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

Novel techniques are being focused on the enrichment of the performance characteristics under different machining processes. Cryogenic is one of such novel practices that tunes the surface integrity with vast variations with the traditional machining processes. Dimensional accuracy, surface roughness, material removal rate with less reduction in scrap of material is one of the prior targets of production process. Wire cut Electro Discharge Machining (WEDM) is one method that satisfy with upgrading performance characteristics. In order to step-up these performance characteristics in attaining superior quality, cryogenics practices have collaborated with the WEDM process. Present paper deals with the reviews of the researchers that have been performed over cryogenic treated WEDM process. Effect of performance characteristics like pulse on, pulse off, current, voltage, wire tension, wire feed is discussed with relation to material removal rate, tool wear rate and surface roughness evolved. Key concept of paper is to include the research ideology with best feasible techniques that can prevail in production practice in order of contribute to the forthcoming researches in industrial and production departments. © 2020 The Authors, published by EDP Sciences.

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A Role of cryogenic in Wire cut EDM process

Fly ash has been receiving the extensive concentration as a strong reinforcing element for Aluminum Matrix Composites (AMCs) to strengthen the properties and cut the price of manufacturing. AA6061 reinforced with various weight percentages of fly ash particulates and a constant weight percentage of SiC were prepared by stir casting technique as it is one of the simplest and cost-effective method for producing AMCs. Wettability of SiC and Fly ash particles with the aluminum was enhanced by fly ash itself. The microstructure, hardness and tensile properties of manufactured AMCs were analyzed. Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) discovered a harmonized dispersion of SiC and fly ash particles with superior bonding with the matrix material. The inclusion of fly ash particles in to aluminum matrix enhanced the microhardness and Ultimate Tensile Strength (UTS) of the AMCs. © 2019 Elsevier Ltd. All rights reserved.

Materials Today: Proceedings

Studies on microstructure and mechanical characteristics of as cast AA6061/SiC/fly ash hybrid AMCs produced by stir casting

The analysis of SCE (specific cutting energy) is vital for determining the machining efficiency. Conventionally, the machining forces are used to determine SCE, which is quantified as the energy that is consumed to remove unit volume of material. To correlate the micro-mechanics of material deformation and small-scale material removal in machining, in this research paper, the SCE has been modelled with consideration of shearing mechanism. While developing the model, small scale material indentation and deformation phenomena have been correlated with complex tool-work interaction behaviour in micro machining. The experiment was conducted for validation of the model for different light-weight materials i.e. Al alloy and Cu alloy. The investigation was done through the analysis of cutting forces and the visual examination of microchip morphology. It was found that the nonlinear increase and sharp fall of specific shearing energy (UShe) occur owing to the variations of the material removal mechanism. This is especially valid for lower values of UCT (undeformed chip thickness). © 2020 Elsevier B.V.

Journal of Materials Processing Technology

Investigation of the specific cutting energy and its effect in shearing dominant precision micro cutting

Cryogenics

Prediction of vapour-liquid equilibria of neon-nitrogen, neon-oxygen and neon-argon mixtures used in JT refrigerators

This work focuses on the dynamic modelling and motion control scheme of a parallel manipulator which has three legs of prismatic-revolute-revolute-revolute joint setup. In each of the legs, the prismatic (P)-joint is active and the rotary (R)-joints are passive. The three legs further join into an end-effector in a right-angled triangle shape. The Euler-Lagrangian approach is followed to achieve the dynamics of the manipulator. The formulations are detailed and simulated. This paper also presents an augmented proportional-derivative (PD) controller along with gravity compensation for the motion control. This control method transforms the closed-loop dynamics of the manipulator into decoupled, and thus it becomes easier to quantify the motion performance. The trajectory tracking performance and its accompanying errors are also discussed. © 2020, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.

Mechanisms and Machine Science

Dynamics and motion control of a three degree of freedom 3-prrr parallel manipulator

The article describes the application of optimization algorithms for solving the problem of determining the workspace of a relative mechanism device, which includes a planar 3-RPS mechanism and a tripod module. Approximation sets of individual modules are used to approximate its workspace in the moving coordinate system. The considered method of approximating a solution set of nonlinear inequalities based on the concept of the non-uniform coverings, describes constraints on the robot geometric parameters. The exterior and interior approximations of the 3-RPS mechanism are obtained. Similarly, an approximation of the restrictions for the tripod module in the moving platform coordinate system is obtained. The constraints with a given accuracy are transferred to the coordinate system of the output using a three-dimensional binary array approximating the workspace. The workspace of the relative mechanism device was obtained on the basis of these results, taking into account the relative manipulation of modules and restrictions on the workpiece geometric parameters. Moving coordinate system is located in the center of the planar 3-RPS mechanism platform. © 2020, Springer Nature Switzerland AG.

Workspace Modelling of a Parallel Robot with Relative Manipulation Mechanisms Based on Optimization Methods

This paper presents the mathematical design and implementation of an actuator fault-tolerant control system for an underwater robot having four rotatable thrusters where the rotatable action of the thrusters is unconventional to a conventional underwater robotic system. Initially, the dynamic model of the robot is presented. Later, a motion control scheme using a backstepping control technique is made to track a desired spatial trajectory. Two techniques of active fault tolerance control viz., Elimination of Column Method, and Weighted-Pseudo Inverse Method are implemented successfully for single actuator faults on an infinity-shaped trajectory, which is a critical aspect of this study as most of the previous literature reported only on set point control. The methods mentioned above are extended to multiple thrusters failure, but both of them could not handle more than a single thruster failure. Hence, an attempt is made to accommodate two thrusters' failure through the line of sight approach by considering the vehicle as under-actuated. The desired vehicle performance is achieved with this approach. Finally, oceanic currents are modeled to simulate the effectiveness of the methods discussed in the paper to prove the performance capabilities of the control system and fault accommodation schemes under realistic conditions. © 2020 Elsevier Ltd

Ocean Engineering

Actuator fault-tolerant control study of an underwater robot with four rotatable thrusters

This paper presents a robust motion control of a sitting-type lower limb rehabilitation robot (LLRR) in its operational-space. The mathematical background of the proposed robot is discussed and its motion control design in the task-space based on a double-loop control approach is derived herein along with its closed-loop system stability analysis. The motion tracking performance analysis of the proposed scheme is demonstrated using computer based numerical simulations. For numerical simulations and to validate the effectiveness of the motion control strategy, the clinically obtained test gait data is used for the desired motion trajectory of the lower limb rehabilitation robot. © 2020, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.

Advances in Intelligent Systems and Computing

Robust Operational-Space Motion Control of a Sitting-Type Lower Limb Rehabilitation Robot

We describe a new and simple strategy based on the Gauss divergence theorem for obtaining centroidal gradients on unstructured meshes. Unlike the standard Green–Gauss (SGG) reconstruction which requires face values of quantities whose gradients are sought, the proposed approach reconstructs the gradients using the normal derivative(s) at the faces. The new strategy, referred to as the Modified Green–Gauss (MGG) reconstruction results in consistent gradients which are at least first-order accurate on arbitrary polygonal meshes. We show that the MGG reconstruction is linearity preserving independent of the mesh topology and retains the consistent behaviour of gradients even on meshes with large curvature and high aspect ratios. The gradient accuracy in MGG reconstruction depends on the accuracy of discretisation of the normal derivatives at faces and this necessitates an iterative approach for gradient computation on non-orthogonal meshes. Numerical studies on different mesh topologies demonstrate that MGG reconstruction gives accurate and consistent gradients on non-orthogonal meshes, with the number of iterations proportional to the extent of non-orthogonality. The MGG reconstruction is found to be consistent even on meshes with large aspect ratio and curvature with the errors being lesser than those from linear least-squares reconstruction. A non-iterative strategy in conjunction with MGG reconstruction is proposed for gradient computations in finite volume simulations that achieves the accuracy and robustness of MGG reconstruction at a cost equivalent to that of SGG reconstruction. The efficacy of this strategy for fluid flow problems is demonstrated through numerical investigations in both incompressible and compressible regimes. The MGG reconstruction may, therefore, be viewed as a novel and promising blend of least-squares and Green–Gauss based approaches which can be implemented with little effort in open-source finite-volume solvers and legacy codes. © 2018 Elsevier Inc.

Journal of Computational Physics

A new Green–Gauss reconstruction on unstructured meshes. Part I: Gradient reconstruction

For improved stability of fluid-conveying pipes operating under the thermal environment, functionally graded materials (FGMs) are recommended in a few recent studies. Besides this advantage, the nonlinear dynamics of fluid-conveying FG pipes is an important concern for their engineering applications. The present study is carried out in this direction, where the nonlinear dynamics of a vertical FG pipe conveying hot fluid is studied thoroughly. The FG pipe is considered with pinned ends while the internal hot fluid flows with the steady or pulsatile flow velocity. Based on the Euler–Bernoulli beam theory and the plug-flow model, the nonlinear governing equation of motion of the fluid-conveying FG pipe is derived in the form of the nonlinear integro-partial-differential equation that is subsequently reduced as the nonlinear temporal differential equation using Galerkin method. The solutions in the time or frequency domain are obtained by implementing the adaptive Runge–Kutta method or harmonic balance method. First, the divergence characteristics of the FG pipe are investigated and it is found that buckling of the FG pipe arises mainly because of temperature of the internal fluid. Next, the dynamic characteristics of the FG pipe corresponding to its pre- and post-buckled equilibrium states are studied. In the pre-buckled equilibrium state, higher-order parametric resonances are observed in addition to the principal primary and secondary parametric resonances, and thus the usual shape of the parametric instability region deviates. However, in the post-buckled equilibrium state of the FG pipe, its chaotic oscillations may arise through the intermittent transition route, cyclic-fold bifurcation, period-doubling bifurcation and subcritical bifurcation. The overall study reveals complex dynamics of the FG pipe with respect to some system parameters like temperature of fluid, material properties of FGM and fluid flow velocity. © 2019, Springer Nature B.V.