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ISSN : 09714588 
CODEN : IEMSEW 

VOLUME 10 
NUMBER 6 
DECEMBER 2003 
CONTENTS
Engineering 

Simple design formula to evaluate the first axisymmetric frequency of moderately thick annular plates subjected to a uniform compressive load at the outer edge 
441 




Cold forging of sintered polygonal disc with bulging of sides 
452 




Bridge afflux in compound channels 
458 
Galip Seckin, Mehmet Ardicloglu, Mustafa Mamak & Serter Atabay 



Onset of instability in RayleighBenard configuration 
465 




MHD laminar plane wall jet flow of power law fluids 
474 




Materials Science 

Damping behaviour of critically deformed 304 stainless steel 
480 




Biofilm formation on structural materials in deep sea environments 
486 




Dielectric properties and a.c. electrical conductivity of aqueous solution grown pure and iodine doped poly (vinyl alcohol) films 
492 




Glass forming ability of TeBiSe based alloys 
498 




Effect of Fe^{3+ }substitution on structural and macromagnetic properties of yttrium iron garnet 
502 
Kunal B Modi, H J Shah, U N Trivedi, R P Vara, M C Chhantbar & H H Joshi 



Annual Index 
507 


Indian Journal of Engineering & Materials Sciences
Vol. 10, December 2003, pp. 441451
Annular plates are commonly used as structural elements in various engineering applications. In many engineering fields, especially those related with aerospace applications, structural systems are almost fully stressed to improve the structural factor and pay load fraction. Evaluation of the first axisymmetric frequency, which is an important design input, of structural elements in the stressed condition is a relatively complex task. In this paper, the applicability of a simple and effective design formula developed earlier by one of the authors with an assumption on the mode shapes of vibration and buckling, is studied with reference to an initially stressed moderately thick annular plate. The initial stress is due to a uniform compressive load at the outer edge of the annular plate. The values of the first axisymmetric frequency of the initially stressed moderately thick annular plates obtained by using the design formula, when compared with those obtained by the powerful and versatile finite element method, for different combinations of boundary conditions at the outer and inner edges, and different ratios of internal to external radii show the efficacy of the design formula.
Indian Journal of Engineering & Materials Sciences
Vol. 10, December 2003, pp. 452457
Investigations on various aspects of cold forging of iron powder preforms, compacted and sintered from atomized iron powder, are reported here. During forging, both the bulging of sides and barreling along the thickness take place. Solution is given for forging without considering inertia effect of an Nsided polygonal sintered disc between two flat dies, taking into account the bulging of sides only. An attempt has been made to determine the die pressures developed during the cold forging of square iron powder preform by using an upper bound approach. The results so obtained are discussed critically to illustrate the interaction of various involved process parameters.
Indian Journal of Engineering & Materials Sciences
Vol. 10, December 2003, pp. 458464
The results of model testing of arch and straight deck bridge constrictions are presented. All tests were carried out in a compound flume that consists of a main channel and two symmetric floodplains set at a fixed bed slope. A simple generalized afflux equation is also proposed. The equation which describes the model characterizes the afflux as a function of Froude number, and blockage ratio in terms of the downstream conditions.
Indian Journal of Engineering & Materials Sciences
Vol. 10, December 2003, pp. 465473
Thermal instability of a fluid layer, confined between two horizontal rigid boundaries, with timeperiodic temperature distribution is studied with the help of the Floquet theory. The timedependent part of temperature is expressed as a Fourier series. Disturbances are assumed to be infinitesimal. Only odd solutions are considered. Numerical results for the critical Rayleigh number are obtained at various Prandtl numbers and for various values of the frequency. Comparisons are made with the known results.
Indian Journal of Engineering & Materials Sciences
Vol. 10, December 2003, pp. 474479
Using similarity transformations, the boundary layer equations, governing the flow of twodimensional jet of electrically conducting nonNewtonian power law fluids in the presence of transverse magnetic field, are reduced to ordinary nonlinear differential equation with conditions prescribed at two boundaries. Then, oneparameter group transformations are introduced to transform the twopoint boundary value problem to initial value problem and finally the initial value problem is solved numerically on computer. Physical quantities of interest, for different values of flow index of power law model and magnetic parameter are tabulated numerically and the velocity distribution is shown graphically. It is found that the fluid flow index and magnetic field have significant effect on the flow.
Indian Journal of Engineering & Materials Sciences
Vol. 10, December 2003, pp. 480485
Metallic materials are used in many applications because of their economy, strength and endurance limit. Fatigue damage is major contributor to failure or fracture in engineering materials. Energy dissipation, termed damping, occurs in engineering metals as a function of the cyclic loading history. Damping behaviour of materials has been estimated using many different experimental techniques, and parameters, i.e., the loss factor versus strain amplitude and frequency range. In order to measure energy dissipation, a damping monitoring method, which estimates the damping factor by vibration excitation, is used in this study. Under a constant cyclic load for high cycle fatigue, the effects of the number of fatigue cycles on damping are studied in 304 stainless steel. An empirical equation has been developed for constant energy increase per cycle up to fatigue crack initiation. Experimental and analytical results are compared. Besides small differences depending on some factors both values are in agreement.
Indian Journal of Engineering & Materials Sciences
Vol. 10, December 2003, pp. 486491
R Venkatesan^{a}, E S Dwarakadasa^{b} & M Ravindran^{a}
Biofilm formation on structural materials in deepsea environment after long duration of exposure is reported here for the first time. Some structural material specimens such as steel, steel with zinc and aluminum anodes and carbon fibrereinforced composite were exposed at depths of 500, 1200, 3500 and 5100 m for 174 days. The bacterial colony formation on these specimens was studied after their retrieval from the ocean. Macrofouling was not found in any of these materials. Carbon fibrereinforced composite did not support bacterial colony formation at all the tested depths. Steel supported bacterial colonies at all depths. Aluminium and zinc anodes did not support bacterial colonies at 3500 and 5100 m depths. This could be related to lower temperatures prevailing at these depths. Also, all the identified bacterial colonies were aerobic as dissolved oxygen was present even at 5100 m depth. Hence, anaerobic conditions did not exist during exposure under these structural conditions. Dissolved oxygen data at the experimental site is also presented and discussed.
Indian Journal of Engineering & Materials Sciences
Vol. 10, December 2003, pp. 492497
R J Sengwa* & Kulvinder Kaur
Poly vinyl alcohol (PVA) films of uniform thicknesses 280, 120, 80, 50 and 25 microns, and also 50 micron PVA films doped with 4, 3, 2 and 1 wt% iodine of PVA weight in aqueous solution have been prepared by solution grown technique. AgPVAAg sandwich structures of film capacitors have been fabricated for their dielectric characterization. The capacitance and dissipation factor of these capacitors are measured in the frequency range 100 Hz100 kHz at 25°C. The dielectric permittivity e¢, loss e¢¢, and a.c. conductivity s, have been determined using the measured values of capacitance and dissipation factor. It is found that the value of e¢ decreases with increase in frequency and increases with the film thickness while dielectric loss e¢¢ shows marked variation with frequency. For iodine doped films, values of e¢ and e¢¢ vary anomalously with the increase in concentration of iodine. From the a.c. conduction studies, it is observed that the a.c. conductivity of pure PVA films increases with the film thickness and vary almost linearly with frequency in the range of 10^{11}  10^{8} S cm^{1}. Further it is found that there is anomalous variation in conductivity of iodine doped PVA film with increase in iodine concentration. From these dielectric studies, it seems that an increase in e¢ and e¢¢ with the increase in PVA film thickness is due to the residual water or variation in degree of syndiotacticity of PVA chain. In case of iodine doped PVA films, the variations in crystalline and complex formation of PVA molecules with iodine are responsible to change the dielectric parameters.
Indian Journal of Engineering & Materials Sciences
Vol. 10, December 2003, pp. 498501
Manish Saxena^{a*}, Animesh Agarwal^{a} & P K Bhatnagar^{b}
In the present work, the relationships for the glass transition temperature T_{g}, the peak temperature T_{p}, and the difference of crystallization temperature and glass transition temperature, (T_{c}T_{g}), for different heating rates have been studied with the increase in Bi content. With the increase in heating rates T_{g}, T_{c}_{ } and T_{p} are found to increase. The glass transition temperature represents the strength or rigidity of the glass structure. This analysis helps in finding the suitability of an alloy to be used in phase transition optical memories/switches.
Indian Journal of Engineering & Materials Sciences
Vol. 10, December 2003, pp. 502506
Kunal B Modi, H J Shah, U N Trivedi, R P Vara, M C Chhantbar & H H Joshi
The structural and bulk magnetic properties of Fe^{3+} substituted yttrium iron garnet with general formulaY_{3x}Fe_{5+x}O_{12 }(x = 0.0, 0.05, 0.15,^{ }0.30 and 0.50) have bean investigated by means of Xray diffraction, EDAX, high field magnetization and low field a.c. susceptibility measurements. It is found that substituted Fe^{3+} ions occupy csites and increase in lattice constant for x > 0.30 is due to presence of Fe^{2+} ions, determined through EDAX, on asites. Variation of magneton number with x can be explained satisfactorily assuming the collinear spin ordering model and Neel temperature values deduced experimentally from a.c. susceptibility measurements are in good agreement to those calculated theoretically.