Bulletin of Prydniprovs'ka State Academy of Civil Engeneering and Architecture

10-15

Authors: Bolshakov V. I., Glushkova D. B.

Purpose. The new methods of surface hardening and creation of special materials are appealed for problem solving of the increasing of exploitation characteristic of materials. Among them a special place is gas-thermal coating. They are used in the different branches of machine-building for protection of the surface of details and machine assemblies from abrasion wearout. In addition, these parts and components during operation can be restored by repeatedly re-coating, that significantly reduces the cost of repair of equipment, reduces the consumption of materials to manufacture new details. Purpose of the work is to establish the influence of the gas-thermal spraying on the hardness of surface coating and to determine the connection between microhardness and structural state. The results. The value of measurements of the microhardness of molybdenum and steel in the surface layer are consistent with character of structural components. The major characteristic of the deposited layer, determining the success work of the coating is its relationship with the substrate surface. Rapid crystallization under the pressure help to create of fine-grained structure. Scientific novelty. The mechanism of formation of the coating by sequentially packaging of greatly deformed particles and the formation of the layered structure are shown. High hardness of the particles of molybdenum of sprayed layer is stipulated by several factors: the ultrafine grain, hardening particles and change of their chemical composition, being created the conditions for senescence hardening. The hardness of steel parts is determined by micro dispersive carbides and hardening of austenite.

21-28

Authors: V. E. Vaganov

Problem statement Among the developed technologies metal-composites production,a special place takes powder metallurgy, having fundamental differences from conventionally used foundry technologies. The main advantages of this technology are: the possibility of sensetive control, the structure and phase composition of the starting components, and ultimately the possibility of obtaining of bulk material in nanostructured state with a minimum of processing steps. The potential reinforcers metals include micro and nano-sized oxides, carbides, nitrides, whiskers. The special position is occupied with carbon nanostructures (CNS): С60 fullerenes, single-layer and multi-layer nanotubes, onions (spherical "bulbs"), nano-diamonds and graphite,their properties are being intensively studied in recent years. These objects have a high thermal and electrical conductivity values, superelasticity, and have a strength approximate to the theoretical value, which can provide an obtaining composite nanomaterial with a unique set of physical and mechanical properties. In creation of a metal matrix composite nanomaterials (CM), reinforced by various CNS, a special attention should be given to mechanical activation processes (MA) already at the stage of preparation of the starting components affecting the structure, phase composition and properties of aluminum-matrix composites. Purpose. To investigate the influence of mechanical activation on the structure and phase composition of aluminum-matrix composites. Conclusion. The results of the study of the structure and phase composition of the initial and mechanically activated powders and bulk-modified metal-composites are shown, depending on the type and concentration of modifying varieties CNS, regimes of MA and parameters of compaction. The study is conducted of tribological properties of Al-CNS OF nanostructured materials.

36-43

Authors: N. L. Zotsenko, Yu. L. Vynnykov, V. L. Sedin

Problem statement. Ramming piles in punched holes (RPPH) differ of high degree of use of supporting capacity of base because of forming in it a compacted zone at the expense of displacement of soil in the volume rammer and compacted material of expansion. The method of their construction almost exclude excavation and formwork, reducing the consumption of concrete, metal, accelerates zero cycle compared to the foundations raised and excavation and immersion into the soil of precast elements. The expansion of the normative base, their design and construction should be for further implementation of of natural objects. The correctness of the geomechanical model of plane and spatial version of finite element method (FEM) should be proved for the calculation of cooperative work of RPPH as part of grillages with base. The most effective kinds of equipment and technological schemes of construction of RPPH should be noticed. Conclusions. The paper presents the main regulations on the design and the arrangement RPPH, corresponding of construction norms of Ukraine. The results of experimental and theoretical studies conducted by the authors for over thirty years, and the experience of the use of these piles on the objects of civil engineering, industrial and agricultural construction made their base. The use of the elastoplastic model with the criterion of Mohr-Coulomb strength for designing of the system "grillage -RPPH- soil" was substantiated. The designing in plane and spatial problems of FEM is proved that in the distance between the axes of adjacent piles up to five diameters is a correct choice of a flat version and simplifying of calculating scheme to the conventional strip foundation. An improved. The method of calculating of RPPH as part of grillages ribbon, where as the width of the foundation was taken a diameter of the broadening of the pile, and the depth of its inception corresponds to the bottom of it. The supporting layer of base under the foundation consist of upper zone, of sufficient sealing and a RPPH in geotechnical practice. The purpose is improvement of the methods of design and construction of RPPH. It should be improved the method of calculating the sediment of RPPH as part of grillages, considering the interaction of zones of influence of the piles. The most reliable way of solving this problem is a comparison of the calculated and measured of sinking lower of natural soil.

54-60

Authors: I. I. Zaiats

Problem statement. Technical and economic indexes of projects of construction of high-rise multifunctional complexes, namely: the duration of construction works and the cost of building products depends on the technology of construction works and method of construction organization, and on their choice influence the architectural and design, constructional and engineering made decisions. Purpose. To reveal the regularity of influence of organizational and technological factors on the duration of construction of high-rise multifunctional complexes in the conditions of dense city building. Conclusion. To reveal the regularity of the influence of organizational and technological factors (the height, the factor complexity of design of project and and estimate documentation, factor of complexity of construction works, the factor of complexity of control of investment and construction project, economy factor, comfort factor, factor of technology of projected solutions) for the duration of the construction of high-rise multifunctional complexes (depending on their height: from73,5 m to100 m inclusively; from100 m to200 m inclusively ) allow us to quantitatively assess their influence and can be used in the development of the methodology of substantiation of the expediency and effectiveness of the realization of projects of high-rise construction in condition of compacted urban development, based on the consideration of the influence of organizational and technological aspects.

68-75

Authors: V. N. Derevianko, A. A. Maksimenko, A. Biegun, H. Hryshko

Problem statement. In activating MgO by electrolyte salts, as a result of formation of non water-resist magnesium silicate hydrate are obtained the durable cement stone having the low water-resist. I. P. Vyrodov considers [9; 5], that magnesia cement curing in mixing with sufficiently concentrated (C > 20 %) solutions MgCl2 is caused with the crystallization of oxyhydrochloride composition: 3MgO∙MgCl2∙11Н2О, 5MgO∙MgCl2∙13Н2О and 7MgO∙MgCl2∙15Н2О. In the lower concentration parts of MgCl2 solution is formed a transitional compound of Mg[(OH)nCl2-n] with isomorphous Mg(OH)2 structure. At very low Cl concentration only Mg(OH)2 is practically formed. Purpose. The Formation of water-resist magnesium silicate hydrates for obtaining of fast curing and solid structure of the magnesia stone. Conclusion. The dependence of the formation of the magnesia stone from the ratio (MgO/MgCl2) of the magnesia cement (MgO) and the magnesium chloride solution (MgCl2) of different density has been identified in order to obtain the best content for oxyhydrochloride 3MgO·MgCl2·11Н2О, 5MgO·MgCl2·13Н2О and magnesium hydroxide (Mg(OH)2). In putting into the system MgO∙–∙H2О of the silicic acid or fine ground quartz grains with size of less than 20 – 30 microns, over 1 month for the magnesium silicate hydrates formation is needed, where from 2 to 5 % of the total number of newgrowths are created. The study is proved by the expert opinion, that magnesium silicate hydrates do not have binding properties, unlike calcium silicate hydrates, and the main role in the system curing is played with the Mg(OH)2 gel recrystallization, which provides the acceptable stone strength (R ≈ 30MPa) in a few years. It has been also established, that in mixing of cement with low concentration MgO solutions of less than 1,5 mol/l (or 13% 1,1g/sm3), the final product in the stone structure is Mg(OH)2. With increasing the sealer (MgCl2 solution) there is formed by turn in structure 3MgO·MgCl2·11Н2О and 5MgО·MgCl2·13H2О. The increase of the sealer concentration to more than 2,5 mol/l (C = 21 % or 1,18 g/sm3) leads to the formation of system MgО∙–∙MgCl2∙–∙H2О consisting of a three phase of pentoxyhydrochloride (5MgО·MgCl2·13H2О), trioxyhydrochloride (3MgO·MgCl2·11Н2О), and remains of non-reacted Mg(OH)2. It has shown in the result of testing that the samples produced from the mixture of cement and bishofit with ρ = 1,28 g/sm3 have the bigges strength.