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

In the present work, a tool holder design has been modified and fabricated, which act as a jet stream tool holder for supplying the cryogenic coolant (liquid nitrogen) to both rake and flank faces of cutting tool simultaneously in a novel way. The present work investigated the effect of cryogenic coolant and turning process parameters on cutting temperature (T), tool flank wear (Vb), material removal rate (MRR) and surface integrity (surface roughness (Ra), surface topography (ST) and microhardness (H)) when it is supplied through the modified tool holder (Mode-I) while machining of 17-4 precipitated hardened stainless steel (PH SS) material and results were compared with the cryogenic coolant supplied at the machining zone with one external nozzle (Mode-II) respectively. Experimental results revealed that Mode-I (proposed cooling approach) significantly reduced the T and Vb wear to a maximum of 61% and 29% respectively when compared to cryogenic cooling with Mode-II approach. It was also found that cryogenic cooling with Mode-I approach affected the surface and subsurface characteristics positively over the cryogenic cooling with the Mode-II approach, which leads to substantial improvement in the final product performance respectively. © 2018, Springer Science+Business Media B.V., part of Springer Nature.

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The Effectiveness of a Novel Cryogenic Cooling Approach on Turning Performance Characteristics During Machining of 17-4 PH Stainless Steel Material

Micro pencil grinding tools (MPGTs) are micro machining tools that have a huge potential for manufacturing fully micro textured surfaces made out of a broad range of hard and brittle materials, finding use in industries like biomedicine and microelectronics. Due to the flexible manufacturing method used to produce MPGTs - the shape of the tool can be adjusted according to the task at hand. Complex freeform microstructures with various cross sections like dovetails or hemispheres can be produced — cross sections that no other process can produce in brittle materials. MPGTs with diameters <50 μm however, suffer from a far too short tool life and far too slow achievable feed rates to make the process economical. As part of the tool development process, a parameter study is needed to understand the influence of some of the more important process parameters like feed rate, rotational speed and the tool inclination angle, as well as the grit size. A full factorial experimental design is conducted to determine the importance of each parameter, using an Analysis of Variance (ANOVA) statistical evaluation method. Using the knowledge obtained from the results of this parameter study, optimum parameters were selected for a second case study. Besides increasing the MPGT tool life, the goal was to achieve feed rates beyond 1 mm/min. © 2019 The Author(s)

Fulltext

CIRP Journal of Manufacturing Science and Technology

Micro grinding 16MnCr5 hardened steel using micro pencil grinding tools with diameters ∼50 μm

Composite materials are having good dynamic properties, specific strength, and specific stiffness. The analytical formulations for dynamic analysis of composite tube shafts are mainly equivalent modulus beam theory (EMBT) and layerwise beam theory (LBT). The EMBT is improved by including coupling effects in the formulation. In the present study, the natural frequencies are calculated using modified EMBT for hybrid composite tube shafts and results are in good match with numerical and experimental work. The of position of CNT inserted layer and amount of CNT added to CFRP, GFRP, and hybrid of CFRP and GFRP composite tube shafts are analyzed. © 2018, © 2018 Taylor & Francis Group, LLC.

Mechanics of Advanced Materials and Structures

The effect of CNT to enhance the dynamic properties of hybrid composite tube shafts

With ever-increasing demand for higher flexibility and higher speeds of operation of high-speed rotating machinery, study of their unbalance responses and stability are of paramount importance. For easier maintenance and transport, weight of such systems is also a critical criterion. In the present study, optimum design parameters of a rotor-bearing system are found by employing multiple multiobjective optimization schemes for simultaneously minimizing unbalance response, maximizing stability limit speed, and minimizing system weight. This is an improvement over previous systems where simple equal weighting of multiple objective functions is carried out to reduce computational challenges. The shaft is assumed to be hollow and modeled as an assembly of 10 two-noded Euler–Bernoulli beam elements with an isotropic disc mounted on it. Genetic algorithm and its multiobjective variant (NSGA-II) are used to find the global optima. The technique of goal programming is identified as a more practical and less computationally challenging alternative to Pareto-based optimization, while yielding an approximate optimum. Complexities arising due to gyroscopic effects and dynamic nature of anisotropic fluid film bearings are also considered, along with practical upper and lower bounds of design variables and maximum von Mises stress developed in the system as constraints. © IMechE 2018.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science

Multiobjective optimization of rotor-bearing systems with an investigation of goal programming approach

A fully coupled formulation is presented for sound radiation from a finite flexible perforated panel set in an infinite rigid unperforated baffle. The panel is excited by a point harmonic force and radiates sound into the acoustic medium on both sides of the baffle. Prior to coupling with the fluid, the change in the inertial and stiffness properties of the panel due to perforations and their effect on the in vacuo natural frequencies and mode shapes are accounted for using the receptance method. The coupled acoustic and structural equations are formulated using the 2-D wavenumber transforms. Since the formulation is in terms of the panel velocity, a certain square root singularity that typically appears in the denominator is avoided. The self- and inter-modal coupling coefficients are evaluated either analytically or numerically. The radiated power, panel mean quadratic velocity and radiation efficiency plots are obtained for different perforation ratios for both center and off-center excitations. At first, our formulation is validated against an unperforated case using a study available in the literature. Next, for our perforated panel case, we assume that both the half-spaces are filled with the acoustic fluid. It is observed that the radiation efficiency decreases with the increase in the perforation ratio, irrespective of the surrounding acoustic medium. However, for the water-loaded panel, the radiation efficiency is found to be lower than when the panel is immersed in air. It is found that for a light fluid like air, a one-way coupled formulation is adequate. The natural frequencies of a water-loaded perforated panel are also presented. It is found that for a given mode, the natural frequency increases with increase in the perforation ratio. © 2018 Elsevier B.V.

Wave Motion

Sound radiation from a finite perforated panel set in a rigid baffle: A fully coupled analysis

The effect of process parameters on temperature distribution in stationary shoulder friction stir welding (SSFSW) and conventional FSW of AA7010-T6 alloy are studied using a three-dimensional heat conduction analysis. The computed results are validated from experimentally measured results reported in independent literature. The tool torque, traverse force and the mechanical stresses on the FSW tool were evaluated analytically using mechanics based principles. The estimated results showed that the tools used in the SSFSW process were more likely to early failure. © 2019, The Minerals, Metals & Materials Society.

Minerals, Metals and Materials Series

Probing Tool Durability in Stationary Shoulder Friction Stir Welding

Printed circuit boards (PCBs) are composite laminate boards used widely in electronic industry. They facilitate the mounting of electronic components on them as well as to make electrical connections in them. Electronic cooling i.e. removal of heat from electronic components is a challenging task. The heat removal rate from the components also depends upon the thermal conductivity of the board over which it is fixed as it is a critical parameter. The challenge which it poses to the thermal engineers is the determination of thermal conductivity of these boards which are inherently anisotropic in nature. The present study aims to estimate the effective in-plane principal thermal conductivities (kxx and kyy) of anisotropic printed circuit boards by solving an inverse heat conduction problem with measured temperatures as input. Therefore, the present methodology involves three major parts namely the direct or forward problem solution, steady state experiments for obtaining temperature measurements and inverse problem solution. The direct problem involves the solution of heat conduction equation along with appropriate boundary conditions and is solved using commercial CFD package, Ansys Fluent. The experiments are done inside a vacuum chamber and steady state temperature measurements are obtained at 18(9 are used for estimation due to symmetry) preassigned locations. Inverse solution methodology employed using artificial neural network (ANN) is used to solve the inverse problem. The methodology is validated with an in-plane isotropic copper clad board by retrieving its in-plane thermal conductivity successfully. Following this, the inverse methodology is employed to estimate the in-plane thermal conductivities of four PCBs which differ in copper trace width and spacing.

Proceedings of the 24th National and 2nd International ISHMT-ASTFE Heat and {\ldots}

Studies on Influence of Anisotropic Thermal Conductivity of Printed Circuit Board on Heat Transfer During Electronic Cooling

Physics of Fluids

Comment on "modifications to the gradient schemes on unstructured cell centered grids for the accurate determination of gradients near conductivity changes" [Phys. Fluids 31, 047104 (2019)]

We propose a numerical framework to solve thermobuoyant flows in enclosures with large temperature differences under the influence of an applied magnetic field. The solution methodology is based on a staggered/nonstaggered finite volume framework which is modified to solve quasiincompressible flows with heat transfer. The present framework solves a single equation for normal momentum at the face wherein a second-order convection scheme and central differencing is adopted for the convective and viscous term, respectively. An implicit solution approach which is first order accurate in time is employed, and the resulting nonlinear system of equations is solved using the Newton–Krylov approach. The momentum field at the cell centroids is reconstructed using an iterative-defect-correction approach. The energy conservation equation is discretized as in a collocated framework, with a first-order upwind scheme for the convective terms and central differencing for viscous terms, in conjunction with implicit Euler time stepping. Thus the equation is linearized by considering the velocity field at the latest available time step, and the resulting linear system of equations is solved, using an incomplete LU (ILU) preconditioned GMRES solver. The proposed approach is, however, still pressure based, but the energy equation is employed to derive the divergence constraint to be used for solution of the pressure correction equation. This leads to a nonsolenoidal velocity field with a variable coefficient poisson equation, which is also efficiently solved using an ILU preconditioned GMRES solver. Validation studies for small and large temperature differences under the action of imposed magnetic field are carried out to ascertain the applicability of the approach. Finally, investigations of magnetohydrodynamic thermobuoyant flow in an enclosure with a heat obstacle are conducted with a view to understand the effect of magnetic field and heat transfer. © 2019 by Begell House, Inc.

Computational Thermal Sciences

The non-boussinesq algorithm for high temperature gradient thermobuoyant flows with magnetic field

The present work address the problems like low productivity, high manufacturing cost and issues with conventional cooling techniques while machining of 17-4 precipitated hardened stainless steel (PH SS). To overcome these problems, optimization studies have been carried out under cryogenic cooling environment. Cryogenic machining (Liquid nitrogen) is an efficient eco friendly machining technique to satisfy the stringent environmental regulations. In the present work, Taguchi incorporated Gray relational analysis (TGRA) and Taguchi coupled Technique for Order Preference by Similarity to Ideal Solution (T-TOPSIS) optimization techniques have been applied for multi response optimization during rough turning of 17-4 PH SS respectively. The obtained result showed that improved performance was found at the TGRA determined optimum cutting conditions when compared T-TOPSIS technique determined optimum cutting conditions respectively. Furthermore, individual and interaction effect of process parameters on turning performance have been discussed using 3D surface plots. © 2018 Elsevier Ltd