Faculty Publications
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Publications by NITK Faculty
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Item Influence of Tool Probe Offset and Traverse Speed on Microstructure and Mechanical Properties of Friction Stir Weld Dissimilar Joints of AA2024-T351 and AA7075-T651(Springer Nature, 2020) Anil Kumar, K.S.; Murigendrappa, S.M.; Kumar, H.The effect of tool probe offset and varying traverse speed on the mechanical and metallographic characteristics of friction stir weld dissimilar joints of AA2024-T351 to AA7075-T651 in butt joint configuration produced using taper-threaded tool with constant tool rotation speed, 650 rpm and plunge depth, 6.2 mm are investigated. The tool traverse speed was varied from 20 to 120 mm/min along the weld length with the different tool probe offset condition. Optical microscopy and scanning electron microscopy are used to characterize the grain size and microstructural modification at the weld nugget zone (WNZ). The effect of different tool offset conditions in conjunction with varying traverse speed results in banded structure of alloys, partial material mixing and unmixed region at the WNZ. The combination of tool offset distance of 1 mm towards AA7075-T651 with traverse speed, 110 mm/min yields maximum ultimate tensile strength, 436 MPa, yield strength, 375 MPa, elongation, 14% and weld joint efficiency, 92%. © 2020, Springer Nature Singapore Pte Ltd.Item A New Forward Model Approach for a Mild Steel Fin under Natural Convection Heat Transfer(Elsevier Ltd, 2015) Kulkarni, A.S.; Kumar, H.; Gnanasekaran, N.This paper reports the correlation for temperature of the mild steel fin which is subjected to heat flux at its base. The study is performed on a two dimensional, steady state and laminar flow model. The numerical model is restricted to natural convection and the fluid under consideration is air. A rectangular mild steel fin (250 mm x 150 mm x 6 mm), aluminium base plate (250 mm x 150 mm x 8 mm) and an extended geometry representing the ambient air condition is modelled and simulated using ANSYS 14.5. Grid independence study is carried out to fix the number of grids in order to find the optimum number of nodes for carrying out simulations. The heat flux (q) at the bottom of the base plate is varied to study temperature distribution, surface heat transfer coefficient (h) and velocity profile of the flow in the boundary layer around the fin. All these parameters are studied by inclining the model at various angles. A multiple regression analysis is carried out to obtain correlation for the temperature in terms of angle of inclination and the heat flux. The main objective of the work is, proposing a model for the estimation of heat flux or heat transfer coefficient from the fin thereby reducing the computational cost of the forward model in the field of inverse heat transfer. © 2015 The Authors.Item Synergestic approach for the simultaneous estimation of heat transfer coefficient and heat flux using fin from steady state heat transfer experiments(Begell House Inc., 2015) Kumar, H.; Kumar, S.; Srinivasa Sagar, K.; Gnanasekaran, N.This paper reports simultaneous estimation of heat transfer coefficient and heat flux from natural convection fin heat transfer. The experimental setup contains rectangular mild steel fin of dimensions (250×154×6 mm) and an aluminium base plate of dimensions (250×150×8 mm). A slot of 4mm depth is created at the center of aluminium plate along its length (250mm) and mild steel fin is press fitted into this slot. Eighteen calibrated K-type thermocouples are used to record the temperature of the base plate and the fin. Beneath the base plate, a heater is placed with the dimensions of the base plate. To restrict the heat loss, bottom and sides of the heater are insulated with glass wool. Steady state experiments are carried out for different heat input. The problem considered is an inverse problem where in heat transfer coefficient and heat flux can be estimated simultaneously for the given temperature data from experiments/surrogate data. The forward model uses Asymptotic Computational Fluid Dynamics (ACFD) to obtain temperature distribution for the assumed inputs (heat transfer coefficient and heat flux). A powerful Markov Chain Monte Carlo method along with Metropolis-Hastings algorithm is used to minimize the objective function. Finally, the estimated values of heat transfer coefficient and heat flux are reported in terms of mean. © 2021, Begell House Inc. All rights reserved.Item Design and development of magneto-rheological brake for optimum casing thickness(Institute of Electrical and Electronics Engineers Inc., 2017) Sumukha, M.H.; Sandeep, R.; Vivek, N.; Lijesh, K.P.; Kumar, H.; Gangadharan, K.The online control of torque by Magneto-Rheological (MR) brake through MR Fluid makes an attractive option to replace the conventional disc brake. The torque provided by the MR brake depends on the magnetic flux generated on the MR fluid by the electromagnet. However the magnetic flux generated in a MR brake depends on the thickness of the casing, properties of MR fluid and material property of the MR brakes. Extensive work has been performed on improving the magnetic properties of MR fluid. However no work has been performed yet, to understand the thickness of the casing required for generating higher magnetic flux on MR fluid. Therefore in the present work, the dependence of casing thickness on the generation of magnetic flux on MR fluid region is studied using ANSYS software. Detailed electro-static analysis has been performed by varying the thickness of the casing and the magnetic flux at the MR fluid was evaluated. Based on the obtained results, MR brake having the desired thickness was developed. The generated magnetic flux values were validated with the reading obtained from Gauss meter. The obtained results are presented. © 2017 IEEE.Item Effect of tool rotation speed on microstructure and tensile properties of FSW joints of 2024-T351 and 7075-T651 reinforced with SiC nano particle: The role of FSW single pass(American Institute of Physics Inc. subs@aip.org, 2018) Anil Kumar, K.S.A.; Murigendrappa, S.M.; Kumar, H.; Shekhar, H.Friction stir welding (FSW) dissimilar joints of aluminium alloys of 2024-T351 and 7075-T651 were produced by reinforcing silicon carbide nano particle (SiCNP) in the rectangular cut groove made on the adjoining surface of the two dissimilar alloy plates joined in the butt configuration. A FSW tool of taper threaded cylindrical shape is used for producing the FSW dissimilar joints reinforced with SiCNP in the weld nugget zone (WNZ) and to produce metal matrix nano composite (MMNC) at the WNZ. In the experimental investigation, the constant FSW tool traverse speed of 40 mm/min and tool plunge depth of 6.2 mm/min is kept as constant, while the FSW tool rotation speed was varied from 400 rpm to 1800 rpm. The effect continuous varying tool rotation speed range from 400 rpm to 1800 rpm along the weld length and on the distribution of SiCNP in WNZ is analysed by conducting macro and microstructure study using optical microscopy (OM) and scanning electron microscopy (SEM) provided with energy dispersive spectrometry (EDS). In the experimental investigation, the combination of continuous varying FSW tool rotation speed range from 900rpm to 1150 rpm, constant tool traverse speed range 40 mm/min and tool plunge depth of 6.2 mm results in defect free, proper distribution of SiCNP and highest tensile properties for the FSW dissimilar joints. The highest ultimate tensile strength (UTS) of 380 MPa and yield strength (YS) of 150 MPa was observed for the combination of FSW tool rotation speed of 1000 rpm and tool traverse speed of 40 mm/min. The increasing in FSW tool rotation speed above 1250 rpm results in non homogeneous distribution of SiCNP in WNZ, excessive flash in the weld crown area and shows decreasing tendency in the tensile properties of the FSW dissimilar weld joints produced with reinforcing the SiCNP in the WNZ. © 2018 Author(s).Item Hardware Acceleration of Optically Labeled Human Genome Sequencing using a Novel Algorithm(Institute of Electrical and Electronics Engineers Inc., 2018) Mulani, K.S.; Kumar, H.; Gaurav, M.K.; Sumam David, S.Recently, reconstruction of the entire DNA sequence from optically labeled genomes has been explored. In this paper, we present details of a novel algorithm for this genome assembly. We elucidate the design methodology and results for a multi-core CPU (1.98x speedup) and FPGA (7.022x speedup) implementation to accelerate the computations. © 2018 IEEE.Item Design of bypass rotary vane magneto rheological damper for prosthetic knee application(International Conference on Adaptive Structures and Technologies, 2019) Saini, R.S.S.; Kumar, H.; Chandramohan, S.; Sujatha, S.In this paper, a bypass rotary vane type magneto rheological (MR) damper suitable for prosthetic knee application is designed. The torque and angular velocity requirements of the normal human knee are used as design limits. In the proposed design, the rotary vane chamber and the MR valve are connected by hydraulic cables and ports and are designed separately. The rotary vane chamber is designed based on the cross-sectional size limits of the normal human knee, while the MR valve is designed with the objective of obtaining the maximum on-state damping torque, minimum weight, and minimum off-state torque. © copyright Environment and Climate Change Canada.Item Analyzing quarter car model with Magneto-Rheological (MR) damper using equivalent damping and Magic formula models(Elsevier Ltd, 2019) Jamadar, M.-E.-H.; Desai, R.M.; Kumar, H.; Joladarashi, S.Mathematical modelling of Magneto-Rheological (MR) damper has been an intriguing field of research ever since the invention of the device itself. An accurate model of MR damper results in development of an efficient controller for a semi-active system with MR damper. Hence, a number of models have been put forward to accurately predict the MR damper behavior. One of these models is Magic formula model. Based on the famous Magic formula used in tire force calculation, this model can be used for representing the peak damper force vs damper piston velocity amplitude graph. This model was later modified to capture the force displacement diagram of MR damper. The former model is denoted as Magic Formula Model-1 (MFM-1) and the latter one is denoted as Magic Formula Model-2 (MFM-2) here onwards. In the current study a commercial MR damper has been tested for various piston velocities and currents. The equivalent damping coefficient is then calculated for the tested conditions. The equivalent damping coefficients are used for analyzing a quarter car model. Two quarter car models with MR damper are simulated, one uses MFM-1 for MR damper and the other uses MFM-2. All the quarter car models are subjected to single pulse input and the sprung mass response is measured in terms of displacement. The RMS error between the response of quarter car model with equivalent damping and quarter car models with MR damper is used to determine the performance of each mathematical model. The study revealed that MFM-1 represents the MR damper behavior more accurate than that of MFM-2. © 2019 Elsevier Ltd.Item Characterization of magnetorheological brake utilizing synthesized and commercial fluids(Elsevier Ltd, 2019) Acharya, S.; Shyam Saini Tak, R.; Bhanu Singh, S.; Kumar, H.Magnetorheological (MR) brakes produce braking torque due to variation in the magnetorheological properties of the MR fluid when external magnetic field is applied. In this study, MR fluids having 70% and 80% weight fractions of iron powder were prepared and MR brake characteristics were tested for prepared MR fluids and a commercial Lord MRF 132 DG fluid. It was found that there was an increase in braking torque with applied current to MR brake at all speeds indicating the MR effect. With increase in weight fraction, there is an increase in braking torque though the reduction in speed is not significant. However, in case of MRF 132 DG fluid, the decrease in rpm is significant especially at higher speeds. Though, the prepared fluids and commercial fluid produce closer braking torque values at higher currents, the increase in braking torque without magnetic field to that with magnetic field at maximum current of MR brake utilizing commercial fluid is very high due to its low viscous torque. Finally, analysis in finite element method magnetics software combined with analytical equations was used to compute torque and compared with experimental results of MR brake utilizing commercial fluid. © 2019 Elsevier Ltd.Item Investigation of static and dynamic properties of cenosphere reinforced polymer matrix composite beams(American Institute of Physics Inc. subs@aip.org, 2019) Bharath, J.; Joladarashi, S.; Nagiredla, S.; Kumar, H.Polymer Matrix Composites (PMC) plays a conspicuous role in engineering application. Cenosphere reinforced polymer matrix composite has higher strength, stiffness, lesser density and also saving in cost. These particulate composites are manufactured to meet several structural requirements. Thus there is a need to study their static and dynamic properties. In this work polymer epoxy polymer composites reinforced with cenosphere are fabricated and their static and dynamic properties are analyzed. Experimental investigation involves fabrication of specimen of polymer matrix reinforced with cenosphere by varying volume fractions of 25%, 30%, 35%, and 40%. Tensile and compressive properties are tested on UTM as per ASTM standard. Microstructures of composites are assessed with SEM and also Model analysis of cantilever beam is performed as per ASTM standard in Engineering Data Management System (EDM 7.0) of Crystal Instruments to study variation of natural frequency in each case. The natural frequency results are compared with the commercially available ANSYS FE software by assigning the material propertied obtained by static analysis. Thus effects of volume fraction of cenosphere on static and dynamic characteristics of particulate composites are studied. © 2018 Author(s).