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

26-30

Authors: V. I. Bolshakov, D. V. Glushkova, Ye. M. Voronova

Problem formulation. Piston rings are subject to wear while in operation. Insufficient wear resistance of materials limits the growth of machines productivity as well as the terms of their exploitation. The required complex of properties of piston rings made of cast iron cannot be always reached by applying traditional methods of heat treatment or chemical heat treatment processing. Thus, application of traditional borating methods associated with diffusion of boron into the solid phase leads to the formation of the working layer exhibiting high brittleness. Therefore, the problem of increasing the wear resistance of piston rings without embrittlement is challenging. The use oflaser heating during borating provides the formation of a new layer with special properties. However, the optimum properties can be achieved only after determining the relationship between the parameters of running a process and the depth of the borated layer. Goal of research. To determine the influence of laser heating parameters on the depth of the borated layer, as the properties of piston rings depend on the depth of the latter. Conclusions. Increase in the speed of displacing parts during laser heating reduces the depth of the borated layer, and increase of the spot diameter enhances the depth of the layer. The phases and structural components of the borated layer were interpreted by means of X-ray and metallographic methods. The results of investigations can be applied to other machine parts, which are subject to intensive wear.

38-41

Authors: V. Volchuk

Problem statement. Each scale level detectesthe new features of the structure of the material describing of it quality. For example, features of the grain structure are revealed in different kind of steel on microstruc ture level, and its parameters greatly influences on the strength properties of the metal. Thus, to select the scale of representation of a fractal object, for instance the elements of structure of roll iron or steel is necessary to determine the interval (1), where observed its self-similarity, and on this interval should be selected the scale, the use of which will allow him to choose adequate fractal dimension. For optimal scale structure of repose is taken one in which at least two adjacent points of the series (2), the fractal dimension is minimal differences between them. This is explained by the fact that this is best observed property of self-similarity structure. An example of the selection of the scale representation of the structure of cast iron rolls execution of SPHN (a) and execution SSHN (b) is shown on interval of increases in the range of ´ 100 to ´ 1000 with a predetermined pitch Dl = 100. The implementation of this phase of research allowed to determine experimentally the optimal scale of representation of structure of iron roll with increasing ´200 for multifractal analysis of its elements: inclusion of the plate and nodular graphit, carbides. Purpose To determine the optimal scale structure representation for iron roll multifractal analysis of its elements: inclusion of the plate and nodular carbides. Conclusion. It was found that the fractal dimension of the structural elements of the test ranged from experimental error 5÷7%, which testifies to the universality of this assessment, and therefore reliability and economic benefits, in terms of the equipping of laboratories expensive metallurgical microscopes with higher resolution.

52-60

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

Problem statement. Phosphogypsum is a very pure raw material [16] with a negative, from a technical point of view, elongated shape of calcium dihydrate crystals (due to the formation conditions), which remains the same after both dehydration in dry air and grinding, this makes technical difficulties relating to further processing of the product into a binder, consequently, water resistance and plasticity of magnesium solutions can be improved by adding primary and secondary phosphates without strength reduction. Famous experts on phosphogypsum Yu. P. Meshcheryakov and N. A. Kolev [8] found, that when adding phosphogypsum instead of natural gypsum during grinding of Portland cement, which is intended to control the setting time of the mixture, there occurred reduction in the initial setting time from 1 h 55 min up to 1 h 36 min (when adding 4 % agent), and the final setting time was decreased from 6 h 15 min up to 6 min. After grinding of phosphogypsum, there appeared a fresh surface, on which the electron emission phenomenon occurs, however, not the entire surface emits, but only the active centres, where field strength reaches 108 V/cm. The positively charged active centres have low CaSO4 2H2O concentration on their surface. Purpose. Specifying the optimal amount of phosphogypsum and ferrous sulphate solution added, studying their impact on the curing mechanism of the magnesia-bishofit composition. Conclusion. To increase the sulphate compound, required for the crystallinity [10] reduction and magnesia stone sealing [4], the ferrous sulphate solution have been added to the composition formulation, ferrous sulphate anions immediately polarize free calcium ions with the formation of CaSO4∙2H2O. P. P. Budkov's experiments [8] prove that the larger the magnesia cement-to-sulphate stone ratio, the lower the setting time of the composition, and the higher the tensile strength of the stone. Moreover, V. V. Shchelyaghin [15] recommended adding ferrous sulphate, formed in tanks for black metal etching with sulphuric acid, to the magnesia-bishofit composition. The scholar replaced up to 50 % of the magnesium chloride solution MgCl2 for the ferrous sulphate solution FeSО4·7H2О, thus improving water resistance of the stone. He also established that ferrous sulphate accelerates setting time of magnesia mixtures and reduces the chance of efflorescence formation on the product. Therefore, based on the results of the research conducted, 5 % of phosphogypsum is the optimal amount to be added to the magnesia-bishofit composition. The additive reduces the setting time of the mixture and increases the strength of the stone, and together with the 5 % ferrous sulphate additive it enables formation of a sealing newgrowth CaSO4 2H2O. Clogging of pores with dehydrite particles and bonding flakes of Fe(OH)3 improves deformation phenomena during curing of the specimens, reduces their water absorption capacity and increases strength.

67-72

Authors: O. N. Shibko

Problem statement. Modern information technology is developing in a globalized economy, the formation of a common information space and as a result, changes relation to the information of participants of market relations. New conditions lead to an increase in the number of parties involved in the creation and use of information, to the increase of the volume of information and the frequency of its use, making the actual task of the operational management of the activity of the staff of the various organizations. Information support includes normative and reference data; the necessary classificatory of technical and economic information; arrays of data needed to solve problems; standardized documents. The main purpose of providing information is timely to give management system, accurate information in particular, decision-makers, necessary and sufficient for making optimal or near-management decisions. Purpose of the article: to study and to improve methods of the design of information support (IS) and of implemented solutions for the objects, the arrangement and forms of organization of the information circulating in the automated control system when it is functioning as an object of a certain structure. Conclusion. Thus, the choice of a method of designing information support determines by the necessity of the development of the mathematical apparatus, providing the formal means of work with information resources. The mathematical apparatus and methods should provide the formulated tasks of designing information support.

81-85

Authors: A. I. Kosolap, A. A. Dovgopola

The problem of optimization of the structure of systems redundancy elements. Such problems arise in the design of complex systems. To improve the reliability of operation of such systems of its elements are duplicated. This increases system cost and improves its reliability. When optimizing these systems is maximized probability of failure of the entire system while limiting its cost or the cost is minimized for a given probability of failure-free operation. A mathematical model of the problem is a discrete backup multiextremal. To search for the global extremum of currently used methods of Lagrange multipliers, coordinate descent, dynamic programming, random search. These methods guarantee a just and local solutions are used in the backup tasks of small dimension. In the work for solving redundancy uses a new method for accurate quadratic regularization. This method allows you to convert the original discrete problem to the maximization of multi vector norm on a convex set. This means that the diversity of the tasks given to the problem of redundancy maximize vector norm on a convex set. To solve the problem, a reformed straight- dual interior point methods. Currently, it is the best method for local optimization of nonlinear problems. Transformed the task includes a new auxiliary variable, which is determined by dichotomy. There have been numerous comparative numerical experiments in problems with the number of redundant subsystems to one hundred. These experiments confirm the effectiveness of the method of precise quadratic regularization for solving problems of redundancy.