63 research outputs found
ПРЕБЫВАНИЕ ГРУППЫ СТУДЕНТОВ БНТУ В РЕСПУБЛИКЕ ПОЛЬША
The paper describes a visit of the BNTU students and lecturers to the Lublin University of Technology for informative and practical training.Рассматриваются результаты пребывания группы студентов и преподавателей БНТУ на учебно-ознакомительной практике в Люблинском техническом университете
Структура и триботехнические свойства хромовых покрытий, сформированных электродеформационным плакированием гибким инструментом
The paper contains results of investigations on structure and tribotechnical properties of chromium coatings formed by a method of electrodeformation cladding with flexible tools (EDCFT). The purpose of these investigations is to assess prospects for application of the coatings as an alternative to galvanic chrome plating which is widely used in manufacturing hydraulic cylinder rods of metal-cutting machines. Rotary metal brushes with a wire pile made of 65Г-steel and 03Х17Н14М2-stainless steel have been used as a flexible tool. A compacted bar obtained by sintering a mixture of pure chromium powders and a nano-sized diamond-graphite blend UDDG has been employed as a donor material for EDCFT. According to results of the research it has been established that alloying elements of wire pile such as chromium and nickel are added to a coating composition while forming coatings a stainless steel brush. So in the case of using brushes with wire pile of 03X17H14M2-stainless steel the amount of chromium and nickel in a clad coating layer is 5.3 and 9.6 times higher in percentage, respectively, in comparison with the coating formed by a 65Г-steel brush that can contribute to improvement of coating corrosion resistance. At the same time, surface relief of the coating has a developed rough structure consisting of chromium microparticles having various size that are tightly packed and elongated in the direction of brush rotation and there are no flaws in the form of discontinuities and delaminations. Tribological tests have been performed under conditions of “boundary lubrication” on a rotary friction machine that implements friction of a rubber indenter on a flat surface of a rotating disk. According to data of the tribotechnical tests it has been ascertained that under conditions of “boundary friction” for such paired samples as “coated disc – rubber roller” chromium coatings formed by the EDCFT method, have the lowest values of a sliding friction coefficient (fтр = 0.023) which are 7.5 times lower than chromium coatings obtained by electroplating. At the same time the wear of rubber rollers in pairs with electroplated chromium coatings has turned out to be less than in pairs with the coating formed by the EDCFT method.. Приведены результаты исследований структуры и триботехнических свойств хромовых покрытий, сформированных методом электродеформационного плакирования гибким инструментом (ЭДПГИ), выполненных с целью оценки перспектив их применения в качестве альтернативы гальваническому хромированию, широко используемому при изготовлении штоков гидроцилиндров металлорежущих станков. В качестве гибкого инструмента применялись вращающиеся металлические щетки с проволочным ворсом, выполненным из стали 65Г и нержавеющей стали 03Х17Н14М2. Материал-донор при ЭДПГИ – компактированный брусок, полученный путем спекания смеси порошков чистого хрома и наноразмерной алмазно-графитовой шихты УДАГ. По результатам исследований установлено, что при формировании покрытий щеткой из нержавеющей стали в состав покрытия привносятся легирующие элементы проволочного ворса, такие как хром и никель. Так, в случае использования щеток с проволочным ворсом из нержавеющей стали 03Х17Н14М2 количество хрома и никеля в плакированном слое покрытия по процентному содержанию соответственно в 5,3 и 9,6 раза больше, чем в покрытии, сформированном щеткой из стали 65Г, что может способствовать повышению коррозионной стойкости покрытий. При этом рельеф поверхности покрытия имеет развитую шероховатую структуру, состоящую из плотно уложенных и вытянутых в направлении вращения щетки различных по размерам микрочастиц хрома, а также сглаженных микровыступов и микроуглублений, дефекты покрытия в виде несплошностей и отслоений отсутствуют. Триботехнические испытания выполнялись в условиях «граничной смазки» на машине трения вращательного типа, реализующей трение резинового индентора по плоской поверхности вращающегося диска. По данным триботехнических испытаний установлено, что в условиях «граничного трения» спаренных образцов «диск с покрытием – резиновый ролик» наименьшими значениями величин коэффициента трения скольжения (fтр = 0,023) обладают хромовые покрытия, сформированные методом ЭДПГИ, которые в 7,5 раза меньше, чем у хромовых, полученных гальваническим осаждением. В то же время износ резиновых роликов в парах с гальваническими хромовыми покрытиями оказывался меньшим, чем в парах с покрытием, сформированным методом ЭДПГИ
Легирование расплава подшипников скольжения на основе баббита
Abstract. A device design is proposed that makes it possible to obtain composite castings of sliding bearings based on babbitt by mixing alloying additives from antifriction powders of solid lubricants (graphite, molybdenum disulfide, etc.) into the melt, having a density significantly lower than the density of babbitt itself. The principle of mixing is based on the use of numerous turbulent flows resulting from the rotation of a gating rod with a wire pile in the melt material, the packing density coefficient of which is not less than 0.1. Due to the suction effect of these flows, non-metallic particles of solid lubricant powder do not float to the surface of the melt and, after crystallization, remain in the body of the casting. The supply of alloying powder of solid lubricant is carried out simultaneously with the supply of the babbitt melt through the central and distribution gating channels made in a rotating rod. Under the action of centrifugal forces, powder particles and melt material flow through distribution channels to the walls of the mold (mold), passing through the rotation zone of the metal pile. In this case, intensive mixing of the powder particles with the melt material occurs due to the suction effect of turbulent flows arising behind the moving pile. In addition, as a result of the rotation of the wire pile, dendritic constituents are crushed in babbitt castings. Metallographic studies of the castings obtained on the developed device have shown that the structure of the casting obtained by traditional technology contains large quantities of solid crystals of intermetallic compounds SnSb and Cu3Sn, while in the structure of the casting obtained using the proposed device, along with the aforementioned intermetallic compounds, particles of solid lubricant C + MoS2 powder embedded in the crystallized melt are observed. Предложена конструкция устройства, обеспечивающего возможность получения композиционных отливок подшипников скольжения на основе баббита путем замешивания в расплав легирующих добавок из антифрикционных порошков твердой смазки (графита, дисульфида молибдена и др.), обладающих плотностью, значительно меньшей по сравнению с плотностью самого баббита. Принцип замешивания основан на использовании многочисленных турбулентных потоков, возникающих вследствие вращения в материале расплава литникового стержня с проволочным ворсом, коэффициент плотности набивки которого не менее 0,1. Благодаря всасывающему воздействию этих потоков неметаллические частицы порошка твердой смазки не всплывают на поверхность расплава и после его кристаллизации остаются в теле отливки. Подача легирующего порошка твердой смазки осуществляется одновременно с подачей расплава баббита через центральный и распределительные литниковые каналы, выполненные во вращающемся стержне. Под действием центробежных сил частицы порошка и материал расплава через распределительные каналы вытекают к стенкам изложницы (формы), проходя через зону вращения металлического ворса. При этом благодаря всасывающему воздействию турбулентных потоков, возникающих за движущимся ворсом, происходит интенсивное смешивание частиц порошка с материалом расплава. Кроме того, в результате вращения проволочного ворса обеспечивается измельчение дендритных составляющих в отливках из баббита. Металлографическими исследованиями полученных на разработанном устройстве отливок установлено, что в структуре отливки, полученной по традиционной технологии, в большом количестве содержатся твердые кристаллы интерметаллидных соединений SnSb и Cu3Sn, в то время как в структуре отливки, полученной с использованием предложенного устройства, наряду с вышеупомянутыми интерметаллидными соединениями, наблюдаются внедренные в закристаллизовавшийся расплав частицы порошка твердой смазки C + MoS2
Electronic properties and phase transitions in low-dimensional semiconductors
We present the first review of the current state of the literature on
electronic properties and phase transitions in TlX and TlMX2 (M = Ga, In; X =
Se, S, Te) compounds. These chalcogenides belong to a family of the
low-dimensional semiconductors possessing chain or layered structure. They are
of significant interest because of their highly anisotropic properties, semi-
and photoconductivity, non-linear effects in their I-V characteristics
(including a region of negative differential resistance), switching and memory
effects, second harmonic optical generation, relaxor behavior and potential
applications for optoelectronic devices. We review the crystal structure of TlX
and TlMX2 compounds, their transport properties under ambient conditions,
experimental and theoretical studies of the electronic structure, transport
properties and semiconductor-metal phase transitions under high pressure, and
sequences of temperature-induced structural phase transitions with intermediate
incommensurate states. Electronic nature of the ferroelectric phase transitions
in the above-mentioned compounds, as well as relaxor behavior, nanodomains and
possible occurrence of quantum dots in doped and irradiated crystals is
discussed.Comment: 70 pages, 38 figure
VISIT OF THE BNTU STUDENTS TO REPUBLIC OF POLAND
The paper describes a visit of the BNTU students and lecturers to the Lublin University of Technology for informative and practical training
Radiogenic lead in the drinking water and in hair and nails samples of Finnish residents [abstract]
Structure and Tribological Properties of Chromium Coatings Formed by Electrodeformation Cladding with Flexible Tools
The paper contains results of investigations on structure and tribotechnical properties of chromium coatings formed by a method of electrodeformation cladding with flexible tools (EDCFT). The purpose of these investigations is to assess prospects for application of the coatings as an alternative to galvanic chrome plating which is widely used in manufacturing hydraulic cylinder rods of metal-cutting machines. Rotary metal brushes with a wire pile made of 65Г-steel and 03Х17Н14М2-stainless steel have been used as a flexible tool. A compacted bar obtained by sintering a mixture of pure chromium powders and a nano-sized diamond-graphite blend UDDG has been employed as a donor material for EDCFT. According to results of the research it has been established that alloying elements of wire pile such as chromium and nickel are added to a coating composition while forming coatings a stainless steel brush. So in the case of using brushes with wire pile of 03X17H14M2-stainless steel the amount of chromium and nickel in a clad coating layer is 5.3 and 9.6 times higher in percentage, respectively, in comparison with the coating formed by a 65Г-steel brush that can contribute to improvement of coating corrosion resistance. At the same time, surface relief of the coating has a developed rough structure consisting of chromium microparticles having various size that are tightly packed and elongated in the direction of brush rotation and there are no flaws in the form of discontinuities and delaminations. Tribological tests have been performed under conditions of “boundary lubrication” on a rotary friction machine that implements friction of a rubber indenter on a flat surface of a rotating disk. According to data of the tribotechnical tests it has been ascertained that under conditions of “boundary friction” for such paired samples as “coated disc – rubber roller” chromium coatings formed by the EDCFT method, have the lowest values of a sliding friction coefficient (fтр = 0.023) which are 7.5 times lower than chromium coatings obtained by electroplating. At the same time the wear of rubber rollers in pairs with electroplated chromium coatings has turned out to be less than in pairs with the coating formed by the EDCFT method
Alloying the Melt of Sliding Bearings Based on Babbitt
Abstract. A device design is proposed that makes it possible to obtain composite castings of sliding bearings based on babbitt by mixing alloying additives from antifriction powders of solid lubricants (graphite, molybdenum disulfide, etc.) into the melt, having a density significantly lower than the density of babbitt itself. The principle of mixing is based on the use of numerous turbulent flows resulting from the rotation of a gating rod with a wire pile in the melt material, the packing density coefficient of which is not less than 0.1. Due to the suction effect of these flows, non-metallic particles of solid lubricant powder do not float to the surface of the melt and, after crystallization, remain in the body of the casting. The supply of alloying powder of solid lubricant is carried out simultaneously with the supply of the babbitt melt through the central and distribution gating channels made in a rotating rod. Under the action of centrifugal forces, powder particles and melt material flow through distribution channels to the walls of the mold (mold), passing through the rotation zone of the metal pile. In this case, intensive mixing of the powder particles with the melt material occurs due to the suction effect of turbulent flows arising behind the moving pile. In addition, as a result of the rotation of the wire pile, dendritic constituents are crushed in babbitt castings. Metallographic studies of the castings obtained on the developed device have shown that the structure of the casting obtained by traditional technology contains large quantities of solid crystals of intermetallic compounds SnSb and Cu3Sn, while in the structure of the casting obtained using the proposed device, along with the aforementioned intermetallic compounds, particles of solid lubricant C + MoS2 powder embedded in the crystallized melt are observed
The contribution of social-environmental factors to the emotional adjustment of Israeli religious Jewish women coping with infertility
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