Increase of Wear Resistance and Contact-Fatigue Strength of Wheel Steel by Plasma Hardening

2018 ◽  
Vol 284 ◽  
pp. 1144-1150 ◽  
Author(s):  
A.T. Kanayev ◽  
A.V. Bogomolov ◽  
A.A. Kanayev
Keyword(s):  
Structural Phase ◽  
Contact Fatigue ◽  
Internal Stresses ◽  
Surface Zone ◽  
Surface Plasma ◽  
Heating Rates ◽  
Near Surface ◽  
Plasma Hardening ◽  
Metastable Structure ◽  
High Level

Metallographic studies of structural-phase states formed in the section of the flange of the wheel band during surface plasma hardening were conducted. It is shown that the formation of several structural zones of different micro hardness is distinctly observed in the depth of hardening, which indicates the formation of a graded-layered structure. It has been confirmed that at superfast heating rates that occur during surface plasma quenching, phase and structural transformations are shifted to high temperatures, greatly changing the kinetics of nucleation and growth of the new phase (austenite). This forms a fine-grained austenite, which turns into a highly disperse martensitic structure, unattainable by traditional methods of heat treatment. It is shown that the main factor leading to strong hardening of the surface layer during plasma treatment is the formation in the near-surface zone of a nonequilibrium metastable structure, which goes over to a narrow zone of complete and incomplete quenching with an inhomogeneous and distorted structure of highly disperse martensite with a high level of internal stresses. The complete wear of the unstressed flange of the tire wheel band is 1.9 mm in 1.1 years, and for hardened flanges, wear is 0.7 mm for 2.6 years.

scholarly journals IMPROVING THE SURFACE STRUCTURE OF MASSIVE PARTS BY THE PLASMA METHOD

2021 ◽  
Author(s):  
I.M Kossanova.Т.Кanayev,A А.U.Аkhmedyanov,I.P. Mazur,
Keyword(s):  
Structural Changes ◽  
Surface Plasma ◽  
High Temperature Region ◽  
Heating Rates ◽  
Plasma Hardening ◽  
Fine Grained ◽  
Kinetics Of ◽  
New Phase ◽  
Phase And Structural Changes ◽  
Structural Zones

An increase in the reliability of the operation of large-sized and massive parts by plasma hardening of their surfaces is substantiated. It has been established that the formation of several structural zones of different microhardness is observed in detail along the depth of hardening, indicating the formation of a gradient-layered structure. It has been proved that at ultrafast heating rates, which occur during surface plasma hardening, phase and structural changes move to the high temperature region, changing the kinetics of the appearance and growth of new phase nuclei. In this case, fine-grained austenite is formed, which is transformed into a highly dispersed martensitic structure, which increases the strength and reliability of the surfaces of the parts.

DISPERSION IN SEISMIC SURFACE WAVES

Geophysics ◽  
1951 ◽  
Vol 16 (1) ◽  
pp. 63-80 ◽  
Author(s):  
Milton B. Dobrin
Keyword(s):  
Surface Waves ◽  
Water Waves ◽  
Seismic Refraction ◽  
Wave Theory ◽  
Wave Dispersion ◽  
Surface Zone ◽  
Surface Wave Dispersion ◽  
Near Surface ◽  
Arrival Times ◽  
Ground Roll

A non‐mathematical summary is presented of the published theories and observations on dispersion, i.e., variation of velocity with frequency, in surface waves from earthquakes and in waterborne waves from shallow‐water explosions. Two further instances are cited in which dispersion theory has been used in analyzing seismic data. In the seismic refraction survey of Bikini Atoll, information on the first 400 feet of sediments below the lagoon bottom could not be obtained from ground wave first arrival times because shot‐detector distances were too great. Dispersion in the water waves, however, gave data on speed variations in the bottom sediments which made possible inferences on the recent geological history of the atoll. Recent systematic observations on ground roll from explosions in shot holes have shown dispersion in the surface waves which is similar in many ways to that observed in Rayleigh waves from distant earthquakes. Classical wave theory attributes Rayleigh wave dispersion to the modification of the waves by a surface layer. In the case of earthquakes, this layer is the earth’s crust. In the case of waves from shot‐holes, it is the low‐speed weathered zone. A comparison of observed ground roll dispersion with theory shows qualitative agreement, but it brings out discrepancies attributable to the fact that neither the theory for liquids nor for conventional solids applies exactly to unconsolidated near‐surface rocks. Additional experimental and theoretical study of this type of surface wave dispersion may provide useful information on the properties of the surface zone and add to our knowledge of the mechanism by which ground roll is generated in seismic shooting.

STUDYING OF SPACE WEATHER ELECTROMAGNETIC PARAMETERS OF IONOSPHERE IN «OBSTANOVKA 1-STEP» EXPERIMENT ON THE RUSSIAN SEGMENT OF THE ISS

2021 ◽  
pp. 20-41
Author(s):  
Stanislav I. KLIMOV ◽  
Valery A. GRUSHIN Valery A ◽  
Kalman BALAJTHY ◽  
Dichko Enchev BACHVAROV ◽  
Serhiy M. BELYAEV ◽  
...  
Keyword(s):  
Plasma Wave ◽  
Space Weather ◽  
Space Station ◽  
Scientific Instrument ◽  
Surface Zone ◽  
Electromagnetic Parameters ◽  
Wave Processes ◽  
Near Surface ◽  
Ionosphere Plasma ◽  
Electric And Magnetic Fields

The program and results of physical research in the international (5 countries) space experiment «The situation (1 stage)», conducted onboard the Russian segment of the International Space Station (ISS) in the period 27.02.2013 to 09.05.2015, is presented. The methods and scientific tasks of the experiment and the composition of the Plasma-wave complex based on the combined wave diagnostics method are described in detail, and designed to conduct geophysical studies through long-term monitoring measurements of the electromagnetic parameters of the ionosphere plasma and plasma-wave processes associated with the manifestation in the ionosphere of the solar-magnetosphere-ionosphere and ionosphere-atmosphere relationships, i. e., parameters of space weather. Studies in the near-surface zone of plasma-wave processes of interaction of an extra-large spacecraft, like ISS, with the ionosphere are necessary for both applied and fundamental geophysical studies. The electric and magnetic fields and currents measured at the surface of the ISS are determined by the parameters of the surrounding ionosphere plasma and the nature of the interaction of the materials on the surface with this medium. Key words: orbital space station, fundamental space research, ionosphere plasma, plasma-wave processes, electromagnetic fields and radiation, scientific instrument, space weather.

scholarly journals On the Use of Rotary-Wing Aircraft to Sample Near-Surface Thermodynamic Fields: Results from Recent Field Campaigns

Sensors ◽  
2018 ◽  
Vol 19 (1) ◽  
pp. 10 ◽  
Author(s):  
Temple Lee ◽  
Michael Buban ◽  
Edward Dumas ◽  
C. Baker
Keyword(s):  
Weather Prediction ◽  
Chemical Properties ◽  
Unmanned Aircraft ◽  
Unmanned Aircraft Systems ◽  
Spatiotemporal Variability ◽  
Near Surface ◽  
Field Campaigns ◽  
High Level ◽  
Rotary Wing

Rotary-wing small unmanned aircraft systems (sUAS) are increasingly being used for sampling thermodynamic and chemical properties of the Earth’s atmospheric boundary layer (ABL) because of their ability to measure at high spatial and temporal resolutions. Therefore, they have the potential to be used for long-term quasi-continuous monitoring of the ABL, which is critical for improving ABL parameterizations and improving numerical weather prediction (NWP) models through data assimilation. Before rotary-wing aircraft can be used for these purposes, however, their performance and the sensors used therein must be adequately characterized. In the present study, we describe recent calibration and validation procedures for thermodynamic sensors used on two rotary-wing aircraft: A DJI S-1000 and MD4-1000. These evaluations indicated a high level of confidence in the on-board measurements. We then used these measurements to characterize the spatiotemporal variability of near-surface (up to 300-m AGL) temperature and moisture fields as a component of two recent field campaigns: The Verification of the Origins of Rotation in Tornadoes Experiment in the Southeast U.S. (VORTEX-SE) in Alabama, and the Land Atmosphere Feedback Experiment (LAFE) in northern Oklahoma.

scholarly journals Modern Geodetic Measurement Techniques in Gravimetric Studies on the Example of Gypsum Karst in the Siesławice Region

2018 ◽  
Vol 35 ◽  
pp. 03002 ◽  
Author(s):  
Sławomir Porzucek ◽  
Monika Łój ◽  
Karolina Matwij ◽  
Wojciech Matwij
Keyword(s):  
Laser Scanning ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Digital Terrain Model ◽  
Field Studies ◽  
Surface Zone ◽  
Three Dimensional Model ◽  
Geodetic Measurement ◽  
Near Surface ◽  
Gypsum Karst

In the region of Siesławice (near Busko-Zdrój, Poland) there are unique phenomena of gypsum karst. Atmospheric factors caused numerous gypsum outcrops, canals and underground voids. The article presents the possibility of using non-invasive gravimetric surveys supplemented with geodetic measurements to illustrate karst changes occurring around the void. The use of modern geodetic measurement techniques including terrestrial and airborne laser scanning enables to generate a digital terrain model and a three-dimensional model of voids. Gravimetric field studies allowed to map the anomalies of the gravitational field of the near-surface zone. Geodetic measurement results have made it possible to accurately determine the terrain correction that supplemented the gravimetric anomaly information. Geophysical interpretation indicate the presence of weathered rocks in the near surface zone and fractures and loosened zones located surround the karst cave.

A Coupled Multibody Finite Element Model for Investigating Effects of Surface Defects on Rolling Contact Fatigue

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Zamzam Golmohammadi ◽  
Farshid Sadeghi
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Surface Defects ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Rolling Contact ◽  
Internal Stresses ◽  
Fe Model ◽  
Elastic Plastic ◽  
Pile Up

A coupled multibody elastic–plastic finite element (FE) model was developed to investigate the effects of surface defects, such as dents on rolling contact fatigue (RCF). The coupled Voronoi FE model was used to determine the contact pressure acting over the surface defect, internal stresses, damage, etc. In order to determine the shape of a dent and material pile up during the over rolling process, a rigid indenter was pressed against an elastic plastic semi-infinite domain. Continuum damage mechanics (CDM) was used to account for material degradation during RCF. Using CDM, spall initiation and propagation in a line contact was modeled and investigated. A parametric study using the model was performed to examine the effects of dent sharpness, pile up ratio, and applied load on the spall formation and fatigue life. The spall patterns were found to be consistent with experimental observations from the open literature. Moreover, the results demonstrated that the dent shape and sharpness had a significant effect on pressure and thus fatigue life. Higher dent sharpness ratios significantly reduced the fatigue life.

scholarly journals Uncertainty of the CO<sub>2</sub> threshold for melting a hard Snowball Earth

2010 ◽  
Vol 6 (4) ◽  
pp. 1337-1350 ◽  
Author(s):  
Y. Hu ◽  
J. Yang
Keyword(s):  
Greenhouse Effect ◽  
Atmospheric Model ◽  
Snowball Earth ◽  
Near Surface ◽  
Cloud Forcing ◽  
Clear Sky ◽  
Critical Issues ◽  
Simulation Results ◽  
High Level ◽  
Hadley Cells

Abstract. One of the critical issues of the Snowball Earth hypothesis is how high level of CO2 is required for triggering the deglaciation. Using Community Atmospheric Model version 3 (CAM3), we study the problem for the CO2 threshold. Our simulations show large differences from previous results (Pierrehumbert, 2004, 2005). At 0.2 bars of CO2, the January maximum near-surface temperature is about 268 K, about 13 K higher than that in Pierrehumbert (2004, 2005), but lower than the value of 270 K for 0.1 bar of CO2 in Le Hir et al. (2007). It is found that the diversity of simulation results is mainly due to model sensitivity of greenhouse effect and longwave cloud forcing to increasing CO2. At 0.2 bar of CO2, CAM3 yields 117 Wm −2 of clear-sky greenhouse effect and 32 Wm−2 of longwave cloud forcing, versus only about 77 Wm−2 and 10.5 Wm−2 in Pierrehumbert (2004, 2005), respectively. CAM3 has comparable clear-sky greenhouse effect to that in Le Hir et al. (2007), but lower longwave cloud forcing. CAM3 also produces much stronger Hadley cells than in Pierrehumbert (2005).

scholarly journals Structural-Phase State, Mechanical Properties, Acoustic and Magnetic Characteristics in the Sustainable Deformation Localization Zones of Power Equipment Made of Structural and Heat Resistant Steels

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1638
Author(s):  
Nikolay Ababkov ◽  
Alexandr Smirnov ◽  
Vladimir Danilov ◽  
Lev Zuev ◽  
Natalya Popova ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Phase State ◽  
Structural Phase ◽  
Magnetic Characteristics ◽  
Internal Stresses ◽  
Power Equipment ◽  
Deformation Localization ◽  
Structural Phase State ◽  
Heat Resistant ◽  
Heat Resistant Steels

The paper presents the results of the analysis of the microstructure, mechanical properties, acoustic and magnetic characteristics of the metal of pipelines that are part of heat and power equipment, after long-term operation, made of structural and heat-resistant steels in the zones of localization of plastic deformation. Samples of 0.2 С steel and 0.12С-1Сr-1Mo-1V steel were studied in the initial state, as well as after operation for 219 and 360 thousand hours, respectively. As a result of the studies carried out for each sample, the phase composition was determined (qualitatively and quantitatively), and the following parameters of the fine structure were calculated: volume fractions of structural components of steel (pearlite and ferrite), scalar and excess ± dislocation density, curvature-torsion of the crystal lattice χ, amplitude of internal stresses (shear stress and long-range stresses). All quantitative parameters of the structure are determined both in each structural component of steel, and in general for each sample. The structure of the metal of all specimens after deformation before the formation of zones of stable localization of deformations consists of a ferrite-pearlite mixture, and for specimens after operation before fracture only of unfragmented and fragmented ferrite. Ferrite, which occupies the bulk of the material, is present both unfragmented and fragmented. For all samples, the ratios ≥ , χ = χpl, σL ≥ σd were calculated, which indicate whether there is a danger of the initiation of microcracks in metal samples. For specimens without operation and after operation without damage in zones of stable localization of deformations, these conditions are met, and for specimens after operation until destruction, they are not met. It was found that the structural-phase state in the zones of localization of deformations has a direct effect on the characteristics of non-destructive tests. Thus, for all investigated samples, the values of such parameters as the delay time of the surface acoustic wave, the attenuation coefficient, the amplitude of the received signal, and the intensity of magnetic noise in the zones of deformation localization were established.

Chemical-heat treatment influence on thermal stability of microstructure, mechanical properties and fracture features of V-Cr-Ta-Zr alloy

2021 ◽  
pp. 36-42
Author(s):  
I.V. Smirnov ◽  
◽  
K.V. Grinyaev ◽  
A.N. Tyumentsev ◽  
A.D. Korotaev ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Thermal Stability ◽  
Structural Phase ◽  
Strength Properties ◽  
Chemical Heat Treatment ◽  
Chemical Heat ◽  
High Level ◽  
Fracture Features ◽  
Zr Alloy

A study of the features of structural-phase state, thermal stability, mechanical properties characteristics and fracture features of V-Cr-Ta-Zr alloy after chemical-heat treatment by the method of nonequilibrium internal oxidation has been carried out. It has been established that, in contrast to chemical-heat treatment in a defect state, the effect of oxygen when introduced into a material with a stabilized structure is observed only at high concentrations. At such oxygen concentrations, which ensure the maximum binding of Zr into particles based on ZrO2, the alloy under study demonstrates a high level of thermal stability and strength properties. These effects are associated with the implementation of disperse strengthening according to the Orowan mechanism by nanosized ZrO2 particles characterized by high thermal stability. The concentration and nature of the distribution of oxygen predetermine the spatial distribution of nanosized ZrO2 particles formed during chemical-heat treatment, which manifests itself in fracture features of the material at different temperatures.

Rain impact soil crust. II. Some effects of surface slope, drop size and soil variation

Soil Research ◽  
1991 ◽  
Vol 29 (2) ◽  
pp. 291 ◽  
Author(s):  
AJ Moss
Keyword(s):  
Drop Size ◽  
Surface Zone ◽  
Special Role ◽  
Soil Crust ◽  
Surface Slope ◽  
Small Surface ◽  
Near Surface ◽  
Loose Packing ◽  
Soil Variation ◽  
Stable Particles

Formation and non-formation of the rain-impact soil crust were studied experimentally over ranges of surface-slope, drop-size and soil variation. In these contexts, the formative process was found to be very versatile. However, stable particles, of a size just movable on the soil surfaces by raindrops, appear to play a special role in preventing crust development. Becoming juxtaposed on the surface, these particles form clusters which allow hydraulic penetration of water from impacting drops, through their large pores. This maintains loose packing in the near-surface zone as opposed to the compaction associated with crust formation where only small surface pores exist. A method of soil modification, involving increasing the proportion of durable, barely rain-movable particles in soils, is suggested as a means of combating crusting on a long-term basis.

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