Rocks in the continental crust are long lived and have the potential to record a wide span of tectonic history in rock fabric. Mapping rock fabric in situ at depth requires the application of seismic methods. Below depths of microcrack closure seismic anisotropy presumably reflects the shape and crystallographic preferred orientations influenced by deformation processes. Interpretation of seismic observables relevant for anisotropy requires assumptions on the symmetry and orientation of the bulk elastic tensor. We compare commonly made assumptions against a compilation of 95 bulk elastic tensors from laboratory measurements, including electron backscatter diffraction and ultrasound, on crustal rocks. The majority of samples developed fabric at pressures corresponding to middle to lower crustal condition. Tensor symmetry is a function of mineral modal composition, with mica‐rich samples trending toward hexagonal symmetry, amphibole‐rich samples trending toward an increased orthorhombic symmetry component, and quartz‐feldspar‐rich samples showing a larger component of lower symmetries. Seventy‐seven percent of samples have a best fit hexagonal tensor with slow‐axis symmetry, as opposed to mantle deformation fabric that usually has fast‐axis symmetry. The best fit hexagonal approximation for crustal tensors is not elliptical but deviates systematically from elliptical symmetry with increasing anisotropy, an observation that affects the magnitude and orientation of anisotropy inferred from receiver function and surface wave observations. We present empirical linear relationships between anisotropy and ellipticity for crustal rocks. The maximum out‐of‐plane conversion amplitudes in receiver functions scale linearly with degree of anisotropy for nonelliptical symmetry. The elliptical assumption results in a bias of up to 1.4 times true anisotropy.

The response to post-weld heat treatment of an 18%Ni (250 grade) gas tungsten arc weld metal has been investigated. The post-weld heat treatments are (a) direct aging at 480°C/3 h/air cooling, (b) solutionising at 815°C/1 h/air cooling+aging at 480°C/3 h/air cooling and (c) homogenisation at 1150°C/1 h/air cooling+solutionising at 815°C/1 h/air cooling+aging at 480°C/3 h/air cooling. Metallographic characterisation of fusion zone revealed pronounced segregation of titanium and molybdenum along the interdendritic and intercellular boundaries. This led, during subsequent aging, to austenite reversion at temperatures much lower than in wrought (unwelded) material. Solutionised treatment at 815°C does not remove the segregation. Homogenisation treatment (1150°C/1 h/air cooling) succeeded in making the composition become homogenised. Mechanical properties including tensile, hardness and impact toughness were evaluated. Tensile test results showed that directly aged weldments exhibited lower strength but higher ductility than the other cases; this was attributed to the presence of reverted austenite. Homogenisation at 1150°C/1 h/air cooling+solutionising at 815°C/1 h/air cooling+aging at 480°C/3 h/air cooling resulted in optimum tensile properties. A substantial increase in fusion zone toughness was observed after homogenisation+solutionising+aged condition due to a decrease in the content of austenite content compared to the directly aged condition. The reduction in microsegregation by diffusion of alloying elements from cell boundaries to the cell during homogenisation treatment is responsible for the decrease in austenite content.

The stratigraphy, structure, and tectonics of the Cauvery, Godavari-Krishna, Palar, and Mahanadi Basins located on the east coast of India are considered on the basis of up-to-date surface and subsurface data with particular reference to their evolution during the Mesozoic Era.The sediments exposed in the respective basins are limited to their western and northern borders and represent a relatively smaller stratigraphic interval as compared to the sequence known to be present in the subsurface.Each of these basins is bordered to the west by down-to-the-basin faults. The structural style and recognisable regional trends of the respective basins parallel those of the Eastern Ghats which were largely responsible for their evolution during the Jurassic period. The basin morphology during Late Jurassic comprised horsts and grabens formed due to tensional forces leading to basin subsidence with localised uplifts. The close of the Mesozoic was marked by a regional easterly regression and basinal tilt and an almost complete cessation of horst and graben development and the formation of an essentially monoclinal post-Mesozoic sedimentary cover.A close similarity between the Mesozoic sedimentary basins on the east coast of India and those on the west coast of Australia is marked inasmuch as their tectonic setting, structural style, lithologic suites and faunal and palynological assemblages are concerned. The study broadly indicates that during the Late Jurassic-Early Cretaceous period the basins on the east coast of India were bordered by land masses similar to those postulated to the west of the West Australian basins.

The role of post-weld heat treatments on the microstructure and mechanical properties of maraging steel laser welds has been investigated. The post-weld heat treatments are (a) direct ageing at 480 • C/3 h/air cooling, (b) solutionizing at 815 • C/1 h/air cooling + at 480 • C/3 h/air cooling, and (c) homogenization at 1150 • C/1 h/air cooling + solutionizing at 815 • C/1 h/air cooling + ageing at 480 • C/3 h/air cooling. The welded + aged and welded + solutionized + aged microstructure consisting of reverted austenite exhibited low strength and toughness. Homogenization treatment resulted in a microstructure free from reverted austenite and subsequent solutionizing and ageing resulted in improved strength and impact toughness.

Use of Jatropha Oil Methyl Ester and Its Blends as an Alternative Fuel in Diesel Engine

No abstract

The present study is aimed at filling the gaps in scientific understanding of the burnishing process, and also to aid and arrive at technological solutions for the surface modifications based on burnishing of some of the commonly employed engineering materials. The effects of various burnishing parameters on the surface characteristics, surface microstructure, micro hardness are evaluated, reported and discussed in the case of EN Series steels (EN 8, EN 24 and EN 31), Aluminum alloy (AA6061) and Alpha-beta brass. The burnishing parameters considered for studies principally are burnishing speed, burnishing force, burnishing feed and number of passes. Taguchi technique is employed in the present investigation to identify the most influencing parameters on surface roughness. Effort is also made to identify the optimal burnishing parameters and the factors for scientific basis of such optimization. Finally, a brief attempt is made to construct the Burnishing maps with respect to strength level (in this case, average micro hardness of unburnished material).

The present work shows the results obtained from experimental investigations of the augmentation of turbulent flow heat transfer in a horizontal tube by means of varying width twisted tape inserts, with air as the working fluid. In order to reduce excessive pressure drops associated with full-width twisted tape inserts, with a lower corresponding reduction in heat transfer coefficients, reduced-width twisted tapes of widths ranging from 10 mm to 22 mm are used, which are lower than the internal diameter of the tube of 27.5 mm. Experiments were carried out for plain tubes with/without twisted tape inserts at a constant wall heat flux and different mass flow rates. The twisted tapes are of three different twist ratios (3, 4 and 5), each with five different widths (26 (full-width), 22, 18, 14 and 10 mm). The Reynolds number varied from 6000 to 13500. Both the heat transfer coefficient and pressure drop are calculated, and the results are compared with those of a plain tube. It is observed that with the inclusion of twisted tape inserts there is a significant increase in the heat transfer coefficients. Correlations are developed for friction factors and Nusselt numbers for a fully-developed turbulent swirl flow, which are applicable to full-width as well as reduced-width twisted tapes, using a modified twist ratio as the pitch to width ratio of the tape.