Anish Kumar - Academia.edu (original) (raw)
Papers by Anish Kumar
Nondestructive Testing and Evaluation, 2015
ABSTRACT
Case Studies in Nondestructive Testing and Evaluation, 2015
Characterization of planar flaws by non-destructive evaluation is crucial from the point of view ... more Characterization of planar flaws by non-destructive evaluation is crucial from the point of view of structural integrity assessment. An approach involving SAFT processing of B-scan image collected by electronic scanning using linear array has been used for detection and characterization of planar flaws. The study was carried out on stainless steel plate with slots inclined at various orientations and carbon steel plates having implanted weld planar flaws.
This paper presents the in-house development and application of a C-scan ultrasonic facility ULTI... more This paper presents the in-house development and application of a C-scan ultrasonic facility ULTIMA 200M2 at the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, carried out in collaboration with the Electronics Division, Bhabha Atomic Research Centre (BARC), Mumbai. The paper describes various constituents of the system developed and also highlights the typical results obtained using this system, including bond integrity assessment of explosive welds and imaging of fuel sub-assembly heads of the Fast Breeder Test Reactor. The system has also been used for imaging both the sides of a one rupee Indian coin. All the finer details of the coin could be extracted, demonstrating the resolution capabilities of the system.
European Journal of Medicinal Chemistry, 2009
A series of novel fullerene derivatives bearing s-triazine moiety have been synthesized by adopti... more A series of novel fullerene derivatives bearing s-triazine moiety have been synthesized by adopting 1,3 dipolar cycloaddition reaction of C60 and azomethine ylides generated from the corresponding Schiff bases of 2,4,6 trisubstituted s-triazine. All the compounds synthesized were characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR and FAB-MS. The compounds were then screened for their antibacterial activity against both gram-positive (Staphylococcus aureus, Bacillus subtilis, Bacillus pumilis) and gram-negative (Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae) bacteria by disc diffusion method. All the compounds were found to be active against these strains at very low concentration and were comparable to standard drug ciprofloxacin.Fullerene–triazine conjugate disrupting the cell wall of bacteria
Journal of Physical Organic Chemistry, 2009
A novel fullerene–ferrocene based donor–bridge–acceptor dyad was synthesized and characterized by... more A novel fullerene–ferrocene based donor–bridge–acceptor dyad was synthesized and characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR and FAB-MS. The dyad with a bilinker comprising of azomethine and ester group was studied for its photo physical properties using absorption spectra and steady-state fluorescence spectra as a function of dielectric constant of the medium. Fluorescence spectra of the dyad studied with excitation at 449 nm showed a weak emission at 742 nm, which got weaker on increasing the dielectric constant of the medium, indicating efficient electron transfer from ferrocene to fullerene. By designing a bilinked structure between the two redox moieties, we obtained a chelating structure which was found to coordinate copper ion efficiently and hence found application as a metal ion sensor. Copyright © 2008 John Wiley & Sons, Ltd.
Scripta Materialia, 2004
This study demonstrates that, three parameters which are microstrain, lattice parameter and cryst... more This study demonstrates that, three parameters which are microstrain, lattice parameter and crystallite size, obtained from X-ray diffraction line profile analysis, can be used in a complementary way to study the precipitation/dissolution of various intermetallics and carbides in nickel base superalloy Inconel 625, without extracting the precipitates from the matrix.
Ndt & E International, 2002
The impact echo technique is based on the use of transient stress waves for non-destructive detec... more The impact echo technique is based on the use of transient stress waves for non-destructive detection of flaws in concrete structures. Impact-echo testing has been carried out for assessment of the structural integrity of the ring beam of a pressurised heavy water nuclear reactor. In order to develop the test procedure for carrying out impact echo testing, mock up calibration blocks were made. The detectability of the impact echo system has also been established in terms of the depth and the lateral dimension of the detectable flaw for the ring beam under consideration. Based on the optimised test parameters identified with the help of the studies carried out on the mock up blocks, impact echo testing was carried out on the ring beam of the reactor containment structure, for assessing its structural integrity.
Ultrasonics, 2015
A signal processing methodology is proposed in this paper for effective reconstruction of ultraso... more A signal processing methodology is proposed in this paper for effective reconstruction of ultrasonic signals in coarse grained high scattering austenitic stainless steel. The proposed methodology is comprised of the Ensemble Empirical Mode Decomposition (EEMD) processing of ultrasonic signals and application of signal minimisation algorithm on selected Intrinsic Mode Functions (IMFs) obtained by EEMD. The methodology is applied to ultrasonic signals obtained from austenitic stainless steel specimens of different grain size, with and without defects. The influence of probe frequency and data length of a signal on EEMD decomposition is also investigated. For a particular sampling rate and probe frequency, the same range of IMFs can be used to reconstruct the ultrasonic signal, irrespective of the grain size in the range of 30-210 μm investigated in this study. This methodology is successfully employed for detection of defects in a 50mm thick coarse grain austenitic stainless steel specimens. Signal to noise ratio improvement of better than 15 dB is observed for the ultrasonic signal obtained from a 25 mm deep flat bottom hole in 200 μm grain size specimen. For ultrasonic signals obtained from defects at different depths, a minimum of 7 dB extra enhancement in SNR is achieved as compared to the sum of selected IMF approach. The application of minimisation algorithm with EEMD processed signal in the proposed methodology proves to be effective for adaptive signal reconstruction with improved signal to noise ratio. This methodology was further employed for successful imaging of defects in a B-scan.
Philosophical Magazine, 2009
Microstructural evolution of M250 grade maraging steel subjected to various thermal-aging treatme... more Microstructural evolution of M250 grade maraging steel subjected to various thermal-aging treatments has been investigated using positron annihilation, X-ray diffraction, hardness and electron microscopy studies. Isochronal aging treatment in the range of 600900K, in steps of 100K, was ...
IEEE Transactions on Nuclear Science, 2014
ABSTRACT Raman Distributed Temperature Sensors (RDTS) are attractive for the monitoring of coolan... more ABSTRACT Raman Distributed Temperature Sensors (RDTS) are attractive for the monitoring of coolant loop systems in nuclear power plants and monitoring of overhead power transmission lines. This paper discusses deployment of RDTS on double walled pipelines of primary sodium circuits in Fast Breeder Reactors (FBR). It is demonstrated as a proof-of-concept on a test loop with water as the leaking medium. Path delay multiplexing is adopted to improve the spatial resolution from 1.02 m to 0.5 m. A second application focuses on the influence of environmental factors on the detectability of defects in the ACSR cables using RDTS.
International Conference on Fibre Optics and Photonics, 2012
Philosophical Magazine A, 2002
In this study, the 1.8 mm thick cold-rolled sheets of 2198-T8 Al-Li alloy were manufactured by fr... more In this study, the 1.8 mm thick cold-rolled sheets of 2198-T8 Al-Li alloy were manufactured by friction stir welding (FSW) at a rotation rate of 800 rpm and a travel speed of 300 mm/min. The microstructure and mechanical properties of different regions of the produced joint were evaluated by means of optical microscopy (OM), transmission electron microscopy (TEM), hardness testing and tensile testing. Results show that the original "pancake" grains became coarser in the heat affected zone (HAZ), transformed into equiaxed grains in the stir shoulder zone (SsZ) and stir pin zone (SpZ), and formed mixed grains with both "pancake" and equiaxed shapes in the thermo-mechanical affected zone (TMAZ). The hardness distribution in the cross-section of the FSW joint exhibited a "basin" shape. When approaching the weld centre, the hardness gradually decreased compared to the base metal (BM). The BM exhibited the highest strength due to the presence of fine T1 phase. In the HAZ, the strength decreased as T1 phase was partially dissolved. In the SsZ and SpZ, in spite of strength contribution from grain refinement, the strength further decreased as T1 phase was fully dissolved. The minimum strength in the TMAZ was related to the reduced amount of T1 phase and the presence of transition layer with sharp gradient of grain size.
Philosophical Magazine A, 2000
The paper discusses the use of ultrasonic spectral analysis for microstructural characterization ... more The paper discusses the use of ultrasonic spectral analysis for microstructural characterization in AISI type 316 stainless steel and modified 9Cr-1Mo ferritic steel (T91/P91). Several specimens of AISI type 316 stainless steel have been heat treated at different temperatures varying ...
Advanced Materials Research, 2013
Journal of Nondestructive Evaluation, 2009
New techniques developed using the array transducer, to image and size the bottom-surface and nea... more New techniques developed using the array transducer, to image and size the bottom-surface and near-through-wall crack-like defects in thick carbon steel components are discussed. Three studies are reported here including (a) Optimal beam steering angle for focused and unfocused inspection using phased array method for bottom-surface crack sizing. (b) A front wall correction algorithm for sizing of near-through-wall crack-like defects. (c) A small aperture technique for sizing of near-through-wall crack-like defects. A Finite Difference Time Domain (FDTD) based simulation was used to study and verify the experimental observations. The application of time domain scheme relative arrival time technique (RATT), to measure the size of the near-through wall crack-like defects for the leak before break (LBB) criterion, was also investigated and found to be insufficient. A conventional SAFT algorithm was used for improving the sizing using the small aperture technique.
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008
This investigation aims to examine structure–property relations of ferrite–bainite dual-phase (FB... more This investigation aims to examine structure–property relations of ferrite–bainite dual-phase (FBDP) steels and to compare these against that of ferrite–martensite dual-phase (FMDP) steels. For this purpose, a series of FBDP and FMDP steels containing wide variation (20–90%) of the harder constituents have been prepared from a low carbon Nb-micro-alloyed base material by suitable heat treatments. Hardness and tensile properties of the developed steels have been examined against the volume fraction of bainite or martensite. The nature of variation of the estimated mechanical properties such as hardness, yield and tensile strength, percentage elongation and strain-hardening exponent with the amount of the harder constituents of the FBDP and FMDP steels exhibits subtle to significant differences. These differences have been explained using the influence of the nature of the microstructural constituents and their mutual interactions. Low carbon FBDP steel with 60–70% bainite appears to possess excellent potential for structural applications.
Journal of Nuclear Materials, 2006
The degradation in mechanical properties of Inconel 625 ammonia cracker tubes occurs during the s... more The degradation in mechanical properties of Inconel 625 ammonia cracker tubes occurs during the service for long duration in heavy water plants. The present study brings out the possibility of using Poisson’s ratio (derived from measurement of time of flight of ultrasonic waves) in combination with hardness measurements, as an effective non-destructive tool for assessment of in-service degradation of Inconel 625 cracker tubes and qualification of re-solution annealing heat treatment for their rejuvenation. Further, the study also indicates the feasibility of extending the life of some of the tubes beyond the presently followed 120 000 h, before they are taken up for re-solution annealing, without affecting their serviceability. However, further studies are required to identify quantitative criterion for Poisson’s ratio and hardness values, for deciding on the basis for removal of the tubes for rejuvenation.
Tetrahedron: Asymmetry, 2013
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Tetrahedron Letters, 2009
A novel water-soluble [60] fullerene-substituted lysine derivative 3 has been synthesized and cha... more A novel water-soluble [60] fullerene-substituted lysine derivative 3 has been synthesized and characterized by elemental analysis, 1 H NMR, 13 C NMR and FAB-MS. The synthetic procedure involved condensation of Boc-protected lysine with terephthaldehyde followed by 1,3-dipolar cycloaddition reaction with C 60 in the presence of sarcosine and finally deprotection of the amino group using trifluoroacetic acid. The synthesized compound 3 exhibited high DNA cleavage efficiency upon visible light irradiation in the presence of NADH.
Nondestructive Testing and Evaluation, 2015
ABSTRACT
Case Studies in Nondestructive Testing and Evaluation, 2015
Characterization of planar flaws by non-destructive evaluation is crucial from the point of view ... more Characterization of planar flaws by non-destructive evaluation is crucial from the point of view of structural integrity assessment. An approach involving SAFT processing of B-scan image collected by electronic scanning using linear array has been used for detection and characterization of planar flaws. The study was carried out on stainless steel plate with slots inclined at various orientations and carbon steel plates having implanted weld planar flaws.
This paper presents the in-house development and application of a C-scan ultrasonic facility ULTI... more This paper presents the in-house development and application of a C-scan ultrasonic facility ULTIMA 200M2 at the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, carried out in collaboration with the Electronics Division, Bhabha Atomic Research Centre (BARC), Mumbai. The paper describes various constituents of the system developed and also highlights the typical results obtained using this system, including bond integrity assessment of explosive welds and imaging of fuel sub-assembly heads of the Fast Breeder Test Reactor. The system has also been used for imaging both the sides of a one rupee Indian coin. All the finer details of the coin could be extracted, demonstrating the resolution capabilities of the system.
European Journal of Medicinal Chemistry, 2009
A series of novel fullerene derivatives bearing s-triazine moiety have been synthesized by adopti... more A series of novel fullerene derivatives bearing s-triazine moiety have been synthesized by adopting 1,3 dipolar cycloaddition reaction of C60 and azomethine ylides generated from the corresponding Schiff bases of 2,4,6 trisubstituted s-triazine. All the compounds synthesized were characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR and FAB-MS. The compounds were then screened for their antibacterial activity against both gram-positive (Staphylococcus aureus, Bacillus subtilis, Bacillus pumilis) and gram-negative (Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae) bacteria by disc diffusion method. All the compounds were found to be active against these strains at very low concentration and were comparable to standard drug ciprofloxacin.Fullerene–triazine conjugate disrupting the cell wall of bacteria
Journal of Physical Organic Chemistry, 2009
A novel fullerene–ferrocene based donor–bridge–acceptor dyad was synthesized and characterized by... more A novel fullerene–ferrocene based donor–bridge–acceptor dyad was synthesized and characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR and FAB-MS. The dyad with a bilinker comprising of azomethine and ester group was studied for its photo physical properties using absorption spectra and steady-state fluorescence spectra as a function of dielectric constant of the medium. Fluorescence spectra of the dyad studied with excitation at 449 nm showed a weak emission at 742 nm, which got weaker on increasing the dielectric constant of the medium, indicating efficient electron transfer from ferrocene to fullerene. By designing a bilinked structure between the two redox moieties, we obtained a chelating structure which was found to coordinate copper ion efficiently and hence found application as a metal ion sensor. Copyright © 2008 John Wiley & Sons, Ltd.
Scripta Materialia, 2004
This study demonstrates that, three parameters which are microstrain, lattice parameter and cryst... more This study demonstrates that, three parameters which are microstrain, lattice parameter and crystallite size, obtained from X-ray diffraction line profile analysis, can be used in a complementary way to study the precipitation/dissolution of various intermetallics and carbides in nickel base superalloy Inconel 625, without extracting the precipitates from the matrix.
Ndt & E International, 2002
The impact echo technique is based on the use of transient stress waves for non-destructive detec... more The impact echo technique is based on the use of transient stress waves for non-destructive detection of flaws in concrete structures. Impact-echo testing has been carried out for assessment of the structural integrity of the ring beam of a pressurised heavy water nuclear reactor. In order to develop the test procedure for carrying out impact echo testing, mock up calibration blocks were made. The detectability of the impact echo system has also been established in terms of the depth and the lateral dimension of the detectable flaw for the ring beam under consideration. Based on the optimised test parameters identified with the help of the studies carried out on the mock up blocks, impact echo testing was carried out on the ring beam of the reactor containment structure, for assessing its structural integrity.
Ultrasonics, 2015
A signal processing methodology is proposed in this paper for effective reconstruction of ultraso... more A signal processing methodology is proposed in this paper for effective reconstruction of ultrasonic signals in coarse grained high scattering austenitic stainless steel. The proposed methodology is comprised of the Ensemble Empirical Mode Decomposition (EEMD) processing of ultrasonic signals and application of signal minimisation algorithm on selected Intrinsic Mode Functions (IMFs) obtained by EEMD. The methodology is applied to ultrasonic signals obtained from austenitic stainless steel specimens of different grain size, with and without defects. The influence of probe frequency and data length of a signal on EEMD decomposition is also investigated. For a particular sampling rate and probe frequency, the same range of IMFs can be used to reconstruct the ultrasonic signal, irrespective of the grain size in the range of 30-210 μm investigated in this study. This methodology is successfully employed for detection of defects in a 50mm thick coarse grain austenitic stainless steel specimens. Signal to noise ratio improvement of better than 15 dB is observed for the ultrasonic signal obtained from a 25 mm deep flat bottom hole in 200 μm grain size specimen. For ultrasonic signals obtained from defects at different depths, a minimum of 7 dB extra enhancement in SNR is achieved as compared to the sum of selected IMF approach. The application of minimisation algorithm with EEMD processed signal in the proposed methodology proves to be effective for adaptive signal reconstruction with improved signal to noise ratio. This methodology was further employed for successful imaging of defects in a B-scan.
Philosophical Magazine, 2009
Microstructural evolution of M250 grade maraging steel subjected to various thermal-aging treatme... more Microstructural evolution of M250 grade maraging steel subjected to various thermal-aging treatments has been investigated using positron annihilation, X-ray diffraction, hardness and electron microscopy studies. Isochronal aging treatment in the range of 600900K, in steps of 100K, was ...
IEEE Transactions on Nuclear Science, 2014
ABSTRACT Raman Distributed Temperature Sensors (RDTS) are attractive for the monitoring of coolan... more ABSTRACT Raman Distributed Temperature Sensors (RDTS) are attractive for the monitoring of coolant loop systems in nuclear power plants and monitoring of overhead power transmission lines. This paper discusses deployment of RDTS on double walled pipelines of primary sodium circuits in Fast Breeder Reactors (FBR). It is demonstrated as a proof-of-concept on a test loop with water as the leaking medium. Path delay multiplexing is adopted to improve the spatial resolution from 1.02 m to 0.5 m. A second application focuses on the influence of environmental factors on the detectability of defects in the ACSR cables using RDTS.
International Conference on Fibre Optics and Photonics, 2012
Philosophical Magazine A, 2002
In this study, the 1.8 mm thick cold-rolled sheets of 2198-T8 Al-Li alloy were manufactured by fr... more In this study, the 1.8 mm thick cold-rolled sheets of 2198-T8 Al-Li alloy were manufactured by friction stir welding (FSW) at a rotation rate of 800 rpm and a travel speed of 300 mm/min. The microstructure and mechanical properties of different regions of the produced joint were evaluated by means of optical microscopy (OM), transmission electron microscopy (TEM), hardness testing and tensile testing. Results show that the original "pancake" grains became coarser in the heat affected zone (HAZ), transformed into equiaxed grains in the stir shoulder zone (SsZ) and stir pin zone (SpZ), and formed mixed grains with both "pancake" and equiaxed shapes in the thermo-mechanical affected zone (TMAZ). The hardness distribution in the cross-section of the FSW joint exhibited a "basin" shape. When approaching the weld centre, the hardness gradually decreased compared to the base metal (BM). The BM exhibited the highest strength due to the presence of fine T1 phase. In the HAZ, the strength decreased as T1 phase was partially dissolved. In the SsZ and SpZ, in spite of strength contribution from grain refinement, the strength further decreased as T1 phase was fully dissolved. The minimum strength in the TMAZ was related to the reduced amount of T1 phase and the presence of transition layer with sharp gradient of grain size.
Philosophical Magazine A, 2000
The paper discusses the use of ultrasonic spectral analysis for microstructural characterization ... more The paper discusses the use of ultrasonic spectral analysis for microstructural characterization in AISI type 316 stainless steel and modified 9Cr-1Mo ferritic steel (T91/P91). Several specimens of AISI type 316 stainless steel have been heat treated at different temperatures varying ...
Advanced Materials Research, 2013
Journal of Nondestructive Evaluation, 2009
New techniques developed using the array transducer, to image and size the bottom-surface and nea... more New techniques developed using the array transducer, to image and size the bottom-surface and near-through-wall crack-like defects in thick carbon steel components are discussed. Three studies are reported here including (a) Optimal beam steering angle for focused and unfocused inspection using phased array method for bottom-surface crack sizing. (b) A front wall correction algorithm for sizing of near-through-wall crack-like defects. (c) A small aperture technique for sizing of near-through-wall crack-like defects. A Finite Difference Time Domain (FDTD) based simulation was used to study and verify the experimental observations. The application of time domain scheme relative arrival time technique (RATT), to measure the size of the near-through wall crack-like defects for the leak before break (LBB) criterion, was also investigated and found to be insufficient. A conventional SAFT algorithm was used for improving the sizing using the small aperture technique.
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008
This investigation aims to examine structure–property relations of ferrite–bainite dual-phase (FB... more This investigation aims to examine structure–property relations of ferrite–bainite dual-phase (FBDP) steels and to compare these against that of ferrite–martensite dual-phase (FMDP) steels. For this purpose, a series of FBDP and FMDP steels containing wide variation (20–90%) of the harder constituents have been prepared from a low carbon Nb-micro-alloyed base material by suitable heat treatments. Hardness and tensile properties of the developed steels have been examined against the volume fraction of bainite or martensite. The nature of variation of the estimated mechanical properties such as hardness, yield and tensile strength, percentage elongation and strain-hardening exponent with the amount of the harder constituents of the FBDP and FMDP steels exhibits subtle to significant differences. These differences have been explained using the influence of the nature of the microstructural constituents and their mutual interactions. Low carbon FBDP steel with 60–70% bainite appears to possess excellent potential for structural applications.
Journal of Nuclear Materials, 2006
The degradation in mechanical properties of Inconel 625 ammonia cracker tubes occurs during the s... more The degradation in mechanical properties of Inconel 625 ammonia cracker tubes occurs during the service for long duration in heavy water plants. The present study brings out the possibility of using Poisson’s ratio (derived from measurement of time of flight of ultrasonic waves) in combination with hardness measurements, as an effective non-destructive tool for assessment of in-service degradation of Inconel 625 cracker tubes and qualification of re-solution annealing heat treatment for their rejuvenation. Further, the study also indicates the feasibility of extending the life of some of the tubes beyond the presently followed 120 000 h, before they are taken up for re-solution annealing, without affecting their serviceability. However, further studies are required to identify quantitative criterion for Poisson’s ratio and hardness values, for deciding on the basis for removal of the tubes for rejuvenation.
Tetrahedron: Asymmetry, 2013
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.
Tetrahedron Letters, 2009
A novel water-soluble [60] fullerene-substituted lysine derivative 3 has been synthesized and cha... more A novel water-soluble [60] fullerene-substituted lysine derivative 3 has been synthesized and characterized by elemental analysis, 1 H NMR, 13 C NMR and FAB-MS. The synthetic procedure involved condensation of Boc-protected lysine with terephthaldehyde followed by 1,3-dipolar cycloaddition reaction with C 60 in the presence of sarcosine and finally deprotection of the amino group using trifluoroacetic acid. The synthesized compound 3 exhibited high DNA cleavage efficiency upon visible light irradiation in the presence of NADH.