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 Theoretical and numerical study of symmetric, in-plane, free vibration of Timoshenko portal frame with open crack(Chinese Society of Theoretical and Applied Mechanics ICF13@cstam.org.cn, 2013) Satyavan, N.M.; Kumar, S.; Murigendrappa, S.M.The local flexibility introduced by cracks changes the vibration behaviour of the structure and by examining this change, crack severity can be identified. This paper presents the natural frequencies of symmetric, in-plane free-vibrations of Timoshenko portal frame with and without open crack for different boundary conditions. Cracked segment is modelled as two segments connected by a massless torsional spring. Considering appropriate compatibility requirements at the crack section in any one of segments and at the junction of two segments, the characteristic equations are established for corresponding boundary conditions and solved for natural frequencies by numerically. Crack location ranging from 20% to 70% of length of segment and crack size ranging from 20% to 60% of depth have been considered. Results obtained analytically are compared numerically using standard commercially available finite element software. The frame has been modelled by using quadratic quadrilateral shell elements and quarter-point singular elements are employed around the crack-tip. It is observed that as expected, with increase in crack depth the change in frequencies of the frame with and without crack increases. The maximum difference between the analytical and numerical results is 7.09% for all the cases considered, which proves usefulness of the data.Item Buckling and Free Vibration Characteristics of a Uniformly Heated Isotropic Cylindrical Panel(Elsevier Ltd, 2016) Bhagat, V.; Jeyaraj, P.; Murigendrappa, S.M.In this paper buckling and free vibration characteristics of an isotropic cylindrical panel subjected to uniform temperature rise has been investigated using finite element method. The procedure involves the determination of critical buckling temperature, which is followed by modal analysis considering pre-stress due to the thermal field in the cylindrical panel. Detailed studies are carried out to analyze the influence of curvature ratio, thickness ratio and aspect ratio on the critical buckling temperature and free vibration behavior of an isotropic cylindrical panel. It has been found that as the curvature ratio and the thickness ratio increases the thermal buckling strength of the cylindrical panel decreases. It has also been found that free vibration frequencies reduce with an increase in temperature and the reduction is more significant for the lowest frequency mode. It is observed that free vibration mode shapes at ambient temperature changes with an increase in temperature. © 2016 The Authors.Item Optimization of buckling strength and fundamental frequency of uniformly heated cylindrical panel using PSO(Institute of Electrical and Electronics Engineers Inc., 2017) Bhagat, V.; Jeyaraj, P.; Murigendrappa, S.M.In the present study, thermal buckling and fundamental frequency of symmetrically laminated cylindrical panel is optimized. Fiber orientation is considered as a design variable for the same. Eigenvalue buckling analysis and modal analysis is performed by using finite element method. Particle swarm optimization is used as optimization technique. MATLAB code is generated to integrate finite element method with particle swarm optimization. Finally, the influence of aspect ratio (L/S), curvature ratio (R/S), thickness ratio (R/h), effect of different weighting factors and boundary constraints on the optimum results are investigated. © 2016 IEEE.Item Detection of damage in spot welded joints using a statistical energy analysis-like approach(International Institute of Acoustics and Vibrations P O Box 13 Auburn AL 36831, 2017) Pankaj, A.C.; Shivaprasad, M.V.; Murigendrappa, S.M.Vibration-based damage detection has been frequently used for low frequency problems. However, there are situations where the damage, like connections of structures with spot welds, mainly affects the highest modes. Energybased approaches such as Statistical Energy Analysis (SEA) is one of the most widely used methods for high frequency analysis that is well-suited for periodic structures. The present work studies the damage detection of joints based on statistical energy analysis-like principles using apparent coupling factors to predict velocity/acceleration responses and detect damage in the spot welds located at various positions on a sub-system (spot-welded plate configurations). Apparent coupling factors have been derived for four cases of spot-welded plates and used further to predict the velocity/acceleration responses using the statistical energy analysis like (SEAL) approach for an assembly of three subsystems (three plates lap joined by spot-welds) for all the possible combinations. The results are discussed, compared, and validated by experimentation and finite element simulations for a healthy and damaged configuration. A database of the predicted values using the SEAL approach for the remaining combinations has been compared with values obtained from finite element simulations. The proposed SEAL-based approach can be effectively applied as a simulation tool to locate the damaged joint in an assembly of subsystems for future use.Item Buckling and Free Vibration Behavior of a Temperature Dependent FG-CNTRC Cylindrical Panel under Thermal Load(Elsevier Ltd, 2018) Bhagat, V.; Jeyaraj, P.; Murigendrappa, S.M.Present study deals with the buckling and free vibration behavior of functionally graded carbon-nanotubes reinforced composite (FG-CNTRC) cylindrical panel exposed to uniform thermal load. Stresses setup due to thermal load and temperature dependent properties influences the buckling and free vibration behavior of the heated structures. Approach employed in the present study consists of static analysis to compute thermal stresses, eigen-value buckling analysis to compute critical buckling temperature and finally modal analysis, taking thermal stresses into account. Influence of different CNTs grading pattern, CNTs volume fraction, geometric parameters, boundary constraints and temperature dependent properties on the buckling strength are investigated. It is observed that hybrid CNTs distribution pattern gives comparatively higher buckling strength and free vibration frequencies. Investigation on free vibration characteristics of the FG-CNTRC panel at elevated temperature signifies that the decline in free vibration frequencies is very drastic at a temperature close to buckling temperature along with temperature dependent properties. c 2017 Elsevier Ltd. All rights reserved. © 2018 Elsevier Ltd.Item Determination of apparent coupling factors for adhesive bonded acrylic plates using SEAL approach(American Institute of Physics Inc. subs@aip.org, 2018) Pankaj, A.C.; Shivaprasad, M.V.; Murigendrappa, S.M.Apparent coupling loss factors (CLF) and velocity responses has been computed for two lap joined adhesive bonded plates using finite element and experimental statistical energy analysis like approach. A finite element model of the plates has been created using ANSYS software. The statistical energy parameters have been computed using the velocity responses obtained from a harmonic forced excitation analysis. Experiments have been carried out for two different cases of adhesive bonded joints and the results have been compared with the apparent coupling factors and velocity responses obtained from finite element analysis. The results obtained from the studies signify the importance of modeling of adhesive bonded joints in computation of the apparent coupling factors and its further use in computation of energies and velocity responses using statistical energy analysis like approach. © 2018 Author(s).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 Development of thermal model to analyze thermal flux distribution in thermally enhanced machining of high chrome white cast iron(American Institute of Physics Inc. subs@aip.org, 2018) Ravi, A.M.; Murigendrappa, S.M.In recent times, thermally enhanced machining (TEM) slowly gearing up to cut hard metals like high chrome white cast iron (HCWCI) which were impossible in conventional procedures. Also setting up of suitable cutting parameters and positioning of the heat source against the work appears to be critical in order to enhance the machinability characteristics of the work material. In this research work, the Oxy - LPG flame was used as the heat source and HCWCI as the workpiece. ANSYS-CFD-Flow software was used to develop the transient thermal model to analyze the thermal flux distribution on the work surface during TEM of HCWCI using Cubic boron nitride (CBN) tools. Non-contact type Infrared thermo sensor was used to measure the surface temperature continuously at different positions, and is validated with the thermal model results. The result confirms thermal model is a better predictive tool for thermal flux distribution analysis in TEM process. © 2018 Author(s).Item Experimental study on internal cooling system in hard turning of HCWCI using CBN tools(American Institute of Physics Inc. subs@aip.org, 2018) Ravi, A.M.; Murigendrappa, S.M.In recent times, hard turning became most emerging technique in manufacturing processes, especially to cut high hard materials like high chrome white cast iron (HCWCI). Use of Cubic boron nitride (CBN), pCBN and Carbide tools are most appropriate to shear the metals but are uneconomical. Since hard turning carried out in dry condition, lowering the tool wear by minimizing tool temperature is the only solution. Study reveals, no effective cooling systems are available so for in order to enhance the tool life of the cutting tools and to improve machinability characteristics. The detrimental effect of cutting parameters on cutting temperature is generally controlled by proper selections. The objective of this paper is to develop a new cooling system to control tool tip temperature, thereby minimizing the cutting forces and the tool wear rates. The materials chosen for this work was HCWCI and cutting tools are CBN inserts. Intricate cavities were made on the periphery of the tool holder for easy flow of cold water. Taguchi techniques were adopted to carry out the experimentations. The experimental results confirm considerable reduction in the cutting forces and tool wear rates. © 2018 Author(s).