Indian Journal of Engineering

Engineering
Studies on interaction of plane turbulent jets in a confined space: mean flow characteristics	7
B H Lakshmana Gowda, T S Dhanasekaran, T Sundararajan & R Natarajan

Tool wear optimization in turning operation by Taguchi method	19
Hari Singh & Pradeep Kumar

Characterization of nanoscale roughness in single point diamond turned optical surfaces using power spectral density analysis	25
Gufran Sayeed Khan, RamaGopal V Sarepaka , K D Chattopadhyay, P K Jain & R P Bajpai

Analysis of reacting flows in an aero-engine afterburner using computational fluid dynamics
Sunil V Unaune & V Ganesan

Backcalculation of pavement layer parameters using artificial neural networks	38
Mehmet Saltan & Serdal Terzi

Finite element analysis of longitudinal debonding between fibre and matrix interface	43
K Aslantas & S Tasgetiren

Numerical solution of the flow of a second-order fluid under an enclosed rotating disc	49
H G Sharma & K S Biradar

Materials Science

Dielectric relaxation in glassy Se₉₀Ge_xIn_10-x	55
N Choudhary, D K Goel & A Kumar

Studies on 2,4,6-trinitrophloroglucinol (TNPG)–a novel flash sensitizer	59
Mehilal, N Sikder, A K Sikder, D V Survase & J P Agrawal

Taguchi approach for investigation of the setting times on cement-based grouts	63
Ozcan Tan & A Sahin Zaimoglu

Compressive strength of lightweight aggregate concrete exposed to temperatures	68
A Ferhat Bingol & Rustem Gul

Studies on interaction of plane turbulent jets

in a confined space: mean flow characteristics

In this paper, the effect of the central jet width in the flow field created due to the interaction of two turbulent jets at impingement angles of a equal to 30° and 45° and a central jet is described. The investigation is carried out for velocity ratios (U_C/U_O) of 1.0, 2.0 and 3.0, where U_C and U_O are the velocities in the central and the outer jets respectively. It is seen from the static pressure analysis that the extents of various recirculation zones are altered significantly when the velocity ratio U_C/U_Ochanges from 1.0 to 2.0 and when the central jet width ratio increase from w/2B=0.064 to 0.127 in both the cases (a=30° and 45°). From the analysis of mean velocity, it is found that the flow structure is significantly different when the width ratio changes from 0.064 to 0.127.

Tool wear optimization in turning operation by

Taguchi method

A design of experiment-based approach is adopted to obtain an optimal setting of turning process parameters (cutting speed, feed and depth of cut) that may yield optimal tool wear (flank wear and crater wear) to titanium carbide coated carbide inserts while machining En24 steel (0.4% C), a difficult-to-machine material. The effects of the selected process parameters on tool wear and subsequent optimal settings of the parameters have been accomplished using Taguchi’s parameter design approach. The results indicate that the selected process parameters affect significantly the tool wear characteristics of TiC coated carbide tool. The predicted optimal values of flank wear width and crater wear depth of coated carbide tool while machining En24 steel are 0.172 mm and 0.244 micron respectively. The results are further confirmed by conducting further experiments

Characterization of nanoscale roughness in single point diamond turned optical surfaces using

power spectral density analysis

Gufran Sayeed Khan, Rama Gopal V Sarepaka, K D Chattopadhyay, P K Jain & R P Bajpai

Power spectral density (PSD) distribution provides an accurate measure of roughness of an optical surface. This article presents an analysis of optical surface roughness generated by single point diamond turning (SPDT) using PSD. For this study, flat 60 mm diameter aluminium-6061 samples are machined for varying tool feed rates, while keeping the other machining parameters constant. The 1-D PSD distributions are computed from the surface roughness data obtained by mechanical profilometer. The PSD distribution of the surface roughness profile is composed of primarily three periodic components, which are correlated to the tool feed rate, material induced vibrations and machine-tool vibrations. An attempt has been made to identify their individual contributions in PSD estimates. This study helps in improving the surface quality by selecting optimum process parameters.

Analysis of reacting flows in an aero-engine afterburner

using computational fluid dynamics

In this paper, reacting flows in an aero-engine afterburner are analyzed using computational fluid dynamics (CFD). A computational procedure is described for calculating the three-dimensional reacting flow fields in a gas turbine afterburner. The computations are based on numerical solution of time-averaged transport equations for mass, momentum, turbulent kinetic energy and dissipation rate using a finite volume formulation. The numerical calculations are performed using SIMPLE (Semi Implicit Method for Pressure Linked Equations). The RNG (Re-normalization Group Theory) k-ε model is used for turbulence modeling. Combustion is modeled using PDF (Probability Density Function). The results for air-fuel ratio of 30 and 46 are obtained and analysed.

Backcalculation of pavement layer parameters using Artificial Neural Networks

In this paper, a new formulation based on Artificial Neural Networks (ANN) is presented for backcalculation of pavement layer moduli. In structural analysis of flexible pavements, the procedures as Layered Elastic Theory, Equivalent Layer Thickness (ELT), and Finite Elements Method (FEM) generally have complex formulations and give approximate results. Therefore, it is extremely difficult to perform realistic analysis for flexible pavements, especially in view of modelling the material properties of layers in these methods. Setting the finite element mesh and iteration procedure of backcalculation takes rather long time. The proposed ANN procedure requires significantly less computation time. ELT method is used for simplicity. It is impossible or very hard to model the visco-elastic and non-linear behaviour of layer materials in layered elastic theory. The use of ANN is proliferating with high rate in simulation. The ability of ANN is to learn complex nonlinear relationships. A new formulation using ANN is presented here.

Finite element analysis of longitudinal debonding between fibre and matrix interface

In this paper, a numerical model developed for the analysis of a cylindrical element of matrix containing a single fibre is presented. A ring-shaped crack is assumed at the interface of fibre and matrix. Both layers in the model are bonded perfectly with the exception of the crack faces. Contact elements, which have bonded feature, are used between fibre and matrix. Displacement correlation method is used to calculate opening-mode and sliding-mode stress intensity factors. These results obtained from the analysis help to understand the debonding phenomenon between fibre and matrix interface.

Numerical solution of the flow of a second-order fluid

under an enclosed rotating disc

The solution of a non-linear boundary value problem arising due to the steady flow of an incompressible second-order fluid (flowing with a small mass rate of symmetrical radial outflow m, taken negative for a net radial inflow) under finite rotating disc (enclosed within a co-axial cylindrical casing) has been obtained numerically using finite difference method. The resulting equations are converted into a set of difference equations. Starting from the known values of flow functions for small values of the Reynolds number, the solution is extended for larger Reynolds number by making use of Newton-Raphson iterative method and Gauss elimination method. Effects of second order forces in the flow on the velocity field have been investigated in detail in the regions of recirculation and no-recirculation for the cases of radial outflow and inflow and illustrated graphically. Such flows are useful in mechanical and chemical industries

Dielectric relaxation in glassy Se₉₀Ge_xIn_10-x

Frequency and temperature dependence of dielectric constant (e') and dielectric loss (e'') are studied in glassy Se₉₀Ge_xIn_10-x, where x = 0, 2, 4, 6, 8 and 10, in the frequency range 1-10 kHz and in the temperature range 293-400 K. The experimental results indicate that no dielectric dispersion exist in glassy Se₉₀Ge₁₀ alloy (x = 10). However, when In concentration increases (x = 8, 6, 4, 2 and 0), dielectric dispersion starts in the above frequency and temperature range. The values of e' and e'' at a particular temperature and frequency increase with the increase in In concentration. An analysis of the observed dielectric loss shows that the Guintini's theory of dielectric dispersion based on two electron hopping over a potential barrier is applicable in the present case.

Studies on 2,4,6-trinitrophloroglucinol (TNPG)¾A novel

flash sensitizer

2,4,6-Trinitrophloroglucinol (TNPG), useful for percussion caps, detonator formulations and dye manufacture, has been synthesized with conventional nitrating agents under mild reaction conditions. The compound is characterized by IR, NMR, mass and elemental analyses. Further, the purity of the compound is confirmed by estimation of nitro groups. Thermal and explosive properties of TNPG have been investigated. The detonation velocity and detonation pressure are also estimated

Taguchi approach for investigation of the setting times on cement-based grouts

Investigations on the effect of the bentonite, fly ash and silica fume on the initial and final setting time of cement-based grouts are reported here. Three additives (bentonite, fly ash and silica fume) were used in the grout mixes to improve the setting time of the grouts. Taguchi method was employed for the experiments and standard L16 orthogonal array with 3 parameters and 4 levels were chosen. Experimental results show that the most efficient materials for the initial and final setting time are silica fume and bentonite, respectively. The initial and final setting times have been found to decrease rapidly with the increase in silica fume and bentonite ratio, while they rapidly increase with the increase of fly ash ratio. The Taguchi method has been found to be suitable for such studies.

Compressive strength of lightweight aggregate concrete exposed to high temperatures

In this paper, effects of high temperatures on the compressive strength of concrete were investigated with the aim to produce a fire resistant concrete. Thus, the mixture groups were determined by replacing pumice for ordinary aggregate in the ratios of 25, 50, 75 and 100% in volume. The temperature values were chosen as 150, 300, 450, 600 and 750°C. The effects of heating duration over the compressive strength were also examined, and the different types of concrete mixtures were heated for one hour, three hours and five hours periods for each temperature values. It was observed that concrete properties were deteriorated at 150°C and the specimens began to lose some of their initial strengths at this temperature. Though a considerable strength lose was not seen between 150-300°C, all types of concrete mixtures continued to lose their compressive strength after 300°C. Every concrete mixture lost a significant part of their initial strength when the temperature is reached up to 750°C. When the lightweight aggregate ratio is increased for each temperature value, the loss of compressive strength of the concrete compared to the initial strength was decreased. It was found that the heating duration does not affect the strength loss significantly but a high temperature is a more significant parameter on the strength loss.

ISSN : 0971-4588		CODEN : IEMSEW
VOLUME 11	NUMBER 1	FEBRUARY 2004