Faculty Publications
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Item Electroslag remelting experiments have been carried out on En 24 steel using two slag compositions in indigeneously constructed 350 KVA DC and 50 KVA AC ESR units. Detailed quantitative characterisation of the inclusions of different types has been carried out using Quantimet Image Analyser. The inclusion content in terms of volume fraction and density (No/mm2) and their size distribution in the refined ingot and the unrefined steel have been assessed. The chemical composition of selected inclusions has been established by electron probe microanalyser (EPMA). These studies are supplemented by scanning electron microscopy on typical fractured specimens. The present study shows that the DC reverse polarity mode of melting using a slag with higher silica content (10 wt%) offers the best conditions with particular reference to removal of inclusions and modification of inclusion morphology as compared to the ingots produced by DC straight polarity and AC modes of melting.(Studies on inclusion characterization in electroslag refined En24 steel) Udupa, K.R.; Subramanian, S.; Sastry, D.H.; Iyengar, G.N.K.1994Item This paper deals with an experimental investigation concerning the open die extrusion (ODE) of three materials of varying physical properties and mechanical properties. Two geometrical configurations (solid and tube) and two methods (by direct and indirect techniques) were considered to examine the influence of these variables in the generation and retention of heat in the deformation zone with the objective of ensuring a greater achievable strain. Studies reveal that solid configuration supports the retention of heat as against tubular configuration. Low thermal conductivity, density, specific heat and high flow stress which characterise 99Ti make this material an excellent candidate for ODE as opposed to AISI 1020 steel and aluminium, which fail to meet all the above physical and mechanical properties. The indirect technique reduces the friction factor and thus enables greater strains to be achieved. © 1997 Elsevier Science S.A.(Elsevier BV, Adiabatic and friction heating on the open die extrusion of solid and hollow bodies) Srinivasan, K.; Venugopal, P.1997Item Analysis of shape parameters of coarse aggregate and their effects on packing density by DIP technique(2006) Nagendra, R.; Dhabale, A.K.; Bai, H.S.; Rajeeva, S.V.In this paper the particle shape parameters are analysed using a sophisticated technique called Digital Image Processing (DIP). The effects of shape parameters on the packing density are studied. The packing density determines the amount of cement paste required to fill the voids between aggregate particles. In this paper the details of experimental investigations carried out on coarse aggregates are presented. Aggregate samples from seven different sources have been used for experimental investigation. The shape parameters determined by DIP technique are correlated with packing density.Item Mooring forces in horizontal interlaced moored floating pipe breakwater with three layers(2008) Hegde, A.V.; Kamath, K.; Deepak, J.C.The paper presents the results from model scale experiments on the study of forces in the moorings of horizontally interlaced, multi-layered, moored floating pipe breakwaters. The studies are conducted with breakwater models having three layers subjected to waves of steepness Hi/L (Hi is the incident wave height and L the wavelength) varying from 0.0066 to 0.0464, relative width W/L (W is the width of breakwater) varying from 0.4 to 2.65, and relative spacing S/D (S is the spacing of pipes and D the diameter of pipe) of 2 and 4. The variation of measured normalized mooring forces on the seaward side and leeward side are analyzed by plotting non-dimensional graphs depicting f/?W2 (f is the force in the mooring per unit length of the breakwater, ? the weight density of sea water) as a function W/L for various values of Hi/d (d is the depth of water). It is found that the force in the seaward side mooring increases with an increase in Hi/L for d/W values ranging between 0.081 and 0.276. The experimental results also reveal that the forces in the seaward side mooring decrease as W/L increases, up to a value of W/L=1.3, and then increases with an increase in W/L. It is also observed that the wave attenuation characteristics of breakwater model with relative spacing of 4 is better than that of the model with relative spacing of 2. The maximum force in the seaward side mooring for model with S/D=4 is lower compared to that for the breakwater model with S/D=2. A multivariate non-linear regression analysis has been carried out for the data on mooring forces for the seaside and leeside. © 2007 Elsevier Ltd. All rights reserved.Item Correlation between Petrographical and engineering properties of Ilkal granites, Karnataka(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2011) Venkat Reddy, D.; Santosh, H.G.; Priyanka, K.Granitic rocks show a variety of engineering properties that may affect quarrying operations, slope stability, mining and the use of rock as a structural as well as architectural material. In present investigation, correlation analysis is carried out for experimental results to study the influence of mineralogical and textural characteristics on physical and strength properties using SPSS software. A variety of granitic rock samples from different parts of Ilkal were subjected to study petrographical and then same samples were tested to determine the specific gravity, bulk and dry density, water absorption, porosity, P-wave velocity, rebound hardness, point load strength index, uniaxial compressive strength and tensile strength. The study revealed that a petrographical characteristic like grain size, mineral composition and the bonding between each mineral of granitic rocks plays a major role in contributing the strength parameters. © 2011 Cafet-Innova Technical Society. All rights reserved.Item Effect of fiber weight fraction on mechanical properties of carbon-carbon composites(2012) Naik, P.S.; Orangalu, S.A.; Londhe, N.V.This article presents the synthesis of carbon-carbon (C/C) composites by preformed yarn (PY) method, by varying the percentage of carbon fiber weight fraction. The PY used was carbon fiber bundle surrounded by coke and pitch which was enclosed in nylon-6. Three types of samples with fiber weight fractions of 30, 40, and 50%, respectively, are fabricated and mechanical properties were studied. In each case, the PY was chopped and filled into a die of required shape and hot pressed at 500°C to get the preform composite. To obtain the carbonized and graphitic structure, the specimen was heat treated at 2500°C followed by soaking for 10 to 12 hrs. Further, two cycles pitch impregnation was done by hot isostatic pressing, to eliminate the voids and to increase the density hence to obtain good mechanical properties. The characteristics such as hardness, flexural strength, and impact strengths were studied. It is observed that, as the carbon fiber percentage increases, the properties also get improved, provided sintering is done at fairly higher temperatures such as 2700°C. The superiority of the new class of C/C composites made by the proposed PY technique over those obtained by the conventional methods is also demonstrated. Copyright © 2012 Society of Plastics Engineers.Item Microstructural characterization and hardness evaluation of friction stir welded composite AA6061-4.5Cu-5SiC (Wt.%)(Defense Scientific Information and Documentation Centre, 2013) Shettigar, A.K.; Salian, G.; Herbert, M.A.; Rao, S.Recent developments in advanced materials research have led to the emergence of new materials having features like low density, high strength to weight ratio, excellent mechanical properties, heat and corrosion resistance. In friction stir welding (FSW), a non-consumable rotating welding tool is used to generate the frictional heat and plastic deformation of the material in the welding zone, which is in the solid state. The advantages of FSW as compared to the fusion welding are high joint strength, less defect weld, uniform distribution of grain structure in the weld zone and low power consumption. AA6061 with 4.5 % weight of copper and 5 % weight of SiC composite material has been prepared to conduct experiment and carry out characterization, evaluation of the mechanical properties. Micro-structural characterization of the weld zone is carried out by scanning electron microscope (SEM). Evaluation of hardness was also carried out across the weld zone. A successful method for FSW of AA6061-4.5(wt.%) Cu-5(wt.%) SiC has been developed. © 2013, DESIDOC.Item Partial molar volumes and compressibilities of glycine betaine in aqueous NaCl solutions at temperatures T=(288.15-318.15)K(Elsevier, 2014) Karanth, V.R.; Bhat, D.The partial molar volumes, partial molar isentropic compressibilities, transfer molar volumes and transfer molar isentropic compressibilities of the system: glycine betaine in aqueous (0.1, 0.2, 0.3, 0.4 and 0.5molkg-1) NaCl solutions at different temperatures were determined using the experimental values of density and speed of sound. The positive transfer molar volumes of the systems indicated the presence of strong solute-solvent interactions. The electrostatic charge-charge interactions (among Na+/Cl- ions and amino/carboxylic groups of glycine betaine) were found to be predominant over the ionic-hydrophobic interactions (among Na+/Cl- ions and CH2/CH3 groups of the glycine betaine) in aqueous solutions. Size of the metal ion was found to influence the volumetric properties to an appreciable extent. © 2014 Elsevier B.V.Item Optical absorption, mechanical properties and FTIR studies of silver-doped barium phosphate glasses(Society of Glass Technology christine@glass.demon.co.uk, 2016) Narayanan, M.K.; Shashikala, H.D.Silver-doped barium phosphate glasses, of composition 50BaO-50P2O5-4Ag2O-4SnO, were prepared by conventional melt quenching and subsequent heat treatment. Prepared glasses were heat treated for a fixed duration of 10 h at different temperatures 400, 450 and 500°C to develop silver nanoparticles of different sizes. Formation and the size of the silver nanoparticles were evaluated using the surface plasmon resonance (SPR) band of the optical absorption spectrum, which revealed that both of them were temperature dependent. Spectral positions of the SPR peaks of the glass samples heat treated at 450 and 500°C were observed around 3.0 eV. Absence of significant size dependent shift in SPR peaks of these samples from 3.0 eV indicates the formation of spherical silver nanoparticles smaller than 20 nm inside the glass matrix, which falls in the quasi-static regime of Mie theory. The effect of heat treatment on the local network structure of the phosphate glass matrix assessed using FTIR spectra shows that formation and growth of silver nanoclusters do not affect the basic metaphosphate network structure. A slight improvement is observed in density as well as in the mechanical properties of the heat treated samples due to densification of the glass matrix by dispersed silver nanoparticles.Item Squeeze casting process modeling by a conventional statistical regression analysis approach(Elsevier Inc. usjcs@elsevier.com, 2016) Gowdru Chandrashekarappa, G.C.; Krishna, P.; Parappagoudar, M.B.During the casting process, the alloy composition, melt treatment modification, processing method, and process variables change the microstructure, thereby affecting the mechanical properties. The hybrid squeeze casting method has been used to limit casting defects, refine the micro-structure, and enhance the mechanical properties. The process variables influence the mechanical and micro-structure properties during squeeze casting. In the present study, we established nonlinear input–output relationships and explored the physical behavior of this process based on the statistical design of experiments and using the response surface methodology. Experiments were conducted to measure the responses in terms of the density, hardness, and secondary dendrite arm spacing. Two nonlinear regression models, i.e., Box–Behnken design and central composite design, were used to conduct experiments, collect experimental data, identify significant process variables, analyze the collected data, and establish the complex input–output relationships. Surface plots were used to explore the effects of the squeeze pressure, pressure duration, pouring, and die temperature on the measured responses. Analysis of variance tests were conducted to evaluate the statistical suitability of the models developed. Furthermore, the accuracies of the predictions made by the models were investigated based on test cases. We found that both of the nonlinear models were statistically adequate and they provided complete insights into the complex nonlinear input–output relationships. Central composite design performed better for the secondary dendrite arm spacing and hardness responses, whereas its performance was the same as that of Box–Behnken design for the density response. The relationships between the responses (i.e., outputs) were established by generating large volumes of input–output data using the nonlinear regression models. We found that the density, hardness, and secondary dendrite arm spacing responses could be obtained by utilizing the nonlinear regression equations and the same set of process variables. Furthermore, the secondary dendrite arm spacing response could be expressed as third order nonlinear functions of density or hardness (structure to property relationship). The results showed that the secondary dendrite arm spacing had inverse relationships with density and hardness, whereas density and hardness had direct relationships. © 2016 Elsevier Ltd
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