Total visitors:2,316 since 08-01-04

Indian Journal of Engineering & Materials Sciences

 

 

 

ISSN : 0971-4588

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

S Renjith & G Venkateswara Rao

 

 

 

Cold forging of sintered polygonal disc with bulging of sides

452

R K Ranjan & S Kumar

 

 

 

Bridge afflux in compound channels

458

Galip Seckin, Mehmet Ardicloglu, Mustafa Mamak & Serter Atabay

 

 

 

Onset of instability in Rayleigh-Benard configuration

465

B S Bhadauria

 

 

 

MHD laminar plane wall jet flow of power law fluids

474

R N Jat & Amilal Kulhari

 

 

 

Materials Science

 

Damping behaviour of critically deformed 304 stainless steel

480

M Colakoglu & K L Jerina

 

 

 

Biofilm formation on structural materials in deep sea environments

486

R Venkatesan, E S Dwarakadasa & M Ravindran

 

 

 

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

 

492

R J Sengwa & Kulvinder Kaur

 

 

 

Glass forming ability of Te-Bi-Se based alloys

498

Manish Saxena, Animesh Agarwal & P K Bhatnagar

 

 

 

Effect of Fe3+ substitution on structural and macro-magnetic 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. 441-451

 

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

S Renjith & G Venkateswara Rao

 

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. 452-457

 

Cold forging of sintered polygonal disc with bulging of sides

R K Ranjana & S Kumarb

 

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 N-sided 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. 458-464

 

Bridge afflux in compound channels

Galip Sekin, Mehmet Ardılıoğlu, Mustafa Mamak* & Serter Atabay

 

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. 465-473

 

Onset of instability in Rayleigh-Benard configuration

B S Bhadauria

 

Thermal instability of a fluid layer, confined between two horizontal rigid boundaries, with time-periodic temperature distribution is studied with the help of the Floquet theory. The time-dependent 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. 474-479

 

MHD laminar plane wall jet flow of power law fluids

R N Jat & Amilal Kulhari

 

Using similarity transformations, the boundary layer equations, governing the flow of two-dimensional jet of electrically conducting non-Newtonian power law fluids in the presence of transverse magnetic field, are reduced to ordinary non-linear differential equation with conditions prescribed at two boundaries. Then, one-parameter group transformations are introduced to transform the two-point 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. 480-485

 

Damping behaviour of cyclically deformed 304 stainless steel

M Colakoglua & K L Jerinab

 

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. 486-491

 

Biofilm formation on structural materials in deep sea environments

R Venkatesana, E S Dwarakadasab & M Ravindrana

 

Biofilm formation on structural materials in deep-sea 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 fibre-reinforced 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 fibre-reinforced 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. 492-497

 

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

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. Ag-PVA-Ag 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 Hz-100 kHz at 25C. 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. 498-501

 

Glass forming ability of Te-Bi-Se based alloys

Manish Saxenaa*, Animesh Agarwala & P K Bhatnagarb

 

In the present work, the relationships for the glass transition temperature Tg, the peak temperature Tp, and the difference of crystallization temperature and glass transition temperature, (Tc-Tg), for different heating rates have been studied with the increase in Bi content. With the increase in heating rates Tg, Tc  and Tp 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. 502-506

 

Effect of Fe3+ substitution on structural and macro-magnetic properties of yttrium iron garnet

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 Fe3+ substituted yttrium iron garnet with general formulaY3-xFe5+xO12 (x = 0.0, 0.05, 0.15, 0.30 and 0.50) have bean investigated by means of X-ray diffraction, EDAX, high field magnetization and low field a.c. susceptibility measurements. It is found that substituted Fe3+ ions occupy c-sites and increase in lattice constant for x > 0.30 is due to presence of Fe2+ ions, determined through EDAX, on a-sites. 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.