scholarly journals Tribological researches of electroerosive processing of steel details of cars

2021 ◽  
Vol 99 (1) ◽  
pp. 66-73
Author(s):  
D. Marchenko ◽  
◽  
K. Matvyeyeva ◽  
Keyword(s):  
Experimental Studies ◽  
Sharp Decrease ◽  
Characteristic Size ◽  
Transfer Film ◽  
Initial Surface ◽  
Structural Elements ◽  
Surface Layers ◽  
Cathode Voltage ◽  
Mode Of Operation ◽  
Surface Irregularities

The article considers the technology of electroerosive treatment of steel friction pairs and presents the results of experimental studies. Analysis of experimental studies has shown that an increase in the anode-cathode voltage leads to a sharp decrease in the microhardness of the surface layer. The study also allowed to determine the characteristic size of the structural elements, the height parameters of the surface roughness. The elemental composition of the initial surface of the sample made of steel 15HGN2TA differs from the composition of the coatings and surface layers of the samples modified by electroerosive treatment with different electrodes. In the mode of operation of the "anode - cathode" system on the cathode surface due to dissipative processes, a thin layer of coating of a stable modified structure is formed. It is shown that the height of surface irregularities in the areas after friction is higher than in the areas of the surface outside the friction track, which is associated with the formation on the surface of the samples of the friction transfer film. It was found that the frictional interaction of steel samples treated by electroerosion method forms a thin film on the friction surface of steel samples, which leads to a change in the topography of surfaces with increasing height of microroughnesses and structuring of the transfer film in the sliding direction. The influence of electroerosive treatment of steel surfaces on the wear resistance of the metal-polymer tribosystem was established and the optimal treatment modes were obtained: voltage U = 145-150 V, capacitor capacity C = 225-230 μF, treatment duration t = 3-4 min / cm2, providing the greatest reduction in speed wear of the polymer counterbody and recommended in the development of technological processes of electroerosive treatment.

scholarly journals Regularities in the formation of wear-resistant coatings on steel samples when machining them with electrical discharge

2021 ◽  
Vol 5 (12(113)) ◽  
pp. 83-90
Author(s):  
Dmytro Marchenko ◽  
Viacheslav Kurepin
Keyword(s):  
Wear Resistance ◽  
Electrical Discharge ◽  
Electrical Discharge Machining ◽  
Operation Mode ◽  
Experimental Studies ◽  
Sharp Decrease ◽  
Transfer Film ◽  
Cathode Voltage ◽  
Wear Resistant Coatings ◽  
Metal Polymer

This paper considers the technology of electrical discharge machining of steel friction pairs and reports the results of experimental studies. Analysis of the experimental studies has shown that increasing the "anode-cathode" voltage leads to a sharp decrease in the micro-hardness of the surface layer. The study has also made it possible to determine the characteristic dimensions of the structural elements, the height parameters of surface roughness. The elemental composition of the resulting surface of a steel 15KHGN2TA sample differs from the composition of coatings and the surface layers of samples modified by electrical discharge machining involving various electrodes. Under the "anode-cathode" system operation mode, a thin layer of coating with a stable modified structure forms on the surface of the cathode due to dissipative processes. It is shown that the height of surface irregularities on sections after friction is higher than on the surface sections outside the friction flow, which is associated with the formation of a friction transfer film on the samples' surface. It was established that the interaction of friction of steel samples treated by electrical discharge machining forms a thin film on the surface of friction of steel samples, which leads to a change in the relief of surfaces with an increase in the height of the micro-protrusions, as well as the structuring of the transfer film in the direction of sliding. The effect of machining steel surfaces by electrical discharge on the wear resistance of metal-polymer tribosystem was established. The implementation of the devised technology could provide a significant increase in the wear resistance of metal-polymer tribojunctions

scholarly journals Thermal Radiation from a Neutron Star in SN 1987A

1988 ◽  
Vol 108 ◽  
pp. 448-449
Author(s):  
Ken’ichi Nomoto ◽  
Sachiko Tsuruta
Keyword(s):  
Neutron Star ◽  
Surface Temperature ◽  
Large Magellanic Cloud ◽  
Initial Surface ◽  
X Rays ◽  
Surface Layers ◽  
Sn 1987A ◽  
Supernova 1987A ◽  
Hot Surface ◽  
Proto Neutron Star

The supernova 1987A in the Large Magellanic Cloud has provided a new opportunity to study the evolution of a young neutron star right after its birth. A proto-neutron star first cools down by emitting neutrinos that diffuse out of the interior within a minutes. After the neutron star becomes transparent to neutrinos, the neutron star core with > 1014 g cm−3 cools predominantly by Urca neutrino emission. However, the surface layers remain hot because it takes at least 100 years before the cooling waves from the central core reach the surface layers (Nomoto and Tsuruta 1981, 1986, 1987).From the hot surface, thermal X-rays are emitted. The detection limit for X- rays from SN 1987A by the Ginga satellite is 3 ×1036 erg s−1 (Makino 1987; Tanaka 1987). If the thermal X-rays are to be observed by Ginga, the surface temperature should continue to be as high as Ts > 8 ×106 (R/10km)−1/2 K until the ejecta becomes transparent. The exact value of the initial surface temperature depends on various factors during the violent stages of explosion, cooling stages of the proto-neutron star through diffusive neutrinos, and possible re-infalling of the ejected material. Therefore, until the surface layers become thermally relaxed Ts may satisfy the above condition.

Viscous Dissipation of Polymer Melt in Micro Channels and Macro Channels

2014 ◽  
Vol 609-610 ◽  
pp. 521-525
Author(s):  
Bin Xu ◽  
Xiao Yu An ◽  
Liang Chao Li ◽  
Guang Ming Li
Keyword(s):  
Shear Rate ◽  
Viscous Dissipation ◽  
Unit Length ◽  
Experimental Studies ◽  
Polymer Melt ◽  
Characteristic Size ◽  
Micro Scale ◽  
Micro Channels ◽  
Macro Scale ◽  
The Difference

Viscous dissipation is the key factor impacting flowing characteristics of polymer melt. In order to study the difference between micro scale and macro scale, experimental studies of viscous dissipation at various shear rate were investigated with several polymers, including PMMA and HDPE, at different temperature when melts flow through 1000μm,500μm,350μm diameter channels of identical aspects ratio in the paper. The results indicate that the temperature rises caused by viscous dissipation increase with increasing shear rate and the temperature rise for some shear rate decreases with increasing melts temperature. The temperature rises decrease significantly with the reduction of the characteristic size of micro channel at the same shear rate. However, the average temperature rises per unit length increase when the character size of channel decreases. This indicates the shear friction gradually increases with the decrease of channel characteristic size. Therefore polymer melt viscous dissipation effects of micro scale dimensions are different from that of macro-scale dimensions.

scholarly journals Contact-deformation mechanism of boundary friction

2020 ◽  
Vol 164 ◽  
pp. 14004
Author(s):  
Alexandr Dykha ◽  
Volodymyr Kukhar ◽  
Viktor Artiukh ◽  
Maxim Aleksandrovskiy
Keyword(s):  
Experimental Studies ◽  
Deformation Mechanisms ◽  
Internal Stresses ◽  
Stress And Strain ◽  
Relative Deformation ◽  
Contact Deformation ◽  
Surface Layers ◽  
Friction Units ◽  
Relationship Of ◽  
The Relationship

Research was conducted to determine the effect of lubricants on stress and strain in the contact of metal surfaces. Experiments were carried out on the introduction of a fixed and moving indenter in contact with a dry and lubricated surface.The steel spherical specimen was pressed into a lubricated and dry metal surface. The microstructures of the structure of the surface layer are studied under various conditions of deformation. The diagrams of the relative deformation of the surface layers are constructed. The mechanism of the formation and distribution of internal stresses for dry and greased contact is described. Experimental studies of the introduction of a moving steel indenter into a lubricated surface have been carried out. The relationship of the deformation mechanisms of lubricated surfaces with their wear resistance is determined. The results obtained are recommended for predicting the durability of lubricated friction units according to the criterion of contact strength.

Modification of μm Thick Surface Layers Using keV Ion Energies

1983 ◽  
Vol 27 ◽  
Author(s):  
L. E. Rehn ◽  
N. Q. Lam ◽  
H. Wiedersich
Keyword(s):  
Elevated Temperature ◽  
Elevated Temperatures ◽  
Diffusion Processes ◽  
Experimental Studies ◽  
Surface Layers ◽  
Enhanced Diffusion ◽  
Radiation Enhanced Diffusion ◽  
Ni Alloy ◽  
Ion Energies ◽  
Radiation Induced

ABSTRACTRoot-mean-square diffusion distances for both vacancy and interstitial defects in metals can be very large at elevated temperatures, e.g. several μm's in one second at 500°C. Consequently, defects that escape the implanted region at elevated temperature can produce compositional and microstructural changes to depths which are much larger than the ion range. Because of the high defect mobilities, and of the fact that diffusion processes must compete with the rate of surface recession, the effects of defect production (ballistic mixing), radiation-enhanced diffusion and radiation- induced segregation become spatially separated during ion bombardment at elevated temperature. Results of such experimental studies in a Cu-Ni alloy are presented, discussed and compared with predictions of a phenomenological model. Contributions to the subsurface compositional changes from radiation-enhanced diffusion and radiation- induced segregation are clearly identified.

Experimental studies of the magnetic and phonon excitations in cobalt fluoride

1968 ◽  
Vol 46 (11) ◽  
pp. 1355-1370 ◽  
Author(s):  
P. Martel ◽  
R. A. Cowley ◽  
R. W. H. Stevenson
Keyword(s):  
Excited States ◽  
Energy Levels ◽  
Experimental Studies ◽  
Slow Neutron ◽  
Magnetic Excitations ◽  
Phonon Spectra ◽  
Mode Of Operation ◽  
Weak Scattering ◽  
Temperature Dependences ◽  
Cobalt Fluoride

The excitations of cobalt fluoride have been studied with the technique of slow-neutron inelastic scattering. A triple-axis crystal spectrometer was used throughout in its constant Q mode of operation. Several of the branches of the phonon spectra were measured and are in reasonable agreement with calculations based on a very simple rigid ion model. The magnetic excitations are of interest because the Co2+ ion has unpaired orbital angular momentum which gives rise to several low-lying energy levels. Excitations have been observed from the ground state to the next three excited states in the antiferromagnetic phase and their dispersion and temperature dependence obtained below, near, and above the Néel temperature. The temperature dependences of the excitations to the different excited states are not the same. The measurements on the magnetic excitation branch of lowest frequency show that, contrary to current theories of magnetism, fairly well-defined magnetic excitations occur to at least 1.5TN Another excitation, which gave a weak scattering intensity, was also observed and it is suggested that this may be associated with a distortion of the crystal structure.

Effect of Tow Sheet Composite Wrap Architecture on Strengthening of Concrete Due to Confinement: I—Experimental Studies

1995 ◽  
Vol 14 (9) ◽  
pp. 1008-1030 ◽  
Author(s):  
Ian Howie ◽  
Vistasp M. Karbhari
Keyword(s):  
Concrete Strength ◽  
Experimental Studies ◽  
Load Carrying Capacity ◽  
Structural Elements ◽  
New Techniques ◽  
Column Type ◽  
Load Carrying ◽  
Concrete Shell ◽  
Original Construction ◽  
Stub Columns

Worldwide there is a need for the renewal of infrastructure because of age, deterioration, misuse, lack of timely repair and maintenance, use of improper materials and/or techniques in the original construction, and even changing needs. Notwithstanding the need for retrofit and repair methods for column-type structural elements, there is also a need for new techniques that would increase the confining action of concrete, as well as enhance the load-carrying capacity and ductility of such structures from a strengthening, rather than a seismic, viewpoint. This study investigates the use of carbon-fiber-reinforced jackets applied to concrete stub columns through the use of tow-sheet-type fabric forms. The primary emphasis is on the investigation of orientation and thickness effects of the composite wraps on the load-carrying efficiency and enhanced ductility of the new structural elements. It was seen that the predominant use of hoop reinforcement provides significant enhancement in concrete strength through confining action and also offers the potential for fabrication of concrete shell-type elements that would enable reinforcing action without the use of steel and the attending problems of corrosion.

scholarly journals Nanoscale Schottky diodes for studying the activity of aluminum nanoparticles in reaction with water

2021 ◽  
Vol 2094 (2) ◽  
pp. 022051
Author(s):  
I Nedrygailov ◽  
N I Chernova ◽  
I V Osliakova
Keyword(s):  
Reaction Rate ◽  
Schottky Diodes ◽  
Experimental Studies ◽  
Characteristic Size ◽  
Electrical Signal ◽  
Aluminum Surface ◽  
Aluminum Nanoparticles ◽  
Production And Consumption ◽  
Reaction With Water ◽  
Kinetics Of

Abstract Hydrogen is a promising fuel for energy storage, transportation, production and consumption. At the same time, hydrogen in its pure form is not found on Earth in large quantities and therefore it is necessary to develop a technology for its production. One of the promising technologies for hydrogen production is the reaction of aluminum nanoparticles with water. At the same time, experimental studies of the elementary mechanisms of this reaction are difficult due to the aggressive properties of a concentrated alkaline solution, which is used to activate the aluminum surface. Here we show that the kinetics of the aluminum-water reaction can be monitored in real time using a Schottky nanodiode sensor, provided that the characteristic size of the nanodiode electrodes does not exceed 10 nm. The investigated nanoparticles are applied to the sensor surface by means of nanofabrication. The charge generated in the aluminum nanoparticles as a result of the reaction creates an electrical signal that is proportional to the rate of the chemical process. This makes it possible to use this technology to study the activity even of small groups of nanoparticles, when the volume of released hydrogen is insufficient to measure the reaction rate.

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