MEAM Seminar Series Spring 2015
For Fall 2014 Seminars, click here.
Seminars are held on Tuesday mornings, with coffee at 10:30 am in the Levine Hall Mezzanine and the seminar beginning at 10:45 am in Wu and Chen Auditorium (unless otherwise noted).
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Yanfei Gao, Associate Professor, Department of Materials Science and Engineering, University of Tennessee
"Convoluted Thermal/Spatial Statistics and Scale Effects in Nanoindentation Plasticity"
Sudden discontinuities, or called pop-ins, are often found on nanoindentation load-displacement curves for single crystals. For defect-free crystals under nano-contacts, the pop-in is a result of homogeneous dislocation nucleation, and the observed fluctuations in the pop-in load result purely from the thermally activated process. At intermediate contact sizes, such fluctuations can arise from the spatial statistics of pre-existing defects. It is found that the convolution of the above thermal and spatial effects exhibits a distinct dependence on the stressed volume size, dislocation density, and geometric factors that describe crystallography and slip anisotropy. Both homogeneous and heterogeneous mechanisms are modeled in a unified framework that predicts how the fluctuations of pop-in loads vary with respect to the above factors. Predictions agree very well with our experiments on Mo and NiAl single crystals. Our method has also been generated to develop a “mechanical probe” of the microscopic structural heterogeneities in the metallic glasses, in which a quantitative relationship between defect density and the ductile-to-brittle transition can be established.
Yanfei Gao is currently an Associate Professor and Director of Graduate Studies of the Department of Materials Science and Engineering, University of Tennessee, and a Joint Faculty in Materials Science and Technology Division, Oak Ridge National Laboratory. His research group focuses on modeling and simulation of plasticity at small length scales, thin-film growth, contact and friction, and constitutive behavior of amorphous alloys, among many others. He has been the PI on five NSF grants and co-PI on a number of other NSF and DOE projects. He has given two invited talks in the Gordon Research Conferences. He received degrees from Tsinghua University (China) and Princeton University, and performed post-doctoral research at Brown University.
Due to the Winter Storm, this event has been Rescheduled for February 17th (see below)
Due to the Winter Storm, this event has been Rescheduled for March 31st (see below)
Nikolaos Aravas, Professor of Computational Mechanics, Department of Mechanical Engineering University of Thessaly, Greece and Visiting Professor, Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania
"Strain-gradientelasticity: Constitutive Modeling and Numerical Techniques"
Theories with intrinsic or material length scales find applications in the modeling of size-dependent phenomena, such as the localization of plastic flow into shear bands. In gradient-type plasticity theories, length scales are introduced through the coefficients of spatial gradients of one or more internal variables. In elasticity, length scales enter the constitutive equations through the elastic strain energy function, which, in this case, depends not only on the strain tensor but also on gradients of the rotation and strain tensors.
We focus our attention on linear strain-gradient elasticity theories. The appropriate Airy stress functions and double-stress functions are identified and the appropriate boundary value problem is formulated. A reciprocity theorem is developed and the corresponding Saint-Venant principle is derived. It is shown also that several “technical theories of beams”, such as axial tension and torsion of pretwisted beams, can be viewed as special cases of a strain-gradient elasticity theory.
In such theories, when the problem is formulated in term of displacements, the governing partial differential equation is of fourth order. If traditional finite elements are used for the numerical solution of such problems, then C1 displacement continuity is required. An alternative "mixed" finite element formulation is developed, in which the displacement and displacement –gradients are used as independent unknowns and their relationship is enforced in an "integral-sense." The resulting finite elements require only C0 continuity and are simple to formulate.
An asymptotic crack-tip solution under plane strain conditions is developed, the corresponding “energy release rate” is determined in terms of the material length scale, and possible fracture criteria are discussed.
Nick Aravas was born (1957) and raised in Thessaloniki, Greece, where he studied Mechanical Engineering at the Aristotle University of Thessaloniki and graduated in 1980. He received his M.S. (1982) and Ph.D. (1984) in Theoretical and Applied Mechanics from the University of Illinois at Urbana-Champaign (UIUC). During his graduate studies he worked as a Teaching and Research Assistant, and in 1982 he received the “J. O. Smith Award for teaching excellence”, which is presented every year by the Department of Theoretical and Applied Mechanics of the UIUC to the “outstanding young teacher in Engineering Mechanics”.
In 1985, he worked as a Senior Engineer in Hibbitt, Karlsson and Sorensen, Inc., the developers of the ABAQUS general purpose finite element program. His academic career started in 1986 when he joined the Department of Mechanical Engineering and Applied Mechanics of the University of Pennsylvania (PENN), where he taught for 11 years. At PENN he held also a secondary appointment in the department of Materials Science and Engineering. His research focuses in the areas of Mechanics of Materials and Computational Mechanics. He is the author or numerous papers in scientific journals, Associate Editor of the ASME Journal of Applied Mechanics, and serves as a reviewer for many scientific journals in the areas of mechanics and materials. His work is recognized internationally and has received a large number of citations by other scientists.
Steven Schmid, Professor, Aerospace and Mechanical Engineering Department, University of Notre Dame
"Selected Topics in Orthopedic Implant Design"
This seminar will present two advances for the orthopedics industry that have been extensively investigated at the University of Notre Dame: the design of minimally invasive implants, and manufacturing options for bone ingrowth scaffolds.
Minimal invasiveness has always been a design goal for the orthopedic implant industry. However, recent advances in surgical techniques, materials and instruments have allowed innovative new designs to come to the fore, allowing a simultaneous reduction in pain, surgery complexity, and rehabilitation time and cost while preserving existing implant costs. New designs exploiting the in vivo phase change are described, with materials research progress emphasized.
Over the past ten years, a novel cellular solid, trabecular metal (TM), has been developed for use in the orthopedics industry as an ingrowth scaffold. Manufactured using chemical vapor deposition (CVD) on top of a graphite foam substrate, this material has a regular matrix of interconnecting pores, high strength, and high porosity. For some implant applications, plastic deformation through stamping is a useful manufacturing approach after CVD, but a better knowledge of the forming properties of TM is required. In this study, a forming limit diagram for TM was obtained using 1.65 mm thick sheets.
Dr. Schmid is a Full Professor in the Aerospace and Mechanical Engineering Department at the University of Notre Dame, where he conducts research in manufacturing, tribology and design, especially as related to orthopedic implants. Dr. Schmid has co-authored twenty books, has written over 90 peer-reviewed papers and over 120 conference papers and presentations. Of his textbooks, Manufacturing Engineering and Technology (with S. Kalpakjian) is the world's most popular manufacturing textbook, and is available in Spanish, Chinese, Italian, Arabic, Greek, German, and Korean editions, with Indonesian and Macedonian translations in process. Manufacturing Processes for Engineering Materials (with S. Kalpakjian), Fundamentals of Machine Elements and Fundamentals of Fluid Film Lubrication (with B. Hamrock and B. Jacobson) are selected titles of his other books. Dr. Schmid has received numerous teaching and research awards, and is a Kaneb Teaching Fellow at the University of Notre Dame. From 2012-2013, he served as the first Faculty Fellow at the Advanced Manufacturing National Program Office, where he was part of the team that developed the preliminary design of the National Network for Manufacturing Innovation.
Denis Cormier, Earl W. Brinkman Professor of Industrial and Systems Engineering, Rochester Institute of Technology
"Multifunctional 3D Printing"
3D printing is the result of 2D images that are printed on top of one another to build up thickness. Although 3D printing has existed for over 20 years, the majority of 3D printers have been designed to work with a single material. However, inkjet and Xerographic printers with three or more print heads/engines have long been used to produce 2D multi-color documents. When multiple print heads are repurposed to deposit functional nanomaterials rather than color pigments, a whole new world of possibilities emerges. Rather than printing parts that serve purely mechanical functions, multifunctional 3D printing technologies have potential to produce parts that perform mechanical, electrical, thermal, optical, and/or chemical functions. Blending multiple materials within a part is not trivial though, and a great deal of development work is needed to realize the tremendous potential of multifunctional 3D printing. This talk will introduce the audience to several multifunctional printing technologies such as Aerosol Jet printing, micro-extrusion, and pulsed photonic curing. Selected multi-material applications will then be presented. Lastly, some open research challenges associated with multifunctional 3D printing will be discussed.
Dr. Denis Cormier is the Earl W. Brinkman Professor of Industrial and Systems Engineering at the Rochester Institute of Technology. He has worked in the area of additive manufacturing (commonly known as 3D printing) for nearly 20 years. Most recently, his research has focused on multi-material functional printing processes and materials. Prior to joining RIT in 2009, he was a professor at North Carolina State University for 15 years where he founded NC State's Rapid Prototyping Lab in 1996. He is a founding member of ASTM’s F-42 additive manufacturing standards group, and he serves as Chairman of the Society of Manufacturing Engineer’s Rapid Technologies and Additive Manufacturing steering committee. He also serves on the editorial advisory boards for two journals - the Rapid Prototyping Journal, and Additive Manufacturing. Dr. Cormier is also a UPenn alum (BS in Systems Engineering, 1989).
Thursday, March 5
Mahmut Selman Sakar, Senior Research Scientist, Institute of Robotics and Intelligent Systems, ETH Zurich
1:45 pm, Levine 307
"Microrobotic Platforms in Bioengineering and Translational Medicine"
Biological systems are exquisitely sensitive to the location, dose and timing of physiologic cues and drugs. This spatiotemporal sensitivity necessitates the development of bioengineering platforms that can apply well-characterized local signals to understand fundamental principles of cellular behavior and to create novel therapeutic approaches for minimally invasive medicine. Microrobotics is a relatively young field in which materials science and microelectromechanical systems (MEMS) technology meet robotics creating the next generation complex machines operating in three-dimensional microenvironments. In this talk, I will present the design and fabrication of untethered magnetic microrobots for targeted and triggered therapy. Several examples will be demonstrated to explain how microrobotic technologies can be utilized to introduce compact and versatile bioengineering platforms. These platforms will be able to perform automated micromanipulation on biological samples with high dexterity and precision and provide critical mechanistic insight on the generation, transmission and coordination of cellular forces during development, regeneration and physiological function.
Mahmut Selman Sakar received the B.S. in Electrical and Electronics Engineering with honors from Bogazici University in 2005 and the Ph.D. in Electrical and Systems Engineering from University of Pennsylvania in 2010. During his doctoral studies, he worked on microrobotics and single cell manipulation under the supervision of Prof. George J. Pappas and Prof. Vijay Kumar. Before joining Institute of Robotics and Intelligent Systems in 2012, he worked as a postdoctoral associate with Prof. Harry Asada in the Department of Mechanical Engineering, Massachusetts Institute of Technology on the generation and optogenetic control of engineered skeletal muscle microtissues. Currently he is a senior research scientist in Prof. Bradley Nelsonís laboratory at ETH Zurich and he is working on the development of microrobotic platforms for several bioengineering applications.
Ellen Kuhl, Associate Professor of Mechanical Engineering, Bioengineering (courtesy), and Cardiothoracic Surgery (courtesy), Stanford University
"Neuromechanics of Human Brain Development"
Convolutions are a classical hallmark of most mammalian brains. Brain surface morphology is often associated with intelligence and closely correlated to neurological dysfunction. Yet, we know surprisingly little about the underlying mechanisms that drive cortical folding. To explore the evolution of brain surface morphology, we have created a neuromechanical model using the nonlinear field theories of mechanics supplemented by the continuum theory of finite growth. Continuum modeling allows us to seamlessly integrate information across the scales and correlate organ-level phenomena such as cortical folding to molecular-level processes such as axonal elongation. We show that our model can predict the formation of complex surface morphologies including symmetry breaking and secondary folding. Computational modeling naturally explains why larger mammalian brains tend to be more convoluted than smaller brains and provides a mechanistic interpretation of pathological malformations of lissencephaly and polymicrogyria. Understanding the role of mechanics during the development of the nervous system may have direct implications on the diagnostics and treatment of neurological disorders including severe retardation, epilepsy, schizophrenia, and autism.
Dr. Kuhl is an Associate Professor of Mechanical Engineering, Bioengineering (courtesy), and Cardiothoracic Surgery (courtesy). She completed her Ph.D in Civil Engineering at the University of Stuttgart, Germany, in 2000. Her professional expertise is living matter physics, the creation of theoretical and computational models to predict the acute and chronic response of living structures to environmental changes during development and disease. Her specific interest is the multiscale modeling of growth and remodeling, the study of how living matter adapts its form and function to changes in mechanical loading, and how this adaptation can be traced back to structural alterations on the cellular or molecular levels. Growth and remodeling can be induced naturally, e.g., through elevated pressure, stress, or strain, or interventionally, e.g., through prostheses, stents, tissue grafts, or stem cell injection. Combining theories of electrophysiology, photoelectrochemistry, biophysics, and continuum mechanics, Dr. Kuhl's lab has specialized in predicting the chronic loss of form and function in growing and remodeling cardiac tissue using patient-specific custom-designed finite element models.
Joint MEAM-ESE Special Seminar
Hiroyuki Fujita, Professor, Institute of Industrial Science and Director, Center for International Research on Micronano Mechatronics (CIRMM)
University of Tokyo
1:30-2:30 pm, Singh Center Glandt Forum
"In situ TEM Observation Using Active MEMS Devices"
Abstract: My research group has investigated MEMS (micro electro mechanical system) fabrication and microactuators since 1986. Recently, we inserted and operated MEMS devices in the specimen chamber of the transmission electron microscope (TEM). We conducted the tensile and shear testing, and the heat transfer measurement of nano junctions while the junctions were in situ observed by TEM. The tensile testing of a silicon junction of a few nm in diameter showed its extraordinary large plastic deformation. The shear deformation of a silver nano junction exhibited series of sub-nm steps correlated with the crystalline spacing of the material; this is like a miniaturized version of stick-slips during frictional motion. Furthermore, the heat transfer through a short and thin, both in a few nm, silicon junction was much higher than the bulk value because of ballistic heat transfer. Also we have built a MEMS liquid cell in which the growth of a gold electrode by electroplating was observed in real time.
Bio: Dr. Fujita’s 20 year career history illustrates his exceptional technical and professional expertise in MR technology development and productization. His cutting edge research experience includes MR RF coil research and coil product development for major global OEM players which combined capture the majority of global market share in MRI systems.
Dr. Fujita is an author of 15 patents, and has published more than 30 technical papers and abstracts over the past 10 years. He is a respected leader in the International Society for Magnetic Resonance in Medicine (ISMRM). Dr. Fujita is also currently involved as PI or Co-PI in several fully funded, ongoing MRI technology projects. Dr. Fujita serves as Adjunct Full Professor of Physics and Radiology, Department of Physics and Department of Radiology (School of Medicine) at Case Western Reserve University, and Adjunct Full Professor, School of Information Technology and Electrical Engineering at The University of Queensland (Australia).
He serves on the Board of Directors/Trustees for numerous organizations, including The Cleveland Orchestra, The Cleveland Foundation, Global Cleveland, Hawken School, The Great Lakes Science Center and the Inamori International Center of Ethics and Excellence at Case Western Reserve University. After attending school at Waseda University in Tokyo, Dr. Fujita came to the United States of America, and received a BA in mathematics and physics from Monmouth College, and a PhD in Physics from Case Western Reserve University.
In recognition of growing a successful high-tech manufacturing company in the United States of America, President Barack Obama and First Lady Michelle Obama invited Dr. Fujita to be an honored guest, and to sit in the First Lady’s Box at the 2012 State of the Union Address.
Eric Shaqfeh, Lester Levi Carter Professor and Department Chair of Chemical Engineering, Stanford University, NAE
"How the Dynamics of Vesicle and Capsule Suspensions in Flow May Affect Your Bleeding Time"
It is well known that individual vesicles or liposomes (i.e. fluid enclosed by a lipid bilayer membrane suspended in a second fluid) are characterized by a remarkable dynamics in flow. For vesicles that are “near spheres” this dynamics includes at least 5 different types of orbits in shear flow that are functions of the viscosity ratio between the inner and outer fluid as well as the Capillary number based on the bending modulus. It is therefore not surprising that a suspension of vesicles is characterized by fascinating collective behavior as well. I will discuss our recent development of a numerical code (based on Loop subdivision) which allows the Stokes flow simulation of non-dilute suspensions of vesicles and capsules at essentially any value of the reduced volume. We will then use these numerical simulations to examine a number of interesting phenomena including: 1) The stability of vesicle shapes in extensional flows, 2) The lift of a vesicle away from a wall and the resulting “Fahraeus-Lindqvist” layer for the flow of a wall-bound suspension of vesicles/capsules, and 3) Platelet margination and adsorption in the microcirculation as a function of hematocrit and its relation to bleeding time.
Eric Shaqfeh is the Lester Levi Carter Professor and Department Chair of Chemical Engineering at Stanford University. He joined Stanford’s faculty in 1990 after earning a B.S.E. summa cum laude from Princeton University (1981), and a M.S. (1982) and Ph.D. (1986) from Stanford University. In 2001 he received a dual appointment and became Professor of Mechanical Engineering. He is most recently (as of 2004) a faculty member in the Institute of Computational and Mathematical Engineering at Stanford. Shaqfeh’s current research interests include non-Newtonian fluid mechanics (especially in the area of elastic instabilities, and turbulent drag reduction), nonequilibrium polymer statistical dynamics (focusing on single molecules studies of DNA), and suspension mechanics (particularly of fiber suspensions and particles/vesicles in microfluidics). He has authored or co-authored over 170 publications and has been an Associate Editor of the Physics of Fluids since 2006. Shaqfeh has received the APS Francois N. Frenkiel Award 1989, the NSF Presidential Young Investigator Award 1990, the David and Lucile Packard Fellowship in Science and Engineering 1991, the Camile and Henry Dreyfus Teacher--Scholar Award 1994, the W.M. Keck Foundation Engineering Teaching Excellence Award 1994, the 1998 ASEE Curtis W. McGraw Award, and the 2011 Bingham Medal from the Society of Rheology. A Fellow of the American Physical Society (2001) and a member of the National Academy of Engineering (2013), he has held a number of professional lectureships, including the Merck Distinguished Lectureship, Rutgers (2003), the Corrsin Lectureship, Johns Hopkins (2003) and the Katz Lectureship, CCNY (2004). He was also the Hougen Professor of Chemical Engineering at the University of Wisconsin (2004) and the Probstein Lecturer at MIT (2011).
George Adams, College of Engineering Distinguished Professor, Department of Mechanical and Industrial Engineering, Northeastern University
"Adhesion and Pull-Off Force of an Elastic Indenter from an Elastic Half Space"
The adhesion between an elastic punch and an elastic half-space is investigated for plane and axisymmetric geometries.The pull-off force is determined for a range of material combinations. This configuration is characterized by a generalized stress intensity factor which has an order less than one-half.The critical value of this generalized stress intensity factor is related to the work of adhesion, under tensile loading, by using a cohesive zone model in an asymptotic analysis of the separation near the elastic punch corner.These results are used in conjunction with existing results in the literature for the frictionless contact between an elastic semi-infinite strip and half-space in both plane and axisymmetric configurations.It is found that the value of the pull-off force includes a dependence on the maximum stress of the cohesive zone model.As expected this dependence vanishes as the punch becomes rigid, in which case the order of the singularity approaches one-half.At the other limit, when the half-space becomes rigid, the stresses become bounded and uniform and the pull-off force depends linearly on the cohesive stress and is independent of the work of adhesion.Thus the transition from fracture-dominated adhesion to strength-dominated adhesion is demonstrated.
Dr. George G. Adams is Professor of Mechanical Engineering at Northeastern University where he has served on the faculty for over thirty years. His areas of expertise are contact mechanics, adhesion, and tribology; MicroElectroMechanical Systems (MEMS), especially RF MEMS switches and micromirrors; and nano-mechanics (including material characterization, adhesion, and mechanical and electrical contacts). He has published about 100 refereed journal papers and has had numerous research grants and contracts with government and industry.
George received his B.S. in Mechanical Engineering from Cooper Union in 1969, and his M.S. and Ph.D. in Mechanical Engineering (Applied Mechanics) from the University of California at Berkeley in 1972 and 1975 respectively. Dr. Adams then became an Assistant Professor of Mechanical Engineering at Clarkson University in Potsdam, New York, and a Research Associate at the IBM Research Laboratory in San Jose, California, prior to joining Northeastern University. Professor Adams was co-founder and the first chair of the Contact Mechanics Technical Committee of the American Society of Mechanical Engineers (ASME). He has served as an Associate Editor of the ASME Journal of Tribology, STLE Tribology Transactions, and of Microsystems Technologies. Dr. Adams is a Fellow of the ASME and STLE, and is College of Engineering Distinguished Professor at Northeastern University.
Saverio Spagniole, Assistant Professor of Mathematics, University of Wisconsin-Madison
"Entrapment, escape, and diffusion of microswimmers in complex environments"
We will begin by addressing the hydrodynamic entrapment of a self-propelled body near a stationary spherical obstacle. Simulations of model equations show that the swimmer can be trapped by a spherical colloid larger than a critical size, that sub-critical interactions result in short residence times on the surface, and that the basin of attraction around the colloid is set by a power-law dependence on the colloid size and swimmer dipole strength. With the introduction of Brownian fluctuations, swimmers otherwise trapped in the deterministic setting can escape from the colloid at randomly distributed times. The distribution of trapping times is governed by an Ornstein-Uhlenbeck process, resulting in nearly inverse-Gaussian or exponential distributions. Analytical predictions are found to match very favorably with the numerical simulations. We also explore the billiard-like motion of such a body inside a regular polygon and in a patterned environment, and show that the dynamics can settle towards a stable periodic orbit or can be chaotic depending on the nature of the scattering dynamics. We envision applications in bioremediation, sorting techniques, and the study of motile suspensions in heterogeneous or porous environments.
Saverio Spagnolie received a Ph.D. in mathematics at the Courant Institute of Mathematical Sciences, then held postdoctoral positions in the Mechanical/Aerospace Engineering department at UCSD and in the School of Engineering at Brown University. He is currently an Assistant Professor in mathematics at the University of Wisconsin-Madison.
April 28 - OPEN SLOT