Indian Journal of
Engineering & Materials Sciences
VOLUME 9 
NUMBER 1 
FEBRUARY 2002 
CONTENTS
Interference
effects on the mean velocities and turbulence intensities behind a tall body due
to a short body in tandem 
5 


Evaluation
of optimum amount of load shedding to prevent dynamic voltage instability in
a longitudinal ac power transmission system 
20 


A short
review of classical Stefan problem 
25 


Section
extrusion from rectangular billet : Experimental verification of the SERR
analysis 
35 


Use of
condensation with boundary characteristics orthonormal polynomials in the
vibration problems 
41 


Magnetic fluid
based squeeze film between two curved plates lying along the surfaces
determined by secant functions 
45 


Transient
free convection flow of a viscous dissipative fluid with mass transfer past a
semiinfinite 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 
58 


Preparation,
characterization and ionic conductivity measurements of (1x) KCl:xZrO_{2 }solid
electrolyte system 
65 


Laserexcited
transition probabilities and oscillator strengths of calcium sulphide doped
phosphors 
(Contd) 69 
H S Bhatti, Sukhwinder Singh, N K Verma & Sunil
Kumar 

Nondestructive
estimation of particle size of finished ceramic products by Xray diffraction
technique 
75 


Microhardness
studies on antimony single crystal 
79 


Note 

Effect of N_{2}plasma
exposure on corrosion of copper wire 
83 

Indian Journal of Engineering
& Materials Sciences
Vol. 9, February 2002, pp.
519
Interference effects
on the mean velocities and turbulence intensities behind a tall body
due to a short body in tandem
B H Lakshmana Gowda^{a}, E G Tulapurkara^{b} & A Kanna Babu^{a}
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 crosssection 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 threedimensional 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. 2024
Evaluation of optimum amount of load shedding to prevent
dynamic voltage instability in a
longitudinal ac power transmission system
G Panda^{a} & A Chakrabarti^{b}
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. 2534
A short review of
classical Stefan problem
K N Shukla
The paper describes the stateofart solution technique for classical Stefan problem. With a short discussion on the wellposedness of heat conduction problem with melting or freezing, some analytical solutions are presented.
Indian Journal
of Engineering & Materials Sciences
Vol. 8, February 2002, pp.
3540
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 threedimensional extrusion of sections unless a continuous velocity field is employed for the analysis. On the other hand, analysis of extrusion of sections with reentrant 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 Isections from rectangular billets through square dies using direct extrusion process. An experimental setup 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. 4144
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 RayleighRitz 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. 4548
Magnetic fluid based
squeeze film between two curved plates lying along the surfaces
determined by secant functions
R M Patel^{a }& G M Deheri^{b}
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. 4957
Transient free
convection flow of a viscous dissipative fluid with mass transfer past a semiinfinite
vertical plate
Fathia Moh. Al Samman^{a}, M Y Gokhale^{b}, V M Soundalgekar^{c}
Transient
free convection flow of a dissipative fluid past a semiinfinite vertical plate
is studied by considering the presence of species concentration. The governing
equations in nondimensional form are solved by implicit finitedifference
technique of CrankNicholson which is stable and convergent. Transient
velocity, temperature and concentration profiles, local and average Skinfriction,
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. 5864
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. 6568
Preparation,
characterization and ionic conductivity measurements of
(1–x) KCl:x ZrO_{2} solid electrolyte system
Archana Gupta^{a} & Anjan Sil^{b}
Solid
electrolytes in the system (1–x) KCl : x ZrO_{2} 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 Xray 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% ZrO_{2}. 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. 6974
Laserexcited transition
probabilities and oscillator strengths of calcium sulphide doped phosphors
H S Bhatti^{a}, Sukhwinder Singh^{a}, N K Verma^{b}, Sunil Kumar^{b}
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. 7578
Nondestructive
estimation of particle size of finished ceramic products by Xray diffraction
technique
K L Barui^{a} & B
Bhattacharya^{b}
Nondestructive
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 Xray pattern. Calibration curve has been drawn on the basis of the
data obtained by standard sieve method as well as proposed Xray 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. 7982
Microhardness studies on antimony single
crystal
Amit H Raval^{a}, Mihir J Joshi^{b} & B S Shah^{b}
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. 8384
Effect of N_{2}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 N_{2}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 N_{2}plasma exposed wire has been evaluated. It is
observed that the rate of corrosion for the plasmairradiated wire is less than
that that observed for unexposed annealed wire. The present investigations
clearly point towards the possible use of plasmabased surface engineering
processes for corrosion protection and possibly for producing wear resistant
materials.