Indian Journal of
Engineering & Materials Sciences

http : // www.niscair.res.in

Total visitors: 804  since 08-12-08

VOLUME 15 CODEN : IEMSEW

NUMBER 5

OCTOBER 2008 ISSN : 0971-4588

CONTENTS

Engineering
Particle tracking in rotating channel flow	365
Krishnan V Pagalthivarthia & Pankaj K Gupta
Ferrography — A procedure for measuring wear rate	377
N Govindarajan & R Gnanamoorthy
Micromechanical analysis of FRP hybrid composite lamina for in-plane transverse loading	382
K Sivaji Babu, K Mohana Rao, V Rama Chandra Raju, V Bala Krishna Murthy & M S R Niranjan Kumar
On the calculation of derivatives of stress intensity factors using fractal finite element method	391
R M Reddy & B N Rao
Materials Science
Synthesis and characterization of boron nitride nanotubes using a simple chemical method	419
S K Singhal, A K Srivastava, B P Singh & Anil K Gupta
Effect of variation of PVP/PVA weight ratio on the behaviour of nanocrystalline silver	425
Manab Mallik & R K Mandal
A self-sustaining reaction for titanium aluminides production via alumino-calciothermic reduction of TiO2	429
Ali Reza Kamali
Characterization of fly ash and it effects on the compressive strength properties of Portland cement	433
Özlem Çelik, Erdem Damcı & Sabriye Pişkin

Indian Journal of Engineering & Materials Sciences

Vol. 15, October 2008, pp. 365-376

Particle tracking in rotating channel flow

Krishnan V Pagalthivarthi & Pankaj K Gupta

The study deals with the numerical simulation of dilute solid-fluid flow in a two-dimensional straight rotating channel using Lagrangian particle tracking method. The developing carrier-phase flow, assumed to be steady in the mean, is computed using Galerkin finite element method. A rotation-modified k-e model is used to account for the effect of turbulence on the mean flow.

One-way coupling is assumed, i.e., the carrier-phase flow affects the particle motion, but not vice-versa. Model coefficients of restitution in the normal and tangential directions are used. The particle equations of motion include drag, pressure, centrifugal, Coriolis, virtual mass, and friction (in case the particle slides along the wall) forces. Mesh refinement and comparison with published numerical results are used to validate the code. Effects of such operating parameters as rotation rate, particle size, specific gravity and coefficients of restitution are discussed.

Indian Journal of Engineering & Materials Sciences

Vol. 15, October 2008, pp. 377-381

Ferrography — A procedure for measuring wear rate

N Govindarajan & R Gnanamoorthy

A contact fatigue phenomenon is most common failure seen in the structural components, which are under high-cyclic fatigue loads. Rail wheels, mating gears, ball bearing and wherever the formal contact between the two structural elements, are affected by contact fatigue failure, is commonly referred as pitting of surface. It can be seen that those structural elements are manufactured by powder metallurgy technology since it has more technical as well as commercial advantages over the conventionally made structural parts. Development in powder metallurgy manufacturing technologies, will give us confident to use of more powder metallurgy structural parts in place of conventional parts. Rolling-sliding contact fatigue (RSCF) experiments on powder metallurgy (PM) steels have been carried out in the laboratories with available experimental set-up. The lubrication oil is collected for regular interval and ferrography test is involved to predict the wear rate of the powder metallurgy steels. Wear morphology of porous steel is predicted.

Indian Journal of Engineering & Materials Sciences

Vol. 15, October 2008, pp. 382-390

Micromechanical analysis of FRP hybrid composite lamina for
in-plane transverse loading

K Sivaji Babu, K Mohana Rao, V Rama Chandra Raju, V Bala Krishna Murthy & M S R Niranjan Kumar

In this paper, the micromechanical behaviour of the square unit cell of a hybrid fiber reinforced composite lamina consisting of graphite and boron fibers embedded in epoxy matrix, has been studied. A three-dimensional finite element model with governing boundary conditions has been developed from the unit cells of square pattern of the composite to predict the Young’s modulus (E₂) and Poisson’s ratios (ν₂₁ and ν₂₃) of graphite-boron hybrid fiber reinforced lamina for various volume fractions. The stresses at the fiber-matrix interfaces induced due to the in-plane transverse loading, that is applied to predict the in-plane transverse Young’s modulus (E₂) and the associated Poisson’s ratios, are also determined from these models. The finite element software ANSYS has been successfully executed to evaluate the properties and stresses. The variation of the stresses at the fiber-matrix interface with respect to the angular location is discussed. The Young’s modulus is found to be increasing with V_f indicating that the stiffness of the composite increases with V_f , The magnitude of the normal stresses at the fiber matrix interface are maximum at θ = 0° as the direction of the load is normal to the surface at this location. This may result in the separation of fiber and matrix leading to debonding. This analysis is useful to realize the advantages of hybrid fiber-reinforced composites in structural applications, and to identify the locations with reasons where the stresses are critical to damage the interface.

Indian Journal of Engineering & Materials Sciences

Vol. 15, October 2008, pp. 391-418

On the calculation of derivatives of stress intensity factors
using fractal finite element method

R M Reddy & B N Rao

This paper presents a new fractal finite element based method for continuum-based shape sensitivity analysis for a crack in a homogeneous, isotropic, and two dimensional linear-elastic body subject to mixed-mode (modes I and II) loading conditions. The method is based on the material derivative concept of continuum mechanics, and direct differentiation. Unlike virtual crack extension techniques, no mesh perturbation is needed in the proposed method to calculate the sensitivity of stress-intensity factors. Since the governing variational equation is differentiated prior to the process of discretization, the resulting sensitivity equations predict the first-order sensitivity of the stress-intensity factors, K_I and K_II, more efficiently and accurately than the finite-difference method. Unlike the integral based methods such as J-integral or M-integral no special finite elements and post-processing are needed to determine the first-order sensitivity of the stress-intensity factors, K_I and K_II. Also a parametric study is carried out to examine the effects of the similarity ratio, the number of transformation terms, and the integration order on the quality of the numerical solutions. One mixed mode numerical example is presented to calculate the first-order derivative of the stress-intensity factors. The results show that the first-order sensitivities of the stress intensity factors obtained using the proposed method are in excellent agreement with the reference solutions obtained using the finite-difference method.

Indian Journal of Engineering & Materials Sciences

Vol. 15, October 2008, pp. 419-424

Synthesis and characterization of boron nitride nanotubes using a simple
chemical method

S K Singhal, A K Srivastava, B P Singh & Anil K Gupta

A simple two-step process is used for the growth of high purity multiwalled boron nitride (BN) nanotubes. In the first step, disordered nanostructured BN powder (aBN) is prepared chemically by heating a powdered mixture of KBH₄ and NH₄Cl (1:1) at 850ºC in N₂ followed by quenching the reaction product. In the second step, BN nanotubes are grown from the as-prepared aBN powder by annealing it at about 1200-1300ºC for 5-10 h in N₂. No catalyst material (Fe, Ni, Co, etc.) is intentionally added to aBN powder. This method of synthesis resulted in high purity multiwalled BN nanotubes of almost uniform diameter (10-30 nm) and length up to 5 µm, and, thus has a high aspect ratio with inherent characteristics of BN nanotubes, which may be useful for different applications. The BN nanotubes have been characterized using various techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The results obtained by this process are also compared with the similar type of BN nanotubes produced employing ball-milling and annealing technique.

Indian Journal of Engineering & Materials Sciences

Vol. 15, October 2008, pp. 425-428

Effect of variation of PVP/PVA weight ratio on the behaviour of nanocrystalline silver

Manab Mallik & R K Mandal

The effect of poly-vinyl-pyrrolidone/poly-vinyl-alcohal (PVP/PVA) weight ratio on the resulting size and shape of nanocrystalline (NC) silver is presented. It is shown that all the NC silver samples investigated, in this study, have displayed face centered cubic structure. The average coherently scattering domain size is estimated with the help of Scherrer equation. Having computed this, an attempt has been made to understand the UV-Vis spectra of the NC sols in terms of localized surface plasmon resonance (LSPR) behaviour. The change in the nature of LSPR in visible range of spectrum of the sols has been attributed to the complex interplay of shape, size and distribution of NC silver.

Indian Journal of Engineering & Materials Sciences

Vol. 15, October 2008, pp. 429-432

A self-sustaining reaction for titanium aluminides production via alumino-calciothermic reduction of TiO₂

Ali Reza Kamali

Titanium aluminides can be produced via an alumino-calciothermic reduction of TiO₂ in presence of KClO₄. This reaction, named KRH process, has been studied in this paper. The results show that after heating of starting materials with rate of 20°C/min, a self-sustaining reaction is ignited at about 550°C which led to the rapid increasing of system temperature to 1950°C during a short time of 192 s with a mean internal heating rate of around 437°C/min.

Indian Journal of Engineering & Materials Sciences

Vol. 15, October 2008, pp. 433-440

Characterization of fly ash and it effects on the compressive strength
properties of Portland cement

Özlem Çelik, Erdem Damcı & Sabriye Pişkin

In this study, the structure of different type of fly ash samples collected from different thermal power plants (Soma Unit IV/ type C, Çatalagzi/type F, Çayırhan / type C, Tunçbilek/ type F) in Turkey has been investigated. The chemical and physical properties, mineralogical composition and particle size distributions of the samples and their effects on the compressive strength properties of ordinary Portland cement (OPC), have been determined by FTIR, XRD, Mastersizer and SEM. Characterization results show that either Soma Unit IV and Tunçbilek or Çatalağzı and Çayırhan fly ash samples give similar structure of peaks in FTIR/ATR separately. Particle size distribution and SEM results also support each other. There are overlaps between characterization results of fly ash samples and compressive strength results of fly ash mortars. The cement mortars are prepared and tested for compressive strength according to the European Standards (EN 196-1). Results indicate that fly ash samples in the ratio of 15% in clinker markedly increases the compressive strength value (61.1 N/mm²) at 90 days. It indicates that decreasing the particle size of fly ash in blended Portland cement causes an increase in compressive strength. This means that fineness is a more effective parameter than chemical composition in improving the strength development of fly ash mortars and it is suggested that fine fly ash can be used to obtain higher compressive strength values.