Journal Articles
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Item Dynamic response of railroad vehicle to rail joints and average vertical profile: A time domain approach(Inderscience Publishers, 2007) Gangadharan, K.V.; Sujatha, C.; Ramamurti, V.One rigid body and three finite element models have been used to study the dynamic behaviour of a typical Electrical Multiple Unit Trailer coach running on Indian suburban tracks. Following eigenvalue analysis, dynamic responses to input excitation from rail joints and Average Vertical Profile (AVP) have been determined in the time domain, using mode superposition technique. Acceleration and displacement response at Centres of Gravity (eg) of car and bogie have been predicted. The analytical results compare well with experimental results and highlight the need to include superstructure elasticity to predict the dynamic response accurately. Copyright © 2007 Inderscience Enterprises Ltd.Item Statistical modeling of a magneto-rheological fluid damper using the design of experiments approach(2007) Shivaram, A.C.; Gangadharan, K.V.In this work, a through-rod-type magneto-rheological (MR) test damper has been designed and fabricated for experimental study. Various factors, such as the magnetic field strength, volume fraction of particles in the MR fluid, shearing gap between piston and cylinder, vibration frequency and amplitude, have been considered as input factors, and the root-mean-square (RMS) damping force as the output factor (response variable). These input factors are varied in two levels (low and high) during the initial phase of experimentation using 25 factorial design; the motivation is to identify the most influential factors. In the second phase of experimentation, the response surface method has been used to identify the modeling equation and to plot the response surfaces. Further, force versus displacement diagrams have been plotted at these factor levels; these give an insight into the damping behaviour of the MR damper. © IOP Publishing Ltd.Item Dynamic response of railroad vehicles: A frequency domain approach(Inderscience Publishers, 2008) Gangadharan, K.V.; Sujatha, C.; Ramamurti, V.A very elaborate Finite Element (FE) model and a rigid body model of a typical electrical multiple unit trailer coach are described. These models were used to find the dynamic response to track irregularities in the frequency domain. The Power Spectral Density (PSD) of track irregularities was used as input to the system. The influence of different track irregularities on dynamic response and coupling between vertical and lateral dynamics was investigated. Extensive experiments were carried out, and analytical results were compared with the measured response. Copyright © 2008 Inderscience Enterprises Ltd.Item Determination of transient and steady state cutting in face milling operation using recurrence quantification analysis(2009) Mhalsekar, S.D.; Mohan, G.; Rao, S.S.; Gangadharan, K.V.Typical face milling operation involves transient and steady state cutting phases. Identification and distinction of the cutting state will primarily help in understanding the fundamentals of forced vibration, deflection and dynamic stability in milling system at the beginning and end of a cutting pass. Such type of investigation has advantages in process planning, tool geometry optimization and on-line fault diagnosis. An effort to provide estimation of transient and steady state cutting has been made using Recurrence Quantification Analysis (RQA) of vibration signals. RQA is a novel nonlinear analytical tool. It starts with construction of recurrence plot using embedded dimension and time delay. The recurrence plot is than quantified resulting in RQA. Face milling of H11 chromium steel has been carried out at two different cutting conditions and analyzed. The resulting RQA parameters could identify and distinguish transient and steady state cutting. © 2006-2009 Asian Research Publishing Network (ARPN).Item FPGA based vibration control of a mass varying two-degree of freedom system(Exeley Inc, 2011) Singh, M.P.; Tripathi, P.K.; Gangadharan, K.V.Controlling of vibration in any system is very challenging problem. In the present work design, fabrication and testing of a variable mass 2-DoF system was presented. The system has been designed to be used as tool to demonstrate the capability of mass variable tuned vibration damper for wide frequency application. All valves and pumps were controlled by a cRIO with onboard FPGA. cRIO with FPGA enable the designer to implement different control algorithms that can be used for real time wide spectrum vibration control. LabVIEW with real time suite was used for algorithm implementation and device control. To avoid sloshing in tanks at different water height a floating roof was used. Its effect on damping was also studied.Item Experimental and finite elements analysis of a tuned mass absorber for vibration isolation(2011) Abhinav Alva, R.; Gangadharan, K.V.A structure under the influence of a harmonic excitation may start vibrating violently when the applied frequency is slowly approaching any one of its natural frequencies. Resonance results in large amplitude levels and vibrations. The possible alternatives to avoid resonance are either to shift the external harmonic frequency or to change the natural frequency of the structure itself. If both the alternatives are not feasible then tuned mass absorbers can be used. The emphasis of the current work is on modeling of a tuned mass absorber to suppress the vibrations of a single degree of freedom system operating at its fundamental natural frequency. System analysis was performed using ANSYS, a commercial finite elements package. ANSYS harmonic analysis was effective in predicting safe operating frequency range for the modified structure which was also verified experimentally. Hence it can be concluded that Finite Element Analysis can be effectively used to model dynamic systems and its response, hence possible solutions could also be sought. The adaptability of the current tuned mass absorber system when subjected to varying external frequencies is a new feature of the design. © 2006-2011 Asian Research Publishing Network (ARPN).Item Recurrence quantification analysis to compare the machinability of steels(2011) Ravish; Umashankar, K.S.; Alva, A.; Gangadharan, K.V.; Desai, V.Machinability, though is a simple term, is difficult to generalize. But nevertheless, it can be realized as the ease or difficulty with which a material can be machined. Assessing the machinability of various materials before they are used in commercial manufacturing is very demanding, as the machinability affects the material removal rate, surface finish of the workpiece, cutting power consumption and tool wear rate. The present work aims at establishing Recurrence Quantification Analysis, a relatively new technique in the study of chaotic systems, as a potential tool to establish and compare the machinability of steels. The technique has its roots in quantifying the Recurrence Plots obtained by the phase space reconstruction of time domain signals. Variation in Determinism, one of the variables of the technique, is used as a mean to establish the comparison of machinability. © 2006-2011 Asian Research Publishing Network (ARPN).Item Machining characteristics of nanocomposites(2011) Umashankar, K.S.; Gangadharan, K.V.; Desai, V.; Shivamurty, B.Nanocomposites were prepared with Al/Al-Si alloys (LM 6 and LM 25) as matrix and multi wall carbon nanotube (MWNT) of 0.25, 0.5, 0.75, 1.0 and 1.5 wt. % as reinforcement through powder metallurgy (PM) followed by sintering and hot extrusion techniques. Fabricated nanocomposites were machined on a Panther 1530/1650 lathe by using tungsten carbide tool. Recurrence quantification analysis (RQA) was used to study the machining characteristics by using cutting force signal stability. Highest value ofdeterminism (DET-one of the RQA parameter) was observed for 0.5 wt.% MWNT reinforced Al and Al-Si nanocomposites. This attributes better machining characteristic due uniformity of the signals. Also it is observed better mechanical properties at 0.5 wt.% reinforced nanocomposite and further reinforcement deteriorate the machinability and mechanical properties. © 2011 VBRI press.Item Machining characteristics of multiwall-CNT reinforced Al/Al-Si composites using recurrence quantification analysis(2011) Gangadharan, K.V.; Umashankar, K.S.; Ravish; Desai, V.Aluminium (Al)/Aluminium alloy composites are emerging as very promising materials, especially in the fields of aerospace and automotive for their various attractive and technically demanding properties. Discontinuously reinforced aluminium metal matrix composites with reinforcements as nanoparticles of ceramics in general and carbon nanotubes in particular have emerged as the forerunner for a variety of general and special engineering and structural applications. In many of the fields where these materials find applications, machining is invariably required for getting correct geometries, dimensions and surface finish of the components. Hence, establishing the machining characteristics of these materials in terms of the deterministic nature of dynamic signals such as cutting force signals and vibration signals is very important and sought after. Machining process has been understood to be nonlinear and chaotic in nature. In this paper a relatively new technique called Recurrence Plots (RP) and Recurrence Quantification Analysis (RQA), a tool to analyse nonlinear and chaotic systems, is used to study the machining characteristics of cast and powder metallurgy Al and Al-Si alloys (LM6 and LM25), CNT reinforced Al/Al-Si composites produced by powder metallurgy route. Cutting force signals were sensed, acquired and analysed using RQA technique. Determinism (DET), which is one of the variables of RQA, indicates the determinism present in a signal. The values of DET were used to compare the machining characteristics. For all the three materials the deterministic nature of the cutting force signal was highest when reinforced with 0.5 weight percentage CNT, followed by respective base alloys produced by powder metallurgy method and casting route. © 2011 Jordan Journal of Mechanical and Industrial Engineering.Item Active vibration control of a smart cantilever beam on general purpose operating system(Defense Scientific Information and Documentation Centre, 2013) Parameswaran, A.P.; Pai, A.B.; Tripathi, P.K.; Gangadharan, K.V.All mechanical systems suffer from undesirable vibrations during their operations. Their occurrence is uncontrollable as it depends on various factors. However, for efficient operation of the system, these vibrations have to be controlled within the specified limits. Light weight, rapid and multi-mode control of the vibrating structure is possible by the use of piezoelectric sensors and actuators and feedback control algorithms. In this paper, direct output feedback based active vibration control has been implemented on a cantilever beam using Lead Zirconate-Titanate (PZT) sensors and actuators. Three PZT patches were used, one as the sensor, one as the exciter providing the forced vibrations and the third acting as the actuator that provides an equal but opposite phase vibration/force signal to that of sensed so as to damp out the vibrations. The designed algorithm is implemented on Lab VIEW 2010 on Windows 7 Platform. © 2013, DESIDOC.