No 4 (2020)

In current conditions, the necessity to produce many high-precision tooling and machines has increased many times over. That is why the improvement of such products manufacture becomes of paramount importance due to the increasing requirements imposed on them. The existing approaches to ensuring the quality and accuracy of high-precision products are not universal and not always can be implemented when producing high-precision goods. For a comprehensive solution to this problem, the authors proposed using an integrated approach - the complex of formalized design procedures of the system for accounting of the requirements to the high-precision products assembly when designing the manufacturing methods of machining. However, for the establishment of relations between the process design and designing preproduction of multi-product manufacture, the transition to the assessment of the production manufacturability of goods and deeper integration of this system into the structure of the system of automated sequencing of manufacturing methods, it is necessary to search for ways to improve the existing approaches of the developed system. The paper considered in detail the enlarged block of design procedures for the analysis of requirements to the assembly of high-precision products, since this stage is directly related to the designing preproduction, and the initial data obtained in the course of its implementation ensure the quality of choice of rational manufacturing methods of machining of parts. The authors propose the techniques to improve mathematical, methodological, and algorithmic support of this enlarged block implementation. The introduction of the proposed solutions will allow performing effectively the design dimensional analysis of a high-precision assembly unit in an automated mode and forming a set of assembly requirements, which, as a result, will allow ensuring the expansion of digitalization of the process design and designing preproduction and the transition to intelligent production systems.

The paper analyzes the information about the effective power of a reverse polarity arc on an aluminum part and the influence of the arc cathode region on it. The study differentiated the effective power of the direct polarity arc into its main components. The authors carried out the experiments to measure the effective power of the reverse polarity arc for aluminum welding. To determine the effective power, the calorimetry was used when hardfacing a wire of 1.2 mm diameter on the Al-Mn alloy plate and the deposited metal then was weighed. Based on the experiment results, the authors calculated an average algebraic deviation of αН∙I hardfacing performance and effective power. As a result, the authors proposed the procedure to determine the electrode wire fusion coefficient at zero stick-out α₀ according to its dependence on the arc current, which increases at electrode diameter decreasing. This coefficient is about 25 % less than that of steel. By assuming a weak dependence of anode power on the arc current, this fact proves the obtained data on the high heat content of electrode metal droplets of an aluminum wire in comparison with a steel wire. At the droplet transfer of electrode metal, the cathode region power of the arc makes the prevailing contribution to the total effective power of the reverse polarity arc. At the current density equal to 175 А/mm², the specific effective power of the cathode region action is q_SC=9.0 W/А, the power of the electrode metal is q_E=4.6 W/А, and the plasma flow power is q_P=5.2 W/А.

The paper considers the turbulence intensity and the fuel chemical composition impact on the flame propagation velocity at the initial and main combustion phases when changing the air-fuel mixture composition. The relevance of the study is caused by the fact that currently, the improvement of conventional engine operation characteristics is mainly achieved through the improvement of the fuel mixture combustion process. However, there are no data on the influence of chemical and gas-dynamic factors on the peculiarities of flame propagation at the initial and main combustion phases. The gas reciprocating internal combustion engine was the object of the research, and the subject of the study was the fuel combustion process. Fuel chemical composition changed due to the promoting addition of hydrogen to the natural gas and variations of the excess-air coefficient. The experiments carried out on the UIT-85 power plant (i.e. under the simulated internal combustion engine conditions) show that the promoting addition of hydrogen stronger influences the flame velocity in the initial combustion phase compared to the second combustion phase, as a combustion source in the first phase is a laminar flame bent front and depends only on chemical and thermo-physical properties of the fuel-air mixture. The analysis of experimental data showed the dual impact of turbulence intensity on the flame propagation velocity. In particular, at the beginning of the combustion process, the fluctuating velocity scarcely influences the flame propagation velocity, as opposed to the main combustion phase, where the flame propagation velocity increases at the increase of turbulence intensity.

The analysis of literature data on the properties of alloys with a semiconductor component shows a significant number of anomalies of physical and mechanical properties left without a comment of the researchers of these alloys. Based on the anomalies in the properties of twelve alloys (Ge-Si, InAs-GaP, GaSb-GaAs, HgTe-CdTe, GaSe-GaS, InSb-AlSb, PbSe-GeTe, Zn-Ge, Ti-Ge, Ge-Tl, ZnTe-HgTe, P-As), the paper attempts to identify a regularity that allows associating these anomalies with state diagrams. For the first time, the authors introduce the concept of phase diagram as a concentration dependence of qualitative changes in crystallization intervals, which allows associating phase diagram with the extremes of physical and mechanical properties of industrially used alloys with a semiconductor component that cannot be explained by the peculiarities of phase composition or structure. The second part of the paper deals with the special aspects of glass formation (amorphization) of multicomponent alloys. Modern literature expresses mutually exclusive judgments about the possibility of using phase equilibrium diagrams to predict the ability to glass-formation, which is well-founded and is probably associated with the absence of a general theory of glass formation. Nevertheless, the analysis of literature data on SiO₂-Na₂O, Ge-S, GeSe-Se, S-Se alloys shows that the glass formation (amorphization) boundaries are associated with phase diagrams. Based on the identified criterion, the paper shows the possibility of using equilibrium state diagrams built for slow-cooled alloys to predict the glass-forming ability of (fast-cooled) alloys.