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.

Performance of Diamond and CBN Single-Layered Grinding Wheels in Grinding Titanium

Abstract: For their unique properties, titanium alloys have found wide application in high-tech engineering. But these alloys are difficult to machine and to grind for their high chemical reactivity and poor thermal properties, which aggravate the grinding zone temperature and its detrimental effects. The objective of this article is a comparison of the grindability of Ti-6Al-4V regarding cubic boron nitride (CBN) and diamond brazed type monolayered grinding wheels under the influence of different environments. In grinding this alloy, cryogenic cooling did not help visibly for both CBN and diamond, but the application of oil and also of alkaline coolant significantly gave the best results.

Experimental investigation on performance of touch-dressed single-layer brazed cBN wheels

Abstract: Electroplated single-layer grinding wheels, in spite of offering unique useful features like geometrical flexibility, large chip accommodation volume in the inter-grit space, etc., produce high transverse surface roughness on the ground surface of the workpiece. Non-participation of all the superabrasive particles (grits) attributes to this limiting factor. Moreover, in plunge grinding the situation is the worst to deal with. This work is an attempt to reduce the same to an acceptable magnitude so that post-grinding finishing operations can be executed effectively. However, this procedure has been implemented on indigenously developed brazed-type single-layer cBN wheels. This class of grinding wheel has been found superior to its galvanically bonded counterpart in the view of larger grit protrusion and flexibility to print any pattern of grit distribution. In this investigation, brazed cBN wheels with different grit distribution patterns have been conditioned by touch-dressing method so that grit tips get micro-conditioned and allow the underlying grits to participate and consequently increase the quality of finish. The outcome of this attempt appeared highly encouraging. A substantial improvement of transverse surface roughness could be achieved with all three categories of brazed wheels and the role of grit distribution pattern in obtaining good finish was thoroughly investigated.

Grinding of Ti-6Al-4V Under Small Quantity Cooling Lubrication Environment Using Alumina and MWCNT Nanofluids

Abstract: Ti-6Al-4V is a difficult-to-grind material as chips tend to adhere to the grit materials of an abrasive wheel due to its chemical affinity. In the present work, it has been attempted to improve the grindability by application of small quantity cooling lubrication (SQCL) technology using nanofluids, namely, multiwalled carbon nanotube (MWCNT) and alumina nanofluid. The suitability of nanofluids was experimentally evaluated in reciprocating surface grinding using a vitrified SiC wheel. Substantial improvement in grindability under the influence of MWCNT nanofluid (SQCL) could be achieved compared to soluble oil (flood). Reduction of specific grinding forces and specific energy was observed due to the combined effect of superior heat dissipation and lubrication abilities; when the latter one was realized through on-site rolling of MWCNT strands, inter-tubular slip and solid lubrication of the film adhered onto the wheel surface. These outperforming characteristics of MWCNT nanofluid helped in retaini...

On bond wear, grit-alloy interfacial chemistry and joint strength of synthetic diamond brazed with Ni-Cr-B-Si-Fe and Ti activated Ag-Cu filler alloys

Abstract: A multi-point brazed diamond tool requires high wear resistance of bonding alloy and strength of the brazed joint. In this work, two active brazing alloys, i.e., Ni-Cr-B-Si-Fe and Ag-Cu-Ti were used for brazing synthetic diamond grits on a medium carbon steel substrate under a high vacuum environment. The performance of the brazed joints was subsequently investigated and compared. The microstructure of the filler alloys was found to play a key role in influencing the bond wear characteristics, grit-alloy interfacial chemistry and strength of the brazed joint. Formation of Cu4Ti compounds in Ag-Cu-Ti alloy and boride and silicide compounds in case of Ni-Cr alloy contributed to the enhancement of hardness of the alloys. The bond wear characteristics of Ni-Cr alloy were substantially superior to that of Ag-Cu-Ti alloy. A single grit test of the brazed samples was carried out to investigate the failure pattern of the brazed joints. Ni-Cr brazed joints predominantly failed at the bond level. The residual stress and microstructural flaws in the form of microcracks at alloy-grit interface of the as-brazed test samples led to such a failure. In contrast, no such crack was detected in the case of Ag-Cu-Ti alloy and the joints failed by ductile fracture of alloy near to the interface, leading to diamond pull out. The present study elucidates the differences in wear, strength of bond and failure pattern of the brazed joints in the light of alloy and interfacial microstructure.

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.