Response of frequency domain in generalized thermoelasticity with two temperatures

The paper is concerned with the time-harmonic deformation in a homogeneous, isotropic, generalized thermoelastic medium with two temperatures. The Hankel transform is employed to solve the boundary-value problem in the frequency domain in the context of two generalized theories of thermoelasticity (Lord and Shulman, Green and Lindsay). The inverse transform integral is evaluated by using the Romberg integration in order to obtain the results in the physical domain. The components of the stresses as well as the temperature and conductive temperature obtained in this manner are computed numerically. The effects of two temperatures are presented graphically.     

A simplified model for biomass pyrolysis in a fluidized bed reactor

A reaction scheme of a set of three parallel reactions followed by a set of two parallel reactions has been used to describe the primary and secondary reactions of biomass pyrolysis in a fluidized bed reactor. A simple first-order kinetic approach has been applied to predict the product yields. The pyrolysis model detailed in this paper is actually a sub-model. The effects of operating parameters on biomass pyrolysis product yield were simulated. Results show that reaction temperature plays an important role in the yield of bio-oil. The model is robust and can predict good results in a gasification environment as well. Good agreement between predicted and published results was obtained.     

Development of High Performance Steel Products in Sail Through R&D Initiatives

Steel Authority of India Limited (SAIL), through its Corporate R&D i.e. RDCIS, has been working incessantly for the development of new steel products with superior quality attributes to meet the requirements of Indian market. The product development activities have always been supported by in-house/collaborative research work which has led to deeper understanding on the process know-how, resulting in launching of cost-effective products in Indian market. Some of the products developed by SAIL in the flat product category include high strength thin gauge HR coil for automobile sectors, SAILMA 550 HI/SAILMA 600 grade plates for penstocks and earthmovers, SAIL HITEN 690 AR plates for automated teller machines chest, high strength plates with guaranteed through thickness ductility for railways and Defence sectors, boiler quality plates (ASTM 387 Gr. 12) for power sector, API X 70 grade HR coils and plates for Linepipe application. In the long products category, EQR TMT rebar, Roof/Rock Bolt (Fe—600) TMT rebars for mines and tunnels, corrosion resistant TMT rebars for construction sector, Al-killed low carbon CC blooms for cold reducers, Al-killed medium carbon CC blooms for forging have been developed recently through R&D initiatives in SAIL. This paper describes some of the products which were recently developed in SAIL.     

Simplified reliability method for spatially variable undrained engineered slopes

A random finite element analysis (RFEA) is employed to study the effect of shear strength spatial variability on the stability of undrained engineered slopes. Based on the RFEA simulation results for 34 (idealized) real engineered slope cases, it is concluded that the coefficient of variation in the spatially variable shear strength and the ratio (vertical scale of fluctuation)/(length of failure curve) have a major effect on the stability reliability. The RFEA simulation results are further used to derive simplified equations for the reliability analysis and the reliability-based design of undrained engineered slopes.     

Cracking of aluminium alloy valve body used in attitude control of satellite launch vehicle – A metallurgical investigation

Aluminium alloys emerged as preferred material for aerospace application, due to their high specific strength, high specific stiffness and ease for fabrication, Al–4.5Zn–1.5Mg aluminium alloy was used for the fabrication of a valve body for an attitude control system of satellite launch vehicles. During one of the functional qualification test, while charging the gaseous medium, a pressure drop was noticed. This was attributed to a leak through a crack opening of the valve body. Detailed metallurgical analysis indicated that the failure was due to stress corrosion cracking (SCC).This paper brings out the metallurgical analysis carried out and remedial measures suggested.     

Preparation of iron‐fortified rice using edible coating materials

Iron‐fortified rice premix (IFRP) was prepared using soaking and spraying method followed by coating with hydroxypropyl methyl cellulose (HPMC), methyl cellulose (MC), combination of HPMC and MC, zein, palmitic acid (PA) and stearic acid (SA). Steaming caused a reduction in iron content in iron‐fortified rice premix than without steaming treatment. Iron content ranged from 1.33 to 7.11 and 1.61 to 4.49 mg g^?1, respectively, in IFRP prepared using soaking and spraying method. Retention of iron in IFRP samples coated with 9% PA, 7% and 9% SA, and combination of HPMC and MC at 2% level, respectively, after washing twice with distilled water was similar (P > 0.05). Retention of iron in these coated IFRP ranged from 87.34% to 89.39% (P > 0.05) as compared to 39.12% in uncoated IFRP. Sensory acceptability indicated the scope for the production of IFRP by spraying of iron solution with iron content 20.1 mg mL^?1, 180‐min tempering time and coating with 2% HPMC and MC followed by drying.     

Compaction studies of alternate solid forms of celecoxib

The aim of this study was to compare the compaction behavior of crystalline celecoxib (CryCEL), amorphous celecoxib (AmCEL) and celecoxib (CEL) – polyvinyl pyrolidone (PVP) – meglumine (MEG) solid dispersion (Ter-Mix) using texture analyzer and hydraulic press for low and high pressures, respectively. Pressure induced devitrification in the amorphous and ternary system was also studied using PXRD. Elastic energy/plastic energy (EE/PE) ratio of AmCEL, CryCEL and Ter-Mix was found to be 1.71, 2.32, and 1.91, respectively at 6.35 MPa. Similar trend was observed at all studied compaction pressures. AmCEL showed significant devitrification, while Ter-Mix showed degree of crystallinity (DOC) of 11.9%, when compacted at tableting pressures of 109 MPa. Parameters ‘a’, ‘1/b’, and ‘Py’ obtained using Kawakita equation and Heckel equation gave values of 0.86, 5.2, and 253.4 MPa for CryCEL, 0.89, 4.85, and 103 MPa for AmCEL and 0.68, 16.1, and 169.6 MPa for Ter-Mix, respectively. The study revealed significant differences in compaction properties of CryCEL, AmCEL, and Ter-Mix. AmCEL was not suitable for compacted solid dosage forms due to pressure induced devitrification. However, stabilized AmCEL in Ter-Mix showed relatively lesser devitrification and can be developed as compacted dosage forms.     

Optimization of electrochemical polymerization parameters of polypyrrole on Mg–Al alloy (AZ91D) electrodes and corrosion performance

We report on the optimum electropolymerization conditions of polypyrrole (PPy) coatings on Mg alloy AZ91D electrodes from aqueous electrolytes of sodium salicylate via cyclic voltammetry (CV). Results show that initial and end potential values during the electrochemical coating procedure play an important role on the adhesion and corrosion performance of PPy films. Corrosion tests of AZ91D electrodes coated with PPy under optimized conditions show a good corrosion performance during 10 days in Na₂SO_4, without peeling off of these thin films.     

High-Temperature Erosion-Corrosion Performance of High-Velocity Oxy-Fuel Sprayed Ni-20 Cr Coating in Actual Boiler Environment

The high-velocity oxy-fuel (HVOF) spray technique was used to deposit Ni-20Cr coating on a commonly used boiler steel ASTM A213 347H. The specimens with and without coating were exposed to the super heater zone of a thermal power plant boiler at a temperature of 973 K (700 °C) under cyclic conditions to ascertain their erosion-corrosion (E-C) behavior. High-temperature oxidation behavior of the specimens was also evaluated under cyclic thermal loading conditions at an elevated temperature of 1173 K (900 °C). Mass change data and thickness loss were measured to formulate the kinetics of E-C/oxidation for the specimens. The exposed specimens were characterized by X-ray diffraction (XRD) and field emission–scanning electron microscopy/energy dispersive spectroscopy (FE-SEM/EDS). The uncoated steel suffered higher E-C in comparison with its coated counterpart in terms of mass loss as well as thickness loss. It was observed that overall mass loss was reduced by 31 pct and thickness loss by 44 pct after the application of the coating. The possible formation of Cr₂O₃ phase in the coated substrate may be suggested to contribute to better E-C behavior. During air oxidation exposures, the coating was found to be intact with only marginal spallation of its oxide scales, which is an indicator of good adhesion between the coating and substrate steel. The air oxidation mass change data indicated that the coating enhanced the oxidation resistance of the steel by 85 pct.     

Effect of fillers and plasticizers on the performance of novel heat and oil‐resistant thermoplastic elastomers from nylon‐6 and acrylate rubber blends

The effects of various fillers (SRF black, silica, and clay) and plasticizers (dibutyl phthalate and dioctyl phthalate) on the mechanical, dynamic mechanical, and rheological properties and on the heat and oil resistance of the thermoplastic elastomeric reactive blends of nylon‐6 and acrylate rubber (ACM) were investigated. The mixing torque behavior of the blends in Brabender Plasticorder shows reduced extent of interaction between the two component polymers in the presence of both fillers and plasticizers. Silica‐filled blends show the highest viscosity increment due to the possibility of reaction between its surface silanol groups and the reactive epoxy groups present in the ACM chain during melt‐blending operation. Though the addition of fillers reduces the processability of the blends, it improves the extensibility as well as the tension set properties of the blends. The mechanical integrity and the damping characteristics of the blends are also improved with the addition of fillers; the latter is evidenced from the dynamic mechanical thermal analysis of the blends. The tensile strength and hardness of the filled blends remain practically unchanged after ageing at 175°C for 72 h and, also, the oil swell does not change appreciably with the addition of fillers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1490–1501, 1999