Faculty Publications

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    Testing of foams
    (Springer Singapore, 2019) Gupta, N.; Zeltmann, S.E.; Luong, D.D.; Doddamani, M.
    Foams are lightweight cellular materials that are widely used in applications such as packaging, thermal insulation, sound absorption, underwater vehicle structures, and as the core in sandwich structures used in aircraft. Testing of foams to obtain reliable properties that are relevant to a given application is a significant challenge. High damping, high compressive or tensile strain, and high volume of air in the structure are among the challenges that make it difficult to apply the common test methods to these materials. For example, use of strain gauges for tensile or compression testing is usually not possible because bonding the strain gauges to the surface of a cellular material may not be possible, the small measurement range of a strain gauge may not be enough to capture the strain in the entire loading range, and microscopic material structure may dominate the measurement. This chapter discusses test techniques that include quasi-static compression, high strain rate compression, impact, dynamic mechanical analysis, vibration methods, and imaging techniques that are relevant to testing of foams. The imaging methods include ultrasonic imaging and microCT-scanning. Test techniques are described and results on representative foam materials are presented to understand the test outcomes. © Springer Nature Singapore Pte Ltd. 2019.
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    Prediction of surface finish and optimization of machining parameters in turning
    (2012) Prasad, D.; Krishna, P.; Rao, S.S.
    Surface roughness plays a crucial role in the functional capacity of machined parts. In this work, experiments were carried out on a conventional lathe for different cutting parameters namely feed, spindle speed, depth of cut and tool nose radius according to Taguchi Design of Experiments. Radial acceleration readings were taken with an accelerometer. Optimum cutting parameters and their level of significance were found using Taguchi analysis (ANOVA). Regression analysis was carried out to identify whether the experimental roughness values have fitness characteristic with the process parameters. Recurrence Plots (RP) were obtained using the sensor signals which determine surface roughness qualitatively and Recurrence Quantification Analysis (RQA) technique was used to quantify the RP obtained. Surface finish was predicted using a feed forward back propagation neural network with RQA parameters, cutting parameters and acceleration data as inputs to the network. The validity and reliability of the methods were verified experimentally. © (2012) Trans Tech Publications.
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    Characterization of aircraft electro hydrostatic actuator using virtual instrumentation
    (Institute of Electrical and Electronics Engineers Inc., 2015) Sp, K.; Desai, V.; Jeppu, Y.V.
    In Aerospace industry, implementation of Automated Test System (ATS) at the assembly and manufacturing floor improves characterization accuracy and plays a vital role to substantiate the airworthiness of the aircraft components. It is very useful in realizing high quality standards of aircraft components by virtue of meeting predefined acceptance test criteria. This paper outlines comprehensive design and development of the noise and vibration monitoring system at assembly and manufacturing floor for characterization of Electro Hydrostatic Actuator (EHA) of aircraft using progressions in virtual instrumentation. In aircraft, the flight control actuation system are powered by centralized hydraulic pumps that are driven by the aircraft engine, while the back-up system are driven by electric or ram turbines. Distributed control of electric actuators with integration of control function in Flight Control Computer (FCC) and power electronics is a cost effective approach. EHA does also play a significant role in electrical actuation system, which use distributed electric power drive in driving a hydraulic transmission system. Hence, before integrating with the primary flight control actuation systems in aircraft, EHA's are required to be subjected to noise and vibration characterization, as part of assembly and manufacturing level testing. This method is intended at replacing the monotonous and time consuming traditional method of noise and vibration characterization of the electric actuators at assembly and manufacturing floor and to improve the reliability of the electric actuation components supplied to the aircraft manufacturers. The tests have been performed using a LabVIEW controlled virtual instrument measurement system that monitored the noise and vibration waveform with reference to the tacho signal. © 2014 IEEE.
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    Experimental study on the dynamic properties of magneto-rheological materials
    (Institute of Physics Publishing helen.craven@iop.org, 2018) Rajpal, R.; Lijesh, K.P.; Kant, M.; Gangadharan, K.V.
    Magneto-rheological elastomer (MRE), is considered to be a smart material, which transFigure their rheological properties with the external applied magnetic field. Due to this novel property, MREs are extensively employed to control the vibration of a system at resonant frequency. Presently, MREs are integrated in a structure through a layer by layer technique and the bigger drawback of this technology is that, in the presence of high transverse shear stresses, de-lamination occurs which may result in failure of the system. To overcome the aforementioned problem, a novel method is proposed to merge the MREs with Fused Deposition Method (FDM). FDM is used to develop the primary structure with cavities using a FDM compatible material and MRE i.e. secondary material is filled in the cavities. It is postulated that the proposed methodology has the capability of reducing the possibility of de-lamination. Now, to investigate the dynamic performance of the developed structure, an experimental test setup was developed by fixing one end of the beam and supplying the desired magnetic field to the beam using an electromagnet. From the test results, It was concluded that, with the increase in the applied magnetic field, the isolation effect of the structure enhanced and it reduced with the shift of electromagnet from the free end to fixed end of the beam. Further, in the case of MRE, high magnetic field is required for achieving satisfactory performance, which results in increase of the electromagnet weight, in turn making the system bulkier. Therefore, the present work endeavours to replace the MRE with MR Fluid (MRF) in the same primary structure and perform a comparison study between MRE and MRF, for the same applied magnetic field. From the experimental results it was envisaged that the MRF depicted better isolation capability than MRE. © Published under licence by IOP Publishing Ltd.
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    Effect of initial stresses on vibration behavior of functionally graded materials
    (Elsevier Ltd, 2020) Swaminathan, K.; Hirannaiah, H.; Rajanna, T.
    Functionally Graded Materials (FGM) is the result of continuous gradation of two or more constituent materials over a certain volume. This type of material overcomes many problems, particularly delamination, cracking and damages which are very frequently found in laminated composite materials. The FGMs are commonly found in space structures, and these structural elements are subjected to various kinds of loadings during its service period, in which in-plane loading is the one which significantly affects the vibration characteristics of the structural elements. In this investigation, the effect of tensile and compressive stresses on vibration characteristics of FG panels has been studied by using finite element technique (FE). For mathematical modelling Poisson's ratio is assumed constant and Young's modulus of elasticity is assumed to vary according to the power-law distribution of volume fraction of the constituents. The plate is modelled by using 8-noded isoparametric element by considering the effect of transverse shear deformation and rotary inertia. The effect of different factors such as volume fraction index, the thickness of the panel, boundary condition and tensile as well as compressive edge loads are considered to study the vibration behaviour of the FGM plate under tensile and compressive uniaxial edge loads. © 2020 Elsevier Ltd. All rights reserved.
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    Experimental investigation of frequency and damping characteristics of magneto-rheological fluid core sandwich beams
    (American Institute of Physics Inc. subs@aip.org, 2020) Nagiredla, S.; Joladarashi, S.; Kumar, H.
    In dynamic systems mechanical vibration amplitudes may range from a few nanometres to meters. When the vibration amplitudes are high the system may lead to failure or lost it function. Structures often tend to failure because of the high vibration amplitudes. These vibrations can be reduced by changing the stiffness or damping of the structure. One of the approaches is semi-active damping achieved by using Magneto-rheological fluid (MRF) as core material in a sandwiched beam. Magneto-rheological(MR) fluids change from fluid state to quasi-solid state when it is activated by a magnetic field. Adding MR fluids to mechanical systems may significantly improve their dynamic response. This study aims to analyse the free vibration response of the cantilever sandwich beam filled with the MR fluid as core material with Magnetic field intensity. A sandwich cantilever beam with Composite material as face layer and Magneto-rheological fluid as core was fabricated. Free Vibration test is performed on a sandwich beam filled with MR fluid under the external magnetic field generated by permanent magnets. Magnitude of Viscoelastic moduli of the MR fluid increases with magnetic field intensity as the fluid becomes semi-solid. The aim of the work is to analyse the influence of Magneto-rheological effect on the beam response with respect to externally applied magnetic field. Vibrations of the beam are registered with magnetic field and without magnetic field strength. Obtained data is utilized to analyse the dependency of magnetic field strength on the beams natural frequency and damping. © 2020 Author(s).
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    Stress, vibration and buckling analyses of FGM plates-A state-of-the-art review
    (Elsevier Ltd, 2015) Swaminathan, K.; Naveenkumar, D.T.; Zenkour, A.M.; Carrera, E.
    This paper presents a comprehensive review of the various methods employed to study the static, dynamic and stability behavior of Functionally Graded Material (FGM) plates. Both analytical and numerical methods are considered. The review is carried out with an emphasis to present stress, vibration and buckling characteristics of FGM plates predicted using different theories proposed by several researchers without considering the detailed mathematical implication of various methodologies. The effect of variation of material properties through the thickness, type of load case, boundary conditions, edge ratio, side-to-thickness ratio and the effect of nonlinearity on the behavior of FGM plates are discussed. The main objective of this paper is to serve the interests of researchers and engineers already involved in the analysis and design of FGM structures. © 2014 Elsevier Ltd.
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    Influence of redmud on the mechanical, damping and chemical resistance properties of banana/polyester hybrid composites
    (Elsevier Ltd, 2014) Veerasimman, V.; Marimuthu, M.; Manikandan, V.; Nagarajan, N.; Jeyaraj, P.
    A novel hybrid composite was developed with the addition of redmud as secondary reinforcing filler with banana fiber reinforced polyester composites (BFRPCs). The effect of varying parameters such as particle size (4, 6 and 13. ?m) and weight percentage (2, 4, 6, 8 and 10. wt%) of redmud were analyzed on static mechanical, free vibration and chemical resistance properties of hybrid composites. The addition of redmud shown enhanced performance compared to the virgin BFRPCs in all the above said properties. The maximum increase of 50% in mechanical strength was observed for the BFRPCs with the addition of redmud having 4. ?m particle size and 8. wt% of filler content compared to pure BFRPCs. The increased value of fundamental natural frequencies with associated modal damping characteristics of redmud filled BFRPCs were found using half-power band width method. All the fabricated composites performed well against various chemicals and it indicates that the resistance to the weight loss is due to the uniformly distributed redmud. To study the effect of redmud on interfacial bonding between the banana fiber and polyester matrix the Scanning Electron Microscope (SEM) image analysis was performed. © 2014 Elsevier Ltd.
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    Vibration analysis of a tapered laminated thick composite plate with ply drop-offs
    (Springer Verlag service@springer.de, 2015) Edwin Sudhagar, P.; Arumugam, A.; Vasudevan, R.; Jeyaraj, J.
    In this study, vibration characteristics of a tapered laminated thick composite plate have been investigated using finite element method by including the shear deformation and rotary inertia effects. The governing differential equations of motion of a tapered laminated thick composite plate are presented in the finite element formulation based on first-order shear deformation theory for three types of taper configurations. The effectiveness of the developed finite element formulation in identifying the various dynamic properties of a tapered laminated thick composite plate is demonstrated by comparing natural frequencies evaluated using the present FEM with those obtained from the experimental measurements and presented in the available literature. Various parametric studies are also performed to investigate the effect of taper configurations, aspect ratio, taper angle, angle ply orientation and boundary conditions on free and forced vibration responses of the structures. The comparison of the transverse free vibration mode shapes of the uniform and tapered composite plates under various boundary conditions is also presented. The forced vibration response of a composite plate is investigated to study the dynamic response of tapered composite plate under the harmonic force excitation in various tapered configurations. It is concluded that the dynamic properties of laminated thick composite plates could be tailored by dropping off the plies to yield various tapered composite plate. © 2015, Springer-Verlag Berlin Heidelberg.
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    Dynamic mechanical analysis and free vibration behavior of intra-ply woven natural fiber hybrid polymer composite
    (SAGE Publications Ltd info@sagepub.co.uk, 2016) RAJESH, M.; Jeyaraj, P.
    Influence of nature of weaving pattern and intra-ply hybridization of natural fibers on dynamic mechanical and free vibration characteristics of woven banana/jute polyester composite has been investigated. Results revealed that basket-type composite has better dynamic properties due to uniform stress distribution in both warp and weft directions. Warp jute fiber and weft banana fiber (WJWB) and both warp and weft banana and jute fiber (WAWBJ) intra-ply hybrid composites have better dynamic mechanical behavior as relatively stronger fiber is oriented along the loading direction. Experimental modal analysis carried out on beam-like samples revealed that warp and weft banana and jute fiber intra-ply hybrid composite has better natural frequencies while huckaback woven and warp banana fiber and weft jute fiber composites have better modal damping factors. © The Author(s) 2015.