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 micro machining processes, achieving the required accuracy and surface quality in the first attempt is of utmost importance. Because, it is challenging to perform a secondary operation in a microscaled structure due to re-positioning inaccuracies. In the micro grinding process, geometrically deviated structures are common due to the low depth of cuts compared to the size of abrasive grits. Moreover, abrasive grits random distribution on the tool surface is also a factor. In most of the cases, the number of grits participating in the grinding process is countable, unlike macro grinding process. Hence, the position of every grit on the micro tool surface is important. In the micro grinding process, geometrically deviated structures are common due to the low depth of cuts compared to the size of abrasive grits. In this case, the depth of cut values will be less than the size of the abrasive grits. In that case, the abrasive grits located at the tool bottom surface highly influence the quality of the component produced. In the present work, a simulation study has been performed for micro grinding process to understand the influence of tool topography on the micro channel geometrical deviations, especially when the depth of cut is less than the size of the grits. Simulation results showed the importance of the number of grits, their protrusion heights and radial positions on the tool bottom surface at small depths of cuts to minimize the geometrical deviations. © Copyright 2018 ASME.

World University root node

ASME 2018 13th International Manufacturing Science and Engineering Conference, MSEC 2018

Visualization of geometrical deviations in micro grinding by kinematic simulations

Diamond burnishing is one of the most popular surface finishing technique used to achieve an excellent surface finish. The aim of the present study is to investigate the effect of process parameters in diamond burnishing of 17-4 PH stainless steel (PH SS) under cryogenic environment. The requirement of a sustainable environment for various machining processes urged to explore the importance of cryogenic burnishing over other cooling techniques. Surface modification was achieved by the application of liquid nitrogen (LN2) during diamond burnishing. The process parameters considered to reduce the surface roughness (Ra) and increase the surface hardness (H) are burnishing speed, burnishing feed and burnishing force. The diamond burnishing experiments were conducted based on the L9 orthogonal array. The significant parameters and the optimal level of each parameters were determined by using analysis of variance (ANOVA) and main effect plots respectively. Multi-response optimization has been carried out for cryogenic diamond burnishing of 17-4 PH stainless steel by using Taguchi's grey relation analysis (TGRA). From the TGRA, it was observed that at burnishing speed 73 m min-1, burnishing feed 0.048 mm/rev and burnishing force 150 N, improved diamond burnishing performance characteristics were obtained. An improvement in grey relation grade (GRG) was found to be 38.47%. Cryogenic diamond burnishing has led to modifications in the microstructure and also an improvement in the subsurface hardness of the material. © 2018 IOP Publishing Ltd.

Fulltext

Materials Research Express

Experimental evaluation of diamond burnishing for sustainable manufacturing

Sound transmission through a fluid-loaded finite perforated panel set in an infinite unperforated rigid baffle is considered. Using a fully coupled formulation in the 2-D wavenumber domain, the transmitted pressure due to an incident plane wave is obtained. The change in the panel resonances caused by the perforations is accounted for. The formulation also takes into account the self- and inter-modal coupling coefficients arising due to the fluid-loading effect. The derivation is almost entirely analytical with numerical computations done at the very end. Transmission loss (TL) curves are plotted for various cases and the physics is discussed. Along the way an uncoupled calculation is also done for the sake of comparison. The results are mainly for a light medium like air. For a light medium, in general, the perforate impedance is lower than the panel impedance. Thus, most of the transmission happens through the perforations. The panel velocity contribution is insignificant and hence the uncoupled calculation is adequate. In general, the absolute perforate impedance increases with increasing frequency. So does the TL. At low frequencies, because the resistive component of the hole impedance increases, the absolute perforate impedance rises. Thus, the TL curves rise at the lower frequencies. This effect is prominent for sub-millimeter hole radii, i.e., for micro-perforations. An important issue with the TL values for perforated panels is that they sometimes acquire negative values at low frequencies. This apparent anomaly is resolved by showing that at low frequencies there is an additional power component that flows from the baffle region onto the panel. Upon inclusion of this additional term, the TL values remain positive at all frequencies. © 2017 Elsevier Ltd

Journal of Sound and Vibration

Sound transmission through a finite perforated panel set in a rigid baffle: A fully coupled analysis

The existence of geometric errors (misalignment and kinematic errors) and joint clearances is an inherent problem in manipulators. In addition, friction between surfaces and gear backlash errors are unavoidable factors in manipulators using geared motors as their joint actuators. This paper presents a potential solution for the above issues through the application of a dual-loop control scheme. The proposed control scheme uses a redundant feedback strategy, i.e., individual joint displacements (at the joint space level) and, end-effector positions and orientation (at the task space level) are obtained as a feedback signal using appropriate sensors. Using this redundant feedback information, the actual error of the joint displacements are computed and rectified the desired joint space trajectory in joint-space trajectory tracking control to achieve the desired task space trajectory. To demonstrate the effectiveness and show overall performance of the controllers, real-time experiments are performed on an in-house fabricated 2-PRP+1-PPR planar parallel manipulator. The experiment results show that the manipulator tracking performance is significantly improved with the proposed dual-loop control scheme. In addition, the controller parameter sensitivity and robustness analyses are performed. © Springer International Publishing AG 2018.

Mechanisms and Machine Science

Dual-loop motion control for geometric errors and joint clearances compensation of a planar 2-PRP+1-PPR manipulator

In this paper, a new family of 3-degree-of-freedom planar parallel manipulators (PPMs), namely U-shape fixed base PPMs starting with an active prismatic joint on each leg, is proposed. In order to identify the best manipulators of this family, comparative kinematic and dynamic performance studies are performed. The kinematic performances are quantified through the local performance index, namely the kinematic isotropy. From the kinematic isotropy analysis results, it is observed that PPR-PRP-PRP, PRP-PRP-PRP and PRR-PRP-PRP configurations have better kinematic design aspects compared to other configurations of this family of U-shape fixed base parallel configurations. Further, from the workspace analysis, it is observed that the PPR-PRP-PRP configuration has a higher value of workspace to the total area required ratio compared to other configurations. This paper also presents a comparative dynamic performance analysis of these top-three U-shape fixed base configurations in terms of dynamic driving performance measures, and energy requirements for three different (fixed base size of the manipulators) aspect ratios under two different loading conditions. From the analyses results, it is perceived that the PRP-PRP-PRP configuration is requiring lower energy and dynamic driving performances than others. These analyses are done with the help of multi-body dynamic software, namely MSC ADAMS, and the results are validated through the help of real-time experiments conducted on in-house fabricated prototypes of these three PPMs. In specific, the energy consumption is measured and compared in this study. Experimental results demonstrated that the PRP-PRP-PRP manipulator displays a considerably better performance in terms of minimum energy requirement. Copyright © Cambridge University Press 2018.

Robotica

Kinematic and dynamic performance investigations of asymmetric (U-shape fixed base) planar parallel manipulators

A new finite-volume flow solver based on the hybrid Cartesian immersed boundary (IB) framework is developed for the solution of high-speed inviscid compressible flows. The IB method adopts a sharp-interface approach, wherein the boundary conditions are enforced on the body geometry itself. A key component of the present solver is a novel reconstruction approach, in conjunction with inverse distance weighting, to compute the solutions in the vicinity of the solid-fluid interface. We show that proposed reconstruction leads to second-order spatial accuracy while also ensuring that the discrete conservation errors diminish linearly with grid refinement. Investigations of supersonic and hypersonic inviscid flows over different geometries are carried out for an extensive validation of the proposed flow solver. Studies on cylinder lift-off and shape optimisation in supersonic flows further demonstrate the efficacy of the flow solver for computations with moving and shape-changing geometries. These studies conclusively highlight the capability of the proposed IB methodology as a promising alternative for robust and accurate computations of compressible fluid flows on nonconformal Cartesian meshes. Copyright © 2017 John Wiley & Sons, Ltd.

International Journal for Numerical Methods in Fluids

A sharp-interface immersed boundary framework for simulations of high-speed inviscid compressible flows

Binary fluid flows distinguished by high-density ratio are of practical importance to many of the engineering applications. Numerical simulations of such flows having sharp discontinuities across the interface is a challenging task and may lead to the generation of spurious velocities if proper care is not taken during discretization. In this regard, we present a consistent and balanced–force algorithm for binary fluid flows with very large density ratios using algebraic volume of fluid technique over three-dimensional hybrid unstructured meshes using a collocated framework. The algorithm emphasizes on the proper force balancing needed at the discrete level and also on the importance of consistent numerical treatment of similar terms across the equations. The efficacy of the formulation is demonstrated through extensive numerical experiments involving strong surface tension and/or gravitational forces. The results clearly indicate the importance of enforcing discrete balance of forces and ensuring consistent treatment of mass and momentum for robust and accurate simulations of multiphase flows. © 2018 Elsevier Ltd

International Journal of Multiphase Flow

A generic algorithm for three-dimensional multiphase flows on unstructured meshes

We present a simple and cost-effective curvature calculation approach for simulations of interfacial flows on structured and unstructured grids. The interface is defined using volume fractions, and the interface curvature is obtained as a function of the gradients of volume fractions. The gradient computation is based on a recently proposed gradient recovery method that mimicks the least squares approach without the need to solve a system of equations and is quite easy to implement on arbitrary polygonal meshes. The resulting interface curvature is used in a continuum surface force formulation within the framework of a well-balanced finite-volume algorithm to simulate multiphase flows dominated by surface tension. We show that the proposed curvature calculation is at least as accurate as some of the existing approaches on unstructured meshes while being straightforward to implement on any mesh topology. Numerical investigations also show that spurious currents in stationary problems that are dependent on the curvature calculation methodology are also acceptably low using the proposed approach. Studies on capillary waves and rising bubbles in viscous flows lend credence to the ability of the proposed method as an inexpensive, robust, and reasonably accurate approach for curvature calculation and numerical simulation of multiphase flows. © 2018 John Wiley & Sons, Ltd.

A cost-effective curvature calculation approach for interfacial flows on unstructured meshes

Particle diameter, particle phase material density and inlet particle volume fraction are three important parameters governing the flow physics of dispersed gas-particle flows. In this work, an inhouse numerical solver is developed to investigate the effects of particle diameter (Stokes number), particle phase material density, inlet particle volume fraction and inlet phase velocities in the flow characteristics of gas-particle flows through vertical and horizontal channels and also in open domains. It is found that, for a constant inlet particle volume fraction, lower diameter particles attain a higher steady state velocity at any section inside the channel than the higher diameter particles; while the corresponding steady state gas velocity at any section increases with increase in particle diameter. On the other hand, for a constant particle diameter, the steady state gas phase velocity at any section decreases with increase in inlet particle volume fraction. Significant changes in both gas and particle velocity and volume fraction profiles have also been observed with inlet slip, i.e., when the velocities of both the phases at inlet are distinct as opposed to being equal, keeping all other flow and physical parameters invariant. © 2018 The Society of Powder Technology Japan

Advanced Powder Technology

A parametric study of dispersed laminar gas-particle flows through vertical and horizontal channels

In the present scenario, metal cutting industries are looking for alternative cooling techniques to conventional cooling to satisfy the stringent environment regulations as well as lower productivity problems while machining of difficult to cut materials. Cryogenic machining is a novel eco-friendly as well as efficient cooling techniques. In present work, an attempt has been made to study the effect of process parameters on turning performance characteristics and the development of correlation models between the input process parameters and output responses while machining of difficult to cut materials 17-4 precipitated hardened stainless steel (PH SS) using response surface methodology (RSM) under the cryogenic cooling environment. The turning process parameters considered in the present study are cutting velocity (v), feed rate (f) and depth of cut (d) whereas responses are tool flank wear (Vb), surface roughness (Ra) and material removal rate (MRR) respectively. RSM based face centered central composite design (CCD) experimental design has been used to perform the experiments. From the conformation test results, it was observed that very good agreement was found between the actual and predicted values, which represent that the developed predictive models are well effective with a maximum of ± 5% error. © 2018, Springer Science+Business Media B.V., part of Springer Nature.