Indian Journal of
Engineering & Materials Sciences
VOLUME 8 / NUMBER 5 / OCTOBER 2001CONTENTS
Engineering
Dynamic studies of a typical payload fairing for different boat tail configurations / 247
V Ramamurti, S Rajarajan & G Venkateswara Rao
High frequency positive series resistance in IMPATT devices / 255
S P Pati, S K Dash & S Satpathy
Computer prediction of the performance of a solar powered solid adsorption refrigerator in some Nigerian cities / 261
E E Anyanwu & N V Ogueke
Materials Science
Prepation of CdIn2S4 thin films by chemical method / 271
H M Pathan, B R Sankapal & C D Lokhande
Influence of WO3 on dielectric properties of zinc phosphate glasses / 275
P Subbalakshmi & N Veeraiah
Effect of frequency and stress ratio on fatigue crack propagation of glass phenolic composite / 285
Nirbhay Singh Ram Khelawan
Structural and dielectric properties of KTiOPO4 ceramic / 289
S N Choudhary, K Prasad R N P Choudhary
Hydration of C4AF in the presence of artificial CaSO4 and lime / 292
S El-Alfi, S Abd-Aleem & H El-Didamony
Synthesis and characterisation of IPP-g-glycidylmethacrylate copolymer / 297
Ragesh B Brahmbhatt, Alpesh C Patel & Surekha Devi
Low temperature synthesis of MoO3 through the use of NH2OH.HCl as reducing agent
N N Mallikarjuna & A Venkataraman / 303
Indian Journal of Engineering & Materials Science
Vol. 8, October 2001, pp. 247-254
Dynamic studies of a typical payload fairing for different boat tail configurations
V Ramamurtia, S Rajarajanb & G Venkateswara Raoc
aDepartment of Applied Mechanics, Indian Institute of Technology, Madras 600 036, India
bLaunch Vehicle Design Group, Vikram Sarabhai Space Centre, Trivandrum 695 022, India
cStructural Engineering Group, Vikram Sarabhai Space Centre, Trivandrum 695 022, India
Received 21 February 2001; accepted 23 July 2001
Payload fairing structure of any launch vehicle protects the payload from the adverse aerodynamic environments besides providing the forward surface. This structure is separated from the core vehicle as soon as the purpose is served. The elastic response of this structure due to the separation force is very important to be considered along with rigid body movements. The boat tail structural element configuration is decided based on the dimensions of the core vehicle and the mission requirements. The displacement response due to separation force of the payload fairing for different boat tail angles is an important input data required to finalise the boat tail angle and the payload fairing configuration in total. Finite element method is employed using three noded triangular plate and shell element and 3D beam element in conjunction with a mode superposition technique to carry out this study for a typical payload fairing. The contribution of the elastic response on the radial gap between the payload envelope and the separated fairing is also reported including a payload fairing configuration without boat tail structure.
Indian Journal of Engineering & Materials Sciences
Vol. 8, October 2001, pp. 255-260
High frequency positive series resistance in IMPATT devices
S P Pati, S K Dash & S Satpathy
P G Department of Physics, Sambalpur University, Jyoti Vihar, Burla 768 019, India
Received 25 August 2000; accepted 3 May 2001
A generalized computer method, which considers drift, diffusion and tunnel currents has been formulated and used to determine the high frequency series resistance (Rs) and its distribution profile along the active layer of a varieties of Avalanche Transit Time (ATT) diode structures. The method is also capable of providing RF properties of the diodes like RF negative resistance (ZR), band width and mean square noise voltage <V2>/df and other parameters at various frequencies. The result indicates generation of high value of Rs, ZR and <V2>/df for lo-hi-lo and hi-lo double drift region (DDR) diodes as compared to flat profile diodes. A comparison of the series resistance (Rs), microwave properties and noise generation of Si, GaAs and InP DDR diodes has also been made in this paper. The Rs distribution profiles for the hi-lo and lo-hi-lo DDRs are observed to have double spike like profile unlike the normal double peak profiles for flat DDRs
Indian Journal of Engineering & Materials Sciences
Vol. 8, October 2001, pp. 261-270
Computer prediction of the performance of a solar powered solid adsorption refrigerator in some Nigerian cities
E E Anyanwu* & N V Ogueke
Mechanical Engineering Department, Federal University of Technology, P.M.B. 1526, Owerri, Nigeria
Received 2 August 2000; accepted 25 June 2001
The computer prediction of the seasonal performance of a solid adsorption refrigerator, using activated carbon/methanol working pair, in seven Nigerian cities is presented. The mathematical model and its computer programme1 are used for this study. The monthly average performance of the refrigerator is found to depend very strongly on the insolation level and its geographical location. Peak methanol generation and cumulative COP ranged over 0.498-1.698 kg and 0.026-0.088, respectively for all the cities. Maiduguri gave the best overall performance followed by Sokoto, Yola, Enugu, Owerri and Port Harcourt in that order. Thus, the refrigerator operation is possible in all the cities throughout the year and in any other city with minimum average daily insolation level of about 12 MJ/m2.
Indian Journal of Engineering & Materials Sciences
Vol. 8, October 2001, pp. 271-274
Preparation of CdIn2S4 thin films by chemical method
H M Pathan, B R Sankapal & C D Lokhande*
Thin Film Physics Laboratory, Department of Physics, Shivaji University, Kolhapur 416 004, India
Received 3 January 2001; accepted 22 May 2001
Semiconducting CdIn2S4 thin films have been deposited on amorphous glass substrates using a chemical method, successive ionic layer adsorption and reaction (SILAR). The influence of preparative parameters on the properties of the films has been studied. The thickness of the film is found to be 0.44 mm. The films have been characterized for structural, optical and electrical transport properties by means of X-ray diffraction, optical absorption, electrical resistivity and thermoelectric power measurements techniques. The films are found to be nanocrystalline with optical bandgap 2.12 eV. The electrical resistivity was of the order of 104 W-cm.
Indian Journal of Engineering Materials Sciences
Vol. 8, October 2001, pp. 275-284
Influence of WO3 on dielectric properties of zinc phosphate glasses
P Subbalakshmi & N Veeraiah
Department of Physics, Nagarjuna University P G Centre, Nuzvid 521 201, India
Received 19 March 2001; accepted 4 July 2001
Dielectric constant e', loss tand and a.c conductivity sa.c of 40 ZnO-xWO3- (60-x) P2O5 (with 0 £ x £ 15) glasses are studied as a function of frequency (in the range 102-105 Hz) and temperature (range 30-300°C). The dielectric breakdown strengths of these glasses are also measured in the air medium. All the dielectric parameters (viz., e', tan d and sa.c) are found to decrease with the increase in the concentration of WO3. Dielectric loss variation with the temperature for the glasses containing WO3 up to 5 mol % exhibited dipolar relaxation effects. These effects are analysed by a pseudo Cole-Cole plot method. The dielectric breakdown strength, the activation energy for a.c conduction are found to decrease with increase in concentration of WO3. These results have been used to throw some light on the structural change in ZnO-WO3-P2O5 glass system with the aid of data on IR spectra and differential thermal analysis of these glasses.
Indian Journal of Engineering & Materials Sciences
Vol. 8, October 2001, pp. 285-288
Effect of frequency and stress ratio on fatigue crack propagation of glass
phenolic composite
Nirbhay Singh & Ram Khelawan
Defence Materials and Stores Research and Development Establishment, G.T. Road, Kanpur 208 013, India
Received 31 January 2000; revised received 25 June 2001
The effects of stress ratio and frequency on the fatigue crack propagation of glass phenolic composite have been discussed in the present investigation. The fatigue crack growth rates at three stress ratios of 0.1, 0.25 and 0.50 have been studied with the first set of specimens whereas the effect of frequency has been studied with the second set of specimens. The study showed that the fatigue crack propagation of this composite is influenced to an appreciable extent by the combined effect of stress ratio and frequency. However, both stress ratio and frequency affect individually also the crack growth rate. All the experiments have been conducted at ambient temperature.
Indian Journal of Engineering & Materials Sciences
Vol. 8, October 2001, pp. 289-291
Structural and dielectric properties of KTiOPO4 ceramic
S N Choudharya, K Prasada & R N P Choudharyb
aUniversity Department of Physics, T.M Bhagalpur University, Bhagalpur 812 007, India
bDepartment of Physics & Meteorology, Indian Institute of Technology, Kharagpur 721 302, India
Received 22 August 2000; accepted 6 July 2001
Ceramic samples of KTiOPO4 are prepared using chemical method. X-ray diffraction (XRD) technique has been used to check the formation of single phase KTiOPO4 compound. The cell parameters obtained by XRD analyses are a = 20.125(8) Å, b = 8.433(1) Å and c = 11.492(4) Å in orthorhombic crystal system. The ceramic samples of KTiOPO4 have been characterized by dielectric studies. The room temperature values of dielectric constant and dielectric loss are found to be 10.32 and 0.12 respectively at 1 kHz.
Indian Journal of Engineering & Materials Sciences
Vol. 8, October 2001. pp. 292-296
Hydration of C4AF in the presence of artificial CaSO4 and lime
S El-Alfia, S Abd-Aleemb & H El-Didamonyc
a Refractories, Ceramics and Building Materials Department,National Research Center
Dokki, Cairo, Egypt
b Faculty of Science, Cairo University, Fayoum, Egypt
c Faculty of Science, Zagazig University, Zagazig, Egypt
Received 10 January 2001; accepted 1 August 2001
The ferrite phase consists of about 8-13 wt% portland cement. This phase has received little attention with regard to its hydration. The aim of present investigation is to synthesize the ferrite phase and study the rate of hydration in the presence of CaSO4 and CaO up to 28-days in suspension. This study is followed by the determination of the free lime as well as combined water contents and the hydration products by the XRD analysis. The results revealed that whatever the amount of CaSO4 the monosulphate AFm was the only phase formed from 6 h up to 28-days and the ettringite AFt was not formed. In the presence of 1 mol CaSO4 and 2 mol CaO, the monosulphate AFm with carboaluminate was the dominant phase at 28-days. When the amount of CaSO4 was increased to 3 mol with the same amount of lime the hydration was retarded in comparison with that containing 1 mol of CaSO4. Very small amount of sulphoaluminate ferrite hydrate was formed with residual reactants such as C4AF,CaSO4 and Ca(OH)2.
Indian Journal of Engineering & Materials Sciences
Vol. 8, October 2001, pp. 297-302
Synthesis and characterization of IPP-g-glycidylmethacrylate copolymer
Ragesh B Brahmbhatt, Alpesh C Patel & Surekha Devi*
Department of Chemistry, Faculty of Science, M.S. University of Baroda, Vadodara 390 002, India
Received 7 June 2000; accepted 11 July 2001
Isotactic polypropylene (IPP) was grafted with glycidylmethacrylate (GMA) using benzoylperoxide as free radical initiator in an inert atmosphere and toluene as solvent at 110°C temperature. Various reaction conditions such as monomer and initiator concentration, time, temperature, medium and atmosphere were optimized for achieving higher % of grafting. Maximum 2.8% grafting was observed. The graft copolymers were characterized by thermal and spectral methods
Indian Journal of Engineering & Materials Sciences
Vol. 8, October 2001, pp. 303-306
Low temperature synthesis of MoO3 through the use of NH2OH.HCl
as reducing agent
N N Mallikarjuna & A Venkataraman*
Department of Chemistry, Gulbarga University, Gulbarga 585 106, India
Received 11 October 2000; accepted 2 July 2001
This paper reports a novel technique for the synthesis of MoO3 through the reduction of ammonium molybdate using hydroxylamine hydrochloride as a reductant. MoO3 is formed upon thermal decomposition of the reduced ammonium molybdate. The progress of the formation of the oxide is understood on the basis of structure and thermal studies.