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

Miniaturization of products has become a major technological challenge in production industries. Material removal in microscopic and sub-microscopic level has become a demand for producing such products. Electro-Chemical Discharge Machining (ECDM) is one of the hybrid non-conventional machining processes to machine materials that are electrically conductive and non-conductive at a micro-level utilizing the principles of Electro Discharge Machining (EDM) and Electro-Chemical Machining (ECM). The most common nonconductive materials machined with this process are various types of glasses, ceramics, composites, etc. In the current paper, a Finite Element Model (FEM) of the ECDM process is carried out in the discharge regime (less than 300 μm) with pulsed DC in a 2D domain to characterize the Material Removal Rate (MRR) as a process output response in borosilcate glass machining. From the model and experiements the value of MRR is found to be 0.373 mg/ min and 0.414 mg/min. It can be considered that there is almost negligible difference in MRR between experimental and model values with 9.9% error variation. Hence the results are validated with experimentation, and there is a good agreement observed between the results. © 2021, Springer Nature B.V.

World University root node

Silicon

Model Prediction and Experimental Study of Material Removal Rate in Micro ECDM Process on Borosilicate Glass

Micro-Electro Chemical Discharge Machining (μ-ECDM) has proved its potential to generate features, structures, and textures on various engineering materials, particularly glass. Researchers have recently explored the process of generating conducting nanoparticles but still completely lacks non-conducting nanoparticles like that of glass. However, glass nanoparticles find wide applications as nanofillers, supplementary cementitious material, heat-insulating additives, density reducing agent, catalyst support, etc. The novelty of the present work lies in the generation of borosilicate glass nanoparticles by an in-house developed μ-ECDM setup with a DC motor actuated gear reduction tool feeding mechanism. Experimentation was carried out based on the face-centered central composite design of response surface methodology (FC-CCD-RSM) to obtain an individual, combined effect of parameters, their significance, and contributions by analysis of variance. The contribution was 73.77% of voltage (V) followed by 14.76% concentration (C), and 6.05% duty factor (DF). Parametric combination of 40 V, 20 wt% C, 40% DF resulted in a minimum average diameter (AD) of 46.51 nm as the response. An empirical model is developed to predict the desired parametric combination responses with a 5.63% average error. © 2021, Springer Nature B.V.

Generation and Characterization of Borosilicate Glass Nanoparticles using in-House Developed μ-ECDM Setup

The objective of the present investigation is to develop and study the thermal and rheological properties of the in-house developed flexible abrasive media. It is a mixer of viscoelastic polymer and plasticizer mixed with micro-abrasive particles, used for removing debris and irregularities present on internal and external complex surfaces used in the aerospace, automotive and medical industries. This paper presents, morphology of the developed abrasive media is captured using the Scanning Electron Microscope (SEM), thermal properties of the abrasive media are studied using Thermo Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) analysis along with tensile properties of the abrasive media ascertained using the universal testing machine. The rheological properties of the media play a major role in media flow over the intricate shapes and removing the material from the surface. To understand the media behavior, further rheological properties such as viscosity, shear stress, storage modulus, loss modulus, loss tangent, and complex viscosity are ascertained with varying shear rate and frequency at different temperature using rheometer. The TGA and DSC results shows abrasive media has good thermal stability and possibility of using the media for finishing process under lower temperature <100 °C. Rheological studies shows the shear thinning behaviour of the media and elastic solid behavior (G′ > G′′) at different temperatures which is suitable for finishing the complex internal and the external features efficiently and effectively. The developed abrasive media is used to finish the hydraulic components which are difficult to access with conventional tools and the results of finishing process are presented. © IMechE 2021.

Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering

Temperature-dependent rheological properties of viscoelastic polymer based flexible abrasive media for finishing process

Age-related hearing loss (ARHL) is a common condition in humans marking the gradual decrease in hearing with age. Perturbations in the tip-link protein cadherin-23 that absorbs the mechanical tension from sound and maintains the integrity of hearing is associated with ARHL. Here, in search of molecular origins for ARHL, we dissect the conformational behavior of cadherin-23 along with the mutant S47P that progresses the hearing loss drastically. Using an array of experimental and computational approaches, we highlight a lower thermodynamic stability, significant weakening in the hydrogen-bond network and inter-residue correlations among β-strands, due to the S47P mutation. The loss in correlated motions translates to not only a remarkable two orders of magnitude slower folding in the mutant but also to a proportionately complex unfolding mechanism. We thus propose that loss in correlated motions within cadherin-23 with aging may trigger ARHL, a molecular feature that likely holds true for other disease-mutations in β-strand-rich proteins. © 2021 The Author(s).

Department Of Biotechnology

Fulltext

Biochemical Journal

Weakening of interaction networks with aging in tip-link protein induces hearing loss

Solar energy is one of the emerging technologies and the use of concentrating power technology is increasing in solar power plants. Parabolic trough collector is a concentrating solar power technology that is situated in the open terrain and subjected to wind loads. The structural stability of these devices under such loads determines the ability to accurately concentrate the rays at the absorber tube, which affects the overall optical and thermal efficiencies. A detailed numerical analysis is carried out at different wind loads and design conditions. It is observed that for a change in velocity from 5 m/s to 25 m/s, slope deviations increase from 1.21 mrad to 3.11 mrad at the surface of the reflector exceeding the shape quality of the mirror panels. Higher yaw angles and pitch angles of 60° and 120° are observed to be decisive in the design of collectors. Roof-mounted collectors experience a 40% higher drag force than ground-mounted collectors at a 0° pitch angle. For the Aluminium trough, the slope deviation at the surface of the reflector is higher by 4.62% than glass. The study will be helpful for engineers and scientists in the design of the parabolic trough collectors. © 2021 Elsevier Ltd

Department Of Civil Engineering

Renewable Energy

Wind load and structural analysis for standalone solar parabolic trough collector

In this work, a non-imaging low concentrating 2.5X Compound Parabolic Concentrator (CPC) truncated to 1.7X has been explored. CPCs inherently form non-uniform distribution of flux on the PVT module which has been mitigated by the integration of optimized homogenizer referred to as Elongated CPC (ECPC). The study involves detailed optical, thermal, and electrical modeling of the ECPC based Low Concentrating Photovoltaic Thermal (LCPVT) system. Optical simulations provide insight into the flux distribution on the PVT panel surface, which is further coupled with a thermal and electrical model for precise prediction of the performance of the system. These models are validated experimentally with a 315 Wp solar panel integrated with ECPC based LCPVT system. Performance evaluation of the system has shown peak thermal efficiency of ∼40% at ΔT of 16 °C, peak electrical efficiency of 12%, and an overall peak exergy efficiency of 15% at 38 Liters per hour (LPH) flow rate. A comparison of outlet water temperature results obtained from the numerical model and experiments has shown an excellent match with a relative error of 4%. Results also show that the increase in mass flow rate from 22 LPH to 38 LPH improves the electrical efficiency by 3% however a drop in ΔT of 2–3 °C is observed. © 2020 Elsevier Ltd

Numerical modeling and performance assessment of elongated compound parabolic concentrator based LCPVT system

Isogeometric Analysis introduced by Hughes et al.[1] has gained importance in the recent times due to its ability to capture accurate solutions and exact geometry representations. In the present study, IGA-Collocation is extended for oscillatory problems in acoustics. Numerical solutions of oscillatory problems often suffer from numerical dispersion errors, which demands use of minimum of ten nodes per wavelength or higher order bases. But employing higher order bases in IGA based on Galerkin approach (IGA-G) is computationally expensive. To overcome this issue, we employed IGA based on Collocation (IGA-C)[2] which is often regarded as a rank sufficient one-point quadrature scheme and has the potential to reduce the computational cost. In the present study, IGA-C with higher order bases is employed for solving rectangular waveguide and oscillating cylinder problems with different wave numbers. The performance of IGA-C is compared with the IGA-G in terms of efficacy and computational time. From the results, the potential of IGA-C is clearly observed in solving wave problems. © 2021, Springer Nature Singapore Pte Ltd.

Lecture Notes in Mechanical Engineering

Isogeometric Collocation for Time-Harmonic Waves in Acoustic Problems

For high precision laser surgery, noninvasive tool for prediction of laser ablation profile beforehand is imperative. The present study proposed a method to utilize nondestructive FTIR and Raman probes for predicting laser ablation profile overcoming the challenge of heterogeneity on individual target tissue. By ascribing the chemical heterogeneity of teeth drive their differential machining capability, the study establishes a correlation between the chemical composition and their ablation parameters (ω0,Deff and Fth). The chemical composition of teeth was obtained by noninvasive tools (FTIR and Raman) in terms of absorption peak intensity. To further correlate with key laser ablation parameters, the laser irradiation study was carried out using 800 nm, 100 fs, Ti:Sapphire laser. The surface morphology of irradiated sample was measured by optical profiler. A strong correlation was observed between laser ablation parameters and peak intensity of phosphate group for both FTIR and Raman spectroscopy. The concentration of phosphate group shows a positive relationship to ablation threshold fluence, while the effective Gaussian beam radius and effective energy penetration depth show negative correlation. Both nondestructive probes show good linearity which enable us to extrapolate the key laser ablation parameters for predicting laser ablation profile on random dentin and enamel samples. The ablation profiles predicted based on both FTIR and Raman are well-matched in dentin, whereas it shows a slight deviation in enamel. The predicted profiles are consistent with experimental results at lower power whereas it shows a slight deviation at higher power due to screening effect. Thus, FTIR and Raman probes can be used to predict laser ablation profile nondestructively in real-time and obviate the need for trial runs. Furthermore, the present study has predicted the laser ablation rate and ablation efficiency for performing laser surgery in optimum laser processing conditions irrespective of teeth heterogeneity. © 2020 Elsevier Ltd

Journal of the Mechanical Behavior of Biomedical Materials

FTIR and Raman as a noninvasive probe for predicting the femtosecond laser ablation profile on heterogeneous human teeth

Propane, n-butane, and their mixtures are commonly used as fuels for various applications. Reliable numerical simulations of flames involving these fuels are most essential to study their efficient use in domestic and industrial burners. Such simulations require a suitable reaction mechanism containing the necessary kinetics to predict key combustion characteristics in flames accurately. However, the use of detailed kinetic mechanisms for these computations is formidable in multidimensional simulations, owing to their large sizes. To address this, in this work, a compact mechanism (45 species, 392 reactions) for propane, n-butane, and their mixtures, suitable for multidimensional simulations is derived and comprehensively validated against available experimental data in flames. The main oxidation pathways retained in this compact model are showcased. One-dimensional (1D) computations of premixed and nonpremixed flames are carried out using FlameMaster and Chemkin-Pro. Two-dimensional (2D) calculations are performed within ANSYS-FLUENT. Here, multicomponent diffusion, thermal diffusion, and radiation submodels are used. Laminar flame speeds, extinction strain rates, and amounts of major species in premixed flat flames are validated using 1D computations. Temperature and major species in propane and n-butane jet diffusion flames are verified in 2D simulations. Further, 2D computations using the compact mechanism also predict the laminar burning velocity of premixed flames of n-butane and propane mixtures established over a Bunsen burner. The ability of the compact mechanism to predict desired targets in premixed and nonpremixed flames is analyzed from a kinetic basis. Validation using 2D simulations demonstrates the usability of the compact mechanism in multidimensional computations. © 2021 Wiley Periodicals LLC

International Journal of Chemical Kinetics

Reduced mechanism for flames of propane, n-butane, and their mixtures for application to burners: Development and validation

Tropical cyclones (TCs) that make landfall over India’s east coast are responsible for significant loss of life along affected coastlines. TCs forming over the Bay of Bengal (BoB) region in October, November, and December have, in the past, intensified significantly at the time of landfall. The effects of climate change on TCs of different strengths and their characteristics such as track, intensity, precipitation, and convective available potential energy over the BoB region have not been well studied. This study explores the effects of climate change on two TCs of very severe cyclonic storm (VSCS) category (TC Vardah and TC Madi), and two other TCs of extremely severe cyclonic storm (ESCS) category (TC Hudhud and TC Phailin) formed over BoB, both in the short term (2035) and long term (2075). The high-resolution Weather Research and Forecasting (WRF) model is used to simulate the TCs under current and future climate conditions. The simulated TC track and intensity in the current climate agree well with the observations. To explore the impacts of climate change on TCs, the mean climate change signal, computed from future projections of the Community Climate System Model (CCSM4) in different representative concentration pathway (RCP) scenarios, is added to current climate conditions by using the pseudo global warming method. Results show a climate change-related reduction in TC translation speed, deepening of TC core, increased maximum surface wind, and increased precipitation over land in future RCP (4.5, 6.0, and 8.5) scenarios. The TCs in future RCP scenarios are seen to be more intensified compared to current climate simulations. Results demonstrate that all VSCS and ESCS category TCs considered in this study are likely to further intensify to the next higher category level with respect to their current classification, particularly in the far future RCP 6.0 and in the far future RCP 8.5 scenarios. The cyclone damage potential index of TC Vardah, TC Hudhud, and TC Phailin is projected to increase in a future warming climate. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.