Faculty Publications
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Item Determination of multiple heat flux transients during quenching of inconel 600 probe(ASM International joanne.miller@asminternational.org, 2013) Ramesh, G.; Prabhu, K.N.The time temperature data at axial and radial locations were measured during immersion quenching oflnconel 600 probes in a mineral oil quench medium. The temperature data and thermo-physical properties were used as input to an inverse heat conduction model for estimating spatially dependent heat flux transients. The estimated temperature data agreed very well with measured temperature data for increasing number of unknown surface heat flux components. The peak heat flux value decreased to a minimum and then increased to a high value in the axial direction. The inverse analysis indicated non uniform nature of wetting front and boiling of mineral oil on the quench probe surface resulting in large temperature gradients within the quench probe. The present work clearly indicates spatial dependence of boundary heat flux transients even for a simple cylindrical probe and the need for their estimation during quenching.Item Effect of load and interface materials on thermal contact resistance between similar and dissimilar materials(Trans Tech Publications Ltd ttp@transtec.ch, 2014) Narayana, S.R.; Narayan, P.K.The thermal contact resistance (TCR) between similar and dissimilar materials (copper, aluminium, brass and type 304 stainless steel) was assessed. Copper foil, aluminium foil, lead and Sn-9Zn lead free solder were selected as thermal interface materials (TIMs). The interfacial contact pressure was varied by application of load on materials in contact. The interfacial heat flux was estimated by solving the inverse heat conduction problem (IHCP). At higher load, the temporal variation of thermal contact resistance showed early occurrence of peak and lower values of TCR. The use of thermal interface materials reduced the contact resistance between the hot source and cold sink materials. Among the interface materials used, Sn-9Zn lead free solder showed the lowest contact resistance. This was attributed to the solid to liquid phase transformation at higher temperatures and the conformance of the interface material to surfaces in contact. Factorial experiments were carried out to determine the significance of experimental variables on TCR. The analysis showed that the effect of applied load on TCR was significant compared to other parameters. © (2014) Trans Tech Publications, Switzerland.Item Assessment of axial and radial heat transfer during immersion quenching of Inconel 600 probe(2014) Ramesh, G.; Prabhu, K.The time-temperature data at axial and radial locations were measured during immersion quenching of Inconel 600 probe in a mineral oil quench medium. The cooling of probe was not uniform during quenching. The variation of cooling rate along the axial direction was found to be higher than around the radial location. Inverse heat conduction problem (IHCP) was solved for estimating heat flux transients from the temperature data and thermo-physical properties of the Inconel probe. Single and multiple unknown heat fluxes were assigned on the metal/quenchant boundary. The error between the estimated and measured temperatures reduced significantly with increase in number of unknown surface heat flux components. The peak heat flux was about 50% lower for assignment of single unknown heat flux compared to multiple unknown heat fluxes at the metal/quenchant boundary. A plot of isotherms indicated gradual and uniform cooling of the quench probe when single heat flux boundary was used. With increase in the number of heat flux components, non-uniform and large temperature variations in the quench probe were observed. The present work outlines the importance of estimation of spatially dependent boundary heat flux transients during quench heat treatment. © 2014 Elsevier Inc.