Vol 25, No 1 (2023)

Introduction. In numerous experimental studies of metal cutting processes on metal-cutting equipment, the existence of some optimal processing mode is noted, which was most vividly formulated by A.D. Makarov in his point on the existence of an optimal cutting temperature (processing speed). Here, by the authors from Russia, the emphasis is on the description of the optimality of cutting processes related to the properties of the processed material and the properties of the tool used in this process. However, there is another opinion in the Western scientific literature, which is generally based on the regenerative nature of vibrations in cutting dynamics. Vibration regeneration is associated with the dynamics of the cutting process, which is significantly affected by a lagging argument reflecting the variability of the cut layer. The connection of these two approaches is seen through the analysis of the stability domain of the dynamic cutting system in the parameter space: cutting speeds and tool wear values. Subject. Based on this, the paper considers the question of the relationship between the optimal according to A.D. Makarov the processing mode and the dynamics of the cutting process, including the regeneration of tool vibrations during metal turning. To do this, two research hypotheses are formulated and numerical modeling is performed in order to determine its reliability. Purpose of the work: to consider the position of A.D. Makarov on the existence of an optimal cutting mode, from the point of view of the stability of the dynamics of metal turning. For this purpose, two hypotheses are put forward in the work to be analyzed. The paper investigates: a mathematical model describing the dynamics of vibration oscillations of the cutting wedge tip, taking into account the dynamics of the temperature formed in the contact zone and its influence on the forces that prevent the forming motions of the tool. Research methods: a series of field experiments was carried out on a metalworking equipment using the capabilities of the measuring stand STD.201-1, the purpose of which was to determine the effect of the thermal expansion of metals on the value of the buoyant force. Based on numerical simulation of the initial nonlinear mathematical models, as well as simulation of models linearized in the vicinity of the equilibrium point, an analysis of the stability of the cutting system with variations in the cutting speed and the amount of tool wear along the flank is conducted. The results of the work. The results of field experiments are presented, which showed a significant linear increase in the force pushing out the tool with an increase in temperature in the contact zone of the tool and the workpiece. The results of simulation of the state and the corresponding phase trajectories when the cutting wedge is embedded in the workpiece, as well as the forces decomposed along the axis of deformation of the tool, are presented. The results of modeling the Mikhailov vector hodograph for a linearized model of the dynamics of the cutting process are presented. Conclusions: The research results have shown that only the second hypothesis put forward by the authors makes it possible to adequately interpret the point put forward by A.D. Makarov. The main addition to the description of the point of A.D. Makarov, the authors consider it necessary to take into account changes in the pushing force with an increase in the temperature of the contact zone of the tool and the workpiece.

Introduction. In real production conditions, the technological modes recommended in the scientific literature do not reflect the declared qualities, due to the fact that it does not take into account many factors inherent in the process of finishing grinding, for example, its stochastic nature, changes in its dynamic properties, an increase in mutual vibrations of the tool and the workpiece that appear due to changes in the state of the technological system, for example, an increase in vibrations machine tool due to uneven tool wear, etc. All previously developed models have a limited scope of application, it does not take into account the fact that the appearance of vibrations leads to fluctuations in the depth of grinding, with accidental contact of grains with the material being processed, where one group of grains cuts off the material, the other gets into the trace of scratches left by previous grains, etc. This leads to changes in the values of material removal, surface roughness and other parameters of the technological system, which directly affects the accuracy of processing and the quality of the machined surfaces. The purpose of the work is to develop mathematical models that establish the relationship between the processing modes and the current parameters of the contact zone during the fine grinding of pinholes, taking into account the mutual vibrations of the tool and the workpiece. The research methods are mathematical simulation using the basic provisions of the theory of abrasive-diamond processing. Results and discussion. The interrelations between the cutting modes and the current input parameters of the contact zone when grinding pinholes are established, taking into account the mutual vibrations of the tool and the workpiece, which make it possible to determine the parameters of the system at the output to avoid cost losses, including reducing the number of defective products and time costs. Non-stationary mathematical dependences are constructed that allow determining the cutting modes during the implementation of the grinding cycle, taking into account the magnitude of relative vibrations and the initial phase. It is established that instead of a steady process, harmonic oscillations are observed caused by deviations in the shape of the circle, the intensity of tool wear and other factors, all of the above has a significant impact on the quality of the machined surface. The obtained models are universal for various characteristics of the tool, however, for a more adequate description of the process, mathematical dependencies are needed that take into account the wear of the tool on various binders, which is the task of further research.

Introduction. Trends in the development and application of modern machine-building systems somehow create the problem of analysis and choice in the presence of alternative objects, or with a large number of comparison criteria - indicators of the effectiveness of objects or systems. The main difficulties in optimizing the solution for designing production systems depend on complex technological problems: a large number of influencing factors and the absence of patterns. The choice of effective objects and systems is often a complex and multi-criteria process that requires a lot of time and, as a result, reduces the efficiency of the organization of production preparation. In this regard, for the preparation and adoption of technical and economic decisions of various complexity in production conditions, a systematic approach is required using the most rational forms and methods of organizing production. The purpose of the work: to create a generalized methodology for the criteria analysis of multivariant systems. The methods of investigation. A methodology is proposed aimed at improving the efficiency of the organization of pre-production due to a reasonable choice from a large number of options. The choice of a rational solution option is based on the ranking of indicators by priority at the time of making a reasonable decision in a specific situation and the type of object and system under consideration. Indicators can be variable, taking into account the specifics of production. Results and Discussion. A comparative analysis of the process of edge cutting machining of the STEF-1 fiber-glass polymer composite material with an interlocking side mill carrying various insert materials is conducted as an example of the practical application of the proposed methodology. As comparison parameters, the period of technological tool life, cutting performance and reduced costs in the implementation of cutting are taken. According to the results of a comparative multi-criteria analysis carried out according to the presented method, it follows that the priority in the system under consideration with the specified parameters for the implementation of the technology is the tool equipped with WC–3Co alloy inserts, which has the highest value of the weight criteria coefficient. According to the results of the analysis, a tool equipped with WC–2TaC–6Co alloy inserts is close in rationality, which allows recommending it as an analogue when choosing. The scope of the proposed application of the methodology is seen if it is necessary to analyze complex multivariant systems/objects. The objects/systems can be both variants of scientific solutions under various conditions of comparability, as well as design, technological solutions, structural and instrumental materials at the selection stage in the design and technological preparation of production, variants of the system implementation algorithm. The comparison parameters can be physical, mechanical, technological, operational properties; technical, economic and quality indicators; specific characteristics and parameters. The proposed technique will reduce the time for making new decisions under varying production conditions. The use of the methodology with known and well-defined parameters characterizing multivariant systems makes it possible to algorithmize, and subsequently automate, the process of organizational and technological preparation of production.

Introduction. Additive technologies make it possible to curb material expenses by reducing allowances for the final dimensional machining of workpieces. For such expensive materials as copper and copper alloys, this method is considerably attractive from a perspective of increasing resource efficiency in production. The operational properties of the C65500 alloy manufactured using additive technologies have not been fully studied and require additional research. The aim of the work is to study the structural and phase state, mechanical and operational properties of C65500 bronze specimens printed using electron beam additive manufacturing technology. In the work, specimens made of C65500 wire with different heat input values are studied, some of which were subjected to thermal treatment and mechanical processing, as well as specimens, manufactured using multi-wire technology. The work uses such research methods as the study of corrosion resistance of bronze specimens using a potentiostat, confocal laser scanning microscopy, friction tests and X-ray phase analysis. Results and discussion. Processing of specimens by plastic deformation (compression) and subsequent annealing leads to the most serious structural changes. Based on X-ray phase analysis, it is found that higher silicon content is observed in the case of the addition of silumins to bronze. The study of mechanical properties shows that the specimens, printed using multi-wire technology, have the highest strength properties. During tribological testing, fluctuations in the value of the friction coefficient are revealed, due to the scheme of the experiment and the combined adhesive-oxidative mechanism of specimens’; wear. The addition of 10 wt.% aluminum filament to bronze in the additive manufacturing process is an effective means for increasing the resistance of the material to electrochemical corrosion and increasing its wear resistance.