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 aluminum alloy AA6061-4wt.% boron carbide (B4C) particulate metal matrix composites were fabricated by the stir casting method. The die-sinker electric discharge machining was performed to make the rectangular mini channels on these composites. The full factorial experimental design that consists of three input conditions, the current (I), discharge duration (T-on), and discharge idle time (T-off) at three levels each (33 = 27 total runs), was used for experimentation. The volume, V, the taper, θ (along with the depth), the lateral overcut (along the width), and the difference in depth, Δd (between total depth and depth up to the tapered profile) at entrance and exit cross-sectional profiles of the channel were considered as output responses. The θ, lateral overcut, and Δd were calculated from the entrance and exit profiles which were obtained by extracting the data points of each channel with the help of an optical profile projector. The computer-aided geometric model was developed to estimate the volume. A set of optimum electric discharge machining parameter levels were identified for maximum V and a minimum of θ, lateral overcut, and Δd. Analysis of variance was performed to identify the significant parameter and the contribution toward output responses. Results showed that the volume was found to be maximum at higher I (8 A) and lower T-On (25 µs) conditions. The taper was found to decrease with the increase in current but both lateral overcut and Δd increased. Both I and T-On are found to be the significant parameters affecting both V and Δd, whereas current is for θ and lateral overcut. In some cases, it was observed that there is a considerable difference in the θ and the lateral overcut values in the entrance and exit portions for the same channel. It is because of the randomly dispersed B4C particles which alter the material removal mechanism. © The Author(s) 2020.

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Measurement and Control (United Kingdom)

A study on geometrical features of electric discharge machined channels on AA6061-4%B4C composites

Discontinuous Galerkin (DG) methods have become mainstays in the accurate solution of hyperbolic systems, which suggests that they should also be important for computational electrodynamics (CED). Typically DG schemes are coupled with Runge-Kutta timestepping, resulting in RKDG schemes, which are also sometimes called DGTD schemes in the CED community. However, Maxwell's equations, which are solved in CED codes, have global mimetic constraints. In Balsara and Käppeli [von Neumann Stability Analysis of Globally Constraint-Preserving DGTD and PNPM Schemes for the Maxwell Equations using Multidimensional Riemann Solvers, Journal of Computational Physics, 376 (2019) 1108-1137] the authors presented globally constraint-preserving DGTD schemes for CED. The resulting schemes had excellent low dissipation and low dispersion properties. Their one deficiency was that the maximal permissible CFL of DGTD schemes decreased with increasing order of accuracy. The goal of this paper is to show how this deficiency is overcome. Because CED entails the propagation of electromagnetic waves, we would also like to obtain DG schemes for CED that minimize dissipation and dispersion errors even more than the prior generation of DGTD schemes. Two recent advances make this possible. The first advance, which has been reported elsewhere, is the development of a multidimensional Generalized Riemann Problem (GRP) solver. The second advance relates to the use of Two Derivative Runge Kutta (TDRK) timestepping. This timestepping uses not just the solution of the multidimensional Riemann problem, it also uses the solution of the multidimensional GRP. When these two advances are melded together, we arrive at DG(TD)2 schemes for CED, where the first “TD” stands for time-derivative and the second “TD” stands for the TDRK timestepping. The first goal of this paper is to show how DG(TD)2 schemes for CED can be formulated with the help of the multidimensional GRP and TDRK timestepping. The second goal of this paper is to utilize the free parameters in TDRK timestepping to arrive at DG(TD)2 schemes for CED that offer a uniformly large CFL with increasing order of accuracy while minimizing the dissipation and dispersion errors to exceptionally low values. The third goal of this paper is to document a von Neumann stability analysis of DG(TD)2 schemes so that their dissipation and dispersion properties can be quantified and studied in detail. At second order we find a DG(TD)2 scheme with CFL of 0.25 and improved dissipation and dispersion properties; for a second order scheme. At third order we present a novel DG(TD)2 scheme with CFL of 0.2571 and improved dissipation and dispersion properties; for a third order scheme. At fourth order we find a DG(TD)2 scheme with CFL of 0.2322 and improved dissipation and dispersion properties. As an extra benefit, the resulting DG(TD)2 schemes for CED require fewer synchronization steps on parallel supercomputers than comparable DGTD schemes for CED. We also document some test problems to show that the methods achieve their design accuracy. © 2020 Elsevier Inc.

Journal of Computational Physics

Optimal, globally constraint-preserving, DG(TD)2 schemes for computational electrodynamics based on two-derivative Runge-Kutta timestepping and multidimensional generalized Riemann problem solvers – A von Neumann stability analysis

The present work describes the evolution of microstructure and enhancement of mechanical properties of friction stir welded AA6061/SiC/FA Hybrid AMCs (HAMCs). Various joints were produced using different traverse speed from 30 mm/min to 80 mm/min. Microstructural analysis was carried out using Optical microscopy and scanning electron microscopy. Mechanical characteristics such as ultimate tensile strength (UTS) and microhardness (Hv) were studied. Sound quality joints were obtained by FSW without any defects. Results showed that the microstructure zones are divided in to nugget zone, thermomechanically affected zone, heat affected zone and base material zone. Uniform and fine grain formation took place at traverse speed of 60 mm/min indicating sufficient amount of heat input at this speed. Accordingly maximum joint efficiency of 90% is obtained at this traverse speed. © 2020 Elsevier Ltd. All rights reserved.

Materials Today: Proceedings

Effect of traverse speed on joint characteristics of FSWed HAMCs

Cryogenic diamond burnishing is an impactful method to enhance the functional performance of the product. In this article, an experimental study on the diamond burnishing of 17-4 precipitation hardenable stainless steel in a cryogenic cooling condition has been presented. This material has excellent corrosion resistance, high strength and enormous applications in the manufacturing industries. The control variables were namely burnishing force, burnishing feed and burnishing force have been studied and modeled for the output responses explicitly surface hardness and surface roughness. The influence of control variables on performance features has been analyzed using response surface graphs. The significant influence of burnishing conditions on the output responses was established by analysis of variance. Desirability function approach has been employed to optimize the multi-performance characteristics. At the corresponding highest desirability, the optimal process parameter combination was found to be burnishing feed = 0.053 mm/rev, burnishing speed = 31.29 m/min and burnishing force = 200 N which yields a minimum surface roughness = 0.199 µm and maximum surface hardness = 397.48 HV. The maximum percentage of error among the predicted and experimental results was found to be 10% and 2%, respectively, for surface roughness and surface hardness. The investigational findings were observed to be in agreement with the predicted value with permissible deviation. © 2020, King Fahd University of Petroleum & Minerals.

Arabian Journal for Science and Engineering

Application of Desirability Approach to Optimize the Control Factors in Cryogenic Diamond Burnishing

The rate of heat generation and plastic deformation of materials should be precisely controlled in order to get a strong and sound weld joint during dissimilar friction stir lap welding (FSLW) of aluminium and steel. The effect interfacial microstructure at the weld joint interface on mechanical properties is elucidated in the present investigation with the help of detailed microstructure evaluation in FSLW of AA6061 and mild steel (MS). The results indicated a substantial variation in interfacial structure from formation of a bi-metallic straight interface, intercalated structure to mechanically mixed zone (MMZ) with the increase in tool rotation speed from 300 rpm to 1700 rpm. In addition, significant differences in the microstructure evolution mechanisms were noticed from the AA6061 side to MS side through the interfacial microstructure. The variation in interfacial structure and corresponding change in the fracture location predominantly affected the mechanical properties of the joints at different tool rotation speeds. The fracture locations in MMZ and intercalated structure showed the highest and lowest lap shear strengths, respectively. © 2020 Elsevier Inc.

Materials Characterization

Elucidation of interfacial microstructure and properties in friction stir lap welding of aluminium alloy and mild steel

Girth friction welding is a novel technique to join co-axial linepipes with an external ring (girth) in solid state and without melting of materials. The ring or the girth is rotated between two pipes under an axial force resulting in frictional heat generation and plastic deformation along the pipe-girth interfaces. The rotation of the girth is stopped after a preset displacement of the pipes while the force is maintained to consolidate the deformed material and form the joint along the girth-pipe interfaces. Since the girth is only rotated and the pipeline sections remain stationary, the process simplifies the in situ assembly operations and enables the joining of complex configurations. As the melting of pipes and girth is avoided, the formation of harmful intermetallic compounds and deterioration of toughness in the heat affected zone are minimized. A comprehensive numerical model is reported in the present work to analyse the influence of key process variables on the rate of heat generation, resulting temperature field and thermal cycles, and the nature of material flow along the pipe-girth interfaces in girth friction welding of duplex stainless steel pipes. The computed results of thermal cycles and joint shapes are validated with the corresponding experimentally measured results. The results showed a favorable balance of the ferrite and austenite phases, and very little presence of the harmful sigma phases in the recrystallized weld-zone, which is difficult in fusion welding processes of similar materials. © 2020

Journal of Manufacturing Processes

An investigation on girth friction welding of duplex stainless steel pipes

Additive manufacturing (AM) is a rapidly developing technology in biomedical, aerospace and automobile industries. However, adoption of this technology on a larger production scale remains limited. This is primarily due to the drawbacks of present AM processes associated with achievable dimensional accuracy and surface integrity of the fabricated component. The average surface roughness (Ra) of the component ranges from 3 μm to 10 μm with stair-stepping effects, balling on surfaces resulting in poor dimensional accuracy. Therefore, post-processing methods like abrasive flow finishing, laser polishing, chemical polishing and traditional finish machining is often used to meet the desired surface integrity and accuracy. However, some of these post-processing methods are quite expensive leading to overall increase in the production cost of the component. On the other hand, methods like etching and sand blasting are time consuming and not suitable for component with intricate geometries. In this paper, low energy wire electrical discharge polishing (WEDP) has been employed to achieve the desired surface integrity and finish. Initially, experiments were conducted to analyse the finishing achieved on planer additive manufactured stainless steel (SS316L) specimens. A significant reduction in roughness of maximum 80 % was obtained at various settings for pulse on time and servo voltage. In addition, SEM and EDS analysis were also carried out to study the microstructure and composition after WEDP. From the study, it was found that the WEDP process is a promising method to finish metallic AMed components. © 2020 The Author(s).

Procedia CIRP

Wire electrical discharge polishing of additive manufactured metallic components

Spark Erosion Machining: MEMS to Aerospace

Spark Erosion Based Hybrid Processes

This project aims to increase the wear resistance of aluminium alloy 5052 (AA5052), which has very good corrosion resistance, ductility, excellent thermal and electrical conductivity. Composites were fabricated using AA5052 reinforced with silicon carbide 3% and alumina 3 & 4% by weight of the matrix, melting temperature 700 & 750 °C and stirring time 3 & 5 min. Maximum micro-hardness and tensile Strength were achieved for the combination of silicon carbide—3%, alumina—4%, melting temperature—750 °C and stirring time—3 min. Composite fabricated for the above said condition is used for wear analysis. The design of experiments was planned in full factorial method with load, speed, time and track diameter as input factors and wear as the response or output factor. The test was performed in pin-on-disc tribometer as per design of experiments. The process parameter combination of 2 kg load, 500 rpm speed, 5 min time and 70 cm track diameter was found to be the optimum condition for minimum wear of the fabricated hybrid composite. Wear resistance was increased by 51%. Speed has the maximum influence with 45.52% contribution, whereas time has the least influence with 7.02% contribution. © 2020, Springer Nature Singapore Pte Ltd.

Lecture Notes in Mechanical Engineering

Investigation on Wear Behaviour of AA5052/SiC/Al2O3 Hybrid Composite Fabricated Using Stir Casting Process

Automation of earth moving machineries is a widely studied problem. This paper focusses on one of the main challenges in automation of the earth moving industry, estimation of loading torque acting on the machinery. Loading torque acting on the excavation machinery is a very significant aspect in terms of both machine and operator safety. In this study, a disturbance observer-assisted control system for the estimation of loading torque acting on a robotic backhoe during excavation process is presented. The proposed observer does not use any acceleration measurements, rather, is proposed as a function of joint velocity. Numerical simulations are performed to demonstrate the effectiveness of the proposed control scheme in tracking the reaction torques for a given dig cycle. Co-simulation experiments demonstrate robust performance and accurate tracking of the proposed control in both disturbance torque and position tracking. Further, the performance and sensitivity of the proposed control are also analyzed through the help of performance error quantifiers, the root-mean-square (RMS) values of the position and disturbance tracking errors. © 2019. The Author(s).