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

This study investigates the forming limits of cryo-rolled Ultrafine Grained (UFG) aluminium sheet for loading conditions relevant to sheet metal forming. It is shown that a combination of nano-particle strengthening with an annealing heat treatment enables the production of cryo-rolled UFG aluminium with up to 12 % higher material strength and 20 % higher formability compared with the unreinforced UFG condition. While nano-particle strengthening does not significantly influence the tensile ductility, it reduces the bend fracture limit by over 50 % due to an increased dislocation density and a diffuse sub-grain structure. The level of the forming limit curves (FLD) of all UFG materials was up to 5 times higher than their uniform tensile elongation and hardening index; this is attributed to a high strain-rate sensitivity, which increased with annealing heat treatment. In roll forming, the UFG aluminium showed similar material behaviour and shape defects as observed for conventional sheet metals in previous studies. However, given the reduced bend fracture limits observed with nano-particle addition, this study suggests that roll forming may not be a suitable manufacturing solution for nano-particle strengthened UFG sheet metal. © 2021 Elsevier B.V.

World University root node

Journal of Materials Processing Technology

Understanding material behaviour of ultrafine-grained aluminium nano-composite sheets with emphasis on stretch and bending deformation

A numerical study is performed to observe the effect of lateral wall proximity on the thermocapillary migration of a droplet. Three-dimensional simulations of the droplet with lateral wall proximity show that the droplet is pulled toward the wall for larger temperature gradients in the ambient and pushed away from the wall at smaller temperature gradients. Parametric studies carried out for migration of a droplet in the vicinity of a wall in a two-dimensional domain show that the droplet behavior is similar to the three-dimensional domain. At different temperature gradients, the final lateral distance of the droplet from the wall does not vary monotonically. The interaction of the temperature field at the leading and trailing ends of the migrating droplet with the wall explains the observed behavior. An extensive parametric study is performed to understand the effect of the Marangoni number, Reynolds number, and property ratios on droplet migration near the wall. Variation in each parameter influences the evolution of temperature both within the droplet and in the ambient fluid. The asymmetric interfacial temperature variation due to the asymmetric evolution of internal circulation within the droplet is correlated with the lateral migration of the droplet. The observations made in the present work reveal physical mechanisms that influence the thermocapillary migration behavior of a droplet near a wall. © 2021 Author(s).

Physics of Fluids

Effect of wall proximity on the lateral thermocapillary migration of droplet rising in a quiescent liquid

Experimental and numerical study of single and double-wall square tube under axial compression was carried out at a displacement rate of 100 mm/min. Two configurations of double-wall tube, viz., parallel and diamond were explored. During axial compression of double-wall tubes, crumpling takes place either at same end or at opposite ends for the two tubes. Deformation at the same end absorbs 3–5% more energy than opposite end crushing. For the same type of crumpling, diamond arrangement absorbs 5–8% more energy than parallel configuration. Two different lengths of unequal tubes for parallel and diamond arrangement were examined. It was observed that unequal length tubes improve crashworthiness characteristics. © 2021, Springer Nature Singapore Pte Ltd.

Lecture Notes in Mechanical Engineering

Energy Absorption Characteristics of Single and Double-Walled Square Tubes Subjected to Axial Crushing

We propose an outlier detection-based statistical approach to identify and locate a defect in composite plates using far fewer number of sensing points compared to conventional imaging techniques. The key steps involved in this computationally inexpensive approach are the random sparse selection of the sensing points through Poisson disk sampling, followed by a two-step outlier detection process based on thresholding and computation of median absolute deviation. The robustness of the proposed technique is explored through extensive simulations involving different defect sizes, random locations on flat plate structures, and various values of signal to noise ratio (SNR). We experimentally demonstrate the feasibility of detection of delamination, whose size is comparable to the ultrasonic wavelength with probability of detection (PoD) better than 90% using <1% of the total number of samples required for conventional imaging, even under conditions wherein the SNR is as low as 5 dB. © 2021 John Wiley & Sons, Ltd.

Department of Electrical Engineering

Structural Control and Health Monitoring

Outlier analysis for defect detection using sparse sampling in guided wave structural health monitoring

The effect of injection strategies of diesel on combustion, performance and emissions of a single cylinder, light duty, common rail, and methanol-diesel dual fuel engine were investigated. Methanol was port injected and experiments were carried out at a speed of 1500 rpm, brake mean effective pressure of 4.3 bar (75% rated load) and methanol to diesel energy share of about 50%. The directly injected diesel was first introduced as a single pulse, then as two pulses – Pilot and main injection and finally as three pulses – pilot, main and post injection. Single pulse injection of diesel resulted in delayed combustion which lowered the combustion stability and brake thermal efficiency. With the pilot main injection strategy combustion rate, peak combustion temperature and combustion stability were enhanced due to increased charge reactivity. Further, hydrocarbon and carbon monoxide emissions were reduced due to the complete combustion of methanol. The pilot with main and post injection strategy could reduce the rate of pressure rise, Nitric oxide levels and average in-cylinder temperature as compared to the pilot main injection mode. Through proper selection of the quantity and timing of the post injected diesel (1.25 mg/cycle and 5°crank angle after top dead center) which is employed along with pilot and main injections, a significant reduction in Hydrocarbon, Carbon mono-oxide, Nitric oxide and Soot emissions with good combustion stability and low ringing index could be achieved in the dual fuel mode. © 2020 Elsevier Ltd

Fuel

Diesel injection strategies for reducing emissions and enhancing the performance of a methanol based dual fuel stationary engine

Cerium-promoted silica supported copper chromite catalyst was synthesized from acid hydrolysis of sodium silicate by sol–gel method. The catalyst was characterized by Brunauer–Emmett–Teller (BET) method, field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), NH3-temperature programmed desorption (NH3-TPD) and pyridine adsorbed Fourier transform infrared spectroscopy (Py-FTIR). Among cerium doped catalysts, 5 wt% of Ce promoted copper chromite supported by 40 wt% of silica (SiCuCr40–Ce5) shows the largest BET surface area. XRD analysis of the reduced form of the catalyst shows both CeO2/Ce2O3 redox system and CuO/Cu2O/Cu redox system. Py-Fourier shows the maximum number of Lewis acid sites for SiCuCr40–Ce5 than others. The highest acetol selectivity with analytical reagent (AR) grade glycerol conversion is observed for SiCuCr40–Ce5 at 200 °C for 3 h in a batch reactor at atmospheric pressure. Cerium promotion lowers the reaction temperature with enhanced glycerol conversion and increased acetol selectivity. Though the above catalyst shows higher conversion for laboratory reagent (LR) grade glycerol but it reduces acetol selectivity. The addition of glucose into the LR grade glycerol further reduces glycerol conversion and decreases the acetol selectivity to zero. This may be due to the presence of iron as impurity in LR grade glycerol. XRD analysis of spent catalyst shows the absence of redox catalytic system and the pore volume reduces identified by BET analysis. Raman analysis of the spent catalyst shows graphite-like carbon deposition in the spent catalyst. © 2021 Chinese Society of Rare Earths

Journal of Rare Earths

Role of cerium as a promoter and process optimization studies for dehydration of glycerol to acetol over copper chromite catalyst

Abstract: The southern peninsular India is characterized by unique climatology with rainfall processes throughout the year from land–ocean contrasts. In addition, the complex terrain induces localized effects causing huge spatial and temporal variability in the observed precipitation. This study aims at evaluating the sensitivity of the high-resolution Weather Research and Forecasting (WRF) model (4 km) to multi-physics parameterizations, 3D variational data assimilation, and domain configuration, in the study domain covering southern peninsular India. Furthermore, the study focusses on the formulation of an ensemble method to improve the simulation of precipitation across seasons. A total of 120 experiments were set up across four crucial rainfall events, of varying spatial extent and duration, dominated by different rainfall generation mechanisms. The assessment of the experiments shows that the model’s cumulus and microphysics schemes have the highest impact on the location, intensity, and spread of the simulated 4-day long Quantitative Precipitation Forecasts (QPFs). Applying cumulus schemes at all domains represented the variability in the QPFs, across space and time, for the precipitation events dominated by convective activity. The cases without cumulus schemes at the convective scale domain (4 km), captured the higher intensity rains during organized cyclonic circulations in the north-east monsoon period. Hence, a 10-member multi-physics ensemble approach including members with and without cumulus parameterization at the fine resolution domain was adopted. The preliminary results demonstrate that the mean from the suggested ensemble approach (n-MPP) performed well in capturing the dynamics of QPFs across the rainfall events, as opposed to a single-member deterministic simulation and mean from larger member conventional multi-physics ensemble approach (c-MPP) without cumulus parameterization at the convective scale. The rank histogram, delta semi-variance plots, and outlier statistics at various lead times clearly showed that the suggested n-MPP was able to capture the high-intensity rainfall, increasing the spread of precipitation forecasts and consequently reducing the occurrence of outliers. Highlights: Evaluated the sensitivity of a high-resolution Numerical Weather Prediction (NWP) model (4 km) with 120 experiments in generating short-term (4-day long) quantitative precipitation forecasts (QPFs).The cumulus and microphysics schemes have the highest impact on the location, intensity, and spread of the simulated rainfall across events dominated by different rainfall generation mechanisms.A 10-member multi-physics ensemble approach including members with and without cumulus parameterization at the fine resolution domain was able to capture the high-intensity rainfall, increasing the spread of precipitation forecasts and consequently reducing the occurrence of outliers. © 2021, Indian Academy of Sciences.

Department Of Civil Engineering

Journal of Earth System Science

A multi-physics ensemble approach for short-term precipitation forecasts at convective permitting scales based on sensitivity experiments over southern parts of peninsular India

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.

International Journal of Vehicle Performance

Simulation and experiments on three-wheeled vehicle on different tracks

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