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Abstract

On the basis of theoretical model of quantum well (QW) with infinitely high walls it was investigated thermoelectric parameters depending on the thickness of the layer of nanostructures IV-VI (PbS, PbSe, PbTe) in the approximation of changing Fermi energy. There have been shown that the dependences of the Seebeck coefficient, electrical conductivity and thermoelectric power factor on well width for lead chalcogenides nanofilms are in good agreement with the experimental data. So, that proves the correctness of used model.

Aim. Experimental investigation of grinding of external cylindrical surfaces of parts by thin abrasive wheels that are inclined to working surface. Methods. The investigation was carried out using the methods of cutting theory, the planning of experiments, statistical processing of experimental results. Results. The thin reinforced abrasive wheels (heightened circular speed gives for these wheels) are proposed to use to work up outer cylindrical surfaces of parts with covering heightened wear resistance and hardness or the details that were received of hard-to-machine materials. The influence of the cutting modes in the production process by thin abrasive wheels on the amount of effective power and the main component of the cutting force during the processing of external cylindrical surfaces of parts were experimentally determined. The empirical relations between production modes and power parameters of the production process were defined for oncoming directions and passing directions of circular speed for the machined cylindrical part and thin abrasive wheel. Scientific novelty. The ratio of production mode by thin inclined abrasive wheels on the effective cutter power and the main component of the cutting force during the processing of external cylindrical surfaces of parts, which were experimentally received, determines that accompanying processing by the increase of cutting depth and circular speed of rotation is accompanied to increase of effective cutter power and the main component of cutting force, and the increase of the longitudinal feed is accompanied to reduce them, but effective cutter power and the main component of cutting force increase during the growth of a feed and circular speed of the part for counter processing, however, these values reduce during the increase of cutting depth. The compatible, paired influence of several factors of processing modes on the power parameters of the process is important during the production process by the inclined thin abrasive wheel. The production process concerns processes with low energy consumption. The effective cutting power does not exceed 0.45 kW for all combinations of cutting modes. Low effective cutting power together with a small contact area of the abrasive wheel with the workpiece determine a small effect on the treated surface of the heating temperature in the processing area that ensures the preservation of the mechanical characteristics of the surface layer, which was obtained in the previous stages of manufacturing the part. Low energy consumption of the production process of cylindrical parts by inclined thin abrasive wheels determines the availability of its practical use. Practical significance. The production process of cylindrical workpiece surface of hard-to-process materials or with thick-layer wear-resistant coatings, which have significant previous surface irregularities, by inclined thin abrasive wheels was proposed to use on operations of rough round grinding or on rough transitions of turning operation. The studied machining process can be implemented on lathes that are equipped with the additional, replaceable high-speed electric drive of rotation of a thin abrasive wheel. The use of the method of processing the outer cylindrical surfaces by thin abrasive wheels provides: the use of low cost cutting tools, reduction of the main processing time due to the greater depths of cutting, increase productivity and reduce the cost of processing and versatility of the process, due to the ability to process the cylindrical surfaces of parts that are formed from a variety of materials with significantly different physical and mechanical properties.

Problem statement. An important requirement is quality assurance of joining materials with minimal overheating of materials, lowering the soldering temperature and suppressing the interaction of the solder with the materials to be soldered. The heating of the solder and the holder should be as uniform as possible and with a minimum temperature difference along the depth. One solution may be to develop more efficient solders and fluxes, adapted to the high heating rates that are typical when using high frequency currents Purpose. Thus, the problems of uniform heating of parts during brazing are relevant. This is necessary for optimal distribution of the electromagnetic field in the contact area Methodology. The effect of the heating rate was investigated. The composition of the flux and solders on the microstructure of the solders and the brazed seam was performed on the joints of HV510 (DIN), HS345 (DIN), HG30 (DIN) hardmetal plates with steel holders made of 5135 (USA) steel with a section of 25×20. Results. The research of the processes showed that during the contact interaction of low-melting and refractory components of the solders, when the tool was soldered, the solder is formed in the seam and proceeds through several stages. Practical value. Contact interaction of copper-zinc melts with iron particles does not lead to complete dissolution of iron particles. This is explained to the low values of the solubility of iron in copper-zinc melts despite the fact that resistive heat release occurs in the particles. Such iron particles (iron-based alloy) act as a dispersed phase in the structure of the composite material.