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Erosion Resistance (erosion + resistance)
Selected AbstractsThe Role of Binder Content on Microstructure and Properties of a Cu-base Active Brazing Filler Metal for Diamond and cBNADVANCED ENGINEERING MATERIALS, Issue 5 2005R. Elsener Melting experiments of Cu-Sn-Ti-Zr filler metal powder containing cellulose nitrate and graphite, respectively, resulted in the formation of nanosized TiC particles in both Cu-rich phase and CuSn3Ti5 intermetallic regions of the alloy (see figure). The variation of the binder type and content allows to tailor the properties of the filler metals in terms of erosion resistance, decisive for a new generation of superabrasive tools. [source] Prediction of concentrated flow width in ephemeral gully channelsHYDROLOGICAL PROCESSES, Issue 10 2002J. Nachtergaele Abstract Empirical prediction equations of the form W = aQb have been reported for rills and rivers, but not for ephemeral gullies. In this study six experimental data sets are used to establish a relationship between channel width (W, m) and flow discharge (Q, m3 s,1) for ephemeral gullies formed on cropland. The resulting regression equation (W = 2·51 Q0·412; R2 = 0·72; n = 67) predicts observed channel width reasonably well. Owing to logistic limitations related to the respective experimental set ups, only relatively small runoff discharges (i.e. Q < 0·02 m3s,1) were covered. Using field data, where measured ephemeral gully channel width was attributed to a calculated peak runoff discharge on sealed cropland, the application field of the regression equation was extended towards larger discharges (i.e. 5 × 10,4m3s,1 < Q < 0·1 m3s,1). Comparing W,Q relationships for concentrated flow channels revealed that the discharge exponent (b) varies from 0·3 for rills over 0·4 for gullies to 0·5 for rivers. This shift in b may be the result of: (i) differences in flow shear stress distribution over the wetted perimeter between rills, gullies and rivers, (ii) a decrease in probability of a channel formed in soil material with uniform erosion resistance from rills over gullies to rivers and (iii) a decrease in average surface slope from rills over gullies to rivers. The proposed W,Q equation for ephemeral gullies is valid for (sealed) cropland with no significant change in erosion resistance with depth. Two examples illustrate limitations of the W,Q approach. In a first example, vertical erosion is hindered by a frozen subsoil. The second example relates to a typical summer situation where the soil moisture profile of an agricultural field makes the top 0·02 m five times more erodible than the underlying soil material. For both cases observed W values are larger than those predicted by the established channel width equation for concentrated flow on cropland. For the frozen soils the equation W = 3·17 Q0·368 (R2 = 0·78; n = 617) was established, but for the summer soils no equation could be established. Copyright © 2002 John Wiley & Sons, Ltd. [source] Predicting Root Density in Streambanks,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 2 2008Candice Piercy Abstract:, Roots of riparian vegetation increase streambank erosion resistance and structural stability; therefore, knowledge of root density and distribution in streambanks is useful for stream management and restoration. The objective of this study was to compare streambank root distributions for herbaceous and woody vegetation and to develop empirical models to predict root density. Root length density, root volume ratio, soil physical and chemical properties, and above-ground vegetation densities were measured at 25 sites on six streams in southwestern Virginia. The Mann-Whitney test was used to determine differences in root density along stream segments dominated by either woody or herbaceous vegetation. Multiple linear regression was used to develop relationships between root density and site characteristics. Study results showed that roots were evenly distributed across the bank face with the majority of roots having diameters less than 2 mm. Soil bulk density and above-ground vegetation were key factors influencing root density. While significant relationships were developed to predict root density, the predictive capabilities of the equations was low. Because of the highly variable nature of soil and vegetation properties, it is recommended at this time that soil erodibility and root density be measured in the field for design and modeling purposes, rather than estimated based on empirical relationships. [source] Erosion-corrosion of laser and thermally deposited coatings exposed in fluidised bed combustion plantsMATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 4 2006A. Hjörnhede Abstract Coated low alloyed steel tubes were exposed in two combustion power plants of the type Circulating Fluidised Bed (CFB) and Pressurised Fluidised Bed Combustion (PFBC). The power plants were fired with wood chips and coal with a small addition of olive seeds, respectively. In addition to laser coating two thermal spray techniques were used; arc-spray (air as carrier gas) and High Velocity Oxy Fuel (HVOF). The sample locations in the PFBC plant were at the highest and lowest loops of a platen immersed in the fluidising bed. The material temperatures in each loop were 450 °C and 400 °C, respectively. The exposure lasted over two firing seasons for a total time of 8089 h. In the CFB plant a probe was located at the cyclone entrance where the material temperature was 630 °C for an exposure time of about 2100 h before being reduced to 480 °C for a further 920 h. The material wastage was determined from metallographic studies on cross-sections of rings cut from the exposed tubes. The nature and chemical composition of the corrosion products and deposits formed were determined by SEM/EDX, Auger spectroscopy, XPS and XRD. Cobalt based coatings show the best performance in both the PFBC plant and the CFB plant, while nickel based coatings are resistant to a corrosive atmosphere but very sensitive to erosion. The degree of corrosion is much larger in the CFB plant as is clearly seen from the chromium carbide containing coating, which totally degraded in this environment. Contrary the performance of the same coating was excellent in the fluidised bed due to its high erosion resistance. The material wastage of a coating with a specific composition is independent of the deposition method. No significant differences in spallation behaviour occurred among coatings deposited with the different techniques. [source] Effects of particle size of Al(OH)3 on electrical properties of EPDM compoundsPOLYMER ENGINEERING & SCIENCE, Issue 4 2000Cheol Ho Lee Effects of particle size of Al(OH)3 (ATH) filler on electrical properties of ethylene propylene diene terpolymer (EPDM)/ATH compounds were studied. It was found that tracking and erosion resistance of EPDM/ATH compounds decreased while dielectric properties and 90°C water resistance were improved with the increase of particle size. Homocharge accumulates in the compounds, which increases first and then decreases with the increase of particle size. This was explained by the change of particle-to-particle distance due to filler size. [source] | |||||||||||||