Morphology of an aluminum alloy eroded by a jet of angular particles impinging at normal incidence

The erosion of an aluminum alloy impinged by crushed glass particles at normal incidence was studied. The erosion patterns were analyzed by scanning electron microscopy, energy dispersive X-ray spectroscopy, and surface profilometer measurements. From the analysis of specimens tested at various driving gas pressures and time intervals, four distinct erosion regions were identified. A study of pit morphology and its relationship to cumulative erosion was made. Cutting wear is believed to be the predominant material removal mechanism; some evidence of deformation wear was found during the incubation period

Solid spherical glass particle impingement studies of plastic materials

Erosion experiments on polymethyl methacrylate (PMMA), polycarbonate, and polytetrafluoroethylene (PTFE) were conducted with spherical glass beads impacting at normal incidence. Optical and scanning electron microscopic studies and surface profile measurements were made on specimens at predetermined test intervals. During the initial stage of damage to PMMA and polycarbonate, material expands or builds up above the original surface. However, this buildup disappears as testing progresses. Little or no buildup was observed on PTFE. PTFE is observed to be the most resistant material to erosion and PMMA the least. At low impact pressures, material removal mechanisms are believed to be similar to those for metallic materials. However, at higher pressures, surface melting is indicated at the center of impact. Deformation and fatigue appear to play major roles in the material removal process with possible melting or softening

A study of the nature of solid particle impact and shape on the erosion morphology of ductile metals

Impulsive versus steady jet impingement of spherical glass bead particles on metal surfaces was studied using a gas gun facility and a commercial sand blasting apparatus. Crushed glass particles were also used in the sand blasting apparatus as well as glass beads. Comparisons of the different types of erosion patterns were made. Scanning electron microscopy, surface profilometry and energy dispersive X-ray spectroscopy analysis were used to characterize erosion patterns. The nature of the wear can be divided into cutting and deformation, each with its own characteristic features. Surface chemistry analysis indicates the possibility of complex chemical and/or mechanical interactions between erodants and target materials

Quality Assessment of Hatchery reared Post Larvae of Tiger Shrimp Penaeus monodon (Fabricius)

The induced maturation and breeding of Penaeus monodon in captivity was first developed in India in seventies (Alikunhi et al 1977; Alikunhi and Hameed Ali 1977; Muthu and Laxminarayana 1977). With the later standardisation of hatchery systems with designs, feeding schedules etc., amenable for convenient operation, shrimp hatcheries started proliferating not only along the Indian coastline but also along the coastline of the countries of the sub-continent

Application of GIS on Environmental Degradation Due to the Offshoots of Highway Development Projects: Central Ethiopian Highlands

Physical land degradation after road building has been observed in Central Ethiopian highlands through gully erosion. In this research work by using a number of methods such as Field observation, gully measurement, GIS technique, the 1997 and 2006 topomap and socio-economic questionnaires, the impacts of the road on land degradation has been studied. It investigates how highway construction in the Ethiopian Highlands affects the gully erosion risk by quantifying the catchment area before and after road construction, the number of gullies created, and its characteristics in two selected cases: Addis Ababa-Fiche and Addis Ababa-Ambo. Accordingly; since the building of the road, 17 new gullies were created immediately down slope of the studied road segments and 8 other gullies at a radical change in its dimensions. The average catchment area is now 58.28 hectares and 74.52 on the road segments of Fiche and Ambo respectively, which is significantly different (p<0.001) from the average pre-road catchment area of 8.45 and 14.52 hectares (paired average). The total surface area occupied by gullies in the side of Fiche road and in the side of Ambo road transects was about 63,892.6 m2 and 59,214.25 m2 respectively. The volume of soil loss was calculated between 12,530.38 m3 and 71,420 m3 from each road segments. The result of statistical analysis indicates that variation of the gully length contributed 95% of variation in the volume of soil loss. The Gully density (5.7m/ha to 14.06m/ha) implies that the sampled roadside areas were moderately to severely degraded. The damages and associated problems of the gullies, as explained by farmers, include loss of land, dissection of farms, and deposition of sediments on growing crops and in extreme cases putting agricultural fields out of production. Hence roads should be designed in a way that keeps runoff interception, concentration and deviation minimal. Techniques must be used to spread concentrated runoff in space and time and to increase its infiltration instead of directing it straight onto unprotected slopes.Key words: Gully erosion Risk, catchment area, Road design, Ecological destruction

A dynamics-driven approach to precision machines design for micro-manufacturing and its implementation perspectives

Precision machines are essential elements in fabricating high quality micro products or micro features and directly affect the machining accuracy, repeatability and efficiency. There are a number of literatures on the design of industrial machine elements and a couple of precision machines commercially available. However, few researchers have systematically addressed the design of precision machines from the dynamics point of view. In this paper, the design issues of precision machines are presented with particular emphasis on the dynamics aspects as the major factors affecting the performance of the precision machines and machining processes. This paper begins with a brief review of the design principles of precision machines with emphasis on machining dynamics. Then design processes of precision machines are discussed, and followed by a practical modelling and simulation approaches. Two case studies are provided including the design and analysis of a fast tool servo system and a 5-axis bench-top micro-milling machine respectively. The design and analysis used in the two case studies are formulated based on the design methodology and guidelines

Redox chemistry of o- and m-hydroxycinnamic acids: a pulse radiolysis study

Radiation chemical reactions of •OH, O•-, N3• and e aq t- with o- and m-hydroxycinnamic acids were studied. The second-orderrateconstantsforthereaction of •OH with ortho and meta isomers in buffer solution at pH7 are 3.9± 0.2 × 109 and 4.4 ± 0.3 × 109 dm3 mol-1 s-1 respectively. At pH 3 the rate with the ortho isomer was halved (1.6 ± 0.4 × 109 dm3 mol-1 s-1) but it was unaffected in the case of meta isomer (k = 4.2± 0.6 × 109dm3mol-1 s-1). The rate constant in the reaction of N3 •with the ortho isomer is lower by an order of magnitude (k = 4.9 ± 0.4 × 108 dm3 mol-1s-1). The rates of the reaction of e aq t- with ortho and meta isomers were found to be diffusion controlled. The transient absorption spectrum measured in the •OH with o-hydroxycinnamic acid exhibited an absorption maximum at 360 nm and in meta isomer the spectrum was blue-shifted (330 nm) with a shoulder at 390 nm. A peak at 420 nm was observed in the reaction of Obb-with the o-isomer whereas the meta isomer has a maximum at 390 and a broad shoulder at 450 nm. In the reaction of the absorption peaks were centred at 370-380 nm in both the isomers. The underlying reaction mechanism is discussed