5. Miscellaneous Publications
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/13843
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Item Damping behaviour of cast and sintered aluminium(2009) Umashankar K.S.; Abhinav A.; Gangadharan, K.V.; Vijay D.Estimating damping in structures made of different materials and processes still remains as one of the biggest challenges. Aluminium is one such pioneer material which is being used extensively in aerospace, automotive and the manufacturing industry. Aluminium components are mainly manufactured by traditional casting and powder metallurgy process. The main objective of this paper is to estimate the damping ratio of aluminium manufactured through powder metallurgy (P/M) process and compare it with the commercially available Cast aluminium. Aluminium powder is compacted, sintered and then it is extruded to the required geometry. Cantilever beams of required size and shape are prepared for experimental purpose and the damping ratio is investigated. Damping ratio is determined by sweep sine test using half power bandwidth method. Free vibration tests also confirmed the damping ratios obtained by sweep sine method. It is observed that damping ratio is higher for sintered aluminium than cast aluminium which may be attributed to increased porosity. © 2006-2009 Asian Research Publishing Network (ARPN). All rights reserved.Item Casting/mould interfacial heat transfer during solidification in graphite, steel and graphite lined steel moulds(2003) Prabhu K.N.; Mounesh H.; Suresh K.M.; Ashish A.A.Heat flow between the casting and the mould during solidification of three commercially pure metals, in graphite, steel and graphite lined steel moulds, was assessed using an inverse modelling technique. The analysis yielded the interfacial heat flux (q), heat transfer coefficient (h) and the surface temperatures of the casting and the mould during solidification of the casting. The peak heat flux was incorporated as a dimensionless number and modeled as a function of the thermal diffusivities of the casting and the mould materials. Heat flux transients were normalised with respect to the peak heat flux and modeled as a function of time. The heat flux model proposed was used to estimate the heat flux transients during solidification in graphite lined copper composite moulds.Item Review of non-reactive and reactive wetting of liquids on surfaces(2007) Kumar G.; Prabhu K.N.Wettability is a tendency for a liquid to spread on a solid substrate and is generally measured in terms of the angle (contact angle) between the tangent drawn at the triple point between the three phases (solid, liquid and vapour) and the substrate surface. A liquid spreading on a substrate with no reaction/absorption of the liquid by substrate material is known as non-reactive or inert wetting whereas the wetting process influenced by reaction between the spreading liquid and substrate material is known as reactive wetting. Young's equation gives the equilibrium contact angle in terms of interfacial tensions existing at the three-phase interface. The derivation of Young's equation is made under the assumptions of spreading of non-reactive liquid on an ideal (physically and chemically inert, smooth, homogeneous and rigid) solid, a condition that is rarely met in practical situations. Nevertheless Young's equation is the most fundamental starting point for understanding of the complex field of wetting. Reliable and reproducible measurements of contact angle from the experiments are important in order to analyze the wetting behaviour. Various methods have been developed over the years to evaluate wettability of a solid by a liquid. Among these, sessile drop and wetting balance techniques are versatile, popular and provide reliable data. Wetting is affected by large number of factors including liquid properties, substrate properties and system conditions. The effect of these factors on wettability is discussed. Thermodynamic treatment of wetting in inert systems is simple and based on free energy minimization where as that in reactive systems is quite complex. Surface energetics has to be considered while determining the driving force for spreading. Similar is the case of spreading kinetics. Inert systems follow definite flow pattern and in most cases a single function is sufficient to describe the whole kinetics. Theoretical models successfully describe the spreading in inert systems. However, it is difficult to determine the exact mechanism that controls the kinetics since reactive wetting is affected by a number of factors like interfacial reactions, diffusion of constituents, dissolution of the substrate, etc. The quantification of the effect of these interrelated factors on wettability would be useful to build a predictive model of wetting kinetics for reactive systems. © 2007 Elsevier B.V. All rights reserved.Item Performance characteristics of horizontal interlaced multilayer moored floating pipe breakwater(2007) Hegde A.V.; Kamath K.; Magadum A.S.The paper presents the results of model scale experiments for the study of wave attenuation by horizontal interlaced, multilayer, moored floating pipe breakwater. A review of some significant floating breakwater models proposed by earlier investigators is included. For a floating breakwater the transmission coefficient (Kt) is influenced by relative width of the breakwater (W/L). Nondimensional graphs indicating the variation of Kt with respect to W/L (with Hi/L as a parameter for different Hi/d values) and Kt versus Hi/L (for a range of d/L values from 0.09 to 0.24) have been plotted. Further variation of Kt with relative depth d/L for different W/L values is also studied. From the experimental study and results obtained, it is found that the transmission coefficient decreases with an increase in relative breakwater width W/L and wave steepness Hi/L for all Hi/d values. In the present study it was observed that performance was better for breakwater configurations of W/L≥0.7 when compared with configurations of W/L<0.7. Further, the experimental results obtained were compared with the output of a mathematical model. From the comparison for Hi/L=0.04, values of Kt obtained from the present experiments were in agreement with those obtained from the mathematical model. © 2007 ASCE.