Free Convection and Mass Transfer Flow of Non-Newtonian Fluid in the Stokes Problem for a Vertical Plate with Thermal Diffusion Effect

An exact analysis of the unsteady free convection and mass transfer flow of non-Newtonian fluid past an impulsively started infinite vertical plate has been presented in presence of thermal diffusion effect. The expression for the velocity field has been obtained by the Laplace transform technique. The influence of Soret number (thermal diffusion parameter) on velocity field is extensively discussed.     

Effect of mean stress (stress ratio) and aging on fatigue-crack growth in a metastable beta titanium alloy, Ti-10V-2Fe-3Al

The effect of mean stress, or the stress ratio (R), on the fatigue-crack growth (FCG) behavior of α-aged and ω-aged microstructures of the beta titanium alloy Ti-10V-2Fe-3Al was investigated. While the mean stress had a negligible effect on the FCG behavior of the α-aged microstructure, a strong effect was observed in the ω-aged microstructure. In particular, the values of the threshold stress-intensity range (ΔK _th ) exhibited a strong dependence on R in the ω-aged microstructure, while this dependence was weak in the α-aged microstructure. These effects seem to arise primarily from fracture-surface roughness-induced crack closure. The crack closure levels for the α-aged microstructure were found to be very low compared to those for the ω-aged microstructure. Transmission electron microscopy and scanning electron microscopy studies of microstructures and fracture surfaces were performed to gain insight into the deformation characteristics and crack propagation mechanisms, respectively, in these microstructures. The microstructure-induced differences in FCG behavior are rationalized in terms of the effect of aging on slip and crack closure.     

Microstructure and properties of quenched-and-aged plates produced from a copper-bearing HSLA steel

For the first time in India, quenched-and-tempered (Q&T) plates of a copper-bearing high-strength lowalloy (HSLA) steel have been commercially developed for naval structural applications. A 50 ton production heat was made through electric arc furnace (EAF)-vacuum arc degassing (VAD) route and continuously cast into 170 mm thick slabs. These slabs were conditioned, reheated in walking-beam furnace and hot rolled in plate mill into plates of 10 to 16 mm thickness. The as-rolled plates were hardened through oil quenching and subsequently tempered (aged) at 630 ‡C to achieve the combination of highstrength and good low-temperature impact toughness. The microstructures of heat treated plates showed fine acicular ferrite with grain sizes ranging between ASTM No. 9 and 10. From the standpoint of tensile properties, Q&T plates of all thicknesses exhibited significantly higher yield strengths than the minimum stipulated value of 552 MPa for HY-80/HSLA-80 steels. The elongation (22.20 to 26.00%) and reduction in area (62.12 to 67.62%) values achieved also exceeded the respective minimum requirements of 20 and 50% stipulated for such steels. The trend in variation of Charpy V-notch (CVN) impact energies at room temperature, -18, and -62 ‡C not only showed significantly higher values than that stipulated for HY-80 and HSLA-100 steels at -18 ‡C, but also indicated that the CVN impact energies achieved (105.15 to 144.25 J) at -62 ‡C were higher than the estimated value of 90 J for HSLA-80/HSLA-100 steels at this temperature.     

Metallurgical Failure Analysis of Cracked Forward Cylinder Head of Advanced Linear Actuator for Aircraft

Precipitation-hardened stainless steel of 15-5PH grade was used for the fabrication of forward cylinder used in advanced linear actuator of aircraft. The component had undergone a series of qualification tests. During one of the accelerated fatigue tests, an external leak was observed after experiencing more than 1,50,000 cycles of fluctuating stress. Subsequent to disassembly, the leak was found to be because of the hair line cracks in the forward cylinder. The cracked component was subjected to a detailed metallurgical investigation to understand the cause of failure. The failure analysis revealed that the fracture initiated at the hard chrome layer and propagated under cyclic loading. This premature failure of the component was attributed to the surface roughness and the presence of the hard chrome layer at the corner contour of the component. This article brings out the details of the investigation carried out and the results achieved.     

Is the ubiquitous presence of barium carbonate responsible for the poor aqueous processing ability of barium titanate?

The ubiquitous presence of barium carbonate (BaCO₃ – BC) as an impurity in barium titanate (BaTiO₃ – BT) has been pointed out as the main reason for the well-known difficulties found by many investigators when attempting to process BT powders in aqueous media. Different and controversial arguments have been put forward to justify the observed aqueous processing difficulties of BT, but a satisfactory explanation is still to be found. With this aim, a systematic study was here undertaken to shed further light on the solid/liquid interactions occurring at the surface of BC and BT particles and their impact on the dispersion ability of both powders, separately and mixed in certain proportions. Long term colloidal stability and high solid loadings (60 vol.%) were obtained for BC, while colloidal instability and a lower maximum content of solids (50 vol.%) could be achieved for BT. This responds to the question risen in the title.     

Solar stills: A review

The availability of drinking water is reducing day by day; where as the requirement of drinking water is increasing rapidly. To overcome this problem there is a need for some sustainable source for the water distillation (purification). Solar still is a useful device that can be used for the distilling of brackish water for the drinking purposes. In this article a review has been done on different types of solar still.     

The formation of diffusion coatings on some low-alloy steels and their high temperature oxidation behaviour: Part 1 diffusion coatings

The thermal stability of aluminised coatings on Fe-alloys containing Ni, Si and Cr and of chromised coatings on Fe-alloys containing Ni and Si has been studied. The results indicate that thermal stability is affected mainly by phase equilibria and diffusion paths have been plotted on the appropriate ternary diagrams.     

Leakage power analysis and reduction during behavioral synthesis

This paper presents a high-level leakage power analysis and reduction algorithm. The algorithm uses device-level models for leakage to precharacterize a given register-transfer level module library. This is used to estimate the power consumption of a circuit due to leakage. The algorithm can also identify and extract the frequently idle modules in the datapath, which may be targeted for low-leakage optimization. Leakage optimization is based on the use of dual threshold voltage (V/sub T/) technology. The algorithm prioritizes modules giving a high-level synthesis system an indication of where most gains for leakage reduction may be found. We tested our algorithm using a number of benchmarks from various sources. We ran a series of experiments by integrating our algorithm into a low-power high-level synthesis system. In addition to reducing the power consumption due to switching activity, our algorithm provides the high-level synthesis system with the ability to detect and reduce leakage power consumption, hence, further reducing total power consumption. This is shown over a number of technology generations. The trend in these generations indicates that leakage becomes the dominant component of power at smaller feature size and lower supply voltages. Results show that using a dual-V/sub T/ library during high-level synthesis can reduce leakage power by an average of 58% for the different technology generations. Total power can be reduced by an average of 15.0%-45.0% for 0.18-0.07 /spl mu/m technologies, respectively. The contribution of leakage power to overall power consumption ranges from 22.6% to 56.2%. Our approach reduced these values to 11.7%-26.9%.