Department of Mechanical Engineering

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    Collapsed dimension method applied to problems involving thermal radiation with participating media
    (2000) Mahanta, Pinakeswar
    Thermal radiation is one of the fundamental modes of heat transfer. It plays a vital role in the design of high temperature engineering devices. While pure radiation addresses very high temperature phenomenon, radiation combined with conduction and/or convection represents high to medium temperature phenomenon. Radiative transfer in participating medium is very complex. This complexity is owing to the three-dimensional nature of radiation combined with complicated mechanisms of absorption, emission and scattering. Further complexity is encountered due to spatial, spectral and temperature dependent thermo-physical properties. Under these circumstances, radiative transfer equation governing the radiative transfer process is of integro-differential form. For very general situation, its solution becomes a formidable task.......
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    Investigation of bromination reactions using organic ammonium tribromide and their applications towards bioactive natural products synthesis
    (2002) Bose, Gopal
    This dissertation describes the successful and unsuccessful results for the preparation of various a-bromoenones from their corresponding acyclic and cyclic enones using organic ammonium tribromides; synthesis of various ring substituted flavones and aurones (which are structurally isomeric with flavones) from their corresponding 2ं-acetoxychalcones by bromination, followed by cyclisation as well as synthesis of 7-bromoaurones and 8-bromoflavones from 2ं-hydroxychalcones. Chapter 1 of this dissertation includes the review on a-bromoenone, a-bromo-2ं-acetoxychalcone and their applications towards the synthesis of flavone. Chapter 2 in part I describes the results of our successful efforts on the preparation of both acyclic and cyclic a-bromoenones from the corresponding enones in one pot, by bromination using organic ammonium tribromide (OATB), followed by dehydrobromination by employing...
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    Combined radiation, conduction and/or convection heat transfer in participating media
    (2003) Talukdar, Prabal
    Thermal radiation is one of the fundamental nodes of heat transfer. It plays an important role in the design of high temperature engineering systems. The analysis and design of combust chambers, porous burners and porous volumetric solar receivers, among many others, are some of the important application areas where consideration of thermal radiation is important. Radiative heat transfer in a participating medium is a volumetric phenomenon. It is characterized by absorption, emission and scattering. The radiative transfer equation and the divergence of radiative heat flux are the two equations governing the radiative heat transfer in a participating medium. In a control volume, conservations of radiative energy in a given direction and over all directions are given by the radiative transfer equation and the divergence of radiative heat flux respectively. The equations governing the radiative heat transfer in a participating medium are integro-differential in nature and their solutions are difficult. The difficulty increases further if the thermophysical and the optical properties vary inside the medium and they are functions of temperature.
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    Dynamic characteristics and stability analysis of rotor mounted on fluid film bearings
    (2005) Kalita, Madhumita
    Stability analysis of high speed machinery based on rigid rotor model mounted on rigid supports was found to be inadequate for stability predictions. Critical speeds of a rotor are frequently computed assuming the bearing to act as rigid supports whereas in actual practice bearings have some flexibility resulting lower critical speeds. Fluid film bearings commonly used in heavy rotating machines play a significant role in the dynamic behavior of rotors as the stiffness and the damping properties of the oil film significantly alter the critical speeds of a rotor. Dynamic coefficients of fluid film bearing are speed dependent and these coefficients also change with the geometry of the bearing and other operating conditions. Hydrodynamic bearings are regarded as the best source of dumping. Generally plain circular bearings do not suit the stability requirements of high-speed machines and precision machine tools and new bearing designs are sought to meet the new requirements. These bearings are usually characterized by their non-circular cross sections which will enhance shaft stability and also reduce power losses and increase oil flow thus reducing temperatures under proper conditions.
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    Flow and conjugate heat transfer study of wall bounded laminar plane jet flows
    (2005) Kanna, P. Rajesh
    Depending upon the distance of the confining boundaries from the discharge, a jet can be analysed as a free jet or a bounded one. If the boundaries (parallel to inlet axis) are sufficiently away from the origin of the jet, the flow is termed as a free jet. However, a bounded jet will occur when it interacts with a parallel wall. Bounded jet flows occur in many engineering applications such as environmental discharges, heat exchanges fluid injection systems, cooling of combustion chamber wall in a gas turbine, automobile demister and others. Bounded jets can be classified into three types: (a) impinging jet aimed toward the boundary; (b) wall jet while fluid is discharged at the boundary; and (c) offset jet from a vertical wall of a stagnant pool issuing parallel to a horizontal solid wall. The present work is aimed to understand the flow and conjugate heat transfer characteristics of wall bounded laminar jet flows. The study is carried out for plane wall jet flow and offset jet flow. Another study covered is plane wall jet flow over backward facing step.
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    Processing and characterisation of ruthenium aluminium alloys
    (2006) Bora, Anil
    There is an ever increasing demand for materials usable at high temperatures and under extreme environmental conditions. The power generation sectors and aerospace industries are fostering the development of alternative materials with lower density, high strength and high application temperature. Material development coupled with improvements on the processing technology efforts of the last two decades has resulted in the availability of multi-component alloys with good high-temperature strength and oxidation resistance. However, it seems that the potential of the conventional materials has been exploited to the maximum extent and hence an intensified research is required in this area of newer materials development. Intermetallic alloys have been identified as an emerging class of materials and have been the subject of studies for many years as the potential replacement for the existing high-temperature materials. A large number of intermetallic alloys such as Ni- Al based alloys, Ti-Al based alloys, Fe-Al based alloys, etc. has already been identified for high-temperature applications. However, the lack of a good combination of room temperature ductility and toughness together with high temperature strength and corrosion resistance are some of the major barriers for their application as high temperature structural materials. Hence, the successful development of newer materials based on intermetallic alloys depends on the improvement of these properties. Though intermetallic ruthenium aluminide (RuAl) phase was identified in 1960, its properties amenable for high temperature structural applications have been unveiled only in the early nineties. These reports on the properties of Ru-Al alloys triggered the scientific research on RuAl. Ru-Al alloys exhibit a combination of high ductility and toughness, high strength and corrosion resistance at high temperatures. The intermetallic phase RuAl has a very high melting point (उ 2060 उC). Due to these basic properties, RuAl is considered as a high-temperature structural material. However, there exist quite a few disagreements in the currently available binary and ternary phase diagrams of this alloy system. Past research activities were directed mostly on the Al rich side of the Ru-Al phase diagram, leaving the Ru rich side of the phase diagram relatively unexplored....
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    Failure analysis of HIP Prosthesis
    (2007) Sivasankar, M.
    The present thesis deals with the study of failure analysis of total hip prosthesis . A complete 3D finite element model has been developed for assessing the failure of hip prosthesis. fatigue life of the prosthesis has been determined using 3D finite element analysis along with residual strength degradation model. A methodology for determination of fatigue constants in residual strength degradation model has been proposed for fatigue life calculation of hip prosthesis.
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    Multi sensor based drill wear monitoring using artificial neural network
    (2007) Panda, Sudhansu Sekhar
    Tool condition monitoring(TCM) is one of the most important activities in modern manufacturing activities. proper implementation of TCM system not only prevents catastrophic failure of tool but also increases the productivity of the industries. Drilling is one of the most common machining operations used in industries and hence monitoring of the drilling condition is of significationt importance in industries. Among different causes of drilling failure gradual wear of the drilling is unavoidable and needs to be monitored to avoid sudden failure of the drill.
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    Computational Investigations of Turbulent rectangular jets in a narrow Channel Crossflow
    (2007) Pathak, Manabendra
    The present work deals with the computational investigation of a practically important and theoretically interesting flow field of turbulent isothermal and heated rectangular jets in a narrow channel crossflow for high velocity ratios. the main objective of the work is to provide a more detialed information about the flow characteristics of this important flow configuration compared with available literture. the other objective is to asses the performance of differnet turbulence models in predicting the behaviour of this flow configuration. the investigation is carried out first for the 2D flow field and subsequently for 3D flow field. In the 2D investigation,....
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    Detection, localization and sizing of a structural flaw a beam based on vibration measurements
    (2007) Karthikeyan, M.
    An identification algorithm is developed in order to detect, locate and quantify a structural flaw in a beam based on vibration measurements. the algorithm gives the flaw flexibility and damping as a by-product and has potential to detect no flaw condition.
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    Vibration Analysis, Control and Optimal Placement of MFC Actuators and sensors on Rotating Thin-Walled Composite cantilever Beams
    (2008) Vadiraja, D N
    In the present thesis, equations of motion are derived using dynamic modelling method for rotating thin-walled composite beams. Coupled equations of motion are derived for arbitrary beam configuration using HamiltonDs principle for higher order shear deformable beam. A non-Cartesian deformation variable representing axial stretch, along with two Cartesian variables representing bending motions are used. Due to this transformation, centrifugal stiffening and gyroscopic coupling effects can be captured in linear potential and kinetic energy equations. This makes the formulation less cumbersome compared to geometrically nonlinear modelling method. Moreover, this method provides the advantage of inclusion of gyroscopic coupling. The effect of gyroscopic coupling makes the structural model more realistic and it has been demonstrated that the gyroscopic coupling cannot be neglected. The mathematical model also includes non-classical effects generally exhibited by rotating composite beams such as anisotropy, heterogeneity, warping and transverse shear. The approximate solutions of equations of motion are obtained using the extended GalerkinDs method. To validate the developed code, the results from the present method are compared with the experimental and theoretical results available in the literature. The predicted results are in good agreement with the results available in the literature. Numerical solutions for rotating composite cantilever beams are illustrated for a composite box beam configuration. Effects of taper, pretwist, presetting and gyroscopic coupling on free and forced vibration of rotating beams are studied. Numerical results reveal that gyroscopic coupling between lagging-extension modes has considerable effect on the system natural frequency, mode shape, forced response and hence cannot be neglected. The structural modelling of rotating composite thin walled beams is extended to include embedded MFC actuators and sensors. The actuators and sensors are considered as distributed over the top and bottom surface of the beam, respectively. The governing coupled equations of motion are derived from the HamiltonDs principle and approximate solution is obtained using extended GalerkinDs method.The reduced order model is formulated with the assumption that the lower order modes have lower energy associated and consequently are the most easily excitable ones. The number of modes in a reduced order model are selected by analyzing convergence of tip displacement and actuator voltage. Thereafter the reduced order model is converted to a state space form for the purpose of controller design. Optimal control algorithms such as linear quadratic regulator (LQR) and linear quadratic Gaussian (LQG) are used to estimate feedback gain. Comparison between bending vibration control performance of monolithic piezoelectric and fibre based piezoelectric actuators/sensors are studied. Distributed piezoelectric model available in the literature is used for monolithic piezoelectric actuators and sensors. It is observed that control effort by using MFC actuators and sensors is significantly less compared to that of monolithic piezoelectric actuators and sensors. Passive effect of monolithic and fibre based piezoelectric actuators on system natural frequencies are studied in numerical experiments. Optimal co...
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    Transient response of a Participating Medium subjected to short-pulse radiation sources
    (2008) Muthukumaran, R.
    Thermal radiation is important in many areas such as internal combustion engines, boilers,furnaces, solar collectors, reentry vehicles, remote sensing, bio-medical imaging and surgery.Its propagation speed in vacuum is 3x10x8 m/s. In many heat transfer problems involving thermal radiation, in which temporal information is sought at time levels above micro-seconds, radiative transfer is essentially an instantaneous process, and thus the time dependent term in the governing radiative transfer equation is neglected.
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    Nonlinear Dynamics of Flexible Cartesian Manipulators
    (2008) Pratiher, Barun
    In this work, the nonlinear dynamic analyses of flexible Cartesian manipulators with elastic, viscoelastic and magnetoelastic beam materials for different applications are carried out. From exhaustive literature review, it is observed that though Cartesian manipulator has been used in many applications such as space exploration, hazardous nuclear power plant, micro surgery, precision manufacturing, and in many other industrial applications, very limited research has been carried out to enhance their productivity by making them lightweight or flexible, as these flexible manipulators cause severe vibration problems. Hence, in this work, an attempt is made to study the flexible Cartesian manipulator and develop some strategy to control the vibration of the presently used elastic manipulators by incorporating viscoelastic and magnetoelastic manipulator. Here, single-link flexible Cartesian manipulator with a payload has been modeled either as an transversely vibrating Euler-Bernoulli beam with roller-support at one end and tip mass at the other end, or as a transversely vibrating cantilever beam with end mass. The roller-supported end is assumed to have periodic motion. In some analyses, to simulate applications like welding, spraying, metal cutting etc. when the endeffector of the manipulator is in contact with the work environment, and has been subjected to forces from the environment, the endeffector of the manipulator has been modeled as a point mass subjected to harmonically varying axial tip force. In this work, 9 different flexible Cartesian manipulator models have been studied. Here, DD AlembertDs principle is used to derive the spatial governing equation of motion for elastic, viscoelastic and magnetoelastic manipulators, which is discretized into their temporal equations of motion by using generalized GalerkinDs method. These nondimensional temporal equations of motion contain many nonlinear terms which include cubic geometric and inertial terms due to large transverse deflection, nonlinear damping terms, and nonlinear parametric excitation terms along with linear stiffness, damping, forcing and parametric excitation terms. Due to the presence of many nonlinear terms, the perturbation methods viz., first and second order method of multiple scales, and method of normal forms are used to reduce the second order temporal equation of motion to a set of first order differential equations, which are then reduced to a set of nonlinear algebraic equation for steady state condition. For different resonance conditions, these reduced equations are solved numerically to find the steady state response of the systems. Taking various physical system parameters such as amplitude and frequency of support motion; mass ratio (ratio of mass of the payload and the beam); static and dynamic amplitude and frequency of axial force and magnetic field; viscous damping; loss factor; material conductivity and relative permeability of the material numerical simulations have been carried out to find the transient and steady state response, their stability and critical bifurcations. Time response, frequency response, instability regions, phase portraits, PoincareDs section, and basins of attraction are used to analyze the system behaviour for different resonance conditions. Initially, study has been carried out to investigate the vibration of harmonically varying roller-supported elastic manipulators with and wi...
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    Soft computing assisted modelling of symmetric and asymmetric cold flat rolling processes
    (2008) Gudur, Prashant P
    Abstract not found
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    Study of turbulent flow and conjugate heat transfer of plane wall and offset jets
    (2008) Vishnuvardhanarao, Elaprolu
    When a fluid is ejected from a nozzle, it forms a jet. A jet can be classified as free jet or bounded jet. If the effect of wall is negligibly small, then it is called a free jet; otherwise it is bounded jet. Bounded jets can be classified into three types: (a) wall jet where the fluid is discharged at the wall (b) offset jet where the fluid is discharged at an offset and parallel to wall and (c) impinging jet aimed towards the boundary. The present study aimed to understand the flow and conjugate heat transfer characteristics of the wall jet, offset jet and combined jet flows. Glauert [1] has defined a plane wall jet as a stream of fluid blown tangential along a plane wall. The wall jet consists of an inner region and an outer region. It is a combination of boundary layer flow over flat plate at inner region and plane free jet at outer region. The velocity profile has a point of inflexion. The surrounding medium of wall jet may be quiescent or co-flow or counter-flow depending upon the applications. Offset jet flow occurs when fluid is discharged from a slot in a vertical wall into the ambient near a horizontal solid boundary parallel to the inlet jet direction. The asymmetric entrainment on both side of the jet causes the flow to deflect towards the wall. This is called the Coanda effect [2]. The offset jet contains different flow features which are different in various regions. The region very close to the jet is dominated by the properties of the free jet. At the reattachment region, the jet can be partly described as impingement jet and in the far downstream, the jet attains the characteristics of the wall jet.
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    Studies on flow instabilities and nonlinear oscillations in natural circullation boiling systems
    (2008) Prasad, Gonella V. Durga
    The present work consists of numerical studies on flow instabilities in natural circulation boiling systems. An exhustive review of literature has been carried out. boiling systems have been modelled using two different approaches: lumped parameter modelling and RELAP5/MOD3.4 code....
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    Finite Element Based Design and optimal Vibration Control of Smart fiber Reinforced composite shell structures using genetic algorithm
    (2009) Roy, Tarapada
    Active vibration control of smart fiber reinforced polymer (FRP) composite structures finds use in high performance structures especially in lightweight composite structures. Proper implementation of such smart structure systems demands complete understanding of their responses and design of an appropriate control system. The present work deals with first development of an improved shell finite element (FE) formulation for coupled thermo-electromechanical analysis of smart FRP shell structures followed by development of genetic algorithm (GA) based methodologies for optimal actuators placement as well as optimal feedback controller. Stress resultant-type KoiterDs shell theory has been used and no restriction has been imposed on the magnitude of curvature components to capture the deep and shallow shell cases. The twist curvature component has been incorporated along with the normal curvatures to keep the strain equations complete. The transverse shear effect has also been considered according to the MindlinDs hypothesis. An improved integer coded genetic algorithm (GA) based open loop procedure has been implemented for optimal placement of collocated sensors and actuators in order to maximize the controllability index incorporating control spillover. Once, the optimal sensor/actuator locations have been obtained, an improved real coded GA based linear quadratic regulator (LQR) control scheme has been developed for optimal vibration control of the smart shell structures under combined thermo-mechanical loading in order to maximize the closed loop damping ratio while keeping actuators voltages within limit. The FE formulations developed in the present work has been compared with analytical solutions for smart shell structures subjected to electrical, mechanical, thermal as well as combined electro-thermo-mechanical loading. It is observed that the developed FE could analyze coupled thermo-electro-mechanical of shell structures for both deep and shallow shells. Results obtained from the present work also show that this combined GA based optimal sensor/actuator placement and GA based LQR control scheme is far superior to conventional active vibration control using LQR control schemes. It is observed that the proposed GA based LQR control scheme along with the optimal placement of actuators could control both the dynamic oscillation due to mechanical load as well as the static displacement due to thermal gradient which was not possible with conventional LQR control scheme. The proposed GA based combined optimal placement and LQR control scheme not only lead to increased closed loop damping ratio but also shows a drastic reduction in input/actuation voltage..
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    Experimental Study, Neural Network Modeling and Optimization of Environment-Friendly Air-Cooled and Dry Turning Processes
    (2009) Sarma, Daba Kumar
    Manufacturing processes are studied scientifically for improving the quality and productivity. Lately, there has been an increasing concern about the consideration of environment in manufacturing [Sheng and Srinivasan, 1995; Gungor and Gupta, 1999; Yan et al., 2007], which is not only related with the protection of human and the surrounding environment, but is also related with the reduction of the resource consumption in manufacturing processes. Green manufacturing and green engineering in general have become popular in industrial processes and products. According to the US Environmental Protection Agency, green engineering is the design, commercialization and use of processes and products, which are feasible and economical while minimizing (a) generation of pollution at the source and (b) risk to human health and the environment. Machining is one of the important and widely investigated manufacturing processes. Nevertheless, the practical implementation of research findings is very difficult due to a variety of factors and the statistical nature of the machining process. For example, the maximum performance in turning can be achieved by selecting the proper process parameters and coolant. However, the cutting behavior is different for each tool-workpiece material combination, besides being dependent on several other factors such as the rigidity of the machine tool. This necessitates conducting of a number of experiments for each tool-work material combination. The rigorous experimental work under various cutting conditions and at different cutting environment can help to take a conclusive decision in achieving the desired performance of the machining. The focus of the present thesis is on exploring the environmental-friendly options for the turning process. Hence, dry turning and aircooled turning processes have been studied. The dry and air-cooled turning processes do not use a cutting fluid, thus avoiding the pollution at the shop floor and...
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    Design Optimization of Active Magnetic Thrust Bearing Systems Using Multi-Objective Genetic Algorithms
    (2009) Rao, Jagu Srinivasa
    In the present work, an optimum design and analyses of active magnetic thrust bearings (AMTB) and hybrid magnetic thrust bearings (HMTB) have been carried out. The active magnetic bearing contains only electromagnets, whereas, the hybrid contains both the electro-magnets and permanent magnets. Initially, the optimization has been carried out using single-objective genetic algorithms (SOGA). Two objectives, namely the power-loss and overall weight of the bearing, are considered one at a time. Different constraints considered are the maximum current density flow in the coil, the maximum flux density flow in the stator iron, the maximum power-loss allowed, and the maximum space occupied by the bearing. Two objectives considered are found to be conflicting. This led to the attempt of optimization by using multi-objective genetic algorithms (MOGA) by considering two objectives simultaneously namely, the power-loss and overall weight of the bearing. The effect of load on the Pareto frontier has been studied, and the load is found out to be an objective in addition to the weight and the power-loss. A complex system of double-acting hybrid magnetic thrust bearings (DAHMTB) with a centralized controller as an integrated system has been optimized by using MOGA. Five objectives are considered with three for the actuator and two for the controller. Additional constraints considered are stability conditions of the controller. Though power amplifiers can be designed with respect to designed controller requirements, sometimes it is not possible to have the required power amplifiers as a standard one, and one has to design the controller by taking the constraints of the power amplifier available at hand. Though centralization of controller requires less number of power amplifiers, but needs some complex winding scheme and control strategies. To go for a simpler winding and control strategies one may have to go for a decentralized actuator, controller and power amplifier in double acting magnetic bearing systems. Hence, the design optimization methodology is extended to the DAHMTB with decentralized controller systems by taking consideration of constraints of the power amplifier, namely the maximum power rating, and the voltage of the power amplifier.