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

The components built using new generation feature based design and manufacturing process, called laser additive manufacturing (LAM) is inherited with tensile residual stress due to rapid heating and cooling during material processing. Laser shock peening (LSP) is an advanced surface engineering process that imparts beneficial compressive residual stresses into materials yielding longer product life by increasing the resistance to many surface-related failures, such as wear. LSP is widely used by various industries including aerospace, power generation, chemical processing, etc. to increase the life of engineering components. This paper reports LSP of LAM built Inconel 718 and the parametric study is conducted by varying peak laser power and number of shots at three different levels. Optimum laser power and number of shots derived using grey relational analysis is found to be 170 mW and 7, respectively for maximum hardness and minimum depth of profile. The investigation show that LSP changed the surface morphology and mechanical properties of the LAM built structure. The surface investigation using optical profilometer and Vickers micro-hardness shows a maximum profile depth of 10 μm and hardness of 360 HV. Residual stress measurement indicates compressive residual stress of 214.9–307.9 MPa on the LAM sample surface after LSP. The wear studies show an improvement by a factor of 1.70 for LSP treated LAM samples as compared to that of as-built condition. This study unwrap avenues for using LSP as property enhancement post-processing technique LAM fabricated structures with geometrical complexities. © 2019, Korean Society for Precision Engineering.

World University root node

International Journal of Precision Engineering and Manufacturing

Post-processing of Laser Additive Manufactured Inconel 718 Using Laser Shock Peening

It is known from recent studies that evaporation induces flow around a droplet at atmospheric conditions. This flow is visible even for slowly evaporating liquids like water. In the present study, we investigate the influence of the ambient gas on the evaporating droplet. We observe from the experiments that the rate of evaporation at atmospheric temperature and pressure decreases in a heavier ambient gas. The evaporation-induced flow in these gases for different liquids is measured using particle image velocimetry and found to be very different from each other. However, the width of the disturbed zone around the droplet is seen to be independent of the evaporating liquid and the size of the needle (for the range of needle diameters studied) and only depends on the ambient gas used. © 2019 Author(s).

Physics of Fluids

Evaporation-induced flow around a droplet in different gases

Purpose: Key challenges in evaluating the performance of a robotic manipulator are disturbances that rise internally and externally. Effects of non-linear disturbances like varying payload and joint friction can adversely affect the tracking performance in a robotic manipulator. This paper aims to discuss motion control of a three-link spatial manipulator using a computed torque observer-based control technique. Design/methodology/approach: The overall motion control problem consists of derivation of kinematic and dynamic model of the manipulator followed by the control design to achieve desired manipulator response. In this study, the manipulator is subjected to uncertain varying load disturbances. The proposed motion controller compensates the effect of the disturbances and guarantees the convergence of tracking error to steady state value. Findings: One major advantage of using observer-based control is positioning accuracy with robustness to parameter uncertainty and fast dynamics response. The performance of the proposed control technique is validated through real-time experiments conducted on the manipulator. The experiment results confirm the superior performance of the control system in achieving perfect tracking. Originality/value: This paper demonstrates an observer-based control technique over a serial spatial manipulator which can be applied different robotic configurations under the effect of varying disturbances. © 2019, Emerald Publishing Limited.

World Journal of Engineering

Development and motion control of spatial serial robotic manipulator under varying disturbances

This paper presents an adaptive backstepping motion control of a sitting- type lower limb rehabilitation robot (LLRR). The kinematics and dynamics of the proposed robot is discussed and its motion control design in the taskspace based on an adaptive backstepping control strategy is derived herein. The closed-loop system stability of the proposed motion control scheme is demonstrated by the Lyapunov’s direct method. Further performance analysis of the proposed system along with the proposed motion control design is demonstrated using computer based numerical simulations. For numerical simulations and to validate the effectiveness of the motion control strategy and the proposed lower limb rehabilitation robot design, the clinically obtained test gait data is used for the desired motion trajectory. © 2019, Springer Nature Switzerland AG.

Mechanisms and Machine Science

Adaptive Backstepping Motion Control of a New Sitting-type Lower Limb Rehabilitation Robot

In the present work, aluminum alloy 6061/SiC/fly ash aluminum matrix composites were welded successfully using friction stir welding process. Microstructure of weld joints was examined using optical microscope and scanning electron microscope. Mechanical properties namely, microhardness and ultimate tensile strength of the joints were studied. The results were correlated to microstructural changes caused by friction stir welding process. Microstructure in the stirred zone exhibits the uniform distribution of SiC and fly ash particles. Especially fine grains were formed on the advancing side than on the retreating side, due to the different variation between tool direction and welding direction. Higher hardness value is observed on the advancing side (132 Hv) than on the retreating side (124 Hv). Transverse tensile test of weld sample exhibits higher joint efficiency of 85.06% with respect to ultimate tensile strength. Fracture study reveals ductile mode of failure. Weld joints got fractured in heat affected zone on the retreating side, which indicates the weakest part of the weld joint. Based on thermodynamic analysis, the optimum heat input was found to be 756 J mm−1, resulting in higher strength of weld joints due to uniform distribution of reinforcement particles in the nugget zone. © 2018, Springer Nature B.V.

Silicon

Microstructure, Hardness and Tensile Properties of Friction Stir Welded Aluminum Matrix Composite Reinforced with SiC and Fly Ash

Application of deep holes is extensively found in the oil and gas industry to manufacture downhole equipment. These deep holes are fabricated in drill collars to deploy delicate sensors downhole for obtaining vital information like temperature, pressure and other geo-physical data from the bottom of the hole. High temperature and corrosion resistant materials like Inconel 718 is often used for drill collars to shield these sensitive communication equipment from the hostile downhole environment. Gundrilling is an established hole making method known for drilling precise and high aspect-ratio (AR>10) holes in conventional materials such as steels, cast iron and aluminium alloys etc. However, gundrilling of Inconel 718 offers unprecedented challenges like excessive tool wear, hole straightness deviation due to poor thermal conductivity and work-hardening tendency of the alloy. Moreover, as the drilling depth increases the deviation is further exacerbated due to the low rigidity of long gundrill shafts. The present study in the Phase 1 introduces a dynamic model using multispan Euler-Bernoulli beam theory to evaluate the effectiveness of coolant pressure and rotation speed during deep hole fabrication in Inconel 718. In addition, experimental investigations have been conducted to validate the model by studying the effects of coolant pressure and rotation speed on straightness of the fabricated holes. It was found that the straightness deviation was 0.37 mm corresponding to 137.89 bar and 1600 rpm coolant pressure and rotation speed respectively. In Phase 2, a non-contacting EDM process was used to fabricate a straight guide hole followed by conventional gundrilling (CG) with optimum pressure (137.89 bar) and speed (1600 rpm) obtained from the Phase 1 trials. The experimental results revealed that the thrust force reduced drastically from 800 N (CG) to 250 N (EDMG). Moreover, a significant improvement in both rake wear and flank wear was also observed. Finally, a straightness deviation of 0.19 mm was recorded for a maximum drilling depth of 350 mm which is 48.65% lesser than CG. From the study, it was found that this novel EDMG process improved the drilling capability of Inconel 718 by reducing the thrust force generated, enhancing tool life and minimizing the straightness deviation. © 2019

Precision Engineering

A novel approach in high performance deep hole drilling of Inconel 718

The present study investigates three different algorithms for the numerical simulation of non-Boussinesq convection with thermal radiative heat transfer based on a low-Mach number formulation. The solution methodology employs a fractional step approach based on the finite-volume method on arbitrary polyhedral meshes. The three algorithms compute the coupled governing equations in a segregated manner using the conservative form of momentum equations in conjunction with a variable coefficient pressure Poisson equation. The first algorithm (Algorithm A) uses conservation of mass and energy equation to compute density and temperature. The other two algorithms (Algorithm B) and (Algorithm C) calculates temperature and density from the equation of state respectively and solves a conservative form of the continuity and energy equation to obtain density and temperature respectively. The energy and mass conservation errors arising due to the use of Algorithms B and C are derived concerning various non-dimensional parameters governing the flow and heat transfer. The significance of these errors is highlighted by performing investigations over a range of Rayleigh, Prandtl, and Planck numbers for various two and three-dimensional natural convection problems with radiative heat transfer. Finally, the role of balancing of the pressure and buoyancy terms is emphasized for robust calculations of large temperature difference thermo-buoyant convection with radiative heat transfer. © 2018 Elsevier Ltd

Computers and Mathematics with Applications

Numerical appraisal of three low Mach number algorithms for radiative–convective flows in enclosures

Secondary finishing operations are the primary requirement of the manufacturing industries to achieve dimensional tolerance of the components. Burnishing is essentially a surface finishing operation usually performed after machining to achieve superfinishing. Diamond burnishing is one of the finest finishing technologies which has been conducted on any surface to attain mirror surface finish. The present work focuses on the development of a correlation model between the process parameters and the output responses while burnishing of 17-4 precipitation hardenable stainless steel using response surface methodology. A novel diamond burnishing tool has been used to analyze the influence of process parameters on output responses in the MQL environment. The control factors considered for the present study include burnishing speed, burnishing feed and burnishing force, and the corresponding output responses considered were surface roughness and surface hardness. The influence of process parameters on output responses has been determined by analysis of variance. Optimization was performed by a multi-objective genetic algorithm. The proposed methodology has been validated by performing experiments at the optimal process parameters, and the achieved results indicate the effectiveness of the diamond burnishing process. © 2019, The Brazilian Society of Mechanical Sciences and Engineering.

Journal of the Brazilian Society of Mechanical Sciences and Engineering

Selection of optimal process parameters in sustainable diamond burnishing of 17-4 PH stainless steel

Studying the deformation and breakup behavior of molten metal droplets is crucial in the context of their atomization to form metal powders. During secondary breakup, droplets deform and then break up. The initial deformation plays an important role in the breakup phenomenon, as it is the first stage that the droplet goes through during its breakup. In this work, secondary breakup experiments were performed at low Weber numbers where the bag breakup mode is predominant and deformation characteristics of the droplet were measured. Since studies on molten metals are scarce, the test liquids included high-surface-tension liquids (molten tin and gallium), as well as water and ethanol, to obtain a wide range of surface tension values (0.71-0.022 N/m). The objectives were to investigate deformation and breakup behavior of molten metals compared to waterlike liquids, to examine the range of Weber numbers corresponding to the bag breakup mode and to check the applicability of the standard Taylor analogy breakup (TAB) model to molten metal atomization. The experimental results show that the deformation and breakup characteristics of molten metal droplets are different from classical waterlike liquids; the extent of deformation and the deformation rate are low for molten metals. To take this into account, a correlation relating the maximum cross-stream length to the initial droplet diameter is proposed. A semianalytical model which predicts the deformation of the droplet is also presented. The results from this model agree well with our experimental results and the literature. The model also performs better than the TAB model for most of the conditions studied. © 2019 by Begell House, Inc. www.begellhouse.com

Atomization and Sprays

Experimental and semianalytical investigation of droplet deformation in a cross-flow

In the present work, application of evolutionary algorithm and gradient-based optimisation techniques are extended towards obtaining minimum drag axisymmetric bodies in hypersonic flows. An attempt has been made to study the comparative performance of greedy and heuristic algorithm-based optimisation algorithm of interest with its application towards generating optimal shape configurations. We compare the performance of memetic meta-heuristic-based shuffled frog-leaping algorithm (SFLA), biological evolution-based genetic algorithm (GA), stochastic method-based simulated annealing (SA) and gradient-based steepest descent (SD) method. The suitability of each optimisation algorithm is analysed for a common test case of minimum drag axisymmetric body with the use of theoretical correlation as its flow solver. This is then followed by the implementation of a computationally expensive but accurate in-house Euler flow solver based on Immersed Boundary (IB) method, which results in a discrete solution space. This naturally results in greater computational cost per function evaluation. Results indicate that evolutionary algorithm-based optimisation technique requires much greater number of function evaluations as compared to gradient-based optimisation technique. Moreover, for a uni-modal problem considered in this work, the choice of gradient-based optimisation method proves to be quite robust and computationally efficient.