The Experts below are selected from a list of 19200 Experts worldwide ranked by ideXlab platform
Farhad Rezai-aria - One of the best experts on this subject based on the ideXlab platform.
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Role of Heat‐Flux Density and mechanical loading on the microscopic Heat‐checking of high temperature tool steels under thermal fatigue experiments
International Journal of Fatigue, 2013Co-Authors: Sabine Le Roux, Farid Medjedoub, Gilles Dour, Farhad Rezai-ariaAbstract:Thermal fatigue of a hot work tool steel (X38CrMoV5) is investigated under various test conditions. A microscopic interconnected Heat‐checking pattern forms on the oxidized surface of the specimen. The evolution of the crack Density and morphology is characterized by Scanning Electron Microscopy (SEM) and image analysis. The effects of the initial hardness, the maximum temperature and the Heating period of the thermal cycle are reported. It is shown that the saturated Heat‐checking Density is independent of the maximum temperature of the thermal cycle, but is dependent on the Heating rate. No significant effect of the initial hardness is observed. In the saturated regime, a linear relationship is established between the Heat‐checking Density and the maximum Heat‐Flux Density applied to the specimen. The saturated crack Density is explained by the difference between the thermo‐mechanical strains of the oxide layer and the steel. A damage criterion, independent of the initial hardness of the steel, is proposed to describe the microscopic Heat‐checking life.
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Role of Heat-Flux Density and mechanical loading on the microscopic Heat-checking of high temperature tool steels under thermal fatigue experiments
International Journal of Fatigue, 2013Co-Authors: Sabine Le Roux, Farid Medjedoub, Gilles Dour, Farhad Rezai-ariaAbstract:Abstract Thermal fatigue of a hot work tool steel (X38CrMoV5) is investigated under various test conditions. A microscopic interconnected Heat-checking pattern forms on the oxidized surface of the specimen. The evolution of the crack Density and morphology is characterized by Scanning Electron Microscopy (SEM) and image analysis. The effects of the initial hardness, the maximum temperature and the Heating period of the thermal cycle are reported. It is shown that the saturated Heat-checking Density is independent of the maximum temperature of the thermal cycle, but is dependent on the Heating rate. No significant effect of the initial hardness is observed. In the saturated regime, a linear relationship is established between the Heat-checking Density and the maximum Heat-Flux Density applied to the specimen. The saturated crack Density is explained by the difference between the thermo-mechanical strains of the oxide layer and the steel. A damage criterion, independent of the initial hardness of the steel, is proposed to describe the microscopic Heat-checking life.
D. Spano - One of the best experts on this subject based on the ideXlab platform.
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Estimating sensible and latent Heat Flux densities from grapevine canopies using surface renewal.
Agricultural and Forest Meteorology, 2000Co-Authors: D. Spano, R. L. Snyder, Pierpaolo DuceAbstract:Fine-wire thermocouples were used to measure high-frequency temperature above and within canopies and structure functions were employed to determine temperature ramp characteristics, which were used in a fundamental conservation of energy equation to estimate sensible Heat Flux Density. Earlier experiments over dense, tall, and short canopies demonstrated that the surface renewal method works, but requires a correction for uneven Heating (e.g. D0.5 for tall, and D1.0 for short canopies). For sparse canopies, the calibration factor was unknown. Experiments were conducted in grape vineyards in California and Italy to determine whether the surface renewal method works in a sparse canopy and to determine if calibration is necessary. Surface renewal data were collected at several heights in the canopies and these were compared with simultaneous 1-D sonic anemometer measurements. The results indicated that the surface renewal technique provides good estimates of sensible Heat Flux Density under all stability conditions without the need for calibration when the data are measured at about 90% of the canopy height. The values were generally within ca. 45 W m 2 of what was measured with a sonic anemometer. Separating the canopy into two layers provided even more accurate estimates of sensible Heat Flux Density without the need for calibration. The best results were obtained when the lower layer was below the bottom of the vegetation and the upper layer included the vegetation. When combined with energy balance measurements of net radiation and soil Heat Flux Density, using a thermocouple and the surface renewal technique offers an inexpensive alternative for estimating evapotranspiration with good accuracy. © 2000 Elsevier Science B.V. All rights reserved.
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Surface renewal analysis for sensible Heat Flux Density using structure functions
Agricultural and Forest Meteorology, 1997Co-Authors: D. SpanoAbstract:Surface renewal (SR) analysis was used to estimate the sensible Heat Flux Density (H) over different crop canopies (grass, wHeat, and sorghum) and the results were compared with eddy covariance measurements. High-frequency temperature traces showed ramp-like structures, and structure functions were used to determine the mean amplitude and duration of these ramps. The ramp characteristics were used to estimate H. A wide range of sensible Heat Flux Density conditions were observed. The accuracy was acceptable, but was dependent on the measurement height, the wind shear at the measurement level, and the time lags used in the structure functions. The use of surface renewal H values in energy balance determination of λE can give results nearly as accurate as those obtained using a sonic anemometer.
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SURFACE RENEWAL ANALYSIS FOR SENSIBLE AND LATENT Heat Flux Density
Boundary-Layer Meteorology, 1996Co-Authors: R. L. Snyder, D. Spano, K. T. PawuAbstract:High frequency temperature measurements were recorded at five heights and surface renewal (SR) analysis was used to estimate sensible Heat Flux Density (H) over 0.1 m tall grass. Traces of the temperature data showed ramp-like structures, and the mean amplitude and duration of these ramps were used to calculate H using structure functions. Data were compared with H values measured with a sonic anemometer. Latent Heat Flux Density (λE) was calculated using an energy balance and the results were compared with λE computed from the sonic anemometer data. SR analysis provided good estimates of H for data recorded at all heights but the canopy top and at the highest measurement level, which was above the fully adjusted boundary layer.
Sabine Le Roux - One of the best experts on this subject based on the ideXlab platform.
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Role of Heat‐Flux Density and mechanical loading on the microscopic Heat‐checking of high temperature tool steels under thermal fatigue experiments
International Journal of Fatigue, 2013Co-Authors: Sabine Le Roux, Farid Medjedoub, Gilles Dour, Farhad Rezai-ariaAbstract:Thermal fatigue of a hot work tool steel (X38CrMoV5) is investigated under various test conditions. A microscopic interconnected Heat‐checking pattern forms on the oxidized surface of the specimen. The evolution of the crack Density and morphology is characterized by Scanning Electron Microscopy (SEM) and image analysis. The effects of the initial hardness, the maximum temperature and the Heating period of the thermal cycle are reported. It is shown that the saturated Heat‐checking Density is independent of the maximum temperature of the thermal cycle, but is dependent on the Heating rate. No significant effect of the initial hardness is observed. In the saturated regime, a linear relationship is established between the Heat‐checking Density and the maximum Heat‐Flux Density applied to the specimen. The saturated crack Density is explained by the difference between the thermo‐mechanical strains of the oxide layer and the steel. A damage criterion, independent of the initial hardness of the steel, is proposed to describe the microscopic Heat‐checking life.
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Role of Heat-Flux Density and mechanical loading on the microscopic Heat-checking of high temperature tool steels under thermal fatigue experiments
International Journal of Fatigue, 2013Co-Authors: Sabine Le Roux, Farid Medjedoub, Gilles Dour, Farhad Rezai-ariaAbstract:Abstract Thermal fatigue of a hot work tool steel (X38CrMoV5) is investigated under various test conditions. A microscopic interconnected Heat-checking pattern forms on the oxidized surface of the specimen. The evolution of the crack Density and morphology is characterized by Scanning Electron Microscopy (SEM) and image analysis. The effects of the initial hardness, the maximum temperature and the Heating period of the thermal cycle are reported. It is shown that the saturated Heat-checking Density is independent of the maximum temperature of the thermal cycle, but is dependent on the Heating rate. No significant effect of the initial hardness is observed. In the saturated regime, a linear relationship is established between the Heat-checking Density and the maximum Heat-Flux Density applied to the specimen. The saturated crack Density is explained by the difference between the thermo-mechanical strains of the oxide layer and the steel. A damage criterion, independent of the initial hardness of the steel, is proposed to describe the microscopic Heat-checking life.
Tusheng Ren - One of the best experts on this subject based on the ideXlab platform.
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determining near surface soil Heat Flux Density using the gradient method a thermal conductivity model based approach
Journal of Hydrometeorology, 2017Co-Authors: Xiaoyang Peng, Joshua L. Heitman, Robert Horton, Tusheng RenAbstract:AbstractIn the gradient method, soil Heat Flux Density at a known depth G is determined as the product of soil thermal conductivity λ and temperature T gradient. While measuring λ in situ is difficult, many field studies readily support continuous, long-term monitoring of soil T and water content θ in the vadose zone. In this study, the performance of the gradient method is evaluated for estimating near-surface G using modeled λ and measured T. Hourly λ was estimated using a model that related λ to θ, soil bulk Density ρb, and texture at 2-, 6-, and 10-cm depths. Soil Heat Flux Gm was estimated from modeled λ and measured T gradient (from thermocouples). The Gm results were evaluated with Heat Flux data GHP determined using independent measured λ and T gradient from Heat-pulse probes. The λ model performed well at the three depths with 3.3%–7.4% errors. The Gm estimates were similar to GHP (agreed to within 15.1%), with the poorest agreement at the 2-cm soil depth, which was caused mainly by the relativel...
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Determining Near-Surface Soil Heat Flux Density Using the Gradient Method: A Thermal Conductivity Model–Based Approach
Journal of Hydrometeorology, 2017Co-Authors: Xiaoyang Peng, Joshua L. Heitman, Robert Horton, Tusheng RenAbstract:AbstractIn the gradient method, soil Heat Flux Density at a known depth G is determined as the product of soil thermal conductivity λ and temperature T gradient. While measuring λ in situ is difficult, many field studies readily support continuous, long-term monitoring of soil T and water content θ in the vadose zone. In this study, the performance of the gradient method is evaluated for estimating near-surface G using modeled λ and measured T. Hourly λ was estimated using a model that related λ to θ, soil bulk Density ρb, and texture at 2-, 6-, and 10-cm depths. Soil Heat Flux Gm was estimated from modeled λ and measured T gradient (from thermocouples). The Gm results were evaluated with Heat Flux data GHP determined using independent measured λ and T gradient from Heat-pulse probes. The λ model performed well at the three depths with 3.3%–7.4% errors. The Gm estimates were similar to GHP (agreed to within 15.1%), with the poorest agreement at the 2-cm soil depth, which was caused mainly by the relativel...
Gilles Dour - One of the best experts on this subject based on the ideXlab platform.
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Role of Heat‐Flux Density and mechanical loading on the microscopic Heat‐checking of high temperature tool steels under thermal fatigue experiments
International Journal of Fatigue, 2013Co-Authors: Sabine Le Roux, Farid Medjedoub, Gilles Dour, Farhad Rezai-ariaAbstract:Thermal fatigue of a hot work tool steel (X38CrMoV5) is investigated under various test conditions. A microscopic interconnected Heat‐checking pattern forms on the oxidized surface of the specimen. The evolution of the crack Density and morphology is characterized by Scanning Electron Microscopy (SEM) and image analysis. The effects of the initial hardness, the maximum temperature and the Heating period of the thermal cycle are reported. It is shown that the saturated Heat‐checking Density is independent of the maximum temperature of the thermal cycle, but is dependent on the Heating rate. No significant effect of the initial hardness is observed. In the saturated regime, a linear relationship is established between the Heat‐checking Density and the maximum Heat‐Flux Density applied to the specimen. The saturated crack Density is explained by the difference between the thermo‐mechanical strains of the oxide layer and the steel. A damage criterion, independent of the initial hardness of the steel, is proposed to describe the microscopic Heat‐checking life.
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Role of Heat-Flux Density and mechanical loading on the microscopic Heat-checking of high temperature tool steels under thermal fatigue experiments
International Journal of Fatigue, 2013Co-Authors: Sabine Le Roux, Farid Medjedoub, Gilles Dour, Farhad Rezai-ariaAbstract:Abstract Thermal fatigue of a hot work tool steel (X38CrMoV5) is investigated under various test conditions. A microscopic interconnected Heat-checking pattern forms on the oxidized surface of the specimen. The evolution of the crack Density and morphology is characterized by Scanning Electron Microscopy (SEM) and image analysis. The effects of the initial hardness, the maximum temperature and the Heating period of the thermal cycle are reported. It is shown that the saturated Heat-checking Density is independent of the maximum temperature of the thermal cycle, but is dependent on the Heating rate. No significant effect of the initial hardness is observed. In the saturated regime, a linear relationship is established between the Heat-checking Density and the maximum Heat-Flux Density applied to the specimen. The saturated crack Density is explained by the difference between the thermo-mechanical strains of the oxide layer and the steel. A damage criterion, independent of the initial hardness of the steel, is proposed to describe the microscopic Heat-checking life.
