Indian Journal of
Engineering & Materials Sciences
CONTENTS
Engineering
Interference effects on the mean velocities and turbulence intensities behind a tall body due to a short body in tandem / 5B H Lakshmana Gowda, E G Tulapurkara & A Kanna Babu
Evaluation of optimum amount of load shedding to prevent dynamic voltage instability in a longitudinal ac power transmission system / 20
G Panda & A Chakrabarti
A short review of classical Stefan problem / 25
K N Shukla
Section extrusion from rectangular billet : Experimental verification of the SERR analysis / 35
P K Kar, S K Sahoo & N S Das
Use of condensation with boundary characteristics orthonormal polynomials in the vibration problems / 41
S Chakraverty
Magnetic fluid based squeeze film between two curved plates lying along the surfaces determined by secant functions / 45
R M Patel G M Deheri
Transient free convection flow of a viscous dissipative fluid with mass transfer past a semi-infinite vertical plate / 49
Fathia Moh. Al Samman, M Y Gokhale & V M Soundalgekar
Materials Science
Preparation of zirconia thin films by tape casting technique as electrolyte material for solid oxide fuel cells / 58A Samson Nesaraj, I Arul Raj & R Pattabiraman
Preparation, characterization and ionic conductivity measurements of (1-x) KCl:xZrO2 solid electrolyte system / 65
Archana Gupta & Anjan Sil
Laser-excited transition probabilities and oscillator strengths of calcium sulphide doped phosphors / (Contd)
69
H S Bhatti, Sukhwinder Singh, N K Verma & Sunil Kumar
Non-destructive estimation of particle size of finished ceramic products by X-ray diffraction technique / 75
K L Barui B Bhattacharya
Microhardness studies on antimony single crystal / 79
Amit H Raval, Mihir J Joshi & S B Shah
Note
Effect of N2-plasma exposure on corrosion of copper wire / 83N P Singh, S C Gupta & B R Sood
Indian Journal of Engineering & Materials Sciences
Vol. 9, February 2002, pp. 5-19
Interference effects on the mean velocities and turbulence intensities behind a tall body
due to a short body in tandem
B H Lakshmana Gowdaa, E G Tulapurkarab & A Kanna Babua
Flow past buildings can be studied by investigating flow past prismatic bodies placed on a base plate and kept in a simulated boundary layer. This investigation examines the effects of interference of two bodies in tandem, on the velocity field and turbulence intensities in the plane of symmetry. The two bodies have square cross-section of side b and have height (h) to width ratios of 1 and 5. The shorter body is kept behind the taller body at distances of 2b, 3b, 4b and 8b. Flow past individual body is also reported. In the case of interference, the flow pattern depends on whether the reattachment of the flow separating from the tall body takes place ahead, on or behind the short body. Due to three-dimensional effects some novel features are observed in the near wake. The presence of the short body influences the flow behind the tall body up to 3 body widths. The detailed data is expected to be useful for validating computer codes.
Indian Journal of Engineering & Materials Sciences
Vol. 9, February 2002, pp. 20-24
Evaluation of optimum amount of load shedding to prevent dynamic voltage instability in a
longitudinal ac power transmission system
G Pandaa & A Chakrabartib
The present investigations deal with criteria for Optimum Amount of Load Shedding (OALS) using a dynamic load model. The amount of load to be shed has been calculated using established parameters of the dynamic load model. In the event of voltage decline, the proposed optimum amount of load shedding criteria can be applied to calculate the minimum amount of load to be shed at any point of time to avoid a voltage collapse. The effect of shunt compensation on load shedding is also investigated. The developed scheme theory has been simulated for a typical longitudinal power transmission system of any urban metropolis of developing countries using digital computer.
Indian Journal of Engineering & Materials Sciences
Vol. 9, February 2002, pp. 25-34
A short review of classical Stefan problem
K N Shukla
The paper describes the state-of-art solution technique for classical Stefan problem. With a short discussion on the well-posedness of heat conduction problem with melting or freezing, some analytical solutions are presented.
Indian Journal of Engineering & Materials Sciences
Vol. 8, February 2002, pp. 35-40
Section extrusion from rectangular billet:
Experimental verification of the SERR analysis
P K Kar, S K Sahoo* & N S Das
The metal flow in the extrusion process is an important factor in controlling the mechanical properties of the extruded products. It is, however, difficult to predict the metal flow in three-dimensional extrusion of sections unless a continuous velocity field is employed for the analysis. On the other hand, analysis of extrusion of sections with re-entrant corners is not easily amenable to techniques employing continuous velocity fields. The spatial elementary rigid region (SERR) technique, which employs a discontinuous velocity field, is eminently applicable for the analysis of this class of problems. Some experimental studies have been carried out with a view to compare it with the theoretical results predicted using the SERR analysis. Experiments are carried out for obtaining square and I-sections from rectangular billets through square dies using direct extrusion process. An experimental set-up has been designed and developed for the said purpose and all extrusions have been carried out using rectangular billets of lead. Comparison of the SERR analysis with the experimental results shows that the SERR method can predict reasonable extrusion loads well within engineering accuracy.
Indian Journal of Engineering & Materials Sciences
Vol. 9, February 2002, pp. 41-44
Use of condensation with boundary characteristic
orthonormal polynomials in the vibration problems
S Chakraverty
Recently tremendous amount of work has been done by using the newly developed method of boundary characteristic orthogonal polynomials in the Rayleigh-Ritz method for the analysis of vibration problems. It is already established that the method provides better accuracy of results, is more efficient, simple and is easier for computer implementation. This paper provides refinement in this method by introducing condensation with the boundary characteristic orthonormal polynomials. The efficiency and reliability of the proposed refined procedure have been shown by a simple example for vibration of a cantilever beam.
Indian Journal of Engineering & Materials Sciences
Vol. 9, February 2002, pp. 45-48
Magnetic fluid based squeeze film between two curved plates lying along the surfaces
determined by secant functions
R M Patela & G M Deherib
It has been sought to analyze the squeeze film behaviour between two curved circular plates, when the curved upper plate approaches the stationary curved lower plate. The lubricant used is a magnetic fluid in the presence of an external magnetic field oblique to the radial axis. The concerned Reynolds equation is solved and expressions for pressure, load carrying capacity and response time are obtained. These expressions are computed numerically and the results are presented graphically. It is found that pressure, load carrying capacity and response time increase with increasing magnetization. Further the analysis tells that the bearing performance might be improved by a proper choice of both the plates. In addition the present investigation underlines that the performance of the bearing in the case of secant curved plates is marginally better than that of exponentially curved plates.
Indian Journal of Engineering & Materials Sciences
Vol. 9, February 2002, pp. 49-57
Transient free convection flow of a viscous dissipative fluid with mass transfer past a semi-infinite vertical plate
Fathia Moh. Al Sammana, M Y Gokhaleb, V M Soundalgekarc
Transient free convection flow of a dissipative fluid past a semi-infinite vertical plate is studied by considering the presence of species concentration. The governing equations in non-dimensional form are solved by implicit finite-difference technique of Crank-Nicholson which is stable and convergent. Transient velocity, temperature and concentration profiles, local and average Skin-friction, Nusselt number and Sherwood number are shown graphically for air. The effects of viscous dissipative heat, Schnidt number, buoyancy ratio parameter on the transient state are discussed.
Indian Journal of Engineering & Materials Sciences
Vol. 9, February 2002, pp. 58-64
Preparation of zirconia thin films by tape casting technique as electrolyte material for solid oxide fuel cells
A Samson Nesaraj, I Arul Raj & R Pattabiraman
The effect of solvents ethyl methyl ketone (MEK), toluene, xylene and ethanol on the properties of thin films of zirconia prepared by the tape casting technique is reported here. It has been found that preparation of the slurry for tape casting plays an important role in controlling the textural properties of the membranes. The rheological features of the cast tapes are satisfactorily related to the solvent ratio. The toluene + xylene solvent system has been found to provide fine casting and sintering. The physical characteristics of the green tapes like thickness, density and weight losses during sintering have also been measured. The rate of heating is determined by TGA analysis of the green tapes. The role of solvents in controlling the properties of tape cast zirconia membranes is also described.
Indian Journal of Engineering & Materials Sciences
Vol. 9, February 2002, pp. 65-68
Preparation, characterization and ionic conductivity measurements of
(1–x) KCl:x ZrO2 solid electrolyte system
Archana Guptaa & Anjan Silb
Solid electrolytes in the system (1–x) KCl : x ZrO2 were prepared by varying x (mol %) from 0.0 to 0.8 in steps of 0.1. The samples were obtained in the form of pellets by powder compaction followed by the solid state sintering process. The samples were characterized by Scanning Electron Microscope and X-ray Diffractometer for their microstructural behaviour and detection of new phases, if any, that would have formed in the samples. The dc conductivity (s) of the samples was estimated from the impedance analysis data in the frequency range 100 Hz to 100 kHz. It has been found that the conductivity enhancement starts taking place appreciably from x=0.4 and attains its maximum at around 70 mol% ZrO2. The enhanced conductivity has been found to be over 3.6´10-6 Scm–1 which is about 20 times higher than that of the base matrix (KCl). The increase in conductivity has been attributed to the space charge layer formation at the dispersoid/matrix interface.
Indian Journal of Engineering & Materials Sciences
Vol. 9, February 2002, pp. 69-74
Laser-excited transition probabilities and oscillator strengths of calcium sulphide doped phosphors
H S Bhattia, Sukhwinder Singha, N K Vermab, Sunil Kumarb
Pulse excitation method has been used to find out the transition probabilities and oscillator strengths of calcium sulphide phosphors, doped with different activators having variable concentrations using ultraviolet laser as the excitation source. These investigations have been carried out at room temperature and at liquid nitrogen temperature. Various strong transitions in these phosphors have been detected and the corresponding oscillator strengths for these transitions have been calculated in terms of emission wavelengths, index of refraction and the transition probability at room temperature and liquid nitrogen temperature. The effect of concentration of the various dopants and the effect of temperature on transition probability and oscillator strength is also studied.
Indian Journal of Engineering & Materials Sciences
Vol. 9, February 2002, pp. 75-78
Non-destructive estimation of particle size of finished ceramic products by X-ray diffraction technique
K L Baruia & B Bhattacharyab
Non-destructive estimation of particle size of finished products is essentially required to judge their suitability for intended applications. For this estimation, a ceramic heating element (SiC rod) of a heat treatment furnace at 1400°C has been chosen. The particle size has been estimated with the proposed method based on counting reflection spots in a back reflection X-ray pattern. Calibration curve has been drawn on the basis of the data obtained by standard sieve method as well as proposed X-ray method from three powder samples of the same material with different particle sizes. The particle size estimated by this proposed method is found to closely match to that by sieve method.
Indian Journal of Engineering & Materials Sciences
Vol. 9, February 2002, pp. 79-82
Microhardness studies on antimony single crystal
Amit H Ravala, Mihir J Joshib & B S Shahb
Microhardness technique is a very good method to study the deformation behaviour of solids. The variation of microhardness with load and temperature shows the possible deformation behaviour and the competitive process occurring therein. In the present paper, a detailed study of the effect of the above parameters and an explanation in terms of the relative deformation modes is given.
Indian Journal of Engineering & Materials Sciences
Vol. 9, February 2002, pp. 83-84
Effect of N2-plasma exposure on corrosion of copper wire
N P Singh, S C Gupta & B R Sood
Corrosion of industrial materials is a slow ongoing process due to aggressive environment. In order to simulate this process in the laboratory, corrosion of annealed copper wire and N2-plasma exposed copper wire by dilute nitric acid has been investigated by monitoring the resistance of copper wire as the corrosion proceeded over eight days period. From resistance measurement as a function of time, corrosion rate (decrease in wire diameter) in m/h for annealed and N2-plasma exposed wire has been evaluated. It is observed that the rate of corrosion for the plasma-irradiated wire is less than that that observed for unexposed annealed wire. The present investigations clearly point towards the possible use of plasma-based surface engineering processes for corrosion protection and possibly for producing wear resistant materials.