. The purpose of researches is to justify the permissible risk of exploitation of mobile agricultural machinery, in array of details and elements of constructions which have accumulated defects (damage). This paper analyzes the kinetics of accumulation of operational defects in the array of parts of individual components (systems) of tractors. MTZ-80 tractors (82) were chosen as the object of research, as one of the most common in Ukraine. To detect cracks, a developed eddy current flaw detector was used, the sensitivity of which allowed to find cracks several millimeters or larger in length without preparing the surface of the controlled parts. It is shown that the kinetic dependences of the accumulation of operational defects in the parts of tractor units in the analyzed range of service life are monotonically increasing, which can be described by exponential functions with a sufficiently high reliability. It is noted that the obtained dependences are similar to the kinetic dependences of the accumulation of static and dynamic (fatigue) damage obtained as a result of laboratory tests of samples of construction materials, which allows to use approaches to the criteria of the limit state of laboratory samples due to the power load to establish the boundary life of mobile agricultural machinery. However, the kinetics of the intensity of the occurrence of operational cracks in the array of tractor parts is not monotonous and has a maximum in the range of about 11-13 years of operation. This service life can be used as a criterion to stop the operation of the tractor, to carry out defectoscopy of parts and to replace defective parts. With such a long service life of the tractor, there is the greatest probability of sudden destruction of the tractor components and the creation of emergencies.

scholarly journals Thermal Stability and Kinetics of Formation of Magnesium Oxychloride Phase 3Mg(OH)2∙MgCl2∙8H2O

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 767 ◽  
Author(s):  
Michal Lojka ◽  
Ondřej Jankovský ◽  
Adéla Jiříčková ◽  
Anna-Marie Lauermannová ◽  
Filip Antončík ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Construction Materials ◽  
Simultaneous Thermal Analysis ◽  
Rietveld Analysis ◽  
X Ray Diffraction ◽  
Sustainable Building ◽  
X Ray ◽  
Kinetics Of Formation ◽  
Magnesium Oxychloride ◽  
Kinetics Of

In this paper, magnesium oxychloride cement with stoichiometry 3Mg(OH)2∙MgCl2∙8H2O (MOC 3-1-8) was prepared and characterized. The phase composition and kinetics of formation were studied by X-ray diffraction (XRD) and Rietveld analysis of obtained diffractograms. The chemical composition was analyzed using X-ray fluorescence (XRF) and energy dispersive spectroscopy (EDS). Furthermore, scanning electron microscopy (SEM) was used to study morphology, and Fourier Transform Infrared (FT-IR) spectroscopy was also used for the analysis of the prepared sample. In addition, thermal stability was tested using simultaneous thermal analysis (STA) combined with mass spectroscopy (MS). The obtained data gave evidence of the fast formation of MOC 3-1-8, which started to precipitate rapidly. As the length of the time of ripening increased, the amount of MgO decreased, while the amount of MOC 3-1-8 increased. The fast formation of the MOC 3-1-8 phase at an ambient temperature is important for its application in the production of low-energy construction materials, which corresponds with the challenges of a sustainable building industry.

scholarly journals Research on the Influence of Bed Joint Reinforcement on Strength and Deformability of Masonry Shear Walls

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2543 ◽  
Author(s):  
Jasiński
Keyword(s):  
Calcium Silicate ◽  
Limit State ◽  
Construction Materials ◽  
Shear Walls ◽  
Ultimate Limit State ◽  
Horizontal Shear ◽  
Wall Stiffness ◽  
The Impact ◽  
Steel Trusses ◽  
Ultimate Limit

The areas of Central and Eastern Europe and, thus, Poland are not exposed to the effects of seismic actions. Any possible tremors can be caused by coal or copper mining. Wind, rheological effects, the impact of other objects, or a nonuniform substrate are the predominant types of loading included in the calculations for stiffening walls. The majority of buildings in Poland, as in most other European countries, are low, medium-high brick buildings. Some traditional materials, like solid brick (> 10% of construction materials market) are still used, but autoclaved aerated concrete (AAC) and cement-sand calcium-silicate (Ca-Si) elements with thin joints are prevailing (> 70% of the market) on the Polish market. Adding reinforcement only to bed joints in a wall is a satisfactory solution (in addition to confining) for seismic actions occurring in Poland that improves ULS (ultimate limit state) and SLS (serviceability limit state). This paper presents results from our own tests on testing horizontal shear walls without reinforcement and with different types of reinforcement. This discussion includes 51 walls made of solid brick (CB) reinforced with steel bars and steel trusses and results from tests on 15 walls made of calcium-silicate (Ca-Si) and AAC masonry units reinforced with steel trusses and plastic meshes. Taking into account our own tests and those conducted by other authors, empirical relationships were determined on the basis of more than 90 walls. They are applicable to the design and construction phases to determine the likely effect of reinforcements on cracking stress that damage shear deformation and wall stiffness.

scholarly journals A Comparative Study of Pre-Engineered and Conventional Multi-Span Industrial Building

2020 ◽  
Vol 10 (1) ◽  
pp. 59-67
Keyword(s):  
Construction Material ◽  
Limit State ◽  
Construction Materials ◽  
Steel Structure ◽  
Industrial Building ◽  
Modern World ◽  
Base Shear ◽  
Actual Structure ◽  
Analysis And Design ◽  
Building Inventory

Steel is one of the oldest construction materials and become a popular construction material in late seventeenth and eighteenth century. Environment friendly, rapid construction, easy availability and better fire rating are some of inherent advantages of steel construction. In current modern world, steel structure contributes a highest number of industrial buildings and sheds in the world building inventory. Pre-Engineered Building concept involves the steel building systems which are predesigned and prefabricated. This particular study includes the design of industrial storage structure which is situated in Mangalore. The actual structure is of pre-engineered structure of 90m width of three spans each span 30m width, and running 42m length and of eave height 6m with roof slope 1:10. The analysis and design is carried out by considering the live loads, dead loads, wind loads and earthquake load using relevant IS codes for the given PEB structure. The whole Pre-engineered building and Conventional steel structure is analyzed by using staad pro V8i SS6 software and designed by limit state method as per IS 800-2007. The moment, shear force and axial force decreases in PEB structure in various components as compared to CSB structure, due to increase in stiffness. Deformation decreases in PEB structure in various components as compared to CSB structure, due to increase in stiffness. Base shear and displacement decreases in PEB structure as compared to CSB structure, due to increase in stiffness. The percentage decrease in weight in PEB structure is 16.28% in comparison to CSB structure, hence cost of PEB structure reduces. Reduction in steel quantity reduces the dead load ultimately reduces the size of the foundation

scholarly journals Modeling the colloidal dispersions: flocculation kinetics though particle dynamics

2019 ◽  
Vol 97 ◽  
pp. 02033
Author(s):  
Vladimir Smirnov ◽  
Evgenij Korolev
Keyword(s):  
Building Materials ◽  
Materials Science ◽  
Numerical Study ◽  
Construction Materials ◽  
Colloidal Dispersions ◽  
Number Density ◽  
Particle Aggregates ◽  
Kinetics Of ◽  
Flocculation Process ◽  
Coagulation Kernel

The problem of stability of colloids recently begins to attract extra attention in construction materials science. This is due to numerous attempts to employ different kind of nanoscale modifiers for production of building materials with enhanced operational properties. Problems of stability and coagulation in colloidal dispersions are studied for several decades, and numerous results were already obtained within framework of Smoluchowski coagulation theory. In the present work we have performed numerical study of the flocculation process and compared the results with well-known ones. It was shown that even for complex pairwise potential the kinetics of number density for isolated particles is not very different from the kinetics which corresponds to constant coagulation kernel. However, for number density of many-particle aggregates we have observed number of peculiarities, including semi-periodic behavior.

scholarly journals ESTIMATION OF DURABILITY AND DEFORMATION PROPERTIES OF CONCRETE AND REINFORCED CONCRETE

2021 ◽  
pp. 49-58
Author(s):  
S.І. Rogovyi ◽  
◽  
L.A. Tsyhanenko ◽  
N.M. Sribniak ◽  
V.M. Lutskovskyi ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Construction Material ◽  
Limit State ◽  
Construction Materials ◽  
Reinforce Concrete ◽  
The State ◽  
General View ◽  
Analytic Model ◽  
Structural Elements ◽  
Deformation Properties

Abstract. The research deals with the main directions of the Reinforced Concrete Theory current improvement on the basis of its incisive analysis. As leading direction in solving such a problem, the modern, well known deformational analytic model is examined. It is implemented on the base of complete experimental diagrams of deformation of different structural materials. The offered methods for improvement of such model suggest the creation and use of the transformed diagrams of deformation of concrete, reinforced elements as well as those structural elements on their basis. The modelling of these diagrams is envisaged on the basis of experimental dependences of complete diagrams for deformation of construction materials taking into account the influence on them of different physical, technological, dynamic and other factors. The general view of the said diagram will be realized by two its branches – ascending and descending, designed by different parametric (key) points. The special interest on the modern stage in development of deformational analytic model presents the design of descending branch of complete diagram on the state of construction material that is recorded by different parametric points. One of the main tasks in designing of such points is standardization of experimental methods in determining the critical values of relative power deformations in the top of a diagram, that correspond to the limit straining of construction material, that does not exceed the board of its durability at a compression. The descending branch of complete diagrams must be designed on condition that the deformation of concrete became consistently waning. The transitional point of this state in sustained and increasing deformation it to be considered as destruction start of material at intensively increasing destructive transformations of its structure. The straining of constructional material on such on-loading area of diagram can diminish to the level of postcritical values, beyond the durability range of stability at a compression, and to correspond to relative deformations in the limit state. Further reduction in tension to the concrete is representative at its dynamic deformation in terms of more intensive development of destructive transformations. Thus the level of relative deformations can increase to the maximally possible values, beyond which a concrete, as structural material, stops to comply with the necessary operating qualities. The long-term experience in initiation, perfection and development of theory of the reinforced concrete, as well as implementation of its modern deformational model of calculation show that there is a number of important vital problems which need to be examined and solved for today. Such problems in the outlined aspect are to be examined in two directions of researches. The first is an improvement of methodology of tests and standardization of methods in obtaining the complete experimental diagrams of the state and their parametrical points which allow to design dependence sb – εb (straining – deformation) with high authenticity by the analytical function for its implementation at the calculations of different structural elements; the second is an improvement of deformational calculation model with help of the transformed diagrams of deformation, as well as more precise definition of some pre-conditions and positions accepted in different existent standards for the calculation of concrete and reinforce-concrete constructions. The essence in solving of the above-said pressing issues set forth in this research.

Direct observations of radiation-enhanced transformations in glass

1983 ◽  
Vol 41 ◽  
pp. 354-355
Author(s):  
J. F. DeNatale ◽  
D. G. Howitt
Keyword(s):  
Glass Matrix ◽  
Diffusion Mechanism ◽  
Bubble Formation ◽  
Silicate Glasses ◽  
Phase Decomposition ◽  
Direct Observations ◽  
Thin Foils ◽  
Oxygen Bubble ◽  
Electron Energy Loss ◽  
Kinetics Of

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.

Irradiation behavior of pyrolytic silicon carbide

1983 ◽  
Vol 41 ◽  
pp. 72-73
Author(s):  
R. J. Lauf
Keyword(s):  
Silicon Carbide ◽  
Fission Products ◽  
Thermodynamics And Kinetics ◽  
Neutron Fluences ◽  
Fuel Particles ◽  
Sic Coatings ◽  
Irradiation Behavior ◽  
Kinetics Of ◽  
Htgr Fuel

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.

The Ordered Phase Formation in Ti-Al-Ga Alloys

1970 ◽  
Vol 28 ◽  
pp. 440-441
Author(s):  
Shiro Fujishiro ◽  
Harold L. Gegel
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Titanium Alloys ◽  
Growth Kinetics ◽  
Stoichiometric Composition ◽  
Good Potential ◽  
Alpha Titanium ◽  
Cold Rolled ◽  
Kinetics Of ◽  
Thermal Stability Of

Ordered-alpha titanium alloys having a DO19 type structure have good potential for high temperature (600°C) applications, due to the thermal stability of the ordered phase and the inherent resistance to recrystallization of these alloys. Five different Ti-Al-Ga alloys consisting of equal atomic percents of aluminum and gallium solute additions up to the stoichiometric composition, Ti3(Al, Ga), were used to study the growth kinetics of the ordered phase and the nature of its interface.The alloys were homogenized in the beta region in a vacuum of about 5×10-7 torr, furnace cooled; reheated in air to 50°C below the alpha transus for hot working. The alloys were subsequently acid cleaned, annealed in vacuo, and cold rolled to about. 050 inch prior to additional homogenization

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