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.
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.
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.
February 10 - OPEN SLOT - NO SCHEDULED SEMINAR
February 17 - OPEN SLOT - NO SCHEDULED SEMINAR
Andrei Shkel, Professor of Mehcanical and Aerospace Engineering, University of California, Irvine
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).
Ellen Kuhlr, Associate Professor of Mechanical Engineering, Bioengineering (courtesy), and Cardiothoracic Surgery (courtesy), Stanford University
Eric Shaqfeh, Lester Levi Carter Professor and Department Chair of Chemical Engineering, Stanford University
Abstract: 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.
Bio: 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). Eric has been married to Terhilda Garrido for 30 years, and they have two children, Stefan, 25, and Elena, 21.
March 31 - OPEN SLOT
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