scholarly journals TECHNOLOGICAL MODE EFFECT OF FINISH GRINDING ON TRIBOTECHNICAL INDICES OF SURFACES MACHINED

2016 ◽  
Vol 2016 (3) ◽  
pp. 94-101
Author(s):  
Анатолий Суслов ◽  
Anatoliy Suslov ◽  
Сергей Бишутин ◽  
Sergey Bishutin ◽  
Владимир Сакало ◽  
...  
Keyword(s):  
Equilibrium State ◽  
Nonequilibrium State ◽  
Wear Intensity ◽  
Test Time ◽  
Surface Layers ◽  
Surface Machining ◽  
Power Effect ◽  
Defect Phase ◽  
Period Constant ◽  
Two Stages

Grinding is the most common finish stage of friction surface machining. The surface machined is transferred in a non-equilibrium state in consequence of thermal and power effect at grinding. During friction part material strives for a more equilibrium state in microcontacts of surface layers due to the presence of a considerable share of a defect phase formed at finish grinding. It is evident that the process of the material transition from a nonequilibrium state (after grinding) into a more equilibrium state (at surface runningin) and mainly defines the character of modes and finish grinding effect upon surface tribotechnical indices (wear intensity, runningin period, constant of friction). The researches were carried out in two stages. In the first stage at the expense of changes of grinding depth and time of surface sparking-out (that is, the intensity and duration of thermal and power effect of grinding on a sample) there were formed surface layers with different parameters on steel samples. In the second stage of investigations there were carried out tribotechnical tests of grinded samples under the same conditions and, in such a way the effect of grinding modes on surface durability was evaluated. On the basis of the results there were revealed the dependences of sample wear on test time and also dependences for the computation of wear intensity in grinded surfaces made of different structural materials. It is shown that at the abrasion there are possi-bilities for considerable increase (up to several times) of machinery surfaces durability by means of grinding depth changes and time of surface sparkingout, as these technological modes define the intensity and duration of thermal and power effects of abrasion upon a surface layer.

An Experimental Corrosion Investigation of Coupling Chloride Ions with Stray Current for Reinforced Concrete

2012 ◽  
Vol 166-169 ◽  
pp. 1987-1993 ◽  
Author(s):  
Mengcheng Chen ◽  
Kai Wang ◽  
Quanshui Wu ◽  
Zhen Qin
Keyword(s):  
Reinforced Concrete ◽  
Chloride Ion ◽  
Current Strength ◽  
Chloride Ions ◽  
Ion Concentration ◽  
Test Time ◽  
Light Rail ◽  
Stray Current ◽  
Concrete Deterioration ◽  
Two Stages

According to the service environment of light rail transit and subway structures, in this paper experiments on the corrosion characteristics of reinforced concrete under single corrosion environment of stray current, single corrosion environment of chloride ions and joint corrosion environment of stray current and chloride ions were respectively carried out. Loading direct current electric field was used to simulate the stray current. The experimental results showed that, the corrosion growth process of the rebar in reinforced concrete under single environment of chloride ions was slow and stable, while that under single environment of stray current being separated two stages, i.e., rapidly increasing stage and stably varying stage. In addition, the rebar of reinforced concrete in stray current alone environment was corroded faster than that in chloride ion alone environment did; when stray current and chloride ion coexist, the stray current speeded up the chloride ion transportation, which gave rise to the increase of the corrosion rate of the rebar of reinforced concrete; the corrosion degree of the rebar depended on the chloride ion concentration, stray current strength and test time. The stronger the stray current strength, the longer the stray current corrosion period and the heavier the chloride ion concentration, the more the corrosion products of the rebar and thus the more serious the reinforced concrete deterioration.

scholarly journals Deterioration of surface layers of tungsten and steel-containing materials in current collection sliding against molybdenum

2021 ◽  
Vol 64 (2) ◽  
pp. 122-128
Author(s):  
M. I. Aleutdinova ◽  
V. V. Fadin
Keyword(s):  
Electrical Conductivity ◽  
Iron Oxides ◽  
Electrical Contact ◽  
Bearing Steel ◽  
Wear Intensity ◽  
Oxide Content ◽  
Molybdenum Oxides ◽  
Sliding Surface ◽  
Surface Layers ◽  
Current Collection

The possibility of improving the characteristics of a dry sliding electrical contact with a current density higher than 100 A/cm2 by using a molybdenum counterbody is considered. It is shown that tungsten or metallic materials containing bearing steel (1.5 % Cr) in sliding against molybdenum at a speed of 5 m/s under electric current, forms a contact with low electrical conductivity and high wear intensity. This observation served as the basis of this work. Using optical and electron microscopy of sliding surfaces it was found that strong adhesion in the interface was the main reason for rapid surface layers deterioration and high wear intensity. A well-known statement was taken into account that adhesion is due to the low oxide content between the contact surfaces. Visual study of molybdenum sliding surface made it possible to establish formation of a thin transfer layer and absence of traces of oxide formation. The same was observed on sliding surface of tungsten that was caused by high temperature of tungsten and molybdenum oxides formation. A layer of iron oxides was observed on sliding surface of steel containing materials. In addition, traces of a thin tribolayer were find out. An increase in concentration of steel in the primary structure led to a slight increase in iron oxides on the sliding surface, but did not lead to a significant increase in electrical conductivity and wear resistance of the contact. Unsatisfactory characteristics of the contact allowed us to conclude that it is impossible to significantly improve sliding parameters with current collection against molybdenum and inappropriateness of its use as a counterbody for these conditions.

Kinetics of Hydrochlorination of Unvulcanized and Vulcanized Latex

1957 ◽  
Vol 30 (1) ◽  
pp. 264-273
Author(s):  
M. Gordon ◽  
J. S. Taylor
Keyword(s):  
Surface Reaction ◽  
Fine Particles ◽  
Particle Surface ◽  
Polymer Chains ◽  
Surface Layers ◽  
Zero Order Kinetics ◽  
Bulk Reaction ◽  
Two Stages ◽  
Low Pressures ◽  
Kinetics Of

Abstract In the van Veersen hydrochlorination of latex, two stages associated with different reaction loci and mechanisms are distinguishable : a surface reaction in an outer shell and a bulk reaction inside the particle. The rate control of the two mechanisms is discussed. The surface reaction stands isolated at low pressures of hydrochloric acid, and is measurable down to about 0.08 atm. of the gas. It affects only about 2 per cent of the rubber in Hevea latex, but up to over 20 per cent of synthetic or selectively creamed Hevea latex with sufficiently fine particles. The saturation of double bonds at the surface locus proceeds in an inward direction from the particle surface, and is limited to about the outer four layers of polymer chains. This restriction is due to the instability of the diffusing reagent in the rubber medium, which also accounts for the enormous nominal reaction order of the surface reaction. This order was found to be about 26 in one run, while the bulk reaction follows zero order kinetics. The kinetics of the isolated surface reaction is shown to be a useful tool in studying the unsaturation of the surface layers in vulcanized latex. By its means it is proved that a surface reaction can also affect latex vulcanization. This is technically important because the film strength of latex decreases critically with increasing vulcanization of the particle surface.

Critical Structures of Metal Destruction Under the Process of Wear

1999 ◽  
Vol 122 (1) ◽  
pp. 361-366 ◽  
Author(s):  
I. I. Garbar
Keyword(s):  
Initial Conditions ◽  
Layer Structure ◽  
Low Carbon Steel ◽  
Maximum Level ◽  
Metal Structure ◽  
Wear Intensity ◽  
Relaxation Processes ◽  
Low Carbon ◽  
Surface Layers ◽  
Critical Structure

Resistance to wear is determined by the ability of the metal structure to change in such a way that it can withstand friction stresses. The structure of surface layers which have undergone wear can be identified as a “critical” structure. This is where destruction takes place. To study the surface structure specimens of low-carbon steel, aluminum and copper were subjected to wear tests and then investigated by X-ray. Under certain test conditions it was found that the changes in the surface layer structure, evidenced by the structural broadening of diffraction lines, reach a maximum level. The tests showed that as one progresses from mild wear to harsher friction conditions and correspondingly higher wear intensity, the structural broadening of the diffraction lines is first increased but than reduced. The results show that under low and moderate wear conditions, the structure of the surface layers is changed by the friction process, the surface layers being hardened by fragmentation. The level of metal hardening corresponds to the friction stresses that occur in the surface layers, and reaches a maximum when the fragment dimensions are minimal. As the friction conditions become more severe, the critical structure of the metal approaches the initial conditions, and therefore its strength is less than that of the hardened structure formed under moderate wear conditions. Such results can be explained by the difference in the rates of the plastic deformation and of plastic relaxation processes. Therefore, the critical structure under the process of wear depends on the friction conditions. To put the mechanical properties of the material to best use, one should choose optimal friction and wear conditions so that the metal will be hardened as much as possible. [S0742-4787(00)04801-3]

scholarly journals Thermalization in a Quantum Harmonic Oscillator with Random Disorder

Entropy ◽  
2020 ◽  
Vol 22 (8) ◽  
pp. 855
Author(s):  
Ya-Wei Hsueh ◽  
Che-Hsiu Hsueh ◽  
Wen-Chin Wu
Keyword(s):  
Numerical Simulation ◽  
Equilibrium State ◽  
Harmonic Oscillator ◽  
Total Energy ◽  
Mechanical Energy ◽  
Nonequilibrium State ◽  
Quantum Harmonic Oscillator ◽  
Damped Harmonic Oscillator ◽  
Random Disorder ◽  
Kinetic And Potential Energies

We propose a possible scheme to study the thermalization in a quantum harmonic oscillator with random disorder. Our numerical simulation shows that through the effect of random disorder, the system can undergo a transition from an initial nonequilibrium state to a equilibrium state. Unlike the classical damped harmonic oscillator where total energy is dissipated, total energy of the disordered quantum harmonic oscillator is conserved. In particular, at equilibrium the initial mechanical energy is transformed to the thermodynamic energy in which kinetic and potential energies are evenly distributed. Shannon entropy in different bases are shown to yield consistent results during the thermalization.

Nonlinear Density Fluctuations and Spatial Heterogeneities near the Colloidal Glass Transition

2002 ◽  
Vol 754 ◽  
Author(s):  
Michio Tokuyama ◽  
Yayoi Terada ◽  
I. Oppenheima
Keyword(s):  
Glass Transition ◽  
Diffusion Equation ◽  
Equilibrium State ◽  
Nonequilibrium State ◽  
Density Fluctuations ◽  
Stochastic Diffusion Equation ◽  
Different Types ◽  
Slow Relaxations ◽  
Initial States ◽  
Colloidal Glass

ABSTRACTHow the spatial heterogeneities play an important role in the dynamics of density fluctuations near the colloidal glass transition is discussed from a new viewpoint. A nonlinear stochastic diffusion equation for the density fluctuations recently proposed by one of the present authors (MT) is numerically solved in two different initial states, an equilibrium state and a nonequilibrium state. Depending on initial states, the dynamics of the spatial heterogeneities are shown to be quite different from each other. Such differences are thus shown to influence the slow relaxations of density fluctuations, leading to different types of two-step relaxations.

scholarly journals CHARACTERISTICS OF DRY SLIDING ELECTRIC CONTACT OF METALS IN CONDITIONS OF CATASTROPHIC WEARING

2019 ◽  
Vol 62 (2) ◽  
pp. 103-108 ◽  
Author(s):  
M. I. Aleutdinova ◽  
V. V. Fadin
Keyword(s):  
Current Density ◽  
Niti Alloy ◽  
Wear Intensity ◽  
Contact Temperature ◽  
Structural Defects ◽  
Dry Sliding ◽  
Sliding Surface ◽  
Surface Layers ◽  
Strong Adhesion ◽  
Steel 1020

The authors have studied the relation between wear intensity, average contact temperature and phase composition of the surface layers ofAISI 1020 steel, copper and NiTi alloy in dry sliding against the steel counterbody under electric current of density higher than 100  A/cm2 . These contact characteristics are considered carefully at the beginning of catastrophic wear, when the surface layers transit to the utmost state. It was noted that relaxation of stresses in the surface layers was due to the structural transformation in normal wear regime. It leads to tribolayers formation. The high strength of the copper tribolayer is first of all due to the formation of FeO oxide on the sliding surface, which prevents adhesion in contact. In addition, signs of a  liquid phase were observed on the copper contact surface. It promoted the low rate of formation and accumulation of structural defects. Emergence of areas of melt and FeO oxide on the sliding surface provides high contact wear resistance. These factors, combined with the high thermal copper conductivity, have caused the tribolayer transition to the limit state at high current density and low contact temperature. The absence of oxides on the sliding surface of the NiTi alloy has caused strong adhesion in the contact, high rate of formation and accumulation of structural defects. Therefore, the tribolayer quickly deteriorates and high wear intensity and rapid increase in the contact temperature are observed with current density increase. Therefore, the catastrophic wear of the NiTi alloy begins at a temperature about 350  °C and at low current density. The sliding surface of AISI 1020 steel contained FeO oxide, therefore strong adhesion is not manifested. Formation of FCC-Fe in tribolayer of AISI steel 1020 is detected, that promotes its accelerated deterioration. Therefore, the tribolayer of AISI steel  1020 transites to the utmost state at a relatively low current density and at a  higher temperature. The presented contact temperatures corresponding to the beginning stages of the utmost state of the tribolayer do not exceed 350  °С. Comparison of these temperatures with the known contact temperatures of other metals made it possible to assert that raising of the contact temperature of any metal higher than 400  °С leads to its utmost state. Therefore the characteristics of metals contact at temperatures of sliding contact higher than 500  °С is not of practical interest.

scholarly journals Structure of X5CrNi18-10 and S355NL Steels after Remelting with the Electric Arc

2012 ◽  
Vol 12 (2) ◽  
pp. 139-142
Author(s):  
S. Adamiak
Keyword(s):  
Surface Layer ◽  
Electric Arc ◽  
Constant Speed ◽  
Surface Layers ◽  
Microscope Examination ◽  
Surface Machining ◽  
Welding Head

Structure of X5CrNi18-10 and S355NL Steels after Remelting with the Electric Arc The work presents the results of the research and tests of the surface machining of the S355NL and X5CrNi18-10 steels with the concentraded stream of heat with the usage of the GTAW method. The surface layers of the tested steels were remelted with the electric arc using the current of the electric arc 50, 100, 150 and 200A. The machining was done in the atmosphere of argon with the constant speed of the welding head. A microscope examination was performed of the obtained structure and measurements of depth, width and hardness of the received surface layer were performed. Moreover the relation between the current of the electric arc and geometry of the remelted layers with their microhardness was examined.

Comments on collision mechanics in ring systems

1984 ◽  
Vol 75 ◽  
pp. 407-422
Author(s):  
William K. Hartmann
Keyword(s):  
Asteroid Belt ◽  
Surface Erosion ◽  
Surface Layers ◽  
Ring Systems ◽  
Eclipse Observations ◽  
Saturn’S Rings ◽  
Saturn's Rings

ABSTRACTThe nature of collisions within ring systems is reviewed with emphasis on Saturn's rings. The particles may have coherent icy cores and less coherent granular or frosty surface layers, consistent with thermal eclipse observations. Present-day collisions of such ring particles do not cause catastrophic fragmentation of the particles, although some minor surface erosion and reaccretion is possible. Evolution by collisional fragmentation is thus not as important as in the asteroid belt.

Altered Fine Structure of B Lymphocytes Correlated with Defective Terminal Differentiation

1973 ◽  
Vol 31 ◽  
pp. 386-387
Author(s):  
Dale E. Bockman ◽  
L. Y. Frank Wu ◽  
Alexander R. Lawton ◽  
Max D. Cooper
Keyword(s):  
Immune Deficiency ◽  
B Lymphocytes ◽  
Plasma Cells ◽  
Present Report ◽  
Specific Antigen ◽  
Terminal Differentiation ◽  
Second Stage ◽  
Two Stages ◽  
Deficiency Diseases ◽  
Cell Line Generation

B-lymphocytes normally synthesize small amounts of immunoglobulin, some of which is incorporated into the cell membrane where it serves as receptor of antigen. These cells, on contact with specific antigen, proliferate and differentiate to plasma cells which synthesize and secrete large quantities of immunoglobulin. The two stages of differentiation of this cell line (generation of B-lymphocytes and antigen-driven maturation to plasma cells) are clearly separable during ontogeny and in some immune deficiency diseases. The present report describes morphologic aberrations of B-lymphocytes in two diseases in which second stage differentiation is defective.

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