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Materials ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 565
Author(s):  
Xueming Fang ◽  
Bingyou Jiang ◽  
Liang Yuan ◽  
Yuxiang Liang ◽  
Bo Ren ◽  
...  

An experimental study on the flow rate and atomization characteristics of a new gas–liquid two-phase flow nozzle was carried out to use high-concentration respirable dust in the workplace of high-efficiency sedimentation coal production based on the gas–liquid two-phase flow nozzle technology. The simulation roadway of dust fall in large coal mines was constructed, and the respirable rock dust produced by fully mechanized mining surfaces was chosen as the research object. The effects of humidity on the capture effect of respirable rock dust were analyzed in the experimental study. The results demonstrated that: (1) the distribution range of the particle size of fogdrops declines with the reduction in fogdrops D50, D[3,2] and D[4,3], which are produced by gas–liquid two-phase flow nozzles. (2) The initial ambient humidity in the simulated roadway was 64.8% RH. After the gas–liquid two-phase flow spray was started, the ambient humidity was elevated by 23.2 to 23.5% RH within 840s and tended to be stable and no longer grew after reaching 88.0–88.3% RH. The initial growth rate of the ambient humidity in the simulated roadway was high, and then was gradually slowed down. (3) Humidity is an important factor influencing the collection of respirable dust. The humidity at 10.0 m leeward of the dust-producing point was increased by 19.6% RH, and the sedimentation rate of respirable dust was increased by 6.73%; the two growth rates were 13.1% RH and 9.90% at 20.0 m; 16.4% RH and 15.42% at 30.0 m; 18.4% RH and 11.20% at 40.0 m. In practical applications of the gas–liquid two-phase flow nozzle in coal mining activities, attention shall be paid to not only the influences of its atomization characteristics on the capture effect of respirable dust but also the influences of the flow rate of the nozzle on the humidity of the working surface. Appropriate gas and water supply pressures shall be chosen according to the space and respirable dust concentration on the working surface to realize a better dust removal effect.


2022 ◽  
Author(s):  
S. Gorbatyuk

Abstract. The paper is devoted to solving the problem of determining the shape of the rolls of helical rolling mills, depending on the specified profile of the deformation zone. A universal calculation method has been proposed, thanks to which it is possible to determine the shape of the working surface of a roll for all types of helical rolling mills (with mushroom-shaped, cup-shaped, barrel-shaped and disc rolls), any relative arrangement of the rolling axis and rolls axes, and various locations of the deformation zone on the rolling axis. The proposed method is implemented as a standalone exe-application with a simple intuitive interface. The application allows you to output the calculation results into txt-files, which can then be imported into CAD systems to create 3D roll models.


2022 ◽  
Author(s):  
N.A. Chichenev

Abstract. A method for increasing the thermal fatigue strength of a tool used in hot forming of bearing rings by applying circular laser tracks to the working surfaces is considered. Laser treatment is carried out with a power of 2.0...2.5 kW by applying on the end face working surface of the tool in the direction from the center to the periphery of the circular tracks with a common center coinciding with the center of the circumference of the end face; the tool is rotated at a constant angular rate, the spot diameter ds for each track is selected according to the dependence ds,i+1/ds,i = 0.85...0.90, and the laser radiation spots of adjacent tracks have a common point of contact. The results of pilot testing are presented, which confirmed the high technical and economic efficiency of the use of laser quenching for ejectors and punches. A tool made by machining, for example, an ejector of an AMP-70 automatic press, is subjected to volume quenching and tempering. The ejector material was steel 3Kh3M3F, quenching temperature in oil – 1030...1050 °С, tempering temperature – 580...610 °С. After volume quenching, additional machining is carried out, usually grinding, in order to remove the decarbonized layer of material formed during heat treatment and to give the working surface the required roughness class. The final stage in the tool manufacturing is the quenching of its working surface by laser treatment. Pilot testing showed that the use of laser treatment made it possible to increase the durability of ejectors of various types by 2 ... 3 times, of deforming punches – by 2.2 times.


2022 ◽  
Vol 16 (1) ◽  
pp. 5-11
Author(s):  
Masakazu Fujimoto ◽  
Keisuke Shimizu ◽  
◽  

This paper deals with the microscopic wear characteristics of ceramic (Seeded Gel, SG) grinding wheels used in creep feed grinding. Creep feed grinding experiments with SG grinding wheels were carried out compared to rose-pink alumina (RA) grinding wheels. To clear the wear characteristics of the wheel working surface in creep feed grinding, changes in the shapes of grain cutting edges were observed by a field emission-scanning electron microscope (FE-SEM). This is a self-sharpening phenomenon based on micro fractures generated on the top of SG grain cutting edges. On the other hand, large fracture and attritious wear effected RA grain cutting edges. In addition, the features of any grain cutting edges were evaluated using attritious wear flat percentage. Changes in attritious wear flat percentage of SG grits maintained constant value and were stable. From these results, the influence of wear mode of the grinding wheel on grinding characteristics parameter, such as grinding force and workpiece surface roughness, is understood.


2021 ◽  
Vol 23 (6) ◽  
pp. 300-306
Author(s):  
N.O. Sitkov ◽  
◽  
T.M. Zimina ◽  
V.V. Luchinin ◽  
A.A. Kolobov ◽  
...  

The development and comparative study of technologies for manufacturing elements of hybrid biosensor systems intended for express biomedical analysis has been carried out. The technological process included the formation of the relief of microfluidic channels, chemical modification of their working surface, deposition of solid-state phosphor layers, sealing of the system, installation of inlet ports and packaging.


Machines ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 366
Author(s):  
Volodymyr Dzyura ◽  
Pavlo Maruschak ◽  
Stoyan Slavov ◽  
Volodymyr Gurey ◽  
Olegas Prentkovskis

The correlation between the service characteristics of the working surfaces of car parts belonging to the rotary body class, and quality parameters—in particular, the height-related roughness parameter Ra—was estimated. Low values of Ra were found to be unable to guarantee an optimal microrelief geometry and, accordingly, high-performance characteristics of the working surface. The oil-accumulation power of the parts was investigated as a primary characteristic of sliding friction using the group of Rk parameters in the Abbott–Firestone diagram, based on the profilogram of the test specimen’s surfaces. The oil-absorption power of the surfaces formed by different technological operations was compared with different microgeometric quality parameter values.


Author(s):  
Н.В. Куценко ◽  
М.В. Грибиниченко ◽  
А.В. Нитяговский ◽  
А.В. Куренский ◽  
О.С. Портнова

В работе рассмотрены результаты численного исследования модели радиального гибридного подшипника с газовой смазкой. Установлено наличие оптимальных значений параметров, определяющих форму смазочного зазора, получены их значения и закономерности влияния на них различных характеристик подшипника. Рассмотрено распределение давления в смазочном слое при различном количестве секторов лепестков. Подтверждено предположение о наличии оптимальных значений параметров, определяющих форму смазочного зазора. И опровергнуто предположение о том, что оптимальные значения этих параметров будут зависеть от значений других параметров подшипника. Выявлен положительный эффект от совместного воздействия газодинамического и газостатического эффектов. Относительно газостатических параметров – выявлен параметр, имеющий оптимальное значение (расстояние от выбранного торца подшипника до линии сетки, на которой располагаются питатели ряда с номером р), которое сохраняет постоянное значение. На основе полученных результатов разработаны основы методики расчета и оптимизации радиальных гибридных подшипников с газовой смазкой, имеющих профилированную рабочую поверхность. The paper considers the results of numerical study of gas-lubricated hybrid radial bearing model. The presence of optimal values of parameters determining the shape of the lubrication gap is established, their values and regularities of influence of different bearing characteristics on them are obtained. Pressure distribution in the lubricating layer at different number of lobe sectors has been considered. The assumption of optimum values of parameters determining the form of the lubrication gap is confirmed. And the assumption that the optimal values of these parameters will depend on the values of other bearing parameters is refuted. The positive effect of the combined effect of gas-dynamic and gas-static effects has been revealed. Concerning gas-static parameters - the parameter which has optimum value (distance from the chosen end face of a bearing to a grid line on which feeders of a row with number p are located) which keeps constant value has been revealed. On the basis of the obtained results the bases of calculation and optimization methodology of radial hybrid bearings with gas lubrication, having profiled working surface, are developed.


Author(s):  
V. Chebotarev ◽  
◽  
I. Kruk ◽  
F. Nazarov ◽  
Y. Chigariev ◽  
...  

Summary. This article is dedicated to the subject of designing additional tools for use with reversible ploughs that cuts and loosens topsoil. The aim is to reduce power consumption spent for soil tillage by using reversible ploughs with roller cultivators. Methods. Theoretical and experimental studies of the topsoil movement on the plough’s wing, the mouldboard and beyond. Results. Analysis of the movement of soil particles falling from the top edge of the plough’s moulboard has allowed to obtain analytical dependence for determining the size range of soil particles based on the geometry of the working surface of the plough’s body (distance from the soil surface to the top edge of the mouldboard, the angles of the edge of the mouldboard) and the kinematic parameters of the soil (speed of the plough and roller cultivator, soil particles speed on the edge of mouldboard, soil particles descent time). A research, on the movement of the soil particles, on the mouldboard surface of the plough's body is presented. The section through the mouldboard perpendicular to the wing of the plough is described by the equation of the "inverted" cycloid and based on it the dependences have been obtained to determine the kinematic parameters of the movement of the soil particles on the surface of the plough’s body, depending on the mouldboard type and properties of the soil. Results obtained in this article allow to design the roller cultivators for reversible ploughs with determined parameters of installation, in which the power consumption costs of the plowing process will be minimal. Conclusions. Obtained analytical dependences, that determine kinematic and technological parameters of the soil movement on the working surface of the plow, the section through the orthogonal wing that has the form of an "inverted"cycloid, the variable design and technological parameters of the plough and the conditions of its operation, allowing to justify the installation parameters of the roller cultivator relative to the plough, taking into account the proposed correction ratio, which depends on the mechanical properties of the soil and its structure.


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