Characteristics Of Surface Layer Research Articles

機械構造用鋼の表面特性に及ぼす微細ショットピーニングの影響

機械構造用鋼の表面特性に及ぼす微細ショットピーニングの影響

Characteristics of thin surface layers of cobalt-based alloys deposited by laser cladding

Thin surface layers of cobalt-based alloys (Stellite 6 and Tribaloy T-900) and 410 stainless steel (SS) were deposited on mild steel substrates by a coaxial laser cladding process. This process could produce a thin surface layer of less than 0.5 mm with low energy input. Laser-clad Stellite 6 and Tribaloy T-900 specimens exhibited refined dendritic microstructure. The interdendritic eutectics consisted of either small carbides or intermetallic compounds randomly distributed in a cobalt-rich solid solution, unlike the lamellar structure as observed in conventional weld overlays. The hardness values of the laser-clad layers were generally higher than those of conventional welding deposits owing to the refined effect. The wear and corrosion resistance of S-6 and T-900 specimens were considerably better compared to those of laser-clad 410 SS specimens. In addition, the T-900 specimen had substantially lower corrosion rates than the S-6 specimen in hydrochloric acid solution. Experimental results indicated that wear and corrosion characteristics of the T-900 specimen were excellent; however, preheating was required to avoid cracking in the laser cladding process.

Air–sea interaction processes in warm and cold sectors of extratropical cyclonic storms observed during FASTEX

Mid-Atlantic measurements from the research vessel (RV) Knorr during the Fronts and Atlantic Storm-Tracks Experiment (FASTEX) are presented, and then used to examine the near-surface environment and air–sea interaction processes during the passage of ten frontal systems. This dataset includes measurements of the surface momentum, sensible-heat and moisture fluxes obtained from three different methods. The inertial dissipation (ID) drag coefficients from the RV Knorr are consistent with the ID data from other measurements in open-ocean storm environments. The covariance drag coefficients are generally larger than the ID values, indicating either the presence of flow distortion problems in the covariance data or a failure of the assumptions inherent to the ID technique at these higher wind speeds. Estimates of the wind speed dependence of the momentum, sensible-heat and latent-heat transfer coefficients are based on averaged values from the two methods. These measurements: (i) contribute significantly to the limited set of surface flux measurements for 10 m neutral winds in the 15–21 m s−1 range; (ii) contain the only ship-based covariance flux measurements successfully obtained in an open-ocean, high wind speed, storm environment; and (iii) include coincident wave-height measurements. The relationships between the surface layer and the synoptic atmospheric environment is examined using composites of atmospheric and oceanic surface-layer characteristics computed in ten storms for which the RV Knorr passed through the open-wave warm sector and the cold front. These composites show minima in the sensible- and latent-heat fluxes, and a maximum in the momentum flux, just before the frontal passage during the warm-sector peak in wind speed. A second momentum flux maximum of comparable magnitude occurs in the middle of the post-frontal regime. Though the warm-sector sensible-heat flux minimum is slightly negative, the sum of the two heat fluxes is positive, suggesting a positive impact on the synoptic development of these storms. Wave heights increase steadily from the eastern half of the warm sector to the frontal passage, remaining high through most of the post-frontal regime before decreasing. Differences between covariance and ID stresses are largest during the times bracketing the cold front when the wave heights and stresses are large. Differences between covariance and bulk stresses are greatest in the pre-frontal low-level jet, when the frequency of waves with periods of 6–9 s maximizes, and in the post-frontal regime where the wind direction veers. Systematic differences between stress direction and wind direction are observed.

Characteristics of Photocatalytic Titania Fabricated by Anodization

The anodic titanium dioxide (TiO2) films for photocatalyst were prepared by anodization in acid solution. The characteristics of surface layer and the photocatalytic efficiency of the anodic film have been investigated. The chemical states of anodic film were analyzed using XPS, and the photocatalytic efficiency was evaluated by the degradation rate of aniline blue. From XPS results the component elements of the electrolyte, P and S, were observed in the anodic film, which were incorporated from the electrolyte into the oxide layer during anodization. The porous TiO2 film exhibited high photocatalytic efficiency for degradation of aniline blue.

Traceflux: a small-scale tracer experiment at a forested site

Results from four successful tracer experiments carried out in a dense forest canopy are presented. For each experiment, sulphur hexafluoride SF 6 was released from a point source in trunk space and air samples were collected at 19 horizontally distributed locations in the canopy. Meteorological measurements include fast-response turbulence data recorded at several locations in and above the forest. Measured mean concentrations of SF 6 are compared against concentrations calculated by an analytical solution to the equation of diffusion. For near neutral and weak unstable conditions the model performs surprisingly well, even though the wind profile and turbulence statistics deviate substantially from surface layer characteristics. Still if more than an estimate of the concentration field is needed a more sophisticated model should be applied.

Improvement of Surface Layer Characteristics by Shot Lining

In the present study, lining of the metal with foils using shot peening was investigated to improve the surface layer characteristics. In the shot peening experiment, the foils set on the metal are pelted with hard particles traveling at a high velocity. The foils are bonded to the metal surface due to plastic deformation induced by the collision of the particles. The foils and the metal are heated to heighten the bondability because of the reduction of flow stress. Lining the metal with the hard powder sandwiched between two aluminum foil sheets was also attempted. In this experiment, a centrifugal shot peening machine wite an electrical heater was employed. The metals are commercially aluminium alloys and magnesium alloys, and the foils are commercially aluminum, titanium and nickel. The effects of shot speed and the heating temperature on the bondability were examined. Wear resistance was also evaluated by grinding. The foils were successfully bonded to the metal surface. It was found that the present method is effective in improving of surface layer characteristics.

Surface passivation and characterization of cobalt–ferrite nanoparticles

In the present study we report on the chemical synthesis, the surface passivation process, the peptization in low pH aqueous medium, and the characterization of cobalt–ferrite nanoparticles. The as produced, passivated and peptized cobalt–ferrite nanoparticles were investigated by atomic absorption measurements, transmission electron microscopy, and Mössbauer spectroscopy. The liquid Helium Mössbauer spectra consist of three well-defined sextets in all the studied samples. The data are discussed in terms of the characteristics of the nanoparticle surface layer and the effects produced by the passivation and peptization/aging processes.

North Brazil current rings viewed by TRMM Microwave Imager SST and the influence of the Amazon Plume

In the western equatorial Atlantic, 5 years of satellite Sea Surface Temperature (SST) measurements (1998–2002) from the cloud penetrating Tropical Rainfall Measuring Mission (TRMM) Microwave Imager reveal SST signatures of rings shedding from the North Brazil Current (NBC) as it separates from the South American coastline north of the Amazon River Delta and retroflects eastward between 5 and 10°N. By removing the spatial-mean SST from a 7° by 7° square of the nearly instantaneous measurements of each satellite pass, the 46.7 day aliasing period of the diurnal solar cycle is reduced, and seven to eight rings are observed per year with relatively warm (cold) SST anomalies of up to 1°C in the first (second) half of the year. The sense of the SST anomalies carried by the NBC rings are determined by the contrast between the NBC SST and the regional SSTs that are influenced by the far-reaching seasonally varying Amazon River freshwater plume. Within a 1.6-year period, 12 of the SST anomalies are validated by in situ mooring array data confirming the predicted sense of the SST anomalies for each season. According to historical hydrographic data, during the first half of the year, the Amazon Plume is generally contained northwest along the coast, whereas during the second half of the year, the Amazon Plume surrounds the NBC retroflection on the west and the north, and from the surface down to 50m, imposing a dramatic surface salinity contrast up to −4 and a surface temperature contrast up to +2°C across the front. The surface layer characteristics of the rings shed from the NBC retroflection reveal varying influence of the Amazon Plume. Of the four rings surveyed in the NBCR experiment, Amazon Plume water is found only on the edges of three surface-intensified rings, whereas it completely covers the surface layer of the one thermocline-intensified ring. The maximum current cores of the NBC and retroflection are observed within tens-of-meters of the edges of the Amazon Plume. As the fresher and typically warmer surface waters associated with the Amazon Plume are buoyant relative to the saltier and typically colder surface waters carried by the NBC, the varying position of the Amazon Plume may seasonally influence the surface dynamics in the region.

Photoinduced, Controlled Generation of Palladium Crystallite Structures in Polyimide Films

Structures of Pd crystallites with nanometer dimensions are formed on the surface of and inside polyimide films by a combination of photochemical and thermal processes. Photoinduced transformations of polyamic acid films containing Pd 2 + complexes prior to thermal curing affect the subsequent thermal imidization of the polymer and reduction of the remaining palladium ions. The extent of photolysis controls the formation and characteristics of surface and subsurface metallic layers as well as the sizes of Pd particles generated within and below the interlayer region. Interference between waves reflected from the continuous embedded Pd layer and waves reflected from the continuous surface metal layer is the origin of the colors observed in photolyzed and cured films. Multicolored areas are a result of nanometer range variations of the interlayer distance. Optical properties typical of Fabry-Perot filters are observed when the thickness of the surface layer and internal metal layer are similar. The etalon-like films experience significant reversible dimensional changes upon exposure to white light.

Engineering of surface layer in material removal machining

Methodology developed for designing and investigation of the characteristics of technological and exploitation surface layer aiming to provide conditions under which a surface layer with predictable characteristics of mate surfaces will be generated is described in the paper. Methodology possesses syntheses of performances for creation and analysis of models for surfaces generated with different types of machining, and import of measured surfaces data. Basis for the surface layer modelling with deterministic and stochastic structure is method of kinematical–geometrical copying of the cutting tool geometry as a function of machining conditions and method of virtual modelling comprising synthesis of theoretical functions simulating also disturbing factors appearing in the process of material removal. Definition of correlation existing between the parameters describing surface geometrical structure and technological parameters for surface machining is also enabled. These activities are performing with support of the originally created software (CADSIM) designed in Visual Basic in interaction with MS Access, AutoCAD and MATLAB.

Transmission Electron Microscopy of Boundary-Lubricated Bearing Surfaces. Part I: Mineral Oil Lubricant

Transmission electron microscopy (TEM) was performed on the near-surface material (depth <500 nm) of tapered roller bearing inner rings (cones) that were tested at two levels of boundary-lubricated conditions in mineral oil with no additives. Site-specific thinning of cross section cone surface sections for TEM analyses was conducted using the focused ion beam (FIB) milling technique. High-resolution structural and compositional characterization of near-surface material and surface layers was performed on an untested cone as well as cones tested at Λ∼1.1 and 0.3. This approach revealed near-surface microstructural distortion and grain size gradients that were attributed to surface finishing operations during manufacture. The characteristics of oxide surface layers and micro-cracks on the tested bearing surfaces were evaluated and found to depend on lubrication conditions.

Nocturnal Surface-Layer Characteristics at the Bottom of a Valley

Nighttime data collected at the bottom of a valley locatedin southern Brazil are studied. The analyzed quantities includemomentum and sensible heat fluxes, turbulence statistics andintermittency factors, and their relationship to the stability parameter.The proper interval for averaging and flux calculations is foundto be 20 min, based on the comparison of the fluxes and therandom error associated in their determination. Each data seriesis classified as calm or windy, according to the mean windspeed. A much better dependency of the variables in terms of thestability parameter is found under windy conditions. Analysis ofthe wind direction and topographic scales indicates that distortioneffects under calm conditions affect the flow, while the flow is inlocal equilibrium for windy conditions. In this case, the sensible heatflux shows a minimum for a value of z/L=0.08, while the momentumflux and the normalized scales of the wind components andtemperature decrease monotonically as the stability increases. Anintermittency factor is proposed and shown to be larger (moreintermittency) for more stable conditions.

Relationship between the thermal vertical structure of Cuban waters and tropical cyclone activity

A study of the oceanic surface layer is presented, taking into account its vertical thermal structure and time-space variability. Oceanographic data from 37 cruises were used. The thickness of the isothermal layer and depth of the 26ºC isotherm were determined. The possible connection between the thermal characteristics of the sea surface layer and tropical cyclone activity was analyzed. The presence of ENSO was considered. We show that the thermal characteristics of Cuban waters are always favorable for tropical cyclone development.

Computer diagnostics of surface characteristics of extended cylindrical objects by the active location technique

A computer-diagnostics method for examining characteristics of surface layers in conducting extended solids, based on treating data on radio-wave scattering by these solids in the meter and centimeter bands, is reported. The problem is reduced to solving a system of nonlinear algebraic equations. The computational algorithm and results of numerical experiments are described. The method allows using, as input data, not only asymptotic scattering diagrams, but also amplitude values of the reflected field measured close to the surface under study. The latter improves solution stability in complex noise-signal situations in which random distortions in receive chains occur.

Computer diagnostics of surface characteristics of extended cylindrical objects by the active location technique

A computer-diagnostics method for examining characteristics of surface layers in conducting extended solids, based on treating data on radio-wave scattering by these solids in the meter and centimeter bands, is reported. The problem is reduced to solving a system of nonlinear algebraic equations. The computational algorithm and results of numerical experiments are described. The method allows using, as input data, not only asymptotic scattering diagrams, but also amplitude values of the reflected field measured close to the surface under study. The latter improves solution stability in complex noise-signal situations in which random distortions in receive chains occur.

Laser-Ellipsometric and Photoelectrometric (EPEM) Video Microprobe

An automatic computerized system simultaneously measuring the thickness of the surface layer and the semiconducting characteristics of oxide and other surface layers on an electrode surface during the corrosion or any other electrochemical studies is described. The automatic recording of ellipsometric parameters and a photopotential at sharply focusing the probing laser beam at a chosen surface site provides the extremely high sensitivity to the microscopically localized passivation and depassivation processes. The phase-modulation principle of recording the ellipsometric parameters with a laser source, which is most promising for the local corrosion–electrochemical investigation, is naturally combined with the technique of measuring photo-emf with the modulation of not only the phase, but also the intensity of the incident radiation. The character of the intensity change with time (the type of modulation) can be arbitrarily set up to the modulation frequencies of hundreds megahertz, which enables one to study photoelectrochemical processes with substantially different characteristic times (such as the lifetime of electron or hole carriers in the surface oxide).

Turbulent characteristics of a semiarid atmospheric surface layer from cup anemometers – effects of soil tillage treatment (Northern Spain)

Abstract. This paper deals with the characteristics of turbulent flow over two agricultural plots with various tillage treatments in a fallow, semiarid area (Central Aragon, Spain). The main dynamic characteristics of the Atmospheric Surface Layer (ASL) measured over the experimental site (friction velocity, roughness length, etc.), and energy budget, have been presented previously (Frangi and Richard, 2000). The current study is based on experimental measurements performed with cup anemometers located in the vicinity of the ground at 5 different levels (from 0.25 to 4 m) and sampled at 1 Hz. It reveals that the horizontal wind variance, the Eulerian integral scales, the frequency range of turbulence and the turbulent kinetic energy dissipation rate are affected by the surface roughness. In the vicinity of the ground surface, the horizontal wind variance logarithmically increases with height, directly in relation to the friction velocity and the roughness length scale. It was found that the time integral scale (and subsequently the length integral scale) increased with the surface roughness and decreased with the anemometer height. These variations imply some shifts in the meteorological spectral gap and some variations of the spectral peak length scale. The turbulent energy dissipation rate, affected by the soil roughness, shows a z-less stratification behaviour under stable conditions. In addition to the characterization of the studied ASL, this paper intends to show which turbulence characteristics, and under what conditions, are accessible through the cup anemometer.Key words. Meteorology and atmospheric dynamics (climatology, turbulence, instruments and techniques)

Electrophysical Characteristics of the Laser-Glazed Surface Layer in Aluminum Oxide Ceramics

Results of a study of the laser-glazed surface of aluminum oxide substrates are reported. The laser glazing causes compositional and structural transformations in the subsurface layer, which results in a substantial change in electrical characteristics of the components.

Surface-Layer Characteristics in the Stable Boundary Layer with Strong and Weak Winds

An extensive meteorological dataset obtained from the plumevalidation experiment conducted by the Electric Power Research Institute (EPRI) atKincaid during 1980–1981 is analysed for studying the characteristic differences in thesurface-layer parameters in strong and weak wind stable conditions. The surface-layerparameters are computed using the similarity functions Φm and Φh proposed byBeljaars and Holtslag. The weak winds are characterized using the geostrophic wind speedas well as the wind speed at the 10-m level. The surface fluxes are found to be finitein weak wind conditions.Empirical formulations for the eddy diffusivities of momentum(KM) and heat (KH), and drag (CD) and heat exchange (CH) coefficients, as powerlaw functions of the bulk Richardson number (RiB), are proposed under both strong andweak wind conditions. Results are close to those based on observations taken from the IndianInstitute of Technology low wind diffusion experiment, the Land surface processes experiment,the Hanford diffusion experiment, the Cabauw field experiment and the Cooperative Atmospheric SurfaceExchange Study 1999 (CASES-99) experiment. In addition, the fluxes obtained fromthe proposed empirical relations are in good agreement with those based on similarity theory as wellas the turbulence measurements taken from the CASES-99 experiment.

Damage to the Metal of Industrial Pipelines in a Hydrogen Sulfide Environment

We studied changes in the mechanical properties of the metal of pipelines of oil- and gas-production equipment after long-term operation. We established that the mechanical characteristics of internal surface layer of the metal change significantly up to a depth of 2 mm. The coefficient of metal degradation depending on the thickness of pipe wall was introduced. We showed that deformation under the action of loads stimulates hydrogen-induced cracking. The corrosion rate at the lower part of a pipeline is 5.5 times as high as at the upper. We also showed the expediency of inhibitor protection of pipelines.