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 recent years, Inconel 718 is widely used in industries like aerospace, oil and gas, and automobile due to their unique combination of hardness, strength, temperature, and corrosion resistance properties. However, these materials pose challenges during conventional machining due to their high work hardening tendency, poor thermal conductivity, and chemical affinity towards the tool material. Consequently, rapid tool wear during the machining of Inconel 718 results in poor productivity. To overcome these issues, a non-contact hybrid electrical discharge and arc machining (HEDAM) process has been developed to machine such difficult-to-cut materials. Firstly, the design and development of the HEDAM circuit has been discussed. Subsequently, the working principle of the newly developed process has been studied followed by its performance comparison with the conventional EDM process. In addition, the material removal mechanism has also been discussed in detail. Finally, experimental results were reported, where holes were drilled using the developed HEDAM process. The HEDAM process has exhibited significant improvements in terms of material removal rate (MRR) which is around 12 times higher and electrode wear ratio (EWR) that is half when compared to conventional EDM. This high performance HEDAM process resulted in successful and efficient drilling of Inconel 718. © 2018, Springer-Verlag London Ltd., part of Springer Nature.

World University root node

International Journal of Advanced Manufacturing Technology

On the design and application of hybrid electrical discharge and arc machining process for enhancing drilling performance in Inconel 718

This paper proposes a planar hybrid manipulator system integrated with a passive serial orthosis for a foot-plate based sitting-type lower limb rehabilitation robot. The proposed robotic system has a modularity which can be easily upgraded to a standing-type body weight support (BWS) mechanism. The detailed design and development of the robot are discussed in this paper along with its kinematic and dynamic analyses. The rehabilitation strategy is described for the field of application. The effectiveness and performance of the proposed mechanism are demonstrated with a clinical gait pattern using a proportional-integral-derivative (PID) control scheme on an in-house fabricated real-time prototype. The prototype experiments are conducted in view of validating the prototype for the therapeutic and gait training motions. © 2017 Elsevier Ltd

Computers and Electrical Engineering

Development and control of a new sitting-type lower limb rehabilitation robot

We numerically investigate the effects of restitution and specularity coefficients on the characteristics of dispersed gas-particle flows through a sudden expansion. The studies are carried out using an indigenous finite volume flow solver in a collocated framework with two-fluid model. Parametric studies are performed to gain insights into the differences in recirculation patterns that arise due to variations in restitution and specularity coefficients. The simulations show that particle-particle interactions, quantified by restitution coefficient (e) have a greater impact on recirculation characteristics than particle-wall interactions, which are quantified by specularity coefficient (ϕ). Studies reveal that the recirculation lengths tend to decrease as particle collisions become more elastic (as e tends to unity) while they increase, as the value of ϕ increases. However, the changes in recirculation length are very gradual and less pronounced when only particle-wall interactions are considered as compared to particle-particle interactions. From the range of parametric variations studied in this work, the maximum recirculation length has been found when the value of ϕ is maximum and that of e is minimum. © 2018 The Society of Powder Technology Japan.

Advanced Powder Technology

Effects of specularity and particle-particle restitution coefficients on the recirculation characteristics of dispersed gas-particle flows through a sudden expansion

Specularity coefficient (ϕ) and particle–particle restitution coefficient (e) are two important parameters governing the flow physics of dispersed gas-particle flows. In this work, a detailed numerical analysis is carried out to get an insight into the effects of these two parameters in the flow hydrodynamics of dispersed gas-particle flows through horizontal channels. Investigations have also been carried out to find the ϕ-e pair for which the phase velocities become an extremum. It has been found that at a particular value of e, both gas and particle velocities at the centerline of the channel increase with increase in the value of ϕ whereas near the wall, they tend to decrease. At a fixed non-zero value of ϕ both gas and particle velocities tend to increase with increase in the value of e. For ϕ equal to zero, which corresponds to free-slip boundary condition for particle velocity, there is no significant variations in gas and particle velocities with changes in e. Out of all combinations of values of ϕ and e investigated herein, it is found that both gas and particle velocities attain a maximum value when both the values of ϕ and e are maximum. © 2018 The Society of Powder Technology Japan

Effects of specularity and particle-particle restitution coefficients on the hydrodynamic behavior of dispersed gas-particle flows through horizontal channels

The present work elucidates the design and performance analysis of a three-dimensional microchannel for its capability in mixing two different liquids. Present studies are based on cross-T micromixer in which obstacles are introduced in the form of three-dimensional curved ribs. The mixing efficiency, quantified by the mixing index (M), has been calculated for the present micromixer. Results are also compared with those having straight ribs and found an enhancement of about 15% in mixing efficiency for obstacles with curved surfaces. However, this superior mixing has been achieved with a lower pressure drop, which provides an added advantage not traditionally realized for passive micromixers. Moreover, extensive parametric studies are also conducted to understand the effect of several geometrical parameters that can influence the mixing which include the height of obstacles (h), number of modules (Nm), angle of inclination (θ) and size of the obstacles and also the inlet Re. However, there has been seen to have certain optimum values of some of the parameters for achieving maximum degree of mixing. The use of the curved ribs is found to provide superior mixing for a wide range of Re. © 2018 Institution of Chemical Engineers

Chemical Engineering Research and Design

Design and performance of a three-dimensional micromixer with curved ribs

Wire Electrical Discharge Machining (WEDM) has established itself for manufacturing of precise and complex shape components for aerospace application due to the high quality requirement of aerospace components such as normal residual stress, no cracks, no recast layer, no porosity; still there is a need to optimize the control parameter settings and evaluate the performance characteristics of the WEDM process. The experiments have been conducted on Inconel 706 which is a newly-developed superalloy specially for aircraft application. A hybrid approach has been used to optimize the material removal rate (MRR) as well as surface roughness (SR) and significant control parameters have been identified using analysis of variance (ANOVA). Microstructure analysis revealed the formation of microglobules, melted debris and microholes on the machined surface, but no microcrack was detected due to the high toughness of the alloy. Energy dispersive X-ray spectroscopy (EDAX) has been carried out to study the metallurgical changes in the WED machined surface. The topography analysis of the curved surface revealed the best surface quality of the machined component at low pulse on time and high pulse off time. A thick recast layer of 39.6 µm was observed at high pulse on time and low servo voltage. Microhardness of the machined surface was changed up to a depth of 70 µm due to cyclic thermal loading during the WEDM process. © 2017, Springer Science+Business Media Dordrecht.

Silicon

Analysis and Optimization of WEDM Performance Characteristics of Inconel 706 for Aerospace Application

Productivity in machining of 17-4 PH stainless steel is adversely affected by the premature failure of tool and poor surface finish as a consequence of high cutting temperatures. Conventional cutting fluids not only create environmental and health problems but also fail to overcome the high cutting temperatures during machining. Cryogenic cooling is an environmentally clean cooling technology for attractive management of machining zone temperatures. The present study investigates the effect of cryogenic liquid nitrogen (LN2 at −196°C) on cutting temperatures, cutting forces (main cutting force, feed force), surface roughness, tool flank wear and chip morphology in turning of 17-4 PH stainless steel with AlTiN PVD-coated tungsten-coated carbide inserts and results were compared to wet machining. In overall, cryogenic machining reduces the cutting temperature, cutting forces, surface roughness and tool flank wear to a maximum of 73.4, 17.62, 44.29 and 55.55%, respectively. Improved chip breakability was found in cryogenic machining. © 2018 Taylor & Francis Group, LLC.

Machining Science and Technology

Comparative evaluations of machining performance during turning of 17-4 PH stainless steel under cryogenic and wet machining conditions

Grain size control of any engineering metal is very important in the hot upsetting process. Generally, the grain size directly controls the mechanical properties and performance of the material. Al-B4C composite finds extensive applications in nuclear industries, defense, and electronic industries. Therefore, the aim of this work is to study the dynamic recrystallization (DRX) behavior of Al-4 wt % B4C composite during the hot upsetting test. Experimental work was performed on sintered Al-4 wt % B4C preforms at various initial relative density (IRD) values of 80%, 85%, and 90%, and over the temperature range of 300-500 C and strain rates range of 0.1-0.3 s1. The DRXed grain size of Al-4 wt % B4C preforms for IRDes, and temperatures and strain rates were evaluated by using an optical microscope. The activation energy (Q) and Zener-Hollomon parameter of sintered Al-4 wt % B4C preforms were calculated for various deformation conditions and IRDes. The mathematical models of DRX were developed as a function of Zener-Hollomon parameter for various IRDes to predict the DRXed grain size. It was found that the DRXed grain size decreases with increasing Zener-Hollomon parameter. Verification tests were done between the measured and predicted DRXed grain size for various IRDes, and absolute and mean absolute error was found to be 9.92% and 8.58%, respectively. Copyright © 2018 by ASME.

Journal of Engineering Materials and Technology, Transactions of the ASME

Microstructure Modeling of Dynamically Recrystallized Grain Size of Sintered Al-4 wt % B4C Composite during Hot Upsetting

This article presents work carried out on a small, 4-stroke, SI engine, incorporated with an ultrasonic atomizer-based fueling system. A disc-type ultrasonic atomizer having good atomization characteristics was incorporated in the air intake path of a single cylinder, two-wheeler engine, replacing the conventional carburetor. This new fueling system was introduced with the aim of reducing the engine fuel consumption, while looking for a possible reduction in exhaust emissions. An electronic control mechanism was devised to change the atomization rate, in order to set the desired equivalence ratio for optimum engine operation. Test results indicate a significant improvement in fuel consumption and brake thermal efficiency, with a good control over the equivalence ratio. The system also allows engine operation at equivalence ratios as low as 0.5 and hence could be adopted for ultra-lean engines. This atomizer fueling system allows the use of closed loop lambda control which is required for meeting stringent automotive emission norms. Copyright © 2018 SAE International.

SAE International Journal of Engines

Fueling an Engine by Ultrasonic Atomization and Its Control

Engineering components can be subjected to normal and/or rotational fretting wear with contacts that are intermittently exposed to the atmosphere. Exposure to the environment may lead to the alteration at the contact due to the changing role of third body particles such as hard oxides which can result in abrasion. The abrasion due to hard oxide particles differs for the closed contact and intermittently opened contact. In the former scenario, the oxides are compacted into tribo-film, while in the latter case they remain loose, leading to bigger role of abrasion. Standard fretting test setup employed to estimate the fretting wear characteristic operates with a constant load such that the contact remains closed between the counter surfaces and does not simulate the opening and closing of the contacts as observed in certain applications. The forceful interruptions to the experiments to simulate open and close condition of the contact require considerable amount of time and effort. In this paper, an accelerated test procedure is proposed and investigated to capture the effect of intermittent opening of the contact without stopping the experiments. A test rig is designed to simulate the opening and closing conditions, and tests were performed with abrasive diamond-like particles. Friction and wear results are compared with those of intermittently contact opening conditions along with operating wear mechanisms. Scanning electron microscope analysis showed that the wear mechanism observed in the case of fretting with intermittent opening of contact is similar to that of fretting with diamond-like abrasives at the contact. © 2017, Springer Science+Business Media, LLC.