Department of Applied Mechanics

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

High performance thermoresponsive soft, controllable and reversible actuators are highly desirable for diverse applications. The practical implementation of the existing poly(N-isopropylacrylamide) (pNipam) based soft thermoresponsive actuators faces serious limitations due to their functional requirement of proximal bulk solvent medium. In this work, addressing this issue, we report the development of a bilayer based actuator composed of a solvent responsive biodegradable polymer and temperature responsive pNipam. The designed bilayer is capable of achieving reversible and irreversible actuation as needed when exposed to a physiological range of body temperature, without any solvent bath around. The solvent or water supplied by the pNipam layer at its lower critical solution temperature (LCST) builds a concentration gradient across the thickness of the polymer layer. The concentration gradient results in a strain gradient, causing an out-of-plane folding of the bilayer. The underlying coupled diffusion-deformation interaction during folding and unfolding is incorporated in the reported finite element model, capable of predicting actuation characteristics under different initial conditions. The combined experimental and modelling effort in this work highlights the possibility of engineering 2-dimensional films into complex 3-dimensional shapes, which could have potential applications in soft machines and robotics. © The Royal Society of Chemistry 2020.

World University root node

Department of Mechanical Engineering

Soft Matter

Controlled shape morphing of solvent free thermoresponsive soft actuators

Surface coatings are mainly applied to protect concrete structures against various environmental conditions. However, the interface between the concrete and coating is a weak link, and interfacial delamination is the primary mode of failure. Fracture resistance is the main design criteria for these materials, and therefore, it is necessary to investigate possible causes of interfacial failure for preventive measures. To this end, we have investigated the potential failure mechanisms and measured interfacial strength by performing a pull‐off adhesion test on epoxy coated cement paste. From the pull‐off adhesion test, adhesive (interface) failure between cement paste and epoxy is predominantly observed. It is observed that the adhesive (interfacial) strength for the sample tested on 50th day is more than the 28 days hydrated sample. This is due to additional curing of cement paste samples after coating epoxy which leads to higher interfacial strength. We also present the phase‐field model (PFM) to predict the adhesive failure for this system. The results obtained from the PFM, i.e., load at failure and crack path are validated against experimental results. Finally, the influence of various material parameters such as elastic modulus and fracture energy of the interface on interfacial fracture behaviour is studied. © The Author(s) 2021.

Department Of Civil Engineering

Fulltext

RILEM Technical Letters

Interfacial fracture behaviour between cement paste and epoxy coating ‐ an experimental and phase‐field approach

The permanence of injected CO2 in deep saline aquifers mainly depends on caprock permeability. Thus, the main objective of this study is to investigate the effect of salinity level in the formation fluid on permeability of siltstone when advective flow of scCO2 is dominant. Siltstone caprock samples were fully saturated with different synthetic brines, which were similar to natural formation fluids. A chemical analysis was conducted for each saturated rock and brine samples to recognize the geo-chemical equilibrium between the formation fluid and caprock since the identification of final brine composition in rock pores is crucial to predict the possible interactions with scCO2 flow. Interestingly, the results show that the caprock is subjected to dissolution during saturation due to ion exchange between caprock minerals and cations in the pore fluid changing the brine elemental composition. The scCO2 permeability experiments were conducted for each saturated sample using a core flooding apparatus for a series of injection pressures. According to the results, scCO2 permeability significantly reduces at high salinity concentrations in brine due to deposition of different types of evaporites in rock pores which significantly depends on the elemental concentration of brine and caprock-brine interaction. It is known as CO2 dry-out phenomenon. © 2019

Energy

Effect of salinity on supercritical CO2 permeability of caprock in deep saline aquifers: An experimental study

The paper investigates the post-buckling behavior of micro-cantilevers within the framework of consistent couple stress theory. The theoretical foundation for carrying out the analysis is formulated in terms of moment and curvature which is apt for solving thin beam problems. A differential equation governing the deflection of micro-cantilever subjected to different boundary conditions is obtained from the developed moment-curvature relationship. Axially loaded micro-cantilevers are solved by using an efficient semi-analytical method which involves removal of singularity. On the other hand solutions to eccentrically loaded micro-cantilevers are determined with the help of purely numerical approach based on iterative shooting method. Profiles of post-buckled micro-cantilevers subjected to different loading conditions are furnished. The obtained results for the micro-cantilever display strong size-dependency due to presence of the material length scale parameter in the developed model. Also the non-classical theory results tend to those from classical theory when the length scale parameter is negligible as compared to the characteristic length of the structure. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

Annals of Solid and Structural Mechanics

Post-buckling involving large deflection of micro-cantilever using the consistent couple stress theory

Building text-to-speech (TTS) synthesisers for Indian languages is a difficult task owing to a large number of active languages. Indian languages can be classified into a finite set of families, prominent among them, Indo-Aryan and Dravidian. The proposed work exploits this property to build a generic TTS system using multiple languages from the same family in an end-to-end framework. Generic systems are quite robust as they are capable of capturing a variety of phonotactics across languages. These systems are then adapted to a new language in the same family using small amounts of adaptation data. Experiments indicate that good quality TTS systems can be built using only 7 minutes of adaptation data. An average degradation mean opinion score of 3.98 is obtained for the adapted TTSes. Extensive analysis of systematic interactions between languages in the generic TTSes is carried out. x-vectors are included as speaker embedding to synthesise text in a particular speaker's voice. An interesting observation is that the prosody of the target speaker's voice is preserved. These results are quite promising as they indicate the capability of generic TTSes to handle speaker and language switching seamlessly, along with the ease of adaptation to a new language. Copyright © 2020 ISCA

Department of Computer Science and Engineering

Proceedings of the Annual Conference of the International Speech Communication Association, INTERSPEECH

Generic indic text-to-speech synthesisers with rapid adaptation in an end-to-end framework

In the current study, experiments are performed on the aero-engine compressor blade model which is fastened to the disc using dovetail joint. Using the technique of photoelasticity, the highly stressed zone is found to be at the interface of the disc and the blade. Cyclic loading is then applied to the disc-blade assembly. Initial experimental observations showed formation of small cracks leading to crack growth and subsequent failure. In this region, a small crack is put and then the growth of crack during cyclic loading is studied till the failure of the specimen. The variation of stress intensity factor with respect to crack length and the number of cycles is evaluated for crack perpendicular to the contact length. Â© 2020, Society for Experimental Mechanics, Inc.

Conference Proceedings of the Society for Experimental Mechanics Series

Analysis of Crack Growth in Compressor Blade Root Subjected to Fatigue

Event-related patterns (EPs) play an essential role in detecting motor imagery (MI) movements of the subject. Due to the difference in the spatial and temporal distribution of brain signals among the subjects, the extraction of EP is a major issue. To rectify this problem, the Hilbert transform (HT) was used for the detection of EPs, and the machine learning (ML) models were implemented for decoding MI movements. The proposed method comprises two steps: initially, μ (8–12 Hz) and β (12–30 Hz) frequency bands were extracted from the raw electroencephalogram (EEG) signal. The HT was implemented on extracted μ and β bands signals and the EPs were calculated. Finally, the EPs were fed into two ML models such as support vector machine (SVM) and logistic regression (LR) for the detection of MI movements. The proposed method was tested on two benchmark datasets (BCI competition-III and IV). The results show that the mean classification accuracy (%CA) and Cohen's kappa coefficient (K) for BCI competition-III and IV were 86.11% & 0.72 and 82.50% & 0.65 respectively, which are higher than several existing methods. © 2020 Elsevier Ltd

Biomedical Signal Processing and Control

Hilbert transform-based event-related patterns for motor imagery brain computer interface

In this study, an attempt has been made to analyze uterine Electromyography (uEMG) signals during Term conditions (pregnancy duration more than 37 weeks of gestational age) using Empirical Mode Decomposition based Detrended Fluctuation Analysis (EMD-DFA). The Term delivery signals are considered from a publicly available database, grouped as T1 (<26 weeks gestational age) and T2 (≥26 weeks gestational age) based on the time of recording, and are subjected to an EMD-DFA algorithm. The double logarithmic plot of the detrended fluctuation function against the scale is analyzed, and the Hurst exponent feature is computed for both groups. The features are statistically analyzed using the Student s t-test. Results show that the EMD-DFA method is able to capture the variations in the fluctuations of uEMG signals under these conditions. The Hurst exponent feature is found to be statistically significant (p-value < 0.005) for both groups. There is an increase in the Hurst exponent feature value in the T2 group, which indicates that T2 signals possess smoother characteristics than T1 signals. Hence, it appears that the proposed approach could aid in investigating variations in the fluctuations of Term delivery signals, differentiating T1 and T2 conditions.. © 2020 Institute of Electronics and Information Engineers. All rights reserved.

IEIE Transactions on Smart Processing and Computing

Empirical Mode Decomposition based Detrended Fluctuation Analysis of Uterine Electromyography Signals in Term Conditions

In this work, an attempt has been made to assess the texture variations of brainstem occurring in the Early Mild Cognitive Impairment (EMCI) condition. Fractal dimension is calculated for the segmented brainstem volume using Higuchi's and Detrending moving average (DMA) method. These measures are validated using Random forest classifier. DMA shows better performance when compared to Higuchi's method in categorising EMCI stage. Thus, the proposed approach using brainstem image's DMA fractal measures with random forest can be used in diagnosis of EMCI. © 2020 European Federation for Medical Informatics (EFMI) and IOS Press.

Studies in Health Technology and Informatics

Identification of EMCI in MR brainstem structure using fractal measures and random forest approach

The mechanistic aspects of process of initiation of a mode-I fatigue crack in an aluminium alloy (AA 2219-T87) are studied in detail, both computationally as well as experimentally. Simulations are carried out under plane strain conditions with fatigue process zone modelled as stress-state–dependent cohesive elements along the expected mode-I failure path. An irreversible damage parameter that accounts for the progressive microstructural damage due to fatigue is employed to degrade cohesive properties. The simulations predict the location of initiation of the fatigue crack to be subsurface where the triaxiality and the opening tensile stresses are higher in comparison with that at the notch surface. Examination of the fracture surface profile of fracture test specimens near notch tip reveals a few types of regions and existence of a mesoscopic length scale that is the distance of the location of highest roughness from the notch root. A discussion is developed on the physical significance of the experimentally observed length scale. © 2019 Wiley Publishing Ltd.