scholarly journals Physical Nature of Strengthening Mechanisms During Extremely Long-Term Operation of Rails

2021 ◽  
pp. 33-39
Author(s):  
Yu.F. Ivanov ◽  
A.A. Yuriev ◽  
V.E. Kormyshev ◽  
X. Chen ◽  
V.B. Kosterev ◽  
...  
Keyword(s):  
Surface Layer ◽  
Relative Content ◽  
Formation Mechanisms ◽  
Strengthening Mechanisms ◽  
Near Surface ◽  
Term Operation ◽  
Rail Head ◽  
Metal Volume ◽  
Lamellar Pearlite

The quantitative estimation of strengthening mechanisms of rails’ surface layer is carried out on the basis of regularities and formation mechanisms of structure-phase states revealed by the methods of modern physical materials science. It is performed at different depths of the rail head along the central axis and fillet of differentially quenched 100-meter rails after the extremely long-term operation (gross passed tonnage of 1411 mln tons). A long-term operation of rails is accompanied by the formation of structural constituent gradient consisting of a regular change in the relative content of lamellar pearlite, fractured pearlite, the structure of ferrite-carbide mixture, scalar, and excess dislocation density along the cross-section of the rail head. As the distance to the rail fillet surface decreases, the relative content of metal volume with lamellar pearlite decreases. However, the relative content of metal volume with the presence of the fractured pearlite structure and ferrite-carbide mixture increases. The contributions caused by the matrix lattice friction, intraphase boundaries, dislocation substructure, presence of carbide particles, internal stress fields, solid-solution strengthening, pearlite component of steel structure are estimated. It is shown that the main mechanism of strengthening in the surface layer is due to the interaction of moving dislocations with low-angle boundaries of nanometer dimensional fragments and subgrains. The main dislocation strengthening mechanism in a near-surface layer at a depth of 2-10 mm is due to the interaction of moving dislocations with immobile ones.

scholarly journals Change in Structural-Phase States and Properties of Lengthy Rails during Extremely Long-Term Operation

2020 ◽  
Vol 21 (4) ◽  
pp. 527-553
Author(s):  
V. E. Gromov ◽  
Yu. F. Ivanov ◽  
V. E. Kormyshev ◽  
A. A. Yuriev ◽  
A. P. Semin ◽  
...  
Keyword(s):  
Carbide Phase ◽  
Structural Phase ◽  
Relative Content ◽  
Formation Mechanisms ◽  
Term Operation ◽  
Dislocation Densities ◽  
Differential Quenching ◽  
Long Operation ◽  
Lamellar Pearlite

The regularities and formation mechanisms of structural-phase states and properties at different depths in the rail heads along the central axis and fillet after differential quenching of 100-meter rails and extremely long operation (with passed tonnage of 1411 million tons gross weight) have been revealed by the methods of the state-of-the-art physical materials science. As revealed, the differential quenching is accompanied by the formation of morphologically multi-aspect structure presented by grains of lamellar perlite, ferrite–carbide mixture, and structure-free ferrite. The steel structure is characterized by the α-Fe lattice parameter, the level of microstresses, the size of coherent-scattering region, the value of interlamellar distance, the scalar and excess dislocation densities. As shown, the extremely long operation of rails is accompanied by the numerous transformations of metal structure of rail head: firstly, a fracture of lamellar pearlite structure and a formation of subgrain structure of submicron (100–150 nm) sizes in the bulk of pearlite colonies; secondly, a precipitation of carbide phase particles of nanometer range along the boundaries and in the bulk of subgrains; thirdly, a microdistortion growth of steel crystal lattice; fourthly, a strain hardening of metal resulting in the increase (by 1.5-fold) in scalar and excess dislocation densities relative to the initial state. A long-term operation of rails is accompanied by the formation of structural constituent gradient consisting in a regular change in the relative content of lamellar pearlite, fractured pearlite, and structure of ferrite–carbide mixture along cross-section of railhead. As the distance to the rail fillet surface decreases, a relative content of metal volume with lamellar pearlite decreases, and that with the structure of fractured pearlite and ferrite–carbide mixture increases. As determined, the characteristic feature of ferrite–carbide mixture structure is a nanosize range of grains, subgrains and carbide-phase particles forming it. The size of grains and subgrains forming the type of structure varies in the limits of 40–70 nm; the size of carbide-phase particles located along the boundaries of grains and subgrains varies in the limits of 8–20 nm. A multiaspect character of steel strengthening is detected that is caused by several factors: firstly, the substructural strengthening due to the formation of fragment subboundaries, whose boundaries are stabilized by the carbide-phase particles; secondly, the strengthening by carbide-phase particles located in the bulk of fragments and on elements of dislocation substructure (dispersion hardening); thirdly, the strengthening caused by the precipitation of carbon atoms on dislocations (formation of Cottrell atmospheres); fourthly, the strengthening being introduced by internal stress fields due to incompatibility of crystal-lattices’ deformation of α-phase structural constituents and carbide-phase particles.

Structure and properties of rails after extremely long-term operation

2020 ◽  
pp. 30-39 ◽  
Author(s):  
Yu. F. Ivanov ◽  
V. E. Gromov ◽  
V. E. Kormyshev ◽  
A. M. Glezer
Keyword(s):  
Surface Layer ◽  
Lattice Parameter ◽  
Crystal Lattice Parameter ◽  
Subgrain Structure ◽  
Structure And Properties ◽  
Term Operation ◽  
Head Section ◽  
Structure Phase ◽  
Defective Surface

The paper reveals regularities and mechanisms of structure-phase states and properties formation of of differentially hardened 100-m rails of DT 350 category after the passed tonnage of 1411 mln. tons brutto. The formation of highly defective surface layer with nanosize (40–50 nm) grain-subgrain structure of pearlite colonies and submicrocrystal (150–250 nm) structure grains with structure free ferrite is detected. The change of hardness, microhardness, crystal lattice parameter, microdistorsion level, scalar and excess dislocation density on the rails head section are analyzed. The possible mechanisms of cementite plates’ transformation at extremely long-term operation are discussed.

Long-term operation of rail steel: Degradation of structure and properties of surface layer

2016 ◽  
Vol 10 (5) ◽  
pp. 1101-1105 ◽  
Author(s):  
V. E. Gromov ◽  
Yu. F. Ivanov ◽  
K. V. Morozov ◽  
O. A. Peregudov ◽  
O. A. Semina
Keyword(s):  
Surface Layer ◽  
Rail Steel ◽  
Structure And Properties ◽  
Term Operation ◽  
Degradation Of Structure

scholarly journals METHANE IN THE SURFACE LAYER OF THE ATMOSPHERE: CURRENT CONTENT, LONG-TERM TRENDS AND INTRAANNUAL VARIABILITY

2020 ◽  
Vol 3 ◽  
pp. 5-21
Author(s):  
V.V. Kuzovkin ◽  
◽  
S.M. Semenov ◽  
◽  
◽  
...  
Keyword(s):  
Surface Layer ◽  
Methane Concentration ◽  
Vertical Mixing ◽  
Time Shift ◽  
Optimal Time ◽  
Co2 Absorption ◽  
Near Surface ◽  
The World ◽  
Long Term Trends

The article is devoted to the empirical analysis of series of monthly mean concentrations of methane in the near-surface layer of the atmosphere from the global network of monitoring stations. They operate within the Global Atmosphere Watch (GAW) under the auspices of the World Meteorological Organization (WMO). The data is freely available at the World Data Center for Greenhouse Gases GAW/WMO (WDCGG) on its website https://gaw.kishou.go.jp/ . The temporal coverage is from the 1980s. Data series from 69 stations are considered, of which 22 stations represent the global background conditions. The rest of the stations are regional. Long-term trends in concentrations and intraannual (inter-monthly) deviations of mean monthly concentrations from long-term trends were studied. The multi-year trend was estimated using a series of 12-month running averages. To exclude systematic differences in methane concentrations, these series were adjusted to the series for the high-latitude Arctic station Alert (82° 30' N, 62° 21' W). The analysis showed that long-term trends are non-linear (including with a known pause in the growth of methane levels in 1999-2006), but are similar at most of the stations under consideration. Exceptions are 6 regional stations classified as ‘abnormal’ for methane. A possible cause of the abnormality is being under the influence of certain sources of methane (anthropogenic or natural). Long-term trends at the rest of the stations are just slightly differ from the average trend for global stations. The series of intra-annual (inter-monthly) deviations of mean monthly concentrations from long-term trends for many stations, even those located at very significant distances from each other, show high correlative similarity. However, it manifests itself at an optimal time shift from 5 months. towards earlier dates up to 6 months. towards later dates. The results of the analysis are consistent with the assumption that the intra-annual variability in methane concentration is largely driven by seasonal factors that are significantly related to latitude, including vertical mixing in the atmosphere and destruction in the troposphere in reactions with hydroxyl. The root-mean-square values of the intra-annual (inter-monthly) fluctuations in methane concentration significantly depend on latitude. The higher the latitude, the greater the overall value. Maximum values are reached in the latitudinal belt 45-50° N, and further, to the north, the Кузовкин В.В., Семенов С.М. 20 values decrease. This character of intra-annual fluctuations in the level of methane content may be explained, among other things, by significant inter-seasonal fluctuations in anthropogenic methane emissions at the indicated latitudes in countries with developed economies located in North America and Western Europe. The estimates of correlations of the series of intra-annual (inter-monthly) fluctuations of the average monthly concentrations of CH4 and CO2 showed that at optimal time shifts, they are rather high, about 0.8. Moreover, this is observed both at some polar stations and at tropical ones. This confirms the assumption that natural seasonal biogeochemical and geophysical processes play a significant role in the formation of intra-annual (inter-monthly) deviations of the methane and carbon dioxide content in the near-surface layer from long-term trends, namely, vertical mixing of air, CO2 absorption on the Earth's surface, destruction of methane in the troposphere in reactions with hydroxyl.

The Role of Lattice Curvature in Structural Degradation of the Metal Surface Layer of a Rail under Long-term Operation

2020 ◽  
Vol 65 (10) ◽  
pp. 376-378
Author(s):  
V. E. Panin ◽  
V. E. Gromov ◽  
Yu. F. Ivanov ◽  
A. A. Yuriev ◽  
V. E. Kormyshev
Keyword(s):  
Surface Layer ◽  
Metal Surface ◽  
Structural Degradation ◽  
Lattice Curvature ◽  
Term Operation ◽  
Metal Surface Layer

Structure-phase states and properties of rail tread surface at long-term operation

2021 ◽  
Vol 64 (1) ◽  
pp. 71-77
Author(s):  
Yu.F. Ivanov ◽  
◽  
V.E. Kormyshev ◽  
V.E. Gromov ◽  
A.A. Yuriev ◽  
...  
Keyword(s):  
Material Science ◽  
Lattice Parameter ◽  
Crystal Lattice Parameter ◽  
Subgrain Structure ◽  
Term Operation ◽  
Structure Phase ◽  
Multiple Transformation ◽  
Lamellar Pearlite ◽  
Differentially Quenched Rails

Using the methods of modern physical material science the investigations of structure-phase states and properties at different depth from tread surface of differentially quenched rails at extremely long-term operation (passed tonnage 1411 mln t) are carried out. The hardness decrease from 37.1 to 35.8 HRC at the depth 2 and 10 mm and microhardness from 1481 to 1210 MPa, respectively is revealed. The established multiple transformation of tread surface structure concludes in: fracture of lamellar pearlite structure and subgrain structure formation of submicronsizes (100-150 nm); precipitation of carbide phase nanoparticles (30-55 nm)along the boundaries and in the volume ofsubgrains; growth of microdistorsions and α-Fe crystal lattice parameter; growth of scalar and excess dislocation density. The suggestions about the possible reasons of observable regularities are made.

scholarly journals Degradation of structure and properties of rail surface layer at long-term operation

2017 ◽  
Vol 33 (12) ◽  
pp. 1473-1478 ◽  
Author(s):  
V. E. Gromov ◽  
Yu. F. Ivanov ◽  
R. S. Qin ◽  
O. A. Peregudov ◽  
K. V. Aksenova ◽  
...  
Keyword(s):  
Surface Layer ◽  
Structure And Properties ◽  
Term Operation ◽  
Degradation Of Structure

scholarly journals Observational evidence of temperature trends at two levels in the surface layer

2016 ◽  
Vol 16 (2) ◽  
pp. 827-841 ◽  
Author(s):  
X. Lin ◽  
R. A. Pielke Sr. ◽  
R. Mahmood ◽  
C. A. Fiebrich ◽  
R. Aiken
Keyword(s):  
Surface Layer ◽  
Surface Temperature ◽  
Current Knowledge ◽  
Observational Evidence ◽  
Lapse Rate ◽  
High Quality ◽  
Near Surface ◽  
Temperature Trends ◽  
Screen Level

Abstract. Long-term surface air temperatures at 1.5 m screen level over land are used in calculating a global average surface temperature trend. This global trend is used by the IPCC and others to monitor, assess, and describe global warming or warming hiatus. Current knowledge of near-surface temperature trends with respect to height, however, is limited and inadequately understood because surface temperature observations at different heights in the surface layer of the world are rare especially from a high-quality and long-term climate monitoring network. Here we use high-quality two-height Oklahoma Mesonet observations, synchronized in time, fixed in height, and situated in relatively flat terrain, to assess temperature trends and differentiating temperature trends with respect to heights (i.e., near-surface lapse rate trend) over the period 1997 to 2013. We show that the near-surface lapse rate has significantly decreased with a trend of −0.18 ± 0.03 °C (10 m)−1 per decade indicating that the 9 m height temperatures increased faster than temperatures at the 1.5 m screen level and/or conditions at the 1.5 m height cooled faster than at the 9 m height. However, neither of the two individual height temperature trends by themselves were statistically significant. The magnitude of lapse rate trend is greatest under lighter winds at night. Nighttime lapse rate trends were significantly more negative than daytime lapse rate trends and the average lapse rate trend was three times more negative under calm conditions than under windy conditions. Our results provide the first observational evidence of near-surface temperature changes with respect to height that could enhance the assessment of climate model predictions.

scholarly journals METHANE IN THE SURFACE LAYER OF THE ATMOSPHERE: CURRENT CONTENT, LONG-TERM TRENDS, AND INTRA-ANNUAL VARIABILITY

2020 ◽  
Vol 4 ◽  
pp. 121-133
Author(s):  
V.V. Kuzovkin ◽  
◽  
S.M. Semenov ◽  
◽  
◽  
...  
Keyword(s):  
Surface Layer ◽  
Methane Concentration ◽  
Vertical Mixing ◽  
Time Shift ◽  
Optimal Time ◽  
Near Surface ◽  
Annual Variability ◽  
The World ◽  
Long Term Trends

The article deals with the empirical analysis of series of monthly mean concentrations of methane in the near-surface layer of the atmosphere from the global network of monitoring stations. They operate within the Global Atmosphere Watch (GAW) under the auspices of the World Meteorological Organization (WMO). The data is freely available at the World Data Center for Greenhouse Gases GAW/WMO (WDCGG) on its website https://gaw.kishou.go.jp/. The temporal coverage is from the 1980s. Data series from 69 stations are considered, of which 22 stations represent global background conditions. The rest of the stations are regional. Long-term trends in concentrations and the intra-annual (inter-monthly) deviations of monthly mean concentrations from long-term trends were studied. The multi-year trend was estimated using a series of 12-month running averages. To exclude systematic differences in methane concentrations, these series were adjusted to the series for the high-latitude Arctic station Alert (82° 30' N, 62° 21' W). The analysis showed that long-term trends are non-linear (in particular, a known pause in the growth of methane levels in 1999-2006 is observed), but are similar at most stations under consideration. Exceptions are six regional stations classified as “abnormal” in terms of methane. Possibly, this abnormality is due to the influence of certain sources of methane (anthropogenic or natural). Long-term trends at the rest of the stations just slightly differ from the average trend for the global stations. The series of intra-annual (inter-monthly) deviations of monthly mean concentrations from long-term trends for many stations (even those located at very significant distances from each other) show high correlative similarity. However, this similarity manifests itself at an optimal time shift from 5 months towards earlier dates up to 6 months towards later dates. The results of the analysis are consistent with the assumption that the intra-annual variability in methane concentration is largely driven by seasonal factors that are significantly related to latitude, such as vertical mixing in the atmosphere and destruction in the troposphere in reactions with hydroxyl. The root-mean-square values of intra-annual (inter-monthly) fluctuations in methane concentration depend significantly on latitude. In general, the higher the latitude is, the greater is the value. The maximum values are reached in the latitudinal belt within 45-50° N, and further to the North the values decrease. This feature of intra-annual fluctuations in the level of methane content may be explained, among other things, by significant inter-seasonal fluctuations in anthropogenic methane emissions occurring at the indicated latitudes in the countries with developed economies located in North America and Western Europe. The correlations of the series of intra-annual (inter-monthly) fluctuations of the monthly mean concentrations of CH4 and CO2 were estimated as rather high, about 0.8, at optimal time shifts, which is observed both at some polar stations and at tropical ones. This confirms the assumption that natural seasonal biogeochemical and geophysical processes play a significant role in the formation of intra-annual (inter-monthly) deviations of methane and carbon dioxide content in the near-surface layer from long-term trends. These processes include vertical mixing of air, CO2 absorption on the Earth’s surface, and destruction of methane in the troposphere in reactions with hydroxyl.

scholarly journals Reduction in DC-Drift in LiNbO3-Based Electro-Optical Modulator

Photonics ◽  
2021 ◽  
Vol 8 (12) ◽  
pp. 571
Author(s):  
Aleksei Sosunov ◽  
Roman Ponomarev ◽  
Anton Zhuravlev ◽  
Sergey Mushinsky ◽  
Mariana Kuneva
Keyword(s):  
Surface Layer ◽  
Operating Point ◽  
Optical Modulator ◽  
Energy Calculation ◽  
Optical Modulators ◽  
Linbo3 Crystal ◽  
Short Term ◽  
Near Surface ◽  
Defective Structure

This study involves the results of research on short-term and long-term DC-drifts in electro-optical modulators based on annealed proton exchange waveguides in LiNbO3 crystals after wafer pre-annealing. The relaxation time of the DC-drift of the operating point for a short-term drift is measured in minutes, and for a long-term drift it is measured in hours and days. DC-drift was measured by applying bias voltage and changing crystal temperature. The obtained results show significant impact on the stability of operating point in EO-modulators after treatment of defective structure of the near-surface layer of a LiNbO3 crystal. Treatment of the disturbed near-surface layer of a LiNbO3 crystal results in the simultaneous reduction in short-term DC-drift and increase in operation stability of electro-optical modulators during long-term measurement of temperature by activation energy calculation.

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