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Jayaganthan R
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Jayaganthan R
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Jayaganthan R
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Jayaganthan, R.
Jayaganthan, Rengaswamy
Jayaganthan, Rangaswamy
JAYAGANTHAN, R.
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133 results
Now showing 1 - 10 of 133
- PublicationA parallel processing technique for electrical tree growth in solid insulating materials using cellular automata(01-01-2000)
;Piriyakumar, A. L. ;Levi, P.; One of the major problems in an electrical insulation structure is its failure while operating at normal voltage stress which is due to electrical treeing. It is well-known that this electrical tree grows progressively and is damaging locally. To analyze the electrical treeing in the laboratory, not being cost effective, computer simulations are used. We have employed a known cellular automata method with new parallel processing techniques to reduce the computation time considering the available parallel processing systems. The major advantage is that the cellular automata algorithm inherently exhibits parallelism paving the way for ample exploitation. Moreover the parallelisation has helped to understand various aspects of electrical treeing also in a simple way. - PublicationAnalysis of Water droplet initiated discharges on silicone rubber insulating material adopting Hilbert huang transform(04-12-2017)
;Sridhar, Arun Keshav ;Mishra, Palash; Water droplet residing on surface of roughened silicone rubber generates corona activity at much lower voltage compared with the virgin specimen. An increase in conductivity of water droplet, under AC voltage, shows a reduction in corona inception. Further, a combination of time series analysis and fractal feature extraction techniques are used to classify the different phases that occurs on application of AC voltage to the water droplet sitting on silicone rubber specimen, in the electrode gap. The fractal dimension and the lacunarity were calculated using the 2D Hilbert energy spectrum obtained with leakage current measured during water droplet initiated discharges, shows inverse relationship. - PublicationA study of undulatory and rotational wave motion in the beam for the locomotion of underwater robots(01-03-2022)
;Govindarajan, GaneshA computational approach to study the undulatory and rotational motion in the beam for underwater locomotion is reported in this work. It is focused to understand different thrust producing mechanisms for robotic application and also to identify the critical parameters affecting the locomotion. The present work is to consider the forces exerted on the beam as it moves relative to the surrounding medium and to relate the propulsive speed of the beam to the form and speed of propagation of the bending waves generated by the beam, where the thrust is predicted using force and velocity relationship. The results show that the propulsive velocity is higher in the higher modes which are due to the higher natural frequency of the beam and results in increases of thrust, due to the increase of wave velocity and decrease of wavelength. It is observed that the thrust is 3.141 N for the propulsive velocity of 2 m/s, and thrust is found to be higher in the higher modes and lower in the lower modes due to smaller wavelength and high amplitude. Fish bends back and forth from head to tail, creating a forward thrust during locomotion and the tail beat amplitude, propulsive velocity and frequency are the parameters influence the thrust propulsion, irrespective of whether they coincide with the resonant frequency of the fish or not. For larger amplitudes and high propulsive velocity, it is observed that the thrust is increasing with amplitude. In the lower modes of undulatory propulsion, the negative thrust is caused by the recovery stroke during bending of the beam and negative pressure developed along the concave portions of the beam bends. A mathematical explanation is provided to solve the rotational locomotion of beam rolling about its longitudinal axis with passing bending waves along its tail. The undulatory movement is more feasible than rotational motion, because the resistance and inertia of the beam moving in a viscous medium are less compared to the rotational movement. - PublicationImprovement of fracture toughness of ultra fine grained Al-Li 8090 alloy processed through multi axial forging(24-05-2019)
;Kapil, Rajat ;Joshi, Amit; ;Gairola, SaurabhVerma, RavirajIn the present work, mechanical properties, microstructural characteristics and fracture behavior of severely deformed Al-Li 8090 alloy processed through multi axial cryo forging has been investigated and compared with the room temperature forged conditions. Enhancement in the mechanical properties, LEFM fracture toughness and EPFM toughness parameter (J-integral) of severely deformed Al-Li 8090 alloy with a cumulative true strain of 1.2, 2.4 and 3.6 is observed at Cryo forged (CF) condition as compared to room temperature forged (RTF) conditions due to the accumulation of higher dislocation density, dislocation substructure and formation of UFG microstructure. Effective retardation of dynamic recovery and climb at liquid nitrogen temperature (LNT, -196 °C) is responsible for higher dislocation accumulation in CF sample compared to the samples subjected to room temperature forging. The improved fracture toughness of CF samples is attributed to the delay in crack initiation as well as crack propagation phase resulting from Hall-Petch strengthening, grain boundary strengthening, and dislocation strengthening. - PublicationMachine-learning-based prediction of corrosion behavior in additively manufactured inconel 718(01-08-2021)
;Mythreyi, O. V. ;Srinivaas, M. Rohith ;Amit Kumar, TiggaThis research work focuses on machine-learning-assisted prediction of the corrosion behavior of laser-powder-bed-fused (LPBF) and postprocessed Inconel 718. Corrosion testing data of these specimens were collected and fit into the following machine learning algorithms: polynomial regression, support vector regression, decision tree, and extreme gradient boosting. The model performance, after hyperparameter optimization, was evaluated using a set of established metrics: R2, mean absolute error, and root mean square error. Among the algorithms, the extreme gradient boosting algorithm performed best in predicting the corrosion behavior, closely followed by other algorithms. Feature importance analysis was executed in order to determine the postprocessing parameters that influenced the most the corrosion behavior in Inconel 718 manufactured by LPBF. - PublicationMechanical Properties and Microstructural Evolution in Al 2014 Alloy Processed Through Multidirectional Cryoforging(01-07-2016)
;Joshi, Amit ;Kumar, Nikhil ;Yogesha, K. K.; Nath, S. K.Mechanical properties and microstructure evolution of Al 2014 alloy subjected to cryoforging (MDF) to a cumulative strain of 1.2, 1.8, and 2.4 were investigated in the present work. The deformed samples after 4 cycles at a cumulative strain of 2.4 shows the formation of ultrafine grain sizes in the range of 100-450 nm with high-angle grain boundaries as observed from TEM analysis. The tensile and hardness of the deformed sample were measured by Universal Testing machine and Vickers hardness Tester, respectively. The tests were also conducted for sample deformed at room temperature to compare with cryo-forged samples. The sample deformed at cryogenic temperature up to a cumulative strain 2.4 shows an improvement of tensile strength, hardness, and apparent fracture toughness (KQ) from 318 MPa to 470 MPa, 103HV to 171 HV, and 23.93 MPa m to 37.7 MPa m, respectively, with decrease in ductility from 18% to 6% as compared with solution-treated alloy. The cryo-forged Al 2014 alloy exhibits an increment of 7% in tensile strength, 3% in yield strength, and 3% in hardness up to cumulative true strain of 2.4 as compared to the samples forged at room temperature. The improvement in tensile properties of MDFed alloy is attributed to dislocation strengthening and grain boundary strengthening effect at both temperatures. The effective suppression of cross slip and climb at liquid nitrogen temperature improves the strength of cryo-forged sample better than that of room temperature-forged alloy. - PublicationDetermination of Mechanical Response and Johnson-Cook Damage Parameters of 17-4 PH Stainless Steel Using FEM(2024-01-01)
;Kalita, BijitThe present work investigates the mechanical responses of additively manufactured 17-4 PH Stainless Steel systematically using finite element method (FEM). Different simulations of tensile tests at room and elevated temperatures are performed on smooth and notched specimens for calculating the parameters of the Johnson-Cook material and damage model. The tensile strength of the 17-4 PH SS alloy notch bar is higher than the smooth bar at room temperature. ABAQUS (Explicit) is used for all FE calculations. Experimental data was used as input to perform all the elastic–plastic simulations in both 2D and 3D through the ABAQUS 6.14 software. The observed simulation results were correlated with the available literature. Strain rate and temperature dependent mechanical properties of AM 17-4 PH stainless steel in different processing conditions are also investigated in this study. - PublicationExperimental and XFEM Simulation of Tensile and Fracture Behavior of Al 6061 Alloy Processed by Severe Plastic Deformation(01-02-2017)
;Balakrishnan, Vasanth ;Roshan, P. ;Goel, Sunkulp; Singh, I. V.The tensile and fracture behavior of ultrafine-grained Al 6061 alloy has been studied by experimental testing and extended finite element method simulation. The ultrafine-grained alloy processed by cryorolling has been produced from its bulk alloy with different thickness reductions. Microstructural features have been evaluated by electron backscattered diffraction. The EBSD results show the formation of subgrains and large number of high-angle grain boundaries in the rolled Al alloy. Mechanical behavior has been investigated using microhardness, tensile test, fracture toughness, and fractography of all samples. The extended finite element method has been used to investigate elastic–plastic deformation behavior of ultrafine-grained Al 6061 alloy. The extended finite element method has been used to simulate tensile and fracture behavior of ultrafine-grained alloy with material constants evaluated from experimentally measured tensile properties. Simulated tensile and fracture properties are in tandem with the experimental results. Ultrafine-grained Al 6061 alloy has shown better tensile strength and fracture toughness as evident from experimental and simulation results. - PublicationStudies on generation and characterization of nano aluminium nitride using wire explosion technique(03-04-2006)
;Sindhu, T. K. ;Chakravarthi, S. R.; The focus of the present work is to produce high purity nanoparticles of aluminium nitride by wire explosion technique and investigate its microstructure and physicochemical behavior by certain physico-chemical diagnostic studies viz. X-ray diffraction, TEM, EDAX, FTIR and TG-DTA. The influence of processing parameters on wire explosion technique is studied in detail. Grain growth kinetics of microstructural evolution of nano aluminium nitride is discussed. Copyright © 2006 Taylor & Francis Group, LLC. - PublicationAn investigation of effect of annealing at different temperatures on microstructures and bulk textures development in deformed Zircaloy-4(01-07-2017)
;Fuloria, Devasri ;Kumar, Nikhil; ;Jha, S. K.Srivastava, D.In the present work, the effect of various annealing temperatures on the microstructural and textural evolution in deformed Zircaloy-4 has been investigated. Zircaloy-4 was subjected to a rolling reduction of 90% corresponding to a true strain of 2.3 along the ND - ED and ND - TD planes of the as-received Zircaloy-4 bar at room (298 K) and cryogenic (77 K) temperatures. Following this, the various deformed conditions of the samples were subjected to annealing treatment at various temperatures such as 400°C, 450°C and 500°C. The deformed samples were characterized by a high dislocation density and nano scale subgrains, which after annealing at various temperatures were marked with annealing twins of nano - size along with some other dislocation configuration. A higher dislocation density and hardness (258.54 ± 2.91 HV) values were observed after annealing the cryorolled alloy along the ND - TD plane at 450°C. This high cold work energy provided by cryorolling along the ND - TD plane, after annealing at 450°C produced an optimum twin growth, which impeded the dislocation motion and slightly increased the hardness along this plane. Finally, the textures evolved after annealing indicated the role of annealing twins combined with < a > prismatic, < c + a > pyramidal & basal glide activity.