Showing papers by "Ternopil Ivan Pul'uj National Technical University published in 2019"

Morphological Characteristics of Dimples of Ductile Fracture of VT23M Titanium Alloy and Identification of Dimples on Fractograms of Different Scale

Abstract: The authors developed a method for the automated detection and calculation of quantitative parameters of dimples of ductile fracture on the digital images of fracture surfaces obtained at different scales. The processing algorithm of fractographic images was proposed, which allowed high quality recognition of the shape and size of dimples to be achieved, taking into account the morphological features of their digital images. The developed method for identifying dimples of various physical and morphological characteristics was tested on the VT23M alloy. The test results showed that the method meets the quality requirements for the automated diagnostics of fracture mechanisms of titanium alloys.

Modeling computational fluid dynamics of multiphase flows in elbow and T-junction of the main gas pipeline

Abstract: The research was performed in order to obtain the physical picture of the movement of condensed droplets and solid particles in the flow of natural gas in elbows and T-junctions of the linear part of the main gas pipeline. 3D modeling of the elbow and T-junction was performed in the linear part of the gas main, in particular, in places where a complex movement of multiphase flows occurs and changes its direction. In these places also occur swirls, collisions of discrete phases in the pipeline wall, and erosive wear of the pipe wall. Based on Lagrangian approach (Discrete Phase Model – DPM), methods of computer modeling were developed to simulate multiphase flow movement in the elbow and T-junction of the linear part of the gas main using software package ANSYS Fluent R17.0 Academic. The mathematical model is based on solving the Navier–Stokes equations, and the equations of continuity and discrete phase movement closed with Launder–Sharma (k–e) two-parameter turbulence model with appropriate initial and boundary conditions. In T-junction, we simulated gas movement in the run-pipe, and the passage of the part of flow into the branch. The simulation results were visualized in postprocessor ANSYS Fluent R17.0 Academic and ANSYS CFD-Post R17.0 Academic by building trajectories of the motion of condensed droplets and solid particles in the elbow and T-junction of the linear part of the gas main in the flow of natural gas. The trajectories were painted in colors that match the velocity and diameter of droplets and particles according to the scale of values. After studying the trajectories of discrete phases, the locations of their heavy collision with the pipeline walls were found, as well as the places of turbulence of condensed droplets and solid particles. The velocity of liquid and solid particles was determined, and the impact angles, diameters of condensed droplets and solid particles in the place of collision were found. Such results provide possibilities for a full and comprehensive investigation of erosive wear of the elbow and T-junction of the linear part of the gas main and adjacent sections of the pipeline, and for the assessment of their strength and residual life.

Determination of crack opening displacement and critical load parameter within a cohesive zone model

Abstract: A semi-analytical approach for investigation of the stress and strain state of a cracked body is presented. A cohesive zone model is used to take into account the failure zones which are formed in front of the crack tip. It is proposed to satisfy the crack smooth closure condition approximately. It allows to get rid of solving nonlinear equations for the cohesive lengths. An effective algorithm is developed to find solutions for the uniform traction–separation law. The algorithm is based on the iterative procedure of determination of contact stresses between crack faces, so the possible contact interaction between crack faces can easily be taken into account. In the case of mixed mode cracks, multiple cohesive zone models are considered.

Influence of test temperature on impact toughness of X70 pipe steel welds

Abstract: Impact toughness of the base metal and welds of the pipe steel of the X70 strength class was investigated and high values were defined. It was particularly important that impact toughness of the weld at temperatures of -40 °C and -20 °C was identical to that of the base material. For specimens W1 and W2 cut from the heat zone of weld by different metods (milling (W1) and plasma method (W2)) at a temperature of -40 °C, it was 1.14 and 1.5 times lower than that of the base metal, respectively. The method of cutting the specimens (milling, or plasma cutting) did not affect the impact toughness of the pipe steel and its welds in the investigated temperature range.

Minimizing Losses During Natural Gas Transportation

Abstract: Abstract The processes of supplying natural gas are accompanied by significant losses. In this regard, the complex problem of minimizing losses and improving the efficiency of energy use is very relevant. Steel pipelines for transportation of oil and gas often cross the tracks or are located parallel to the lines of electric power transmission lines of alternating current. Most dangerous from the corrosive point of view of the combination of the chemical composition of the soil electrolyte and the vagal current density were established.

Researching of the concentration distribution of soluble layers when mixed in the weight condition

Abstract: The analytical and experimental analysis of the processes associated with the formation of structural systems, which includes adsorption, its main paths of formation, patterns of influence on the structure of the environment and its behavior at deformation influences is carried out. The ways of choosing the optimal variant of the adsorption diffusion process for providing the maximum or minimum value of parameters (criterion) are proposed. The physical essence of the relation of the length of the sorbent layer with the time of its protective action (number of bound substance) is considered, which allows to practically characterize the work of the sorbent layer under dynamic conditions. It is noted that the determination of dynamic combined power flow influences during the process of mixing of components plays an important role in the structure formation of the suspension and promotes the construction of calculations for the construction of mixing equipment. The obtained data give an answer a series of questions about the theory of adsorption and diffusion (adsorption actions of van der Walsh forces on surfaces) and the ability to regulate the effect of combined power flows directly affect these process transformations (concentrations). For a illustration and understanding of the general execution of research, depending on the method of applying force, the degree of its previous dispersion and its physical and mechanical properties, a scheme of causal relationships between components and parameters that determine the change in the structure of the components in mixing process on a new discrete machine. The principle of discrete-momentum mixing of components in the weight condition and mechanical influence of the formable working body is considered. Based on the process of mixing the components in the working chamber of the machine, a mathematical model is proposed.

Mechanical Characteristics and Wear Resistance of the Cladding Layers Obtained by Melting of Cored Wires with Simultaneous Vibration of Substrate

Abstract: Abstract A wear proof layer was obtained by applying vibration with a frequency of 100 Hz and amplitude of 0; 70; 300 μm to the cored wire of Fe-Cr-B-C doping system during welding. It was shown that horizontal vibration affects the grinding process of boride inclusions: their average diameter reduces from 175 to 5 μm, and the amount of (FeCr)2B plastic phases increases during the redistribution of phases. Wear resistance of the metal, which was deposited using horizontal vibration with an amplitude of 300 μm, increases by 2.3-2.5 times due to wear with the fixed and unfixed abrasive material, and by 2.8 times due to wear under impact loads. For restoration and strengthening of large-size parts, it is proposed to add Al-Mg powder (Al = 47 - 53 %, Mg = 53-47% wt. %) to the CW charge to increase wear resistance of the deposited metal of the Fe-Cr-B-C system. This contributes to the dispersion of the boride inclusions, the average diameter of which decreases from 70 to 5 μm. In the structure of the deposited metal of the Fe-Cr-B-C system, inclusions of the complex alloyed nitrides are extricated with an average size less than 1.0 μm. As a result, the average value of microhardness increases from 700 to 900 HV. Wear resistance of the deposited metal increases by 1.5 times due to wear with the fixed and unfixed abrasive material, and by 2.0 times due to wear under impact loads.

Methods and Means of Knowledge Elicitation in Chinese Image Medicine for Achieving the Tasks of Its Ontological Modeling

Abstract: The substantiation of a complex of methods and means of knowledge elicitation in Chinese Image Medicine (CIM) for the tasks of its ontological modeling in addition to the development of intellectualized information systems is the topical issue of the article. The methods of specific knowledge elicitation from the CIM experts has been defined in the research, the templates of questionnaires for a group survey have been developed as well, the axiomatic-deductive strategy of the structural and logical organization of the acquired knowledge has been used, according to this data a fragment of the diagnostic ontology of the CIM has been implemented.

Formation of microbial biofilms on stainless steel with different surface roughness

Abstract: The physical essence of the formation and influence of bacteria on the surface of technological equipment in the dairy industry is considered as an essential factor leading to contamination of dairy products and is a major hygienic problem. The ability of microorganisms on the surfaces of technological equipment to form biofilm forms and requirements for steel grade, relief, and its roughness were analysed. The effect of surface roughness on promoting or preventing adhesion and reproduction of biofilm forms of bacteria, which reduce the efficiency of sanitary processing of dairy equipment and thereby increase the microbial contamination of dairy products with shortened shelf life, is substantiated. Research about the process of bacterial adhesion to the surface of metals with different roughness depending on the size and shape is presented. It is found that on the surface of stainless steel with roughness 2.687 ±0.014 micron film formation process in Escherichia coli and Staphylococcus aureus are similar from 3 to 24 hours and does not depend on the size of the bacteria, and accordingly allows us to argue that rod-shaped and coccid bacteria attach freely in the hollows of the roughness are the beginning of the process of the first stage of biofilm formation. It is found that on the surface of stainless steel with roughness 0.95 ±0.092 micron film formation process in S. aureus is more intense than in E. coli. Thus, within 3 hours of incubation, the density of biofilms formed S. aureus was 1.2 times bigger than biofilms E. coli, by the next 15 hours of incubation formed biofilms S. aureus were, on average, 1.3 times denser. It is established that S. aureus due to its spherical shape is able to fit in the hollows of the roughness 0.95 ±0.092 μm and faster to adhere to the surface at the same time. E. coli, due to its rod-like shape, with such surface roughness, can adhere to the cavities only over its entire length. It is proved that by surface roughness 0.63 ±0.087 μm film intensity S. aureus was, on average, 1.4 times faster than E. coli, for roughness 0.16 ±0.018 micron film formation process took place equally for S. aureus and E. coli, but biofilms were lower in density than those formed on roughness 0.63 ±0.087 micron. Studies suggest that the use of equipment in the dairy industry with a roughness of less than 0.5 microns will reduce the attachment of microorganisms to the surface and reduce the contamination of dairy products.

Data Procesing Problem at Remote Measurements of Parabolic Antenna Dimensions

Abstract: A peculiarities of geometric dimension and positions measurement with non-contact technique are presented. An order and accuracy of computational procedures at automatic data processing are presented.

Information Support for the Fractal Antennas Construction

Abstract: An information support for fractal antennas constraction in the shape of different iterations Koch curve and Sierpinski carpet are presented. Material presented can be used for fractal antennas production by wire technology or by typing on a dielectric basis.

Variation of Relief Topography and Hardness of Surface Layers of Materials Due to Impact-Oscillatory Loading

Abstract: It was shown previously that cyclic loading can be used to extend the fatigue life of sheet plastic materials subjected to the preliminary impact-oscillatory loading. This type of loading causes dynamic non-equilibrium processes (DNP) in materials, which lead to the formation of dissipative structures in materials and on their surface. The density of these dissipative structures is less than that of the base metal. In this paper, the results of investigations into the relief and hardness of surface layers modified by impact-oscillatory loading are analyzed on the example of five structural materials. The signs of a regular, orderly system of microextrusions formed on flat surfaces of all materials due to DNP are considered along with the alignment of roughness parameters Rz and Ra of relief profiles. The effect of impact-oscillatory loading is one of the main causes that lead to the extension of the fatigue life of materials.

Axiomatic-deductive strategy for it discipline content formation

Abstract: The paper presents the axiomatic-deductive strategy of organizing the content of an academic discipline with the help of ontological approach in the e-learning systems in the field of information technologies. The authors have taken into account that the necessary property of the system of axiomatic statements is their consistency. On the basis of axiomatic-deductive strategy, new approaches to the formation of the discipline content are proposed. It is proved that the system of true statements of an academic discipline is based on its terminology-conceptual apparatus, in particular, axiomatic statements. The developed mathematical structures that describe the axiomatic-deductive substrategy of the organization of the academic discipline general statements and the taxonomically oriented substrategy of the deployment of the academic discipline content are presented in the article. This ensures the transition from the content form of representation of the set of statements of the academic discipline to its presentation by means of artificial languages of mathematical logic. The use of descriptive logic ensures the formalization of the procedure for displaying an axiomatic informal system in an axiomatic formal system. The mathematical structures describe and detail the abstract logical-semantic core of the academic discipline in the form of a group of axiomatic systems. It is noted that the basic core of the content of academic discipline contains its basic concepts and judgments. This ensures a strictly logical transition from abstract general concepts and statements to the concepts and assertions of the lower level of universality and abstraction. It is noted that in order to accommodate the content of an academic discipline is advisable to develop a taxonomically oriented sub-strategy based on the multiple application of operations of general concept division. The mathematical structures allow for analysis of a generalized structure of interactions between the verbal level of the description of the academic discipline subject area, the formal level of description of the subject area and the description of the subject area at the level of computer ontology, which is implemented through the formalization, interpretation, encoding and decoding in the computer-ontology development environment. As an example of the application of the proposed axiomatic-deductive strategy, the elements of the glossary and taxonomies of the concepts of the discipline "Computer Logic", which are embodied in the Protege environment with the help of OWL ontology description language have been developed.

Onto-oriented expert system for supporting diagnostic and therapeutic decisions in the field of Chinese image medicine

Abstract: The article is devoted to the development of onto-oriented decision-making support expert system for Chinese image medicine (CIM). The detailed structure of the diagnostic CIM ontology and its sub-ontology is presented: nosological ontology, topological diagnostic ontology and ontology of methods for obtaining sensory-image diagnostic information. The use of diagnostic ontology as the basis for modeling the semantic space of the CIM, the accumulation and use of this knowledge in the expert system for diagnostic and therapeutic decision-making support in CIM is substantiated; the scheme is developed and the algorithm of such an expert system is described.

The conceptual foundations of the axiomatic-deductive strategy of e-learning course knowledge organization with high semantic quality

Abstract: The article presents the conceptual foundations of the axiomatic-deductive strategy (ADS) organizing of e-learning course (ELC) knowledge and text, which satisfies the requirements for ELC semantic quality. The basic composition of the ADS of the educational content organizing is proposed, that contains its three substrategies, namely, the axiomatic-deductive substrategy (ADSS) of the ELC terminological-conceptual apparatus (TCA) organization, the ADSS of the ELC statements organization and the taxonomically oriented substrategy (TOS) of ELC content deployment. In the logical-semantic core (LSC) of the e-learning course semantic space (ELCSS) highlighted a metadisciplinary logic-semantic core (MDLSC), the actual abstract logic-semantic core (LSC) and the sets of partial logical-semantic areas of the ELCSS. All ELC knowledge is divided into two large groups: an axiomatic group of knowledge and an derivative group of knowledge. The ADS of organization of ELC knowledge and text provides the availability of a distinct, dense, adjusted composition of knowledge organizing about the ELC subject area.

Analysis of the insemination of the mesophilic and psychrotrophic microflora of frozen fish

Abstract: The article presents the results of research on the dehiscence of frozen fish with mesophilic and psychrotrophic microflora. Physico-chemical and organoleptic changes which appear in fish during refrigeration are connected with the life of the psychotropic group of microflora, which is more active than mesophilic. Fish are a nutrient medium for the development of microorganisms of all groups, due to its high nutritional and biological value, so the fish are perishable food products, the conditions and terms of their storage require appropriate temperature regimes to stop the development of microorganisms. The aim of the work was carrying out a comparative analysis of insemination of frozen fish with mesophilic and psychrotrophic microflora to make an amend to standards according to microbiological criteria. The microbial number in frozen fish samples was estimated with the temperature of (30 ± 1) ºC incubation of crops for 72 hours (mesophilic microflora) and incubation for 10 days (psychrotrophic microflora) with the temperature (6.5 ± 0.5) ºC. It was identified that there were taken the samples from frozen fish with a quantity of mesophilic bacteria to 102 CFU/g, 1.4-1.8 times (p <0.05) more psychotropic microorganisms. The researched samples with the number of mesophilic microorganisms from 103 to 104 CFU/g were contaminated with psychotropic microflora, which in 1.7-6.8 times (p <0.05) exceeded the content of the mesophilic microflora. With such amount of mesophilic microorganisms, on average of up to 25% of samples, this had a content of psychotrophs of more than 105 CFU/g of fish. According to the content of mesophilic bacteria the samples of frozen fish, which were mathed to a certain norm of 5 × 104 CFU/g, basically in the number of psychrotrophic microflora did not correspond to this indicator, and exceeded it 2 times or more. In the cold period of the year, 63.6 ± 2.1% of frozen fish samples were mesophilic bacteria containing less than 101 CFU/g. At the same time, samples with such content mesophilic bacteria in the warm period of the year was 9.0%, or 7.0 times (p <0.05) less. In addition, in the cold period of the year, only 9.0% of samples were detected, which, according to the content of mesophilic bacteria exceeded the maximum allowable level. At the same time, during the warm period, the number of samples with an excess of mesophilic bacteria content was 27.3 ± 0.3%. Practically the same pattern was observed regarding the insemination of the psychrotrophic microflora in these periods of the year, which was characterized by the fact that in the warm period of the year, frozen fish contains a large number of psychrotrophic microorganisms. Consequently, the results of studies on the amount of microflora in the warm period of the year established 3,0 times (p <0,05) more samples of frozen fish, which, according to the content of mesophilic bacteria, exceeded the maximum permissible level compared with the cold period of the year. It was established that samples of frozen fish containing mesophilic microorganisms less than 101 CFU/g were most unevenly contaminated with psychrotrophic microflora. Among these samples, only 30.1 ± 1.4% were with the number of psychrotrophic microflora less than 101 CFU/g, at the same time, 60.0 ± 0.5% of the samples were contaminated with a psychrotrophic microflora of 101 to 105 CFU/g and 10, 0 ± 0.2% over 105 CFU/g. In the study of frozen fish samples with the number of mesophilic bacteria from 101 to 102 CFU/g revealed a coincidence in the content of psychrotrophs in only 16,7 ± 0,3% of samples, and 33,3 ± 0,3% of fish samples were with the content of psychrotrophic microflora from 102 to 103 CFU/g and 103 to 104 CFU/g and 16.7 ± 0.3% were contaminated with psychrotrophy more than 104 CFU/g. It was established that samples of frozen fish containing mesophilic microorganisms less than 101 CFU/g were most unevenly contaminated with psychrotrophic microflora. Among these samples, only 30.1 ± 1.4% were with the number of psychrotrophic microflora less than 101 CFU/g, at the same time, 60.0 ± 0.5% of the samples were contaminated with a psychrotrophic microflora of 101 to 105 CFU/g and 10, 0 ± 0.2% over 105 CFU/g. In the study of frozen fish samples with the number of mesophilic bacteria from 101 to 102 CFU/g revealed a coincidence in the content of psychrotrophs in only 16,7 ± 0,3% of samples, and 33,3 ± 0,3% of fish samples were with the content of psychrotrophic microflora from 102 to 103 CFU/g and 103 to 104 CFU/g and 16.7 ± 0.3% were contaminated with psychrotrophy more than 104 CFU/g. It was found that that the psychrotrophic microflora of frozen fish is quantitatively predominantly content of mesophilic bacteria several orders of magnitude. During the warm period of the year, more samples of frozen fish were detected in 3,0 times (p <0,05), which, according to the content of mesophilic bacteria, exceeded the maximum permissible level in comparison in the cold period of the year. It was found that 92,6 ± 2,5% of frozen fish samples were in compliance with the requirements of DSTU 4868: 2007. The fish is frozen. At the same time, during the fish evaluation, the contents of the psychrotrophic microflora showed that samples exceeding 5 × 104 CFU/g was in 2.6 times (p <0.05) more than the mesophilic bacteria content. In future the generic and species composition of the psychrotrophic microflora of frozen fish will be studied and the fish evaluating criteria according to the psychrotrophs in order to make corrections according to the microbiological criteria. Key words: frozen fish, psychrotrophic microflora, mesophilic bacteria, contamination, microbial number.