Department of Mechanical Engineering

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Three-wheeled vehicles are used both for public and private transport. A 6 degrees of freedom (DOF) mathematical model of a three wheeled vehicle is developed for predicting its ride behaviour. Simulations are carried out on this model and responses of the sprung and unsprung masses are found on different tracks like; i) Half circular bump; and ii) Trapezoidal. Sprung mass and unsprung mass accelerations are compared with experimental results and discrepancies between simulation and experiments are found. In order to bridge this gap, the paths traced by the tyre for the two different profiles are obtained as 2D layouts and differences between the analytical road input and the actual input traced by the tyre are found out. The simulated responses of the 6 DOF model are validated on the two different tracks using the paths traced by the tyres as input and good correlation is found between experimental results and simulations. Copyright © 2021 Inderscience Enterprises Ltd.

World University root node

International Journal of Vehicle Performance

Simulation and experiments on three-wheeled vehicle on different tracks

The paper aims to evaluate the performance of the Lagrange-based finite element method and the non-uniform rational B-splines isogeometric analysis of time-harmonic acoustic exterior scattering problems using high-order local absorbing boundary conditions, in particular based on the Karp’s and Wilcox’s far-field expansions. The analysis of accuracy and convergence of both methods is achieved by observing the effect of the order of the approximating polynomial, the number of degrees of freedom, the wave number, and the absorbing boundary conditions tuning parameters. It is concluded that, regardless of the polynomial order, IGA provides a higher accuracy per degree of freedom compared to the traditional Lagrange-based finite element method. © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

Fulltext

Mathematical and Computer Modelling of Dynamical Systems

Non Uniform Rational B-Splines and Lagrange approximations for time-harmonic acoustic scattering: accuracy and absorbing boundary conditions

This work presents a locking-free smoothed finite element method (S-FEM) for the simulation of soft matter modelled by the equations of quasi-incompressible hyperelasticity. The proposed method overcomes well-known issues of standard finite element methods (FEM) in the incompressible limit: the over-estimation of stiffness and sensitivity to severely distorted meshes. The concepts of cell-based, edge-based and node-based S-FEMs are extended in this paper to three-dimensions. Additionally, a cubic bubble function is utilized to improve accuracy and stability. For the bubble function, an additional displacement degree of freedom is added at the centroid of the element. Several numerical studies are performed demonstrating the stability and validity of the proposed approach. The obtained results are compared with standard FEM and with analytical solutions to show the effectiveness of the method. © This work is licensed under a Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

CMES - Computer Modeling in Engineering and Sciences

Bubble-enriched smoothed finite element methods for nearly-incompressible solids

In this work, we propose a framework for an adaptive contact analysis in deformable solids using the effective error indicator from the scaled boundary finite element method (SBFEM) with a quadtree decomposition. Further, the SBFEM is implemented with the commercial finite element software, Abaqus, to perform the contact analysis by employing the user element subroutine (UEL) feature. The SBFEM error indicator coupled with the quadtree decomposition is implemented in Matlab and allowed to interact with the Abaqus using .inp file for an adaptive refinement. The detailed implementation of the framework, input data format, and the UEL subroutine which is one of the key features of the proposed work are clearly explained. The effectiveness of the proposed framework is demonstrated by solving several contact problems of engineering significance. The developed SBFEM code can be downloaded from https://github.com/nsundar/sbfem. © 2020 Elsevier Masson SAS

European Journal of Mechanics, A/Solids

An adaptive scaled boundary finite element method for contact analysis

AA2024-T351 alloys are widely used in aerospace and automotive industries due to their high strength to weight ratio and ductility. The present paper investigates the machinability of AA2024-T351 material with uncoated carbide tools. Orthogonal machining experiments were performed at varying cutting speeds and feed rates with a constant depth of cut. Machinability studies were done using cutting forces, coefficient of friction and chip morphology. As the feed rate increased both cutting force and feed forces were found to be increased whereas the coefficient of friction decreased. Chip formation process was significantly influenced by the operating conditions. In addition, the shear angle and contact length were determined analytically. © 2021 Elsevier Ltd. All rights reserved.

Materials Today: Proceedings

Machinability studies of AA2024-T351 alloy with uncoated carbide tool

Metal powders are often made by gas atomization of liquid metal. During the process, liquid metal which flows from a melt delivery tube (MDT) is atomized by high speed gas discharging from a gas nozzle. In this work, the effect of the melt delivery tube position on atomization outcomes such as the yield, mass median diameter, and spread of the particle size distribution, is studied experimentally. A melt atomization setup (pilot-scale) is used to produce tin powder by gas-atomization. Three MDT positions, namely, intruded, extruded and flush with respect to the gas nozzle, are chosen for this study. Three pressure regimes (atmospheric, aspiration and pressurization) are established by varying the relative distance between the MDT and the gas nozzle exit for the three positions. Experimental investigations revealed that the intruded position produces powder with lower mean particle sizes and lower spread than the extruded configuration. The intruded position also gives a significantly higher yield compared to the extruded and flush positions at low gas flow rates, and hence appears to be the most suited for metal atomization using a free-fall configuration. © 2021 The Society of Powder Technology Japan

Advanced Powder Technology

Experimental investigation on the effect of melt delivery tube position on liquid metal atomization

Artificial intelligence (AI) and more specific subsets of AI such as machine learning (ML) and deep learning (DL) have become widely available in recent years. Open source software packages and languages have made it possible to implement complex AI based data analysis and modeling techniques on a wide range of applications. The application of these techniques can expedite existing models or reduce the amount of physical testing required. Two data sets were utilized to examine the effectiveness of multiple ML techniques to estimate experimental outcomes and to serve as a substitute for additional testing. To achieve this complex multi-variant regressions and neural networks were utilized to create estimating models. The first data sets of interest consist of a pool fire experiment that measured the flame spread rate as a function of initial fuel temperature for 8 different fuels, including Jet-A, JP-5, JP-8, HEFA-50, and FT-PK. The second data set consists of hot surface ignition data for 9 fuels including 4 alternative piston engine fuels for which properties were not available. When properties were not available multiple imputation by chained equations (MICE) was utilized to estimate fluid properties. 10 different ML techniques were implemented to analyze the data and R-squared values as high as 92% were achieved. © 2021, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

AIAA Scitech 2021 Forum

Artificial intelligence application in combustion modeling

This work was carried out to bring out the differences in drop weight low velocity impact behavior of two quasi-isotropic (QI) laminates. These laminates were made of AS4/914 carbon fiber reinforced plastic (CFRP). The layup sequence chosen was [0/45/-45/90]2Sand [0//90/45/-45]2S.Two types of impactors were employed for the impact tests. One is a hemispherical-end and the other is of a conical-end. Coupon level specimens were supported on all four sides during the impact test. The impact energy was calculated for the laminates and the difference, as a comparison, in each case is presented. It has been observed that the layup sequence has a significant effect on the impact resistance of the laminates under hemispherical impactor. In the case of conical impactor, both the laminates were perforated while absorbing similar energy levels. © 2021 Elsevier Ltd. All rights reserved.

An experimental study on impact behavior of quasi-isotropic CFRP laminates

The National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute. © 2021, The Author(s).

Solar Physics

Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)

Void fraction distributions in helical coils of various diameters are computationally estimated with inlet mass flux, degree of subcooling and wall superheat as inputs. The heat flux wall partitioning method in wall boiling model is used for numerical simulations of subcooled forced convection boiling. The effect of input parameters on axial variation of void fraction is studied. The void fraction in axial direction starts increasing under the presence of subcooled liquid for a tube of large coil diameter. In comparison, the increase in void fraction in axial direction for a small coil diameter tube is less but the rise in liquid temperature is larger. The reasons of the deviations are ascertained by examining the phase distribution contours. The phase distribution is found to be different at constant vapor fraction values for varying mass flux and coil diameters. Empirical relations are given for estimating void fraction based on drift flux model. From the computational results, a correlation for estimating vapor quality for helical coil under varying conditions is proposed. A correction factor that accounts for the curvature effect is incorporated for evaluating distribution parameter and drift velocity. © 2021 Elsevier Ltd