Emanuela Del Gado
Tuesday, May 29, 2018 - 8:15am 9:15am - W16 - Kresge Main
Provost’s Distinguished Associate Professor
Department of Physics
Georgetown University, Washington, DC
Sustainable concrete and cement: A soft matter in construction
Emanuela Del Gado
Abstract: Concrete and cement are the foundation of our global infrastructure and have a key role in the growth which is required to support a world population projected to surge past 9 billion by mid-century, with more than 70% living in urban areas. More than 20 billion tons of concrete are produced every year, more than any other material on Earth, such that concrete production is responsible for 10% of the whole anthropogenic production of CO2. Reducing CO2 emissions for concrete production, designing and optimizing material performances, resilience and durability is hence crucial to a sustainable growth and to meet Greet House Emissions reduction goals.
Strength and other mechanical properties of concrete rely on cement (its main binding agent) and the control of the formation/gelation of calcium-silicate-hydrates (C-S-H). Lack of scientific insight into the structure and mechanics of C-S-H is a major obstacle to optimizing material performances and developing greener formulations of concrete. In recent years electron microscopy imaging, nano-indentation tests, X-rays and neutron scattering, NMR analysis, and atomistic simulations have elucidated several structural and mechanical features concentrated within a few nanometers. A potential breakthrough has been combining such experimental insights with novel fundamental understanding gained through modeling and numerical simulations, which use statistical and condensed matter physics approaches to tackle the structural and mechanical complexity of the material over critical lengthscales. These achievements provide novel opportunities to transform cement production and use.
Biosketch: Emanuela Del Gado is a theoretical physicist working on engineering motivated problems. She uses statistical mechanics and computational physics to investigate materials with structural and dynamical complexity, from model amorphous solids, gels and glasses, to new green formulations of cement.
Prof. Del Gado received her undergraduate degree (Laurea in Physics, cum laude) at the University of Naples "Federico II" in Italy, where she also obtained a PhD in Physics in 2001. She has been a Marie Curie Fellow at the University of Montpellier II in France and a post-doctoral researcher at ETH Zurich in Switzerland, and hold visiting positions at ESPCI (France) and MIT. Before joining Georgetown University, Emanuela was the Swiss National Science Foundation professor in the Department of Civil Environmental and Geomatic Engineering at ETH Zurich.
Professor Del Gado's research interests are in the areas of statistical mechanics and computational physics; structure, cooperative dynamics and nonlinear mechanics of amorphous solids, gels and glasses; nanoscale structure and mechanics of cement gels; self-assembly of nanoparticles and fibrils at liquid interfaces; biomimetic coatings and mechanics of tissues.
Christian Hellmich
Tuesday, May 29, 2018 - 1:00pm 2:00pm - W16 - Kresge Main
Professor for Strength of Materials and Computational Mechanics
Dept of Civil Engineering
Vienna University of Technology (TU WIEN) Vienna, Austria
Towards unified hierarchical modeling of hard and soft biological tissues
Christian Hellmich
Abstract: Traditionally, the realms of hard and soft tissue biomechanics are strictly separated: hard tissue biomechanics is typically based on elasto-plastic or elasto-damage formulations in the small strain regime, while soft tissue biomechanics has its roots in hyperelastic rubber modeling. Both of these two traditional approaches face the challenge of highly scattering material parameters, which rarely allow for reliable predictions of untested situations.
In the hard tissue realm, this challenge has been met with the advent of engineering micromechanics in the early 2000s. Key ingredients of this success were the hierarchical sequencing of traditional homogenization schemes such as two-phase Mori-Tanaka and self-consistent schemes, the extension from two-phase to multi-phase systems, and the consideration of eigenstrains and their upscaling characteristics, which paved the way towards a unified vision of bone multiscale biomechanics,encompassing poro-elasticity, poro-plasticity, and creep; all based on a few “universal” mechanical properties of bone’s elementary components: collagen, hydroxyapatite, and water.
Can this success be repeated also for soft tissues? The lecture will give an affirmative answer, based on recently developed theoretical tools allowing for the modeling of load-induced changes in the tissue micro-morphology, as it evolves under large strains at different observational levels.
Biosketch: Dr. Christian Hellmich, M.ASCE, F.EMI, Full Professor at the Department of Civil Engineering of the Vienna University of Technology (TU Wien), is the director of the Institute for Mechanics of Materials and Structures. At TU Wien, he received his engineering, PhD, and habilitation degrees (in 1995, 1999, and 2004, respectively). From 2000 to 2002, he was a Max Kade Postdoctoral Fellow in the Department of Civil and Environmental Engineering at the Massachusetts Institute of Technology. He is well known for his well-ˇvalidated material and (micro)structural models, in terms of theoretical foundations and applications to concrete, soil, rock, wood, bone, and biomedical
implants, up the structural level (tunnels, pipelines, biological organs such as the skeleton) -ˇ with complementary experimental activities if necessary. On these topics, he has directed various interdisciplinary and multinational research consortia, and he has published more than 125 papers in international refereed scientific journals.
Pedro Miguel Reis
Friday, June 1, 2018 - 8:00am 9:00am - W16 - Kresge Main
Flexible Structures Laboratory
Institute of Mechanical Engineering
École Polytechnique Fédérale de Lausanne (EPFL), Switzerland
Shell-buckling revisited: “Everybody loves a buckling problem!”
Pedro Miguel Reis
Abstract: From viral capsids and fuel tanks, to architectural domes, slender shells are ubiquitous in natural and engineered structures. The mechanics of shells is tightly intertwined with the underlying geometry and the onset for instability is a classic problem in structural mechanics. Since the golden era of shell buckling in the 1960’s, a plethora iof theoretical and computational studies have addressed this canonical problem, but there is a striking lack of precision experiments to corroborate the multitude of predictions. We have recently revisited this old field by introducing a framework of precision model experiments to thoroughly quantify both the buckling onset, as well as the postbuckling regime of pressurized spherical shells. Central to this effort, we have devised a robust, versatile, and precise fabrication mechanism to rapid prototype thin shells of nearly constant thickness that contain precisely designed geometric imperfections. By systematically varying the amplitude of these defects, we study the effect that these imperfections have on the buckling strength of our spherical shells. Small deviations from the spherical geometry result in large reductions in the buckling pressure and our experimental results agree well with some existing theories. We then perform a broader exploration for other classes of defects, for which theoretical predictions are yet to be developed. Our ultimate goal is to develop a predictive foundation for the mechanisms that affect the knockdown factors of spherical shells towards a rational design framework that goes beyond the prevailing empirical status quo.
Biosketch: Pedro M. Reis is a Professor of Mechanical Engineering at the École Polytechnique Fédérale de Lausanne (EPFL), Switzerland. His research group, the Flexible Structures Laboratory, is dedicated to the fundamental understanding of the mechanics of slender structures and their intrinsic geometric nonlinearities. Prof. Reis received a B.Sc. from the University of Manchester, UK (1999), a Certificate of Advanced Studies in Mathematics (Part III Maths) from St. John’s College and DAMTP, University of Cambridge (2000) and a Ph.D. from the University of Manchester (2004). He postdoc positions at the City College of New York (2004-05) at the ESPCI in Paris (2005-07). He joined MIT in 2007 as an Instructor in Applied Mathematics in the Department of Mathematics. In 2010 he moved to MIT’s School of Engineering, with dual appointments in Mechanical Engineering and Civil & Environmental Engineering, first as the Esther and Harold E. Edgerton Assistant Professor and after 2014 as Gilbert W. Winslow Associate Professor. In October 2013, the Popular Science magazine named Prof. Reis to its 2013 “Brilliant 10” list of young stars in Science and Technology. He has also received the 2014 CAREER Award (NSF), the 2016 Thomas J.R. Hughes Young Investigator Award (Applied Mechanics Division of the ASME), the 2017 GSOFT Early Career Award for Soft Matter Research (APS) and he is a Fellow of the APS.
More information on the activities of his research group can be found in the following link: https://flexlab.epfl.ch/en/
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Roger Ghanem
Thursday, May 31, 2018 - 9:00am 10:00am - W16 - Kresge Main
Professor of Engineering Technology
Civil and Environmental Engineering and Aerospace and Mechanical Engineering
University of Southern California | USC Viterbi School of Engineering
Physics, Structure, and Uncertainty: Probabilistic Learning for Risk Mitigation
Roger Ghanem
Abstract: Increasingly, critical decisions are demanded for situations where likelihoods are not sufficiently constrained by models. This could be caused by the lack of suitable mathematical models or the inability to compute the behavior of these models, or observe the associated physical phenomena, under a sufficient number of operating conditions. In many of these situations, the criticality of the decisions is manifested by the need to make inferences on high consequence events, which are typically rare. The setting is thus one of characterizing extreme events when useful models are lacking, computational models are expensive, or empirical evidence is sparse. We have found adaptation and learning to provide transformative capabilties in all of these settings. A key observation is that models and parameters are typically associated with comprehensive constraints that impose conservation laws over space and time, whose solution yields spatio-temporal fields, and that require comprehensive calibration with exhaustive data. Decisions typically depend on quantities of interest (QoI) that are agnostic to this complexity and that are constructed through an aggregation process over space, time, or behaviors.
A regularization can thus be imposed by allowing the QoIs to drive the complexity of the problem. But then one has to learn the QoIs.
This talk will describe recent procedures for probabilistic learning of QoIs using both orthogonal projections and manifold learning. Both approaches are applied to science and engineering problems where models are either too expensive to compute or too inconclusive to provide acceptable interpolation to data. In both cases, probabilistic inferences are possible as required by risk assessment and probability-based design.
Biosketch: Roger Ghanem is the Gordon S. Marshall Professor of Engineering Technology at the University of Southern California. He works in probabilistic modeling and numerics. Ghanem is past president of EMI, and currently serves on the Executive Council of the USACM and as Chair of the SIAM Special Interest Group on Uncertainty Quantification. He is a fellow of EMI, USACM and AAAS.
Nadia Lapusta
Thursday, May 31, 2018 - 1:00pm 2:00pm - W16 - Kresge Main
Professor of Mechanical Engineering and Geophysics
Department of Mechanical and Civil Engineering & Seismological Laboratory
California Institute of Technology
Under the hood of the earthquake machine
Nadia Lapusta
Abstract: Many major faults, such as the San Andreas in California, separate two tectonic plates that slowly move past each other in opposite directions. Some of the faults remain locked for many years and then slip in sudden dramatic rupture events perceived as earthquakes. These occasional dynamic motions co-exist with much slower, quasi-static fault slips that can now be imaged by geodetic methods. We will present the current physical understanding and numerical modeling of these processes that incorporate laboratory-derived fault friction laws, shear heating, and effects of pore fluids. The models can reproduce all stages of the past behavior of some fault segments – including locked, slowly moving, and earthquake-producing – with remarkable qualitative, and often quantitative, agreement. In part, they reveal the potential physics behind the unexpected extreme events, such the 2011 Mw 9.0 Tohoku earthquake in Japan that caused up to 40-meter tsunami and numerous casualties. Such continuum-mechanics-based models, when further developed, will enable us to incorporate our increasing understanding of earthquake source physics into the assessment of seismic hazards and seismicity response to perturbations of natural or anthropogenic origins.
Biosketch: Nadia Lapusta is a Professor of Mechanical Engineering and Geophysics at the California Institute of Technology. She has received her undergraduate education in Applied Mathematics and Mechanics from Kiev State University in Ukraine and the PhD degree in Engineering Sciences from Harvard University. Her interdisciplinary research group works in the areas of computational mechanics of geomaterials, earthquake source physics, fundamentals of friction and fracture, and solid-fluid interactions. She serves as the leader of the Fault and Rock Mechanics group of the Southern California Earthquake Center (SCEC) and the Vice Chair of the Executive Committee of Deformation Experimentalists at the Frontier of Rock and Mineral Research (DEFORM).
Lydia Bourouiba
Friday, June 1, 2018, 2018 - 1:00pm 2:00pm - W16 - Kresge Main
Esther and Harold E. Edgerton Career Development Professor
Assistant Professor, Civil and Environmental Engineering and Mechanical Engineering
Affiliate Faculty of the Institute for Medical Engineering and Science
Harvard-MIT Health Sciences and Technology (HST) Faculty
Unsteady fluid fragmentation
Lydia Bourouiba
Abstract: Understanding secondary droplet formation from fluid fragmentation is critical for industrial, environmental, and health processes including for predicting and controlling the transport of pathogen-bearing droplets created from contaminated fluids or surfaces. Despite the complexity and diversity of modes of unsteady fluid fragmentation into secondary droplets, universality across geometry and fluid systems emerges. We will discuss results from our recent joint experimental and theoretical investigations elucidating the role of unsteadiness in shaping a ubiquitous, yet neglected class of fluid fragmentation problems. In particular, we revisit fundamental assumptions of hydrodynamic instability and reveal how unsteadiness and multi-scale dynamics couple to select the sizes and speeds of secondary droplets generated. The implications for human health and food safety will be discussed.
Biosketch: Prof. Lydia Bourouiba is the Esther and Harold E. Edgerton Career Development Professor at the Massachusetts Institute of Technology. She directs the Fluid Dynamics of Disease Transmission Laboratory. Her research specializes in joining advanced mechanical, physical, and biological experiments and applied mathematics to elucidate the fundamental fluid dynamics governing the multiscale dynamics of pathogen transmission in human, animal, and plant populations where drops, multiphase, and complex flows are at the core. Such understanding is important to develop novel disease mitigation and pathogen control strategies in human health and agriculture. More on her recent work can be found at lbourouiba.mit.edu.