Hypsometric Integral Estimation Methods and its Relevance on Erosion Status of North-Western Lesser Himalayan Watersheds

Assessment of erosion status of a watershed is an essential prerequisite of integrated watershed management. This not only assists in chalking out suitable soil and water conservation measures to arrest erosion and conserve water but also helps in devising best management practices to enhance biomass production in watersheds. The geologic stages of development and erosion proneness of the watersheds are quantified by hypsometric integral. The estimation of hypsometric integral is carried out from the graphical plot of the measured contour elevation and encompassed area and by using empirical formulae. In this study, efforts were made to estimate the hypsometric integral values of the Sainj and Tirthan watersheds and their sub watersheds in the Lesser Himalayas using four different techniques, and to compare the procedural techniques of its estimation and relevance on erosion status. It was revealed that the hypsometric integral calculated by elevation–relief ratio method was accurate, less cumbersome and easy to calculate within GIS environment. Also comparison of these hypsometric integral values revealed that the Sainj watershed (0.51) was more prone to erosion than the Tirthan watershed (0.41). Further, the validation of these results with the recorded sediment yield data of 24 years (1981–2004) corroborated that the average annual sediment yield during this period for Sainj watershed (0.53 Mt) was more than that of the Tirthan watershed (0.3 Mt). Thus, the hypsometric integral value can be used as an estimator of erosion status of watersheds leading to watershed prioritization for taking up soil and water conservation measures in watershed systems.     

钢基表面激光熔覆金属陶瓷涂层的抗磨蚀性能研究

证明了采用ＣＯ２激光熔融预涂覆于钢基体表面的金属陶瓷粉末，能够获得与钢呈冶金结合的金属陶瓷熔覆层。这种金属陶瓷熔覆层与镍基自熔合金粉末的熔覆层比较，抗气蚀和抗磨蚀性能有显著提高。     

Stability and Erosion in Grassed Channels

Grass is a cost-effective form of erosion control. Since grass prevents erosion, the relationship between grass properties and erosion rate in grassed open channels is highlighted and analyzed within the context of channel stability. The deformation of grass caused by the flow’s momentum has been taken into consideration. Results are in good agreement with the available experimental erosion rate data for grassed channels. The purpose of this paper is to show that the amount of deformation of a grass channel lining due to flow can be used to estimate the erosion rate, and, as a result, lining deformation can be used as an indicator of channel stability. The method is simple enough to be useful for design.     

Impact of rigid angular particles with fully-plastic targets Part II: Parametric study of erosion phenomena

The erosion of substrates of arbitrary dynamic hardness and friction coefficient, due to the impact of individual angular particles, was analyzed with the purpose of predicting crater size, shape, and rebound parameters as a function of incident particle velocity, angle, orientation, and shape. A rigid-plastic theory due to Hutchings (International Journal of Mechanical Sciences 1997; 19:45–52), developed for square plates impacting frictionless surfaces, is generalized for arbitrarily shaped particles impacting surfaces having nonzero friction. The specific case of symmetric angular particles of arbitrary angularity is studied in detail. The model is shown to match Hutchings’ [1] experimental data for square steel plates on smooth steel surfaces. In a companion paper (Papini, Spelt, under review), a parametric study of the input parameters is presented.     

Erosion, corrosion and erosion–corrosion of EB PVD thermal barrier coatings

Electron beam (EB) physical vapour deposited (PVD) thermal barrier coatings (TBCs) have been used in gas turbine engines for a number of years. The primary mode of failure is attributed to oxidation of the bond coat and growth of the thermally grown oxide (TGO), the alumina scale that forms on the bond coat and to which the ceramic top coat adheres. Once the TGO reaches a critical thickness, the TBC tends to spall and expose the underlying substrate to the hot gases. Erosion is commonly accepted as a secondary failure mechanism, which thins the TBC thus reducing its insulation capability and increasing the TGO growth rate. In severe conditions, erosion can completely remove the TBC over time, again resulting in the exposure of the substrate, typically Ni-based superalloys. Since engine efficiency is related to turbine entry temperature (TET), there is a constant driving force to increase this temperature. With this drive for higher TETs comes corrosion problems for the yttria stabilised zirconia (YSZ) ceramic topcoat. YSZ is susceptible to attack from molten calcium–magnesium–alumina–silicates (CMAS) which degrades the YSZ both chemically and micro-structurally. CMAS has a melting point of around 1240 °C and since it is common in atmospheric dust it is easily deposited onto gas turbine blades. If the CMAS then melts and penetrates into the ceramic, the life of the TBC can be significantly reduced. This paper discusses the various failure mechanisms associated with the erosion, corrosion and erosion–corrosion of EB PVD TBCs. The concept of a dimensionless ratio D/d, where D is the contact footprint diameter and d is the column diameter, as a means of determining the erosion mechanism is introduced and discussed for EB PVD TBCs.     

Effect of micro ploughing during fine particle peening process on the microstructure of metallic materials

In this study, the mechanism of microstructural changes induced by fine particle peening (FPP) treatment was analyzed. Ti–6Al–4V alloy specimens treated with FPP, using tool steel particles with a peening time ranging from 0.1 to 30 s were prepared and examined. Observation of the specimen with short-term FPP treatment revealed that two types of collision dents were formed by the micro abrasive behavior between collided particles and specimen surface. One was the “indented dent,” formed by particles that collided with the surface vertically, and the other was the “ploughed dent,” accompanied by a heap of piled-up material that was ploughed aside during the formation of this dent. Analyses using energy dispersive X-ray spectroscopy (EDS) revealed the presence of particle fragments transferred to the ploughed dents, although no fragments were observed on the indented dents. With an increase in peening time, transferred fragments were embedded into treated materials by deformed material due to a micro ploughing effect. The Fe-rich region became deeper as the particle fragments were embedded. Finally, a lamellar microstructure with a high concentration of Fe was formed by FPP treatment. The effects of micro ploughing during the FPP process on the lamellar modified microstructure formation were clarified. One effect was an enhancement of metal transfer from particles to substrate because virgin metallic surface was exposed; and the other was the mechanical mixing of transferred elements into the substrate.     

Abrasive jet micro-machining of planar areas and transitional slopes in glass using target oscillation

Analytical models are presented which allow the prediction of the shape, sidewall slope, and depth of abrasive jet micro-machined planar areas and transitional slopes in glass using a novel technique in which the target is oscillated transversely to the overall scan direction. A criterion was developed to establish the minimum oscillation velocity to ensure negligible surface profile waviness in the scanning direction. If the oscillation velocity is sufficiently greater than the scanning velocity, the target receives an approximately uniform energy flux, resulting in a high degree of flatness for both masked and unmasked planar areas micro-machined in glass. It was also found that particle scattering from the mask edge caused the sidewalls of a planar area to be very shallow, on the order of a few degrees. Two methods were investigated to machine planar areas with increased sidewall slope using target oscillation: (i) machining micro-channels adjacent to the planned planar area, and (ii) target oscillation with an obliquely oriented nozzle. Among these two methods, target oscillation with an obliquely oriented nozzle created steeper sidewalls and was easier to implement, but it also caused appreciable mask under-etching. A major distinction between the target oscillation approach and a previously published method that was based on the superposition of the erosion profiles of adjacent nozzle scans, is that the latter is capable of machining an arbitrary surface profile over a large area, whereas the present target oscillation technique is intended only for the machining of flat planar areas at a single elevation. For such applications it is the preferred approach.     

Aerial Assessment of Ephemeral Gully Erosion from Agricultural Regions in the Pacific Northwest

Soil erosion from agricultural areas continues to be problematic in terms of both financial and environmental measures. Ephemeral gullies contribute to the soil loss both by the volume of sediment eroded from the gullies and because they act as delivery channels for surface erosion. High resolution aerial imagery was used to quantify the amounts and locations of ephemeral gullies in the subbasins of the Potlatch River system. Areal ephemeral gully erosion rates varied from 33.6?mt/km2 (0.15 U.S. t/acre) in the Big Bear Creek Subbasin to 88.4?mt/km2 (0.39 U.S. t/acre) in the Middle Potlatch Creek Subbasin representing 2.3–7.7% of the total surface sediment load. An erosion potential index was proposed to assist resource managers predict gully locations at the watershed scale using readily available remote sensing and geographic information system layers.     

柴达木盆地北缘中生界剥蚀厚度恢复

认为地层剥蚀厚度能否根据压实规律来恢复,其决定因素并非是新沉积层厚度是否大于剥蚀厚度;当不整合面以上新沉积层对不整合面以下老地层施加的压力大于被剥蚀地层(剥蚀前)对不整合面以下老地层施加的压力时,不整合面以下老地层的压实规律被破坏,无法用声波时差法恢复剥蚀厚度,否则可以恢复。据此,以用声波测井资料恢复的地层剥蚀厚度为依据,结合未被剥蚀地层厚度趋势延伸法、盆地构造演化分析法,对柴达木盆地北缘中生界剥蚀厚度进行了恢复,认为柴达木盆地北缘剥蚀量从西向东增大,昆特依坳陷和冷湖构造带的剥蚀量(约500m)大于其东部南八仙、鱼卡等地区(约100m),潜西—冷湖四号地区剥蚀量最大(最大可超过1400m)。图5参4(梁大新摘)