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Srinivasa R. Bakshi

Bio: Srinivasa R. Bakshi is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Spark plasma sintering & Carbon nanotube. The author has an hindex of 34, co-authored 99 publications receiving 4515 citations. Previous affiliations of Srinivasa R. Bakshi include Naval Postgraduate School & Indian Institutes of Technology.


Papers
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TL;DR: In this paper, the effect of adding different forms of carbon such as graphite flakes (GF), graphene nano-platelets (GNP) and carbon nanotubes (CNT) on the microstructure evolution and wear behavior of CoCrFeMnNi multi-component alloy fabricated by mechanical alloying and spark plasma sintering were investigated.

10 citations

Journal ArticleDOI
TL;DR: In this article, the effect of graphene nano-platelet (GNP) addition on the microstructure and sintering kinetics of ZrB2 during spark plasma sinterings was presented.
Abstract: In this paper, the effect of graphene nano-platelet (GNP) addition on the microstructure and sintering kinetics of ZrB2 during spark plasma sintering (SPS) is presented. SPS was carried out at 1800 °C temperature and 50 MPa pressure. GNP addition resulted in an increase in the relative density from 84% to 97%. Retention of GNPs after SPS was confirmed through Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) in conjunction with X-ray diffraction (XRD) and Raman spectroscopy. The effect of GNP reinforcement on sintering kinetics, microstructure and mechanical properties (Vickers micro hardness and indentation fracture toughness) are discussed. The ZrB2 -GNP samples showed different activation energies at different temperature ranges which are explained based on the likely processes that are involved during sintering. Final stage of sintering exhibited lower activation energy during which the GNP aided grain boundary sliding enhancing the densification. Several toughening mechanisms such as GNP fracture, GNP shearing, GNP bending and GNP pullout were observed.

9 citations

Journal ArticleDOI
TL;DR: In this article, friction stir welding of 3-mm-thick AA6061-T6 Al alloy and AZ31B-H24 Mg alloy sheets was carried out in lap configuration with Al alloy on top.
Abstract: In the present work, friction stir welding of 3-mm-thick AA6061-T6 Al alloy and AZ31B-H24 Mg alloy sheets was carried out in lap configuration with Al alloy on top. Experiments were carried out by varying the pin length (3.25, 3.75, and 4.25 mm) and tool rotation speed (600, 800, and 1000 RPM). Microstructures of the joint cross-section revealed the presence of a compound intermetallic layer along the interface consisting of Al-rich (Al3Mg2) intermetallic compound near the Al alloy side, and Mg-rich intermetallic compound (Mg17Al12) near the Mg alloy side. The formation of a eutectic mixture of Mg solid solution and Mg17Al12 was observed at the hook on either side. Two modes of failure were observed; Mode 1 through the interface and Mode 2 due to failure of the sheet. The Mode 1 failure strengths obtained were the highest (148 ± 6 N/mm) compared to the literature and were obtained for the 3.25 and 3.75 mm pin at 800 RPM. A lap shear strength of 212 ± 6 N/mm was obtained with 4.25 mm pin length at 600 RPM, which is the highest reported so far and was attributed to Mode 2 failure. The effect of interface pull-up, angle of the interface at the advancing side, and distribution of intermetallic compounds on the lap-shear strength are discussed.

9 citations

Journal ArticleDOI
TL;DR: In this article , the surface and sub-surface modifications during wire cut EDM and EDM of Zirconium diboride (UHTC) and ZrB2-GNP along with the surface characterization of the copper electrode (EDM tool).
Abstract: Zirconium diboride is a potential ceramic for high temperature applications because of its combination of properties, such as very high melting point, high hardness, elevated temperature strength, good thermal and electrical conductivity. Although the near net shape components are made from this material, machining is required to create additional features for the application requirements. This ceramic's high hardness and low fracture toughness make it very difficult to use the conventional processes for machining. The good electrical conductivity of this ceramic makes electrical discharge machining (EDM) the preferred machining process. This paper presents the surface and sub-surface modifications during Wire cut EDM (WEDM) and EDM of ZrB2 an ultra high temperature ceramic (UHTC) and ZrB2-GNP (ceramic matrix composite with 7 vol% Graphene Nano Platelets) along with the surface characterization of the copper electrode (EDM tool). Scanning Electron Microscope (SEM) with Energy Dispersive Spectroscopy (EDS) and Raman spectroscopy (for GNPs) were used to characterize the melt-solidified layer and the recrystallized region. The presence of micro cracks and pores was observed in the melt-solidified layer. Growing dendrites of ZrB2 were observed in the high magnification SEM images of the melt-solidified layer surface. Under the melt-solidified layer, a recrystallized fine grain structure was observed with reduced porosity compared to the rest of the bulk. After the WEDM of ZrB2-GNP (7 vol%), the stacks of cut GNP were retained, whereas GNPs were damaged after EDM The end surface of the copper electrode showed the partial deposition of ZrB2 and the formation of a micro scale pattern on it. The effect of peak current and pulse ON time on surface roughness (Sa), material removal rate (MRR) and relative tool wear (%) were studied for ZrB2-GNP (7 vol%) The results indicated that the surface roughness (Sa), MRR and the relative tool wear (%) increase with increasing peak current. The rise in pulse ON time also increases surface roughness (Sa) and MRR but reduces the relative tool wear rate (%)

9 citations

Journal ArticleDOI
TL;DR: In this paper, a two-step process was proposed in which a dense layer of Al was deposited on the Ti alloy by cold metal transfer method, formed a dense Al3Ti gradient reaction layer at their interface to improve adhesion in a single step.
Abstract: Recent advances in alumina ceramics are focused toward innovative processing routes to improve their mechanical reliability while retaining their superior wear resistance, which might be possible if a thin layer of dense alumina can be formed on a metallic substrate such as Ti–6Al–4V with high mechanical strength. For this purpose, we propose a new two-step process in which a dense layer of Al deposited on the Ti alloy by cold metal transfer method, formed a dense Al3Ti gradient reaction layer at their interface to improve adhesion in a single step. Subsequent micro-arc oxidation treatment transformed Al layer to a graded alumina layer in which γ-alumina decreased and α-alumina increased with increasing depth. Abrasion of outer regions revealed underlying pure α-alumina regions with high Vickers hardness matching with that of sintered alumina. The designed alumina/Ti alloy hybrid can be a potential candidate for wear resistance applications.

7 citations


Cited by
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01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal ArticleDOI
01 Apr 1988-Nature
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

9,929 citations

Journal ArticleDOI
01 Feb 2013-Science
TL;DR: Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.
Abstract: Worldwide commercial interest in carbon nanotubes (CNTs) is reflected in a production capacity that presently exceeds several thousand tons per year. Currently, bulk CNT powders are incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters. Advances in CNT synthesis, purification, and chemical modification are enabling integration of CNTs in thin-film electronics and large-area coatings. Although not yet providing compelling mechanical strength or electrical or thermal conductivities for many applications, CNT yarns and sheets already have promising performance for applications including supercapacitors, actuators, and lightweight electromagnetic shields.

4,596 citations

01 Jun 2005

3,154 citations