Department of Mechanical Engineering

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

Numerical investigations to assess the performance of different flux schemes for the spatial discretisation of the Euler equations have been performed. The schemes employed in the study include flux vector and flux difference splitting schemes as well as hybrid schemes. The schemes are cast in an unstructured high-order finite volume framework and are studied on typical engineering problems in the supersonic and hypersonic regimes. While all the flux schemes perform well in the supersonic and low hypersonic range, their performance show a marked change in the high Mach number regimes. Numerical experiments suggest that the AUSM family of schemes is the most accurate while the Rusanov scheme is the most robust for the range of Mach numbers considered in the study. These studies indicate that a robust and accurate numerical solver for high-speed compressible flows necessitate the use of blended schemes that provide a right balance between accuracy and numerical dissipation. © 2014 Inderscience Enterprises Ltd.

World University root node

Progress in Computational Fluid Dynamics

Performance comparison of flux schemes for numerical simulation of high-speed inviscid flows

Titanium and its alloys are well known for their difficult machinability nature. Because of Ti-6Al-4V alloy’s strong chemical affinity, high temperature and pressure during the grinding process, the formed chips easily weld onto the grinding wheel surface. This phenomenon reduces the wheel life and diminish the surface quality. To control the effect of temperature, most grinding operations today employ cutting fluids. These fluids help in improving the surface quality and increasing the wheel life. However, because of environmental and economic concerns, industries are now looking for sustainable alternative cooling techniques such as cryogenic cooling. The aim of this study is to present the application of liquid nitrogen cryogenic cooling as an alternative cooling technique for grinding Ti-6Al-4V alloys. To compare the effect of cryogenic condition, experiments were conducted under both dry and wet (soluble oil) conditions. Experimental results proved the effectiveness of cryogenic cooling in reducing the grinding force, obtaining better surface finish, and being less damaging to the surface condition. Finally, multiple regression models were developed to predict the normal force and tangential force in cryogenic condition. The developed models have been validated with experimental data, and the maximum prediction error of the model for normal and tangential forces was less than 12% and 9%, respectively. © 2014, IMechE. All rights reserved.

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture

Grindability improvement of Ti-6Al-4V using cryogenic cooling

Synchronous lateral vibration is a frequent cause of machine failure and is probably the most common source of machine noise and vibration. Among the broad ranges of faults that cause synchronous vibration, mass unbalance and bow are the most common faults present in the rotor and hence their detailed understanding is required. In the present study, a rotor model having both mass unbalance and bow is analyzed to find the influence of these faults on the synchronous response. The synchronous response of a rotor is a function of influence coefficients due to mass unbalance and bow. The influence coefficients are analytically derived using transfer matrix method for rotor bearing system having both mass unbalance and bow. The correction unbalance vector required to balance the rotor at its first bending critical speed is computed using these analytically derived influence coefficients and the rotor responses measured at a speed much lower than the first bending critical speed. The balancing method needs a good mathematical model for the rotor system in finding the influence coefficients for mass unbalance and bow. This procedure helps in estimating the correction mass in a single trial run and using a single balancing plane, thus reducing the cycle time for balancing flexible rotors. Experiments are carried out on a test rig to verify the procedure. © 2012 The Author(s).

JVC/Journal of Vibration and Control

Balancing of flexible rotor with bow using transfer matrix method

Precise detection of the misalignment can reduce maintenance cost, power loss and improve life of rotating machinery. In this paper, Hilbert Huang Transform (HHT) of the run-up response of a rotor is used to detect coupling misalignment. A finite element analysis is carried out to simulate desirable level of possible parallel and angular misalignment. All the best conventional detection techniques like Fourier spectrum analysis, Continuous Wavelet Transform are compared with results obtained by HHT. The effect of Signal to Noise Ratio and angular acceleration on all the methods to detect misalignment is discussed. The comparison of the methods is oriented towards detecting least possible misalignment level. Finally, experiments are performed on a test rotor rig to detect induced misalignment using the proposed method. It is observed that this method is sensitive to low misalignment, and consumes less testing time. Copyright © 2014 by ASME.

Proceedings of the ASME Turbo Expo

Detection and monitoring of shaft misalignment in rotors using hilbert huang transform

In this study, displacement and strain energy mode shapes obtained from the structure, are processed using continuous spatial wavelet transforms for damage identification. A cantilever and simply supported beam are analysed in ANSYS to obtain mode shapes by performing modal analysis both for damaged and undamaged conditions. Different wavelets are processed to choose the best mother wavelet for detecting crack, a representation of damage. The dimensions of crack like depth are varied from 0.5 mm. Spatial distribution of wavelet coefficients obtained is used for identifying the damage. The quantification of the damage is done by using Lipchitz constant. It is observed that by using strain energy mode shapes the percentage of damage (crack) identification level can be improved than by using displacement mode shapes. The minimum damage level that the strain mode shape can identify is approximately 3% of the element thickness, whereas with displacement mode shapes, it is about 7% of the element thickness. Different types of crack configurations like single surface crack, double surface cracks and internal cracks are simulated and studied using both the modal methods. It is observed that the strain energy mode method could identify internal cracks also. © (2014) Trans Tech Publications, Switzerland.

Applied Mechanics and Materials

Damage identification and quantification in structures using wavelet analysis

A defect-free rolling element bearing has a varying stiffness. The variation of stiffness depends on number of rolling elements, their configuration and cage frequency. The time-varying characteristics of the stiffness results in a parametric excitation. This may lead to instability which is manifested as high vibration levels. An FEM simulation is performed to evaluate stiffness in each configuration of rolling elements and is used to study the variation of direct stiffness and cross coupled stiffness. The obtained stiffness variation is expanded into a Fourier series to form the equation of motion for the bearing vibration. As the stiffness varies with cage frequency, stiffness term in the equation of motion is periodic with parametric excitation. Hence, the equation of motion is a 2-DOF coupled Mathieu equation. Based on Mathieu parameters and cage frequency there exists unstable rpm ranges for a particular bearing. Floquet theory is employed to find out the stable and unstable regions. This involves finding out maximum Floquet exponent using Monodromy matrix. The results obtained through Floquet theory are in agreement with the numerical solution of the governing equations.

INTERNOISE 2014 - 43rd International Congress on Noise Control Engineering: Improving the World Through Noise Control

Parametrically excited vibration in rolling element bearings

Several calorimetric techniques are available for the sequential estimation of thermal conductivities of composites by conducting heat balance successively along the principal directions. Such methods are time consuming and require three samples for estimating the properties. The hollow core, in combination with rigid face sheets, helps in achieving a high strength to-weight ratio, as demanded by its application. Because the manufacturing process of composites inevitably gives rise to a joint resistance between the face sheets and the core, due to the presence of an adhesive, its effect becomes detrimental in the estimation of effective thermal transport properties. A combination of several values of tridimensional effective thermal conductivities may lead to same temperature distribution; hence, the problem is ill posed in nature and requires regularization prior, an engineering intuition, or a combination of both.

Journal of Thermophysics and Heat Transfer

Joint conductance effects on estimation of effective thermal conductivities of anisotropic composites

Adsorption of proteins on membrane surfaces plays an important role in cell biological processes. In this work, we develop a two-dimensional fluid model for proteins. The protein molecules have been modeled as two-dimensional convex and soft particles. The Lennard-Jones potential for circular particles and Kihara (12,6) potential for elliptical particles with hard core have been used to model pairwise intermolecular interactions. The equation of state of the fluid model has been derived using Weeks-Chandler-Andersen decomposition and it involves three parameters, an attraction, a repulsion, and a size parameter, which depend on the shape and core size of the molecules. For validation of the model, a two-dimensional molecular dynamics simulation has been performed. Finally, the model has been applied to study the adsorption of proteins on a flat membrane. In comparison with the existing model of hard and convex particles for protein adsorption, our model predicts a higher packing fraction for the adsorption equilibria. Although the present work is based on Lennard-Jones-type interaction, it can be extended for other specific soft interactions between convex molecules. Thus the model has general applicability for any other two-dimensional adsorption systems of molecules with soft interaction. © 2014 American Physical Society.

Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

Two-dimensional convex-molecule fluid model for surface adsorption of proteins: Effect of soft interaction on adsorption equilibria

This study addresses the dynamic modelling and indirect disturbance compensation control of planar parallel robotic motion platform with three degrees of freedom (3-DOF) in the presence of parameter uncertainties and external disturbances. The proposed planar parallel motion platform is a singularity free manipulator and has three manipulator legs located on the same plane linked with a moving platform. Of the three aforementioned manipulator legs, two legs have a prismatic-revolute-prismatic (PRP) joint configuration each with only one prismatic joint deliberated to be active, and the other leg consists of prismatic-revolute-prismatic (PPR) joint configuration with one active prismatic joint. The closed form kinematic solution (both forward and reverse kinematics) for the platform has been obtained in completion. In addition, the dynamic model for the platform has been communicated using the energy based Euler-Lagrangian formulation method. The proposed controller is based on a computer torque control with disturbance compensation integrated with it. Disturbance vectors comprising disturbances due to parameter variations, payload variations, frictional effects and other additional effects have been estimated using an extended Kalman filter (EKF). The EKF proposed for this specific platform uses only position and orientation measurements for estimation and noise mitigation. Simulations with a characteristic trajectory are presented and the results have been paralleled with traditional controllers such as the proportional integral derivative (PID) controller and computed torque controller (CTC). The results demonstrate satisfactory tracking performance for the proposed controller in the presence of parameter uncertainties and external disturbances. © 2014 Elsevier Ltd.

Robotics and Computer-Integrated Manufacturing

Indirect disturbance compensation control of a planar parallel (2-PRP and 1-PPR) robotic manipulator

The importance of fineness ratio in determining the aerodynamic shapes of minimum-drag, zero-lift axisymmetric bodies in inviscid hypersonic flows is investigated using a shape optimization framework. The framework employs modified Newtonian theory for surface pressure computation, Bezier curves for geometric parameterization and a steepest-descent approach for minimization of the wave-drag coefficient. Studies are performed on axisymmetric bodies of a given length for fineness ratios varying from 1 to 6 and Mach numbers ranging from 6 to 12. It is shown that the optimal axisymmetric body for a given freestream Mach number is blunt-nosed for smaller fineness ratios but becomes sharp-nosed at larger fineness ratios. The fineness ratio at which the optimal body of revolution transitions from blunt-nosed to sharp-nosed is found to be nearly constant at hypersonic speeds and is around 3. Results indicate that the optimal bodies derived from the framework are superior in terms of wave drag to the von Kármán ogive but comparable to the 0.7 power-law body. High-resolution Euler simulations of these optimal forebodies demonstrate that, while the modified Newtonian theory underpredicts the wave drag for lower values of the similarity parameter, the derived configurations remain "near-optimal" for the entire range of the similarity parameter in the hypersonic regime. The study hints at the possibility of multiple near-optimal configurations in inviscid hypersonic flows and affirms the utility of the present framework as a low-fidelity approach for the design of minimum-drag configurations. Copyright © 2013 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.