Applied Mechanics Seminar Series

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Title
Correcting Movement Errors And Learning From Them Using a Lateralized Brain

Speaker
Dr. Pratik Mutha
University of New Mexico, USA

Date: 20.11.2012 ; Time: 3.00 p.m.

Venue: Aerospace Engineering, ClassRoom2.

Abstract
The ability to learn new motor skills, such as playing a piano or riding a bicycle, is a hallmark of human behavior. However, the principles and neural mechanisms that underlie this capacity for motor learning remain elusive. We investigated the neural substrates critical for motor learning using arm reaching movements in healthy individuals and stroke patients as a model system. Learning was assessed by examining how subjects adapt their movements in response to errors induced using novel perturbations. We found a striking deficit in adaptation following lesions to parietal regions of the left cerebral hemisphere regardless of the arm used to perform the task, thus uncovering a left lateralized neural substrate critical for such learning. In contrast, we noted a marked disruption in the correction of the ongoing movement in response to the perturbation-induced errors following damage to lateral prefrontal regions of the right hemisphere.

These patients remarkably however, showed absolutely no deficit in adaptation as seen with left parietal damage. We confirmed and subsequently detailed the nature of this right lateralized online correction deficit using a task that specifically tests the ability to modify an ongoing movement in response to unexpected changes in the location of a target to be reached. Our findings thus identify, for the first time, distinct,lateralized neural substrates that mediate online correction of movement errors and subsequent learning based on those errors. Such a lateralized system may have emerged over the course of evolution to optimize the use of neural resources while still adequately supporting both functions.

About the Speaker
Dr.Pratik Mutha is a research associate at University of New Mexico, VA Med center, Albuquerque, NM, USA & Penn State University, USA. Earlier, he obtained his PhD from Penn State's prestigious kinesiology program working in the area of motor lateralization. His research interests include motor learning in health and disease, motor lateralization, control of human movements and rehabilitation.

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Title
Sustainable Engineering Alternatives

Speaker
Prof. Srinivas Veeravalli
Applied Mechanics, IIT Delhi

Date: 09.10.2012 ; Time: 4.30 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics.

Abstract
The problems created by modern technology and ‘development’ are easily seen all around us. The magnitude of the problem is also now well appreciated as evidenced by the volume of research and discussion on topics such as ‘Sustainability’, ‘Environmental Impacts’, ‘Global Warming’ etc. What is not so readily appreciated, however, is that the problem stems from the very method of modern science. Consequently, any quick fix to these environmental impacts is also likely to fail.
We argue that traditional engineering structures are based on a different method and science and are inherently more benign. Thus, understanding the method and presuppositions underlying these traditional structures would help us address present day problems. We wish to emphasize that it is the method that is crucial not merely the scale or form of these structures. Some examples of traditional engineering ‘The Grand Anicut’ on the Cauvery, the ‘Kuin-Par’ system of Rajasthan and ‘Pitcher Irrigation’ are presented in support of this argument.

About the Speaker
Professor Srinivas Veeravalli received his B. Tech in Mechanical Engineering, IIT Bombay in 1983 and Ph.D in Mechanical & Aerospace Engineering, Cornell University in 1989.

He was a Post-doctoral Fellow at Center for Turbulence Research, NASA Ames & Stanford University from 1989-91.

He has been a faculty in the Dept. of Applied Mechanics, IIT Delhi since 1991.

He was also Head, Dept. of Mechanical Engg. SDMCET Dharwad from 2002-04.

His research interests are fundamental studies of turbulent flows like studying role of hydrodynamic stability theory in understanding the dynamics of wall turbulence and response of boundary-layers to high free-stream turbulence. His interest is in studying examples of traditional engineering with a view to understanding the design method and science on which they are based. The long term goal is to develop a design method that is inherently benign.

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Title
Quantifying Nonlinearities from Dynamic Responses of Wave Energy Device

Speaker
Dr. Vikram Pakrashi
School of Engineering, University College Cork, Ireland

Date: 28.08.2012 ; Time: 3.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics.

Abstract
The European offshore wind power production target is 460 GW installed capacity by 2050, as compared to the worldwide target of 1150 GW. The market for offshore energy investments is about €360 billion in the European Union (EU), of which perhaps €60 billion may be assigned to the Irish Sea zone. Offshore wave and wind devices, globally, are expected to play a key role is shifting power generation towards more sustainable alternatives as compared to the existing situation. However, offshore wave devices are dynamic structures exhibiting significant nonlinearity in their dynamic responses even under standard operating conditions. To analyse, assess, monitor or control these devices, it is important to quantify the degree to which the system is nonlinear. Approaches towards such quantification are extremely useful if it can be carried out from output-only conditions. The talk will discuss scaled tests on wave device in an ocean wave basin and will present some approaches towards identifying and quantifying the nonlinearity present in the system.

About the Speaker
Dr. Vikram Pakrashi, School of Engineering, University College Cork, Ireland is a Chartered Engineer with extensive experience in maintenance and management of key infrastructure systems through his doctoral, postdoctoral and industrial experience. Vikram’s research interests are in dynamical systems and risk based assessment applied to bridge engineering, onshore/offshore renewable energy devices and sustainable transportation. He represents the structural engineering interests related to health monitoring, energy harvesting and control of infrastructure systems within the School of Engineering in University College Cork.

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Title
Sediment Transport by Shallow Supercritical Flows

Speaker
Dr. Suryadevara Madhusudana Rao
University of Mississippi-USDA-ARS National Sedimentation Laboratory, Oxford, MS, USA

Date: 31.01.2008 ; Time: 4.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics.

Abstract
Laboratory flume experiments of shallow overland flow show that the sediment transport is not a random phenomena but occurs in a highly organized manner. The organization reveals evolution of bed covered by sediments with several scales ranging from saltation of particles at very low concentrations to movement in wave forms. This seminar describes the optical probe measurements of granular sediment in the saltation mode. Poly-dispersed sand grains of size = 1.2mm, 0.725mm and mono-dispersed glass beads of size =0.8 mm were invariably added into the shallow water stream (Froude numbers, Fr > 1) of a slightly inclined (slope < 1%) Aluminium metal channel. Solid concentration (defined as the fraction of the illuminated area of an optical probe covered by passing solids) and the solid cloud propagation velocities were estimated from the recordings of pre-calibrated single probe and twin probe photonics, respectively. Poly-dispersed sand particles exhibited greater resistance to the flow compared to the mono-dispersed glass beads. Velocity estimates from the cross-correlation of twin photonic probe signals showed smaller grain velocities at relatively high solid concentration values due to the intensive grain interaction. However, turbulence modulation and reduction in the particle drag at relatively small solid concentration values depicted an acceleration of grains. At a limiting value of the grain addition rate, the saltating grains start settling into an organized mode thus exhibiting a threshold condition for sediment transport. This critical condition was associated with the modulation of roll waves and happens when most of the energy in the roll waves was consumed by the transported sediment. It was observed that particle interaction mechanism plays a very significant role and although the energy is supplied by the hydraulic condition of water flow, the bed evolution is embedded in the "DNA equivalent" of grain movement process. The interrelationship between hydraulic condition and sediment characteristics were explained by considering a two phase flow model based on St. Venant equations of shallow water flow and the dry granular flow. A drag reduction analysis proposed for a simple arrangement of spherical particles moving in series supported the experimental findings on the initial increase of grain velocity at relatively small solid concentration.

About the Speaker
Dr. Madhusudana Rao is currently working as a Research Associate at the National Sedimentation Laboratory. He is also an Adjunct Faculty at the school of engineering as Research Assistant Professor, University of Mississippi. He obtained his Ph.D in Chemical Engg. from IIT Madras (1997). He is a member of American Society of Mechanical Engineers, ASME (current) and American Institute of Chemical Engineers, AIChE (1999-2000). He worked as an Research Engineer/ post-doctoral researcher at the National University of Singapore during 1997-2002 before he moved to USA.

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Title
DNA as a Fluctuating Elastic Rod and its Implications in Biology

Speaker
Prashant Purohit,
Mechanical Engineering and Applied Mechanics
Department at the University of Pennsylvania, Philadelphia

Date: 17.01.08 ; Time: 4.00 p.m.

Venue: Newton Hall (Aerospace Bldg) Dept.of Applied Mechanics

Abstract
Several decades of experimental and theoretical research into the mechanics of DNA has lead to a theory that describes it as a fluctuating elastic rod with well characterized bending and twisting moduli. This presentation will summarize some of our recent work on applications of this theory where we show how twisting and superhelical stress in DNA play a role in the energetics of protein mediated DNA loops. Such loops are the key to many crucial biological processes such as transcription, replication/repair and site-specific recombination. We will also present an application of the fluctuating rod model to some recent single molecule experiments on torsional buckling and plectoneme formation in DNA. In these experiments a piece of DNA several hundred nanometers in length is subjected to simultaneous tensile and torsional stress by means of an optical trap. As a final application of the fluctuating rod model we will present results from some experiments on short actin filaments where we have been able to determine the variance of their transverse Brownian fluctuations as a function of the position along the filaments.

About the Speaker
Dr Prashant Purohit is an assistant professor in the Mechanical Engineering and Applied Mechanics department at the University of Pennsylvania, Philadelphia. He did his Ph.D. at Caltech with Professor Kaushik Bhattacharya, Caltech.

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Title
Surface Thermal Capacity : A New Property of Fluid-Fluid Interfaces

Speaker
Kausik S.Das,University of Toronto

Date: 09.01.08 ; Time: 4.00 p.m.

Venue: CRC 207, Solid Mechanics Division, Dept.of Applied Mechanics

Abstract
The interface between two immiscible fluids causes an asymmetry in the intermolecular forces experienced by molecules in this region and gives rise to unique structural and dynamical properties different from the bulk fluid properties. The Gibbs description of a single-component, equilibrium system containing two fluid phases separated by a curved interface defines an excess number of moles, and an excess internal energy. In this talk, the generalization of the energy boundary condition for fluid-fluid interfaces that includes the transport of Gibbs excess internal energy will be discussed. A new surface property, the surface thermal capacity, appears in the resulting energy boundary conditions and explains the observation that water evaporates at a much higher rate than predicted by existing theories during thermocapillary convection. The energy boundary condition at the interface shows that the velocity and temperature fields are coupled, this new coupling comes through `surface thermal capacity’. Apart from evaporation, the effect of this surface thermal capacity on the stability of general thermocapillary flow and heat transfer will also be discussed.

About the Speaker
Kausik S. Das did his Ph.D in 2002 from IACS, Kolkata. He was then associated with a NASA project in UCSB with Prof. G.M. Homsy, followed by an EPSRC project in University of Strathclyde Glasgow and University of Oxford. He is currently working in a Canadian Space Agency project in University of Toronto with Prof. Stephen Morris and Prof. C.A. Ward. His main research interests are stability of fluid flow, heat and mass transfer in fluids in micro/nano tubes, fluid induced energy technology and flow through porous media.

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Title
Thermal convection at moderate Rayleigh numbers:
Non-Boussinesq effects 

Speaker
Dr. A. Sameen, International Centre For Theoretical Physics
Trieste, Italy

Date: 03.01.08 ; Time: 4.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
We study the effects of severe non-Boussinesq conditions on thermal convection at  moderate Rayleigh numbers of 2 x 10^6 < Ra < 2 x 10^9  by resorting to direct numerical computations of  low temperature gaseous helium. The properties of helium are allowed to depend on the temperature around a mean of 5.4  K. The Nusselt number is shown to decrease as the system departs from the Boussinesq approximation. For the Rayleigh numbers chosen here, the role of viscosity in thermal convection is limited to smudging the plume generation at the bottom surface, while the thermal expansion coefficient is demonstrated to have a huge impact on heat transport.

About the Speaker
Dr A. Sameen obtained his PhD from the Department of Aerospace Engineering, Indian Institute of Science . Currently, he is with the International Centre for Theoretical Physics pursuing research on thermal convection. His areas of specialisations are hydrodynamic stability and transition, compressible flows and thermal convection.

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Title
Trends in Modeling and Simulation of Aerospace Structures 

Speaker
Dr.S.Viswanath, Deputy Director(Retired), National Aerospace Laboratory, Bangalore

Date: 23.11.07 ; Time: 3.30 PM.

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
Designing an aircraft for certification under a weight class involves accurate simulation of stiffness, strength, mass and C.G. of airframe components. Adaptation of right combination of material systems for different subcomponents in order to achieve minimum structural weight satisfying the required static and dynamic margins are possible through simulation of the behaviour of the structure at various levels. The simulation of the behaviour could be based either on numerical modelling of the prototype or testing of a scaled model of the prototype. The trends in modelling and simulation of several aerospace structures for different applications like aircraft components (Hansa & Saras), launch vehicles (PSLV&GSLV), reentry launch vehicle (RLV) and radomes undertaken at NAL in the recent years will be highlighted. The presentation would conclude with the identification of a few areas for further development.

About the Speaker
Dr. S Viswanath retired as Deputy Director, National Aerospace Laboratories, Bangalore. He was the associate project director for SARAS and HANSA3 aircraft projects at NAL. He holds a doctoral degree from IISc and has over a hundred publications in various areas of structural analysis. He was a member of the review committees of various national aerospace programmes like LCA, GSLV, and is a fellow of the Aeronautical Society of India.

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Title
Quantitative assessment of mechanical properties of tissues 

Speaker
Dr. S. Ramakrishnan, Assistant Professor,
Department of Instrumentation Engineering,
Madras Institute of Technology, Anna University, Chennai

Date: 21.11.07 ; Time: 4.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
The assessment of mechanical behaviour of soft tissues is important in medical diagnosis to differentiate tumors and surrounding tissues. Several methods have been proposed to estimate the tissue-stiffness or stiffness dependent tissue-responses following a mechanical stimulus. Most of them are expensive, invasive or are performed on deceased tissues. Hence, there is a need for minimally invasive devices to perform quantitative measurements of tissue properties invivo. In this direction, an attempt has been made to design a piezo resonator to quantify localized tissue stiffness and to differentiate normal and abnormal soft tissues. In this seminar, the principle of operation, design issues, specifications and possible applications of this resonator will be discussed.

About the Speaker
Dr. S. Ramakrishnan, Assistant Professor, Department of Instrumentation Engineering, Madras Institute of Technology, Anna University, Chennai, obtained his Ph.D. in Biomedical Engineering at the Department of Applied Mechanics, IIT Madras. He was a DAAD long term fellow at Technical University, Aachen. His current interests include application of soft computing techniques to enhance the diagnostic relevance of medical instruments and design and development of medical devices for the assessment of tissue and bone mechanics.

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Title
Innovative Off-Chip Mechanically Compliant Interconnects for
Next-Generation Microelectronic Packaging

Speaker
Professor Suresh K. Sitaraman, Ph.D.

Director, Computer-Aided Simulation of Packaging Reliability (CASPAR) Lab

The George W. Woodruff School of Mechanical Engineering
Georgia Institute of Technology, Atlanta

Date: 20.06.07 ; Time: 11.00 a.m

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
Advances in integrated circuit (IC) design and fabrication continue to challenge and push the microelectronic packaging technology in terms of size, performance, cost, and reliability. It is projected by the Semiconductor Industry Association (SIA) in their International Technology Roadmap for Semiconductors that in the next ten years, an IC will have several billion transistors compared to a few hundred million transistors in today's ICs. Accordingly, the node size in IC components will shrink to 22 nm by 2016 and 14 nm by 2020 requiring high-density chip-to-substrate interconnects. With the convergence of the clock frequency between the chip and the package based on ITRS projections, the package interconnections are expected to support high-speed signals in the multi-gigahertz range in the near future. This requires the fine-pitch (20-70mm) chip-to-substrate interconnects support high frequency signals (>20GHz) and supply adequate power to the chip (>200W). Furthermore, with the low-strength low-K dielectric material on the die, the chip-to-substrate interconnects should not delaminate or crack the dielectric. There is no viable solution available today to meet these interconnect requirements.

The ongoing work at Georgia Institute of Technology, aims to design, fabricate, assemble, and test an innovative technology utilizing compliant chip-to-substrate interconnect structures for next-generation microelectronic packaging. Wafer-level batch fabrication, lead-free solder attachment, no-underfill processing, reworkability, large-area processing, scalability, and fine-pitch are some of the highlights of the proposed interconnect technology. The proposed helix-like compliant interconnects will be fabricated using LIGA-like process consisting of sequential plating and photolithography. In combination with electrical and thermo-mechanical models, aggressive test vehicles consisting of several thousand I/O connections on a 10x10 mm die, far exceeding various roadmap projections for the next 10 years, are being fabricated, assembled, and experimentally tested. The proposed interconnects are expected to provide a viable solution for microelectronics industry for years to come.

About the Speaker
Dr. Suresh Sitaraman is a Professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. Prior to joining Georgia Tech in 1995, he was with the IBM Corp. His expertise is in the area of Thermo-Mechanical Design, Modeling, Reliability, and New Technologies Micro/Nano Systems. He has guided a group of post-doctoral, doctoral, master's and undergraduate students and has published more than 150 papers in journals and conferences. His co-authored papers have won the best paper award from IEEE Transactions on Components and Packaging Technologies in 2001 as well as in 2000. Dr. Sitaraman received the Outstanding Faculty Leadership Award for the Development of Graduate Research Assistants, Georgia Institute of Technology in 2006, the Metro-Atlanta Engineer of the Year in Education Award in 1999, Outstanding Faculty Education Award from the Packaging Research Center in 1998, and the NSF-CAREER (formerly President's Young Investigator) Award in 1997. He serves as an Associate Editor for IEEE Transactions on Advanced Packaging. He is also an ASME Fellow.

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Title
Electroosmotic Flow through micro-channels 

Speaker
Dr.P.Nithiarasu, School of Engineering, University of Wales Swansea, United Kingdom

Date: 15.12.06 ; Time: 4.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
Improving human health via numerical modeling is a relatively a new topic. Over the last five years, patient specific numerical simulation has received a great deal of attention from engineering community. This is due to recent developments in image processing, mesh generation and state of the art modeling tools. The topic is highly interdisciplinary and it is very common nowadays for engineering scientists to team up with practicing, medical scientists.

This talk summaries the current state of the art in patient specific modeling. It also discusses various difficulties associated with such modeling and identifies areas for further development. The speakers own experience in modeling the human upper airways will be briefly presented.

About the Speaker
Dr.P.Nithiarasu, graduated from Madurai Kamaraj University in 1994, M.Tech from University of Kerala in 1992 and Ph.d IIT Madras. He is now Senior Lecturer, school of Engineering, Swansea University. He received the 1998 Most outstanding Paper Award,MCB University and 2002 Zienkiewicz Silver Medal and Prize. In 2004, he received the Young Scientists in Computational Engineering Sciences Award

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Title
Multiscale Modeling of Shape Memory Alloys

Speaker
Dr.Srikanth Vedantam, Department of Mechanical Engineering , National University of Singapore

Date: 03.01.07

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
Most materials possess microstructure of some form or the other. It is well-known that the presence of fine length-scale sub-structures such as grains, twins, or second phase precipitates, strongly affects the constitutive response of materials. Historically, constitutive modeling approaches treated materials differing solely in their microstructure as different materials. Many currently technologically important materials such as shape memory alloys or nanocrystalline materials possess microstructure which evolves with either thermal or mechanical loading. In these cases it is necessary to incorporate the evolution of the microstructure into the constitutive modeling approach to be able to accurately predict the mechanical response of these materials.

This talk will focus on constitutive modeling of shape memory alloys at two different length scales. Shape memory alloys are technologically important materials which possess microstructure capable of evolving with temperature and stress, leading to a wide range of interesting behaviors. We first present a discrete mesoscale approach which demonstrates the temperature induced structural phase transformations found in shape memory alloys. The mesoscale model highlights the importance of discreteness effects in the constitutive modeling. In the latter part, we present a continuum theory motivated by a mesoscale model. The continuum theory describes the rate dependence of pseudoelastic hysteresis in shape memory alloys to very good accord.

About the Speaker
Dr. Srikanth Vedantam obtained his undergraduate degree from the Indian Institute of Technology, Madras, India. His MS and ScD degrees were from the Penn State University and Massachusetts Institute of Technology respectively. After obtaining his doctoral degree in 2000, Dr. Vedantam worked in GE Global Research Labs in Niskayuna, NY for about three years. Since 2003, Dr. Vedantam is an Assistant Professor of Mechanical Engineering at the National University of Singapore, Singapore.

Dr. Vedantam's research interests lie in the constitutive modeling of novel materials. He has been granted 11 US patents and has co-authored 13 journal and conference publications.

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Title
Equilibrium configurations and the Roche limit for spinning ellipsoidal  soil-like asteroids

Speaker
Dr.Ishan Sharma, Department of MechanicaL Engg, Kanpur 

Date: 02.11.06 ; Time: 4.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
Recent research has suggested that asteroids might be particle aggregates held together by self-gravity alone. This has important implications on the possible equilibrium shapes of spinning asteroids. As in the case of spinning fluid masses, which only form Jacobi ellipsoids, Maclaurin spheroids, etc., not all shapes and spins may be compatible with a granular rheology. To study this issue, we take an asteroid to be an ellipsoid and its interior to be composed of a rigid-plastic, cohesion-less soil.

Using an approximate volume-averaged procedure, it is possible then to derive regions in spin-shape parameter space where equilibrium solutions can exist. The results that we find are the same as those reported by Holsapple (2000), but are obtained with much less effort. It is also possible to investigate the dynamics of such spinning asteroids and attempt to recover the results of Richardson et al. (2004), who determined equilibrium shapes of smooth spherical aggregates by numerically studying their passage into equilibrium. As a final application of this approximate procedure, the Roche limit for a satellite tidally interacting with a central planet is derived, and is in complete agreement to the one obtained by Davidsson (2001).

About the Speaker
Dr.Ishan Sharma, graduated from IIT Kanpur in 1994 before completing his Ph.d in Theoretical and Applied Mechanics at Cornell University. He was a research fellow at Department of Applied Mathematics and Theoretical Physics, Cambridge University. He is now Assistant Professor, Department of Mechanical Engineering, IIT Kanpur

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Title
From instabilities to drop ejection in capillary waves 

Speaker
Dr.A.P.Baburaj, Department of Applied mechanics, IIT Madras

Date: 30.08.06 ; Time: 4.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
The talk deals with an experimental study of parametrically excited non-linear surface waves. Water and FC-72 are studied with forcing frequencies in the range of 25 to 100 Hz; gravity-capillary waves are formed. For a given frequency, the wave pattern evolution with forcing amplitude has been determined up to droplet ejection. With increase in driving acceleration, meniscus waves, change to parametric instability, which then exhibit azimuthal modulations to rapidly become chaotic at the drop ejection point. The mean wave length at the drop ejection threshold is close to the wavelength from the inviscid dispersion relation; the wavelengths can be approximated by a Gaussian distribution. We introduce a gravity-capillary scaling, which helps us to deduce the crossover from gravity to capillary dominated breaking. The mean wave acceleration at breaking is an order of magnitude larger than the container acceleration. We propose that the droplet ejection rate is likely to depend, in addition to the wave frequency, on the wavelength, and hence the liquid properties. Drop sizes scale with the most unstable wave length and show an inviscid capillary dominated wave breakup. The drop sizes are distributed lognormally, indicating multiplicative processes behind the formation of different drop sizes.

About the Speaker
Dr.A.P.Baburaj completed his PhD from IISc and post doctoral research from LEGI-CNRS, France. He is currently a faculty of Applied Mechanics, IITM. His research interests include convection, interfacial phenomena and physico-chemical hydrodynamics.

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Title
Residual Stress Measurement on Aluminium Alloy Components using High Speed Hole Drilling

Speaker
Prof.S.Annamalai Pillai, Head, Experimental Mechanics Division Structural Design & Engineering Group

Date: 19.07.06 ; Time: 4.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
Residual stresses or hidden stresses are those which remain in the material in the absence of any external forces or thermal gradients. They are difficult to measure non-destructively; they add to stresses due to applied loads and have adverse influence on stress corrosion are cracking. Reliable measurements of these stresses are extremely important to prevent failure of components. The talk will give an introduction to residual stresses, its various sources,different methods for its measurement and their relative merits. The high speed hole drilling method will be described along with a few case studies on aluminium alloy components. Use of photoelastic technique for residual stress estimation will also be discussed.

About the Speaker
Dr.S.Annamala Pillai is currently the Head, Experimental Mechanics Division, Structural Design & Engineering Group, VSSC. Dr.Pillai obtained his PhD in Aerospace Engg from IIT Madras. His research intersts include experimental stress analysis and fracture mechanics, NDT &E and associated optical measurement techniques. He is a life member and chapter executive committee member of Indian Society for Nondestructive Testing and editor of the journal IMAGE

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Title
Numerics and experiments of free-surface effects in crack propagation

Speaker
Prof.Eckart Schnack, Institute of Solid Mechanics, Karisruhe University

Date: 21.06.06 ; Time: 4.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
In general, crack propagation in 3D-structures cannot be reduced to a series of plane problems along the crack front, due to the existence of some 'corners' on the crack front, where the elastic fields are of a three-dimensional nature. Here, we concentrate on the intersection of the crack front through a free surface of the solid, which is one of the most important of such cases. The singular exponents and corresponding singular modes of Kondratiev’s expansion for arbitrarily-inclined crack geometries are computed in order to obtain the asymptotics for the strain energy release rate (SERR). Numerical results for the SERR distribution along the crack front of a single edge notched (SEN) specimen under different kind of loadings are presented in a number of case studies. Under special consideration of some 3D effects near the free surface, experimental findings from related fracture experiments and 3D FE-analyses are compared with the theoretical results obtained by the asymptotic analysis.

About the Speaker
Prof. Eckart Schnack is currently the head of Institute of Solid Mechanics at Karlsruhe University (TH), Germany. He is also an Honorary Professor at Azerbaijan Civil-Engineering University and Azerbaijan Technical University. His main areas of research are Fatigue and Damage Modeling, Structural Optimization, Fracture Mechanics, Microstructural and Micromechanical Modeling, Experimental and Computational Methods and Composite Materials. Dr. Schnack is a member of the Editiorial Board of the Journal of Structural Optimization and a reviewer for several scientific journals and research organisations.

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Title
Characterization of Anisotropy and Tensile Splitting Phenomenon in X-100 Steel

Speaker
Dr.Anuradha Banerjee, Department of Applied Mechanics , IIT Madras

Date: 16.03.06 ; Time: 4.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
A prototype X100 pipe steel belonging to the high strength low alloy family exhibited abrupt axial splitting, before final failure, in tensile specimens oriented in the rolling direction (RD). Overall plastic anisotropy arising from crystallographic texture due to cold rolling in the manufacturing process led to highly-ovalized necking profiles having minimum dimension perpendicular to the splitting plane. The splitting plane follows the interface between the matrix and a hard planar band of micro-structural heterogeneity near the plate and specimen mid-thickness. Elongated void growth was evident on the matrix side split surface, while the band side was observed to be much smoother.

To characterise the observed anisotropy, the experimental results were simulated using a Taylor-type polycrystalline plasticity model accounting for both initial and evolving texture. A traction-separation law defining a cohesive surface at specimen mid-plane was used to simulate the splitting process. The imposed deformation level at which splitting initiates in the simulations depends mainly on the peak separation stress,while the extent of splitting and associated load-drop increases with decreasing work of separation. A mechanistic description of the splitting process is proposed by correlating the fractographic evidence to quantitative estimates from the simulations.

About the Speaker
Anuradha Banerjee obtained her B.Tech. in Mechanical Engineering from IIT Kanpur, M.S. from Purdue University and Ph.D. from University of Glasgow. After her post-doctoral work at MIT, she is now a faculty member in Applied Mechanics at IIT Madras. Her research interests are theoretical and experimental aspects of fracture.

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Title
A Demonstration of Clinical and Applied Hypnosis

Speaker
Dr.Prof.Peter Fernandez, Professor (Rtd), Chief of the Institute of Mental Health in Chennai

Date: 01.03.06 ; Time: 4.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
Though understanding of Hypnosis has advanced a great deal, the phenomenon is still a mystery. General characteristics of Hypnosis and theories of Hypnosis will be discussed. Application of Hypnosis such as Hypnotherapy and Hypnotic Analgesia will be the focus of the talk. A short discussion of research issues will follow a demonstration of Hypnosis.

About the Speaker
Prof. Fernandez retired as Professor of Psychiatry and the Chief of the Institute of Mental Health in Chennai. He was a Professor and HOD of the Department of Psychiatry at Sri Ramachandra Medical College, Chennai. A council member of International Society of Hypnosis, he is now the director of DR.Fernandez Home for Disabled at Chennai, a model ehabilitation centre for Chronic Mental Patients.

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Title
Probabilistic Safety Assessment of Ageing Structures Subjected to Randomly Vibrating Loads

Speaker
Dr.Sayan Gupta, Technische Universiteit Delft

Date: 22.02.06 ; Time: 4.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
The safety assessment of ageing structures, subjected to dynamic loads, involves estimating the risk of failures due to overloading and due to accumulative effects of structure deterioration caused by fatigue, over a period of time. The uncertainties in specification of loads, material properties and structure behavior, are manifested in the structure response. This implies the need for adopting probabilistic frameworks for the safety assessment. This talk presents some new analytical techniques for time variant reliability assessment of randomly vibrating structures. Here, the loads are modeled as random processes. The probabilistic properties of the structure response are obtained from principles of random vibrations. Using mathematical theories of random processes, new analytical formulations are developed which predict the structure failure probabilities due to overloading and due to random fatigue and estimate their lifetime. These formulations take into account the effect of load combinations due to vector random loadings and non-Gaussianity of the structure response. For structural systems characterized by multiple failure modes, analytical approximations for the structure reliability are developed that take into account the correlation between the various failure modes, when the components are  assumed to be in series configuration. The developed techniques are illustrated through numerical examples and the predictions are compared with those obtained from Monte Carlo simulations. It turns out that these methods require significantly less computational efforts. These methods can be used for the lifetime prediction and reliability assessment of ageing vibrating structures, such as, aircrafts, oil rigs, industrial installations and machinery.

About the Speaker
Dr.SayanGupta is currently a postdoctoral fellow at TuDelft.  He graduated  from Jadavpur University and then did his masters and Phd from IISC, Bangapore.

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Title
Multi-modality endoscopic optical imaging for the early diagnosis of cancer in body cavities

Speaker
Dr.Sujatha Narayanan Unni, NTU, Singapore

Date: 9.01.06;    Time: 4.00 p.m.

Venue: Newton Hall, Dept.of Applied Mechanics

Abstract
Cancer growths found in body cavities are a leading cause of death all over world. The cancer in the colorectal region of the body, which represents one of the most common malignant tumors, has become the second leading cause of death around the world, requiring urgent attention for its diagnosis and follow-up treatment. Early detection of colon cancer is highly important in today's medical field, due to its greater survival rate at this stage. The currently available methods for colon cancer diagnosis are still at the research and development stages within the context of early detection capability, which is indicated by tiny polyps at the surface / subsurface of the mucosal layer. In this seminar, an all fiber optic endoscopic diagnostic tool called endo-speckle-fluoroscope is presented, which is capable of the early diagnosis of the disease using its incorporated diagnostic modalities, such as normal imaging, speckle imaging and fluorescence spectrum analysis. This seminar deals with the design details of the endoscope system for realizing the multi-modality disease diagnostics, followed by experimental validation. Also, various theoretical aspects involving the probe and colon surface parameters are considered and related analyses are presented while using the probe in each of the diagnostic modalities. It is expected that the presented approach here may provide an answer to the replacement of current biopsy based procedures in the long run.

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