Amitava Ghosh

Bio: Amitava Ghosh is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Grinding & Machining. The author has an hindex of 23, co-authored 87 publications receiving 1507 citations. Previous affiliations of Amitava Ghosh include Indian Institute of Technology Guwahati & Indian Institute of Technology Kharagpur.

Assessment of spray quality from an external mix nozzle and its impact on SQL grinding performance

Abstract: Spray quality is the critical factor which decides the efficacy of Small Quantity Lubrication (SQL) technology in a high specific energy involved machining process like grinding. Yet, the understanding about spray quality, the actual process mechanics and its effect on machining performance is inadequate. The present work is an attempt to establish a correlation between the spray input variables, quality of the spray and machining performance of SQL grinding through modelling and experiments. Using computational fluid dynamic techniques, the variation of droplet size, droplet velocity, number of droplets and heat transfer coefficient have been analysed at different input parameters and the computed trends have been verified and validated. CFD modelling of spray indicates that it is possible to produce aerosol medium with high heat dissipation ability at moderately high air pressure and low flow rate. It also shows that any increase in atomising air pressure favourably leads to notable increase in wetting area and also results in substantial enhancement in heat dissipation ability. Reduction of residual stress is thus remarkably good. On the other hand, grinding fluid flow rate, if increased, offers significantly better lubricity and reduces the grinding force which also reduces tensile residual stress. Short spell grinding test results are found to be in good agreement with CFD results.

High Speed Turning of AISI 4140 Steel Using Nanofluid Through Twin Jet SQL System

Abstract: Application of small quantity lubrication (SQL) technology in high speed machining is being recognized as a sustainable approach for achieving suitable cooling/lubrication in machining zone. Present investigation focused on effectiveness of SQL with nanofluids in high speed turning of AISI 4140 steel with a TiN-top coated multilayered carbide insert and explored the advantages of using a twin-jet SQL system instead of a single jet one. SQL system was developed in-house with external-mix nozzles. The experiment was conducted varying the cutting velocity at two different feed rates (0.05mm/rev and 0.10mm/rev) with conventional coolant and nanofluids. Immediate improvement in machinability and the quality of turned surface was observed with twin-jet nanofluid SQL. A significant reduction of force and specific energy could be achieved by using 3vol% alumina and 1vol% multi walled carbon nano tube (MWCNT) nanofluid instead of soluble oil. The MWCNT nanofluid was found to be superior to alumina nanofluid in reduction of tensile residual stress. Such a reduction is typically an indirect indication of reduction of cutting zone temperature, which could be achieved due to enhanced level of lubricity at chip-tool interface and enhanced level of heat dissipation ability of the nanofluids. Improvement in retention of sharpness of tool cutting edges was also observed under nanofluid-SQL environment, which could have played important role in improvement of surface quality.Copyright © 2013 by ASME

Performance enhancement of single-layer miniature cBN wheels using CFUBMS-deposited TiN coating

Abstract: This work investigated the effectiveness of TiN coating in enhancing the performance of two different types of single-layer cBN grinding wheels. One was galvanically bonded type where galvanic metal layer covered less than 50% of the grit height. In this paper, it is termed as underplated wheel. The other one was brazed cBN wheel which was developed in-house. In this case, the grits were bonded by a braze alloy layer. TiN coating, well known for its anti-wear and anti-friction characteristics, finds use in cutting tools and tribological applications. In this case study, such TiN was successfully deposited on the above-mentioned two types of grinding wheels with a dual cathode closed-field unbalanced magnetron sputtering (CFUBMS) system. Performance of those TiN-coated wheels was compared with that of uncoated counterparts in terms of grinding force and percentage of grit failure. Grinding tests were carried out in plunge mode and under dry condition. Experimental results clearly revealed the fact that the role of TiN coating was not that significant in reducing the friction at the wheel-workpiece contact zone. However, it was able to substantially reduce grit pullout of the underplated cBN wheel. On the other hand, uncoated brazed cBN wheel did not suffer from grit pullout, but severe premature breakage of cBN grits at the bond level was observed. This was remarkably arrested when TiN coating was applied on the active surface of the wheel.

Light Absorption and Energy Transfer in the Antenna Complexes of Photosynthetic Organisms.

Abstract: The process of photosynthesis is initiated by the capture of sunlight by a network of light-absorbing molecules (chromophores), which are also responsible for the subsequent funneling of the excitation energy to the reaction centers. Through evolution, genetic drift, and speciation, photosynthetic organisms have discovered many solutions for light harvesting. In this review, we describe the underlying photophysical principles by which this energy is absorbed, as well as the mechanisms of electronic excitation energy transfer (EET). First, optical properties of the individual pigment chromophores present in light-harvesting antenna complexes are introduced, and then we examine the collective behavior of pigment−pigment and pigment−protein interactions. The description of energy transfer, in particular multichromophoric antenna structures, is shown to vary depending on the spatial and energetic landscape, which dictates the relative coupling strength between constituent pigment molecules. In the latter half...

Biopolymer Aerogels and Foams: Chemistry, Properties, and Applications.

Abstract: Biopolymer aerogels were among the first aerogels produced, but only in the last decade has research on biopolymer and biopolymer-composite aerogels become popular, motivated by sustainability arguments, their unique and tunable properties, and ease of functionalization. Biopolymer aerogels and open-cell foams have great potential for classical aerogel applications such as thermal insulation, as well as emerging applications in filtration, oil-water separation, CO2 capture, catalysis, and medicine. The biopolymer aerogel field today is driven forward by empirical materials discovery at the laboratory scale, but requires a firmer theoretical basis and pilot studies to close the gap to market. This Review includes a database with over 3800 biopolymer aerogel properties, evaluates the state of the biopolymer aerogel field, and critically discusses the scientific, technological, and commercial barriers to the commercialization of these exciting materials.