MEAM Seminar Series Fall 2016
For Summer 2016 Seminars, click here.
Seminars are held on Tuesday mornings beginning at 10:45 am in Wu and Chen Auditorium, in Levine Hall (unless otherwise noted).
To be added to the MEAM Events mailing list (which sends notifications regarding all departmental seminars and events) please email us at email@example.com.
"Mechanics with Two Temperatures?"
In the study of amorphous solid deformation, one concept that has arisen is the notion of an "effective temperature," which coexists with and is typically distinct from the usual temperature that one would measure from a standard thermometer. This second temperature reflects the disordered nature of the packing structure, and has been suggested in many studies to play a key role in the plastic flow response of these materials. Past efforts have largely defined this temperature by analogy rather than axiomatically through first principles approaches, which begin with rigorous expressions of continuum energy balance and entropy imbalance. Hence, the concept of an effective temperature has been difficult to reconcile within a rational thermomechanical framework. How exactly is this quantity a temperature? How can a material have two simultaneous temperatures? Why is it necessary to treat this as a temperature rather than just some internal state variable? My goal for this talk is to explain how to rigorously incorporate and rationalize the two-temperature concept within a thermodynamically consistent, finite-deformation, continuum framework for deforming amorphous solids. The format of this talk will be more along the lines of a pedagogical lecture, with an emphasis on building and clearly explaining the framework rather than fitting to a specific material. We will show that many of the salient features observed of glassy solids --- e.g. slow aging phenomena, shear-rejuvenation, and shear-band diffusion --- emerge naturally from this framework.
Professor Ken Kamrin received a BS in Engineering Physics and a minor in Mathematics at UC Berkeley in 2003, and a PhD in Applied Mathematics at MIT in 2008. Kamrin was an NSF Postdoctoral Research Fellow at Harvard University in the School of Engineering and Applied Sciences before joining the Mechanical Engineering faculty at MIT in 2011, where he was appointed the Class of 1956 Career Development Chair. Kamrin's research focuses on constitutive modeling and computational continuum mechanics for large deformation processes, with interests spanning elastic and plastic solid modeling, viscous and non-Newtonian flows, amorphous solid mechanics, upscaling and continuum homogenization, and analytical methods in mechanics. Kamrin has been awarded fellowships from the Hertz foundation, US Defense department, and National Science Foundation. Kamrin received the 2010 Nicholas Metropolis Award from APS for work in computational physics, the NSF CAREER Award in 2012, the 2015 Eshelby Mechanics Award for Young Faculty, the Ruth and Joel Spira Teaching Award from the MIT School of Engineering in 2016, and will receive the 2016 Journal of Applied Mechanics Award from the ASME Applied Mechanics Division.
Alison E. Patteson, Ph.D. Candidate
Advisor: Paulo Arratia
"Particle, Polymer, and Phase Dynamics in Living Fluids"
11:00 a.m., Glandt Forum, Singh Center for Nanotechnology
Flocks of birds, schools of fish, and jams in traffic surprisingly mirror the collective motion
observed in the microscopic wet worlds of living microbes, such as bacteria, algae, and
sperm cells. While these small organisms were discovered centuries ago, scientists have only
recently examined the dynamics and mechanics of suspensions that contain these swimming
particles. Recent studies reveal that the gait and speed of swimming cells depends on the
suspending fluid’s rheology and that a moving swimmer induces fluid flows that can
simultaneously modify the fluid’s rheology. These findings suggest means to control the transport of microbes, their collective behavior, and the bulk rheology of living fluids. How this two-way, non-linear coupling between swimmer and fluid at microscopic scales affects the dynamics and properties at macroscopic scales remains unclear. Is it possible - as in classical, passive mechanics and thermodynamics - that effective equations of state can describe these active, far from equilibrium systems?
To this end, I conduct experiments with the model organism and active colloid, the bacterium
Escherichia coli, and use polymers (< 1 μm), particles (1-10 μm), and phase-separated
mixtures (> 100 μm) to probe the non-equilibrium dynamics of bacterial suspensions. I begin
by examining the hydrodynamic interactions between swimming E. coli and particles that
range in size from above and below the bacteria length. For dilute suspensions of bacteria in
Newtonian fluids, I find that larger particles can diffuse faster than smaller particles - a feature
absent in passive fluids, which may play an important role in particle transport in bio- and
geo-physical settings populated by microbes.
Next, I investigate E. coli dynamics in non-Newtonian polymeric solutions. I find that even small amounts of polymer in solution can drastically change E. coli gaits: cells tumble less and move faster, leading to an enhancement in cell translational diffusion and a sharp decline in rotational diffusion. I show that tumbling suppression is due to fluid viscosity while the enhancement in swimming speed is mainly due to fluid elasticity. Visualization of single fluorescently-labeled DNA polymers reveals that the flow generated by individual E. coli is sufficiently strong that polymers can stretch and induce elastic stresses in the fluid. These, in turn, can act on the swimming cell in such a way to enhance its transport.
Lastly, I probe the interplay between kinetics, mechanics, and thermodynamic of active fluids by examining the structure and dynamics of an active-passive phase interphase. I create this interface by exposing regions of an dense bacterial swarm to UV light, which locally immobilizes the bacteria. I find that the interface stabilizes the collective motion of the bacteria, generating larger and longer-lasting vortex structures compared to the bulk. The vortices, in return, etch the interface, generating interface curvature and controlling the interface’s propagation. The local interface curvature correlates with the local interface velocity, suggesting an active analog of the Gibbs-Thomson boundary condition.
This work explores the links between motility, fluid flow, and particle transport in E. coli suspensions that bridge Newtonian and non-Newtonian suspending fluids and bacterial concentrations that range from dilute and non-interacting to dense and collectively-moving. My results have implications for the burgeoning field of active soft matter, including insight into their bulk rheology, how material properties are defined and measured, and their thermodynamics and kinetics.
Roseanna Zia, Assistant Professor, Department of Chemical and Biomolecular Engineering, Cornell University
"'Phase Mechanics’ of Arrested Colloidal Gels: A New Paradigm for Yielding and Phase Transitions in Soft Matter"
Understanding kinetically arrested phase transition in complex media, and its influence on structure-property relationships, has been identified as one of the grand challenges for the future of soft matter science. Fundamental discovery in this area will advance the next frontier in reconfigurable ‘smart’ materials developed for their hierarchical structure, amenability to biological functionalization, and extraordinarily flexible delivery. Colloidal gels and glasses are an important class of such materials and are the subject of an emergent field of study in which much focus is placed on predicting yield behavior. More fundamentally, colloids serve as a paradigmatic model system for molecular phase transitions, where a vast separation in timescales between colloid and solvent particles provides a powerful means by which to “slow down” fast relaxation processes to study phase behavior. Colloidal equilibrium phase diagrams have thus been constructed following this idea. However, colloidal gels represent “arrested” states of phase separation, where the same interparticle attractions that promote phase separation also inhibit it, freezing in a non-equilibrium microstructure to form a visco-elastic network. In contrast to attempts to place them on equilibrium phase diagrams, we argue that such gels must exit the equilibrium phase diagram. We show that when interparticle bonds are O(kT), thermal fluctuations enable ongoing particle migration and a (logarithmically) slow march toward full phase separation. However, as will be shown, external fields and forces open a pathway from arrested to equilibrium phases, and I will propose a non-equilibrium phase diagram as the foundation for “phase mechanics”, a new view of states of arrested colloidal matter.
Today’s talk will center on our large-scale dynamic simulation studies of flow-induced phase transitions in colloidal gels, both as mechanical solid-to-liquid yield and as force-activated release from kinetic arrest. Our simulations reveal the surprising result that gel yield can occur with loss of fewer than 0.1% of particle bonds, with no network rupture; rather, localized re-entrant liquid regions permit yield and flow. Analysis of the evolving osmotic pressure and potential energy reveals the interplay between bond dynamics and external stress that underlies mechanical yield.
Roseanna N. Zia is an Assistant Professor of Chemical and Biomolecular Engineering and a James C. & Rebecca Q. Morgan Sesquicentennial Faculty Fellow at Cornell University. She received her Ph.D. from the California Institute of Technology in Mechanical Engineering in 2011 with Professor John F. Brady, specializing in the theory of colloidal hydrodynamics and suspension mechanics, where she developed a novel non-equilibrium equation of state for colloidal dispersions. Zia subsequently conducted post-doctoral research in the study of colloidal gels via large-scale dynamic simulation at Princeton University, in collaboration with Professor William B. Russel. Prior to her studies at Caltech she worked as a mechanical engineer in the automotive industry in Detroit, specializing in the design of mechanisms and pyrotechnically actuated devices for occupant restraints; during this time she earned an M-Eng degree at the University of Michigan. Her undergraduate degree, a B.S. in Mechanical Engineering, was obtained at the University of Missouri.
Zia serves as an Associate Editor for the Journal of Rheology, and on the Advisory Board of the journal Physics of Fluids.
Dr. Zia’s work in colloidal systems focuses on the development of predictive theory to elucidate the micro-mechanical underpinnings of macroscopic material behaviors in complex fluids and other soft matter, with a focus on non-equilibrium systems. Problems of interest include the storage of the microstructural entropy that underlies mechanical stress, the use of forces and fields to release colloidal gels from kinetic arrest, testing the paradigms of the glass transition in colloidal glasses, and computational models of intracellular transport.
Thursday, September 22
M. Ani Hsieh, Associate Professor, Mechanical Engineering and Mechanics Department, Drexel University
"The Human-Ocean Interface: Autonomous Systems for Marine Earth Sciences"
2:00 p.m., Towne 337
Robotics and autonomous systems can serve as an interface that enables us to interact more richly and extensively with the world we live in. Consider our global ocean which covers over two-thirds of the Earth’s surface, drives worldwide climate weather patterns, and houses the world's largest repository of biodiversity and mineral resources. As land based animals, we can better understand the many intricate physical, biological, and chemical processes in our oceans that impact our daily lives through the use of robotics and automation technology. However, there are significant autonomy challenges in working in geophysical fluid environments like the ocean. Unlike their aerial and ground counterparts, underwater robots operate in a communication and ocalization-limited environment where their dynamics are tightly coupled with the environment. While the tight-coupling between vehicle and environment dynamics makes control challenging, it provides a unique opportunity for robots to exploit environmental forces to improve and prolong their autonomy. In this talk, I will highlight our recent efforts in using robotics to better understand the dynamics of the geophysical fluid environment. By looking at the ocean through a dynamical systems lens, I show how we can move towards a vision of a robotic human-ocean interface.
M. Ani Hsieh is an Associate Professor in the Mechanical Engineering & Mechanics Department at Drexel University. She received a B.S. in Engineering and B.A. in Economics from Swarthmore College in 1999 and a PhD in Mechanical Engineering from the University of Pennsylvania in 2007. Her current work focuses on developing a general control and coordination framework for distributed sensing and monitoring of dynamic and uncertain environments by mobile robot teams. She is a recipient of a 2012 Office of Naval Research (ONR) Young Investigator Award and a 2013 National Science Foundation (NSF) CAREER Award.
Christian Franck, Assistant Professor, Department of Mechanical Engineering, Brown University
"High Resolution, Large Deformation 3D Traction Force Microscopy"
Traction force microscopy (TFM) is a powerful approach of quantifying cell-material interactions, which over the last two decades has contributed significantly to our understanding of cellular mechanosensing and mechanotransduction. Recent advances in three-dimensional (3D) imaging and traction force analysis (3D TFM) have highlighted the significance of the third dimension in influencing various cellular processes. Yet irrespective of dimensionality almost all TFM approaches have relied on a linear elastic theory framework to calculate cell surface tractions.
This talk presents a new high-resolution 3D TFM algorithm, which utilizes a large deformation formulation to quantify cellular displacement fields with unprecedented resolution. The results feature some of the first experimental evidence that cells are indeed capable of exerting large material deformations, which I will demonstrate in my talk using two different examples. The first focuses on quantifying the role of integrin engagement during force generation and motility in human neutrophils in 2D, 2.5D and 3D environments. The second example provides some of the first traction measurements on single Schwann cells, which are capable of maintaining significant actin stress fibers by exerting large material deformations on very soft materials.
Christian Franck is a mechanical engineer specializing in cellular biomechanics and new experimental mechanics techniques at the micro and nanoscale. He received his B.S. in aerospace engineering from the University of Virginia in 2003, and his M.S. and Ph.D. from the California Institute of Technology in 2004 and 2008. Dr. Franck held a post-doctoral position at Harvard investigating brain and neural trauma before beginning his appointment at Brown in 2009.
His lab at Brown has developed unique three-dimensional full-field imaging capabilities based on confocal microscopy and digital volume correlation, which can deliver quantitative descriptions of cellular surface traction and mechanical properties in soft materials in all three dimensions. His lab uses these three-dimensional microscopy techniques to understand specific problems ranging from the migration mechanisms in neutrophils to the injury evolution of neurons in traumatic brain injury.
October 4: Tedori-Callinan Seminar
Jayathi Y. Murthy, Dean and Professor of Mechanical Engineering, Henry Samueli School of Engineering and Applied Sciences, University of California at Los Angeles
"Topology Optimization for Thermal-Fluid Problems Using Unstructured Finite Volume Schemes"
Topology optimization is a method for developing optimized geometric designs that maximize a quantity of interest (QoI) subject to constraints. Unlike shape optimization, which optimizes the dimensions of a template shape, topology optimization does not start with a pre-conceived shape. Instead, the algorithm builds the geometry iteratively by placing material pixels in a specified background domain, aiming to maximize the QoI subject to a constraint on the volume of material or other constraints. The power of topology optimization lies in its ability to realize design solutions that are not initially apparent to the engineer. Topology optimization, though well established in structural applications, has not percolated to the thermal-fluids community to any great degree. However, the methodology has immense application potential in the area of fluid flow, heat and mass transfer, particularly with the advent of 3D printing.
In this talk, we describe recent work on topology optimization based on widely-used unstructured finite volume schemes employing co-located sequential pressure-based solvers. In our work, the solid isotropic material with penalization (SIMP) approach is used in conjunction with a gradient-based optimization algorithm. Sensitivity derivatives of the QoI with respect to design variables are computed through a discrete adjoint method. The Method of Moving Asymptotes (MMA) is used for optimization. A hallmark of sequential pressure-based methods schemes is that the complete Jacobian is never assembled, causing difficulties with using gradient-based schemes. An important contribution of the work is the development of an automatic differentiation library, ℛapid, to compute accurate Jacobians and other necessary derivatives to address this issue. An essential feature of ℛapid is that it is not necessary to write new code to find sensitivities when new physics, such as turbulence models, are added, or when new cost functions are considered. The methodology is demonstrated on a variety of heat conduction and laminar and turbulent flow and heat transfer problems. The methodologies developed here are very general and are easily translated to use in industry, and for problems with more complex physics and more realistic constraints.
Jayathi Murthy is Dean of the Henry Samueli School of Engineering and Applied Science and Distinguished Professor of Mechanical Engineering at UCLA. She received her Ph.D degree from the University of Minnesota in the area of numerical heat transfer and has worked in both academia and in industry. She served as Director of PRISM: NNSA Center for Prediction of Reliability, Integrity and Survivability of Microsystems at Purdue University. During her employment at Fluent Inc., a leading vendor of CFD software, she developed the unstructured solution-adaptive finite volume methods underlying their flagship software Fluent, and the electronics cooling software package ICEPAK. More recently, her research has addressed sub-micron thermal transport, multiscale multiphysics simulations of MEMS and NEMS and uncertainty quantification in these systems. She is the recipient of the IBM Faculty Partnership award 2003-2005, numerous best paper awards, the 2009 ASME EPPD Woman Engineer of the Year Award and the 2012 ASME EPPD Clock Award. In 2012, she was named a distinguished alumna of IIT Kanpur, India, and was recently named a recipient of the ASME Heat Transfer Memorial Award. Prof. Murthy serves on the editorial boards of Numerical Heat Transfer and International Journal of Thermal Sciences and is an editor of the 2nd edition of the Handbook of Numerical Heat Transfer. She has served on numerous national committees and panels on electronics thermal management and CFD, and is the author of over 280 technical publications.
Joel D. Boerckel, Assistant Professor, Department of Aerospace and Mechanical Engineering, University of Notre Dame
"Developmental Mechanobiology and Regeneration"
1:30 p.m., Glandt Forum, Singh Center for Nanotechnology
Igor Bargatin, Class of 1965 Term Assistant Professor, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
"Plate Mechanical Metamaterials"
My talk will focus on novel ultra-lightweight plate materials recently developed in my group at Penn. Using a periodic three-dimensional patterning, we have fabricated free-standing plates up to 2 cm in size out of aluminum oxide (alumina) films as thin as 25 nm. They weigh as little as 0.1 gram per square meter, and have the ability to “pop back” to their original shape, without damage, even after undergoing multiple sharp bends by more than 90 degrees. More recently, we also combined multiple ultrathin layers of alumina to create a nanoscale analogue of paper-based cardboard. I will discuss the mechanical properties and possible applications of this new class of mechanical metamaterials.
George Gogos, Professor, Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln
"Femtosecond Laser Formation of Self-Organized Micro/Nanostructures on Metallic Surfaces and their Thermal/Fluids Applications"
The use of micro/nanostructured surfaces has become very promising in research areas such as heat transfer enhancement, drag reduction/enhancement, anti-icing and bacteria growth prevention. Through the use of femtosecond laser surface processing techniques, we have demonstrated the control of self-organized micro/nanostructure formation on a wide range of metals including a number of stainless steel alloys, aluminum, nickel, titanium, Inconel 740H, Zircaloy-4 and copper. Three specific classes of structures are presented: above surface growth mounds (ASG-mounds), below surface growth mounds (BSG-mounds) and nanoparticle covered pyramids (NC-pyramids). These unique structures form through a balance of material ablation, fluid flow, and material redeposition that is determined by the laser fluence and the number of pulses used during processing. Within each structure class, we present the ability to fine tune the size and shape of the surface structures. We demonstrate how the self-organized micro/nanostructures and changes in surface chemistry, produced through femtosecond laser surface processing, can be used to functionalize the wetting properties. Through pool boiling experiments we show enhanced two phase heat transfer characteristics, increased Critical Heat Flux and an extraordinary shift in the Leidenfrost temperature for delayed film evaporation. Preliminary results in co-annular flow show drag reduction both for superhydrophilic and superhydrophobic surfaces.
Dr. George Gogos holds a B.S. degree in Mechanical Engineering from the Massachusetts Institute of Technology (1980) and an M.S. (1982) and PhD (1986) degrees in Mechanical Engineering from the University of Pennsylvania. After he completed his studies, he joined Rutgers University as an Assistant Professor and in 1993 moved to the University of Nebraska – Lincoln as an Associate professor where he is currently a Professor in the Department of Mechanical Engineering. He conducts research in fuel combustion, with emphasis on droplet combustion, droplet vaporization at elevated pressures and microgravity combustion. In addition, he conducts research in a number of interdisciplinary areas that require his expertise in the thermal/fluids sciences, such as rapid DNA multiplication for detection of biological agents (rapid PCR development), blast wave mitigation, rotational molding and propane flaming for weed control in agronomic crops. Over the past four years his research emphasis is on femtosecond laser formation of self-organized micro/nanostructures on metallic surfaces and their thermal/fluids applications. His research is funded by NSF, NASA, NIH, ARO, ONR, USDA, Boeing, ConAgra and other industries. He has co-authored more than 140 technical papers in archival Journals and Conference Proceedings. He teaches undergraduate and graduate courses in combustion, fluid mechanics, heat and mass transfer processes, thermodynamics and computational heat transfer and fluid flow.
Aaron Wemhoff , Associate Professor, Department of Mechanical Engineering, Villanova University
"Quantifying Nano-Enhancement in Organic Phase Change Materials"
Organic phase change materials (PCMs) use the latent enthalpy of the solid-liquid phase transition for energy storage. PCMs are useful as thermal barriers in construction materials for energy-efficient buildings, for energy storage using intermittent renewable power sources (e.g., solar and wind), and as a passive cooling mechanism for portable electronics. One current disadvantage of PCMs for energy storage lies in their low thermal diffusivity, which inhibits their ability to allow for uniform heating to achieve a full phase transition during heating or cooling. Therefore, researchers have investigated the use of nanoparticles to improve the thermal diffusivity of PCMs, and inconclusive results have been reached regarding the impact the nano-enhancement has had on the PCM. This problem is exacerbated when nanoparticle agglomeration is taken into account, and little work has been done on how the PCM molecular structure impacts the energy storage capability. Therefore, this talk discusses the creation of a multi-scale modeling framework to quantify the impact the PCM molecular structure and nano-enhancement have on the PCM performance, and conclusions are provided regarding how aspects of the nano- and micro-scales impact the overall bulk properties and performance of the nano-enhanced PCMs.
Dr. Aaron Wemhoff is currently an Associate Professor and Director of Graduate Studies in the Department of Mechanical Engineering at Villanova University. He joined Villanova in 2008 after three and a half years as a Thermal-Fluids Engineer at Lawrence Livermore National Laboratory. He earned his PhD in Mechanical Engineering in 2004 from UC Berkeley. Dr. Wemhoff currently serves as Chair of the ASME K-20 Committee on Computational Heat Transfer, is Past Chair of the Philadelphia Section of ASME, and is a Regional Editor for the International Journal of Transport Phenomena. His research interests include computational heat transfer, microscale heat transfer, and energy efficient system design. He is the author or co-author of over 60 peer-reviewed publications and has either given, or mentored students in, over 40 additional presentations.
Yale Goldman, Professor, Department of Physiology, University of Pennsylvania
"Mechanics and Material Properties of Dynein, the Cell's Spindly, Multi-Functional Cargo Carrier"
Dynein is an dimeric intracellular molecular motor that walks processively toward the minus end of cytoskeletal filaments, microtubules (MTs), using splitting of ATP as the fuel. Dyneins drive the motility of eukaryotic cilia and flagella, and are responsible for a wide range of other functions including the transport of cargo toward the center of the cell such as trash vesicles in neurons, alignment of the cell division apparatus, and segregation of the chromosomes during mitosis. Disruption of dynein-mediated neuronal transport has been implicated in neurodegeneration, and mutations in dynein and dynein associated proteins can cause a range of diseases including developmental and degenerrative neurological deficits. Despite the importance of dynein function, the mechanism by which dynein walks along the MT is not yet well understood.
The force-generating mechanism of dynein differs from those of the other cytoskeletal motors. To examine the structural dynamics of dynein’s stepping mechanism in real time we have used polarized total internal reflection fluorescence microscopy with nanometer accuracy localization to track orientation and position of single motors. By measuring the polarized emission of individual quantum nanorods coupled to the ring-shaped motor domain, we determined the angular position of the ring and found that it rotates relative to the MT while walking. The observed rotations are quite small, and occur more than twice as frequently as successful forward steps. These results are inconsistent with the power-stroke mechanism used by the other motors, in which Angstrom-sized structural changes at the active ATP-binding site are amplified into nanometer translations along the MT by a lever arm with mechanical disadvantage. Instead, the small rotations support a model in which inter-head strain when both heads are attached rotates the rings through bending and hinging of a flexible stalk which connects the ring with the MT. Mechanical compliances of the stalk and hinge at its tip were estimated by a 3.3 μs molecular dynamics simulation. The mechanical properties of the stalk cause the dynein motor to wobble and vary its stepping mechanism, a bit tipsy but not drunk, enabling it to navigate around obstacles and serve as a smart intracellular machine.
Yale obtained MD and PhD degrees at the University of Pennsylvania and was a Post-doctoral Fellow at University College London, UK. He is a professor of Physiology, former director of the Pennsylvania Muscle Institute at the School of Medicine, University of Pennsylvania and Associate Director of the Nano/Bio Interface Center. His laboratory studies molecular motors and protein synthesis. For these studies, he developed novel biophysical methods including laser photolysis of caged nucleotide substrates, nanometer tracking of position and orientation of single fluorescent probes and ultra-fast feedback infrared optical traps.
Andreas Polycarpou, Meinhard H. Kotzebue '14 Professor and James J. Cain Chair, Department of Mechanical Engineering, University of Texas A&M
"Tribology of Thin Films for Next Generation Material Systems Including Extreme High Temperature Conditions"
Modern devices that include rubbing components are expected to meet higher performance requirements under extreme operating conditions, thus rendering traditionally low cost materials and liquid lubrication ineffective. Tribology has emerged as one of the fields that contribute to the solution of environmental problems through the development of materials, products and solutions less hazardous or harmful to the environment. The air-conditioning and refrigeration industry, for example, has addressed this issue of greener technology shifting its attention towards advanced compressors that use environmentally friendly refrigerants and oil-less conditions. Similar cases are currently under investigation for oil & gas/energy applications. Under oil-less conditions, it becomes necessary to implement some type of advanced protective coatings on the interacting surfaces to withstand stringent rubbing conditions. Extreme operating conditions also include high to very high temperatures up to 1000°C. In this presentation, we present recent work using several polymeric-based high bearing coatings, including PTFE-based, PEEK-based and a newly developed aromatic thermosetting polyester (ATSP) -based coating. Some of the ATSP-based coating systems exhibited almost zero wear under both dry and boundary lubricated conditions. We also present work on a high temperature coating (HfB2-based) that is currently under development for extremely high temperature conditions.
Dr. Polycarpou received his Ph.D. from the University at Buffalo. Before joining Texas A&M in 2012, he was the Wilkins Professor and Associate Department Head at the University of Illinois Urbana-Champaign. He was also the Founding Department Chair of Khalifa University (Abu Dhabi) from 2011-2012, while on leave from the University of Illinois. Before that, he was a post-doctoral fellow at the Technion and a staff scientist at Seagate Technology. Dr. Polycarpou’s research interests include tribology, micro/nano tribology, nano mechanics, and advanced interface materials. Recent emphasis has been on micro/nanoscale contact problems with application to micro-devices, as well as the tribology of devices for reduced energy and improved environmental-related impact. Polycarpou is the author of about 200 archival journal papers, and numerous book chapters, volume proceedings, a dozen patents and conference papers. Polycarpou won numerous national and international awards, including the ASME Burt L. Newkirk Award, the National Science Foundation Faculty CAREER Award, the Xerox Award for Faculty Research, the STLE Edmond E. Bisson Award, a Fulbright Scholar, the ASME K.L. Johnson Best Paper Award and the STLE Walter D. Hodson Award. Polycarpou is active in the tribology and mechanics communities, where he served in many posts, including Chairing the ASME Tribology Division. He was also an Associate Editor for the ASME Journal of Tribology, serves on several Editorial Boards, has organized numerous conferences including being the Chair of the 2009 International Joint Tribology Conference. Dr. Polycarpou is currently serving on several honors and awards committees, as well as on the Executive committee of ASME’s Department Heads Council.
Eric Loth, Rolls-Royce Commonwealth Professor and Chair, Department of Mechanical and Aerospace Engineering, University of Virginia
“Morphing Rotor for Extreme Scale Wind Turbines"
To alleviate the mass-scaling issues associated with conventional upwind rotors in order to allow extreme-scale wind turbines (≥ 10-MW), a down-wind aligned morphing rotor concept is proposed. The concept employs a downwind rotor with blades whose elements are relatively stiff (no intentional flexibility) but with hub-joints that can be unlocked to allow for moment-free downwind alignment. Aligning the combination of gravitational, centrifugal, and thrust forces along the blade path reduces downwind cantilever loads, resulting in primarily tensile loading. The blade curvature can be fixed based on design conditions so that morphing is achieved with a single degree of freedom using a near-hub joint for coning angle. To quantify potential mass savings, a downwind load-aligning rotor two-bladed was investigated with a near-hub hinge to allow morphing as a function of wind speed. The morphing rotor had a 25% reduced mass of 33% but also a higher tip speed and and a slight loss in power (3%). The morphing schedule between cut-in and rated conditions resulted in a downwind angle that varied linearly cutt-in and rated conditions. Preliminary aeroelastic analysis and unsteady simulations (e.g. at gust and off-design conditions) indicate this concept is feasible and may allow the world's largest wind turbine. However, there there are challenges regarding tower shadow, blade segmentation, morphing mechanics and levelized cost of energy reduction.
Eric Loth received his PhD in Aerospace Engineering at the University of Michigan in 1988 and is currently the Chair of Department of Mechanical & Aerospace Engineering at the University of Virginia and a Rolls-Royce Professor. His research on wind energy has focused on offshore extreme-scale morphing concepts and has been featured in dozens or articles including: USA Today, MIT Technology Review, and Popular Science. Loth has authored over 200 publications and has received honors and awards from NSF, NASA, and the Department of the Navy. He was named a Fellow of the American Society of Mechanical Engineers, of the National Center for Supercomputing Applications, and Magdalene College of Cambridge University.