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Bio: Dr. Pablo Zavattieri is a Professor of Civil Engineering and University Faculty Scholar at Purdue University. Zavattieri received his BS/MS degrees in Nuclear Engineering from the Balseiro Institute (Argentina) and PhD in Aeronautics and Astronautics Engineering from Purdue University. He worked at the General Motors Research and Development Center as a staff researcher for 9 years, where he led research activities in the general areas of computational solid mechanics, smart and biomimetic materials. His current research lies at the interface between solid mechanics and materials engineering. He has focused on the fundamental aspects of how Nature uses elegant and efficient ways to make remarkable materials and their translation to engineering materials. He has contributed to the area of biomimetic materials by investigating the structure-function relationship of naturally-occurring high-performance materials at multiple length-scales, combining state-of-the-art computational techniques and experiments to characterize the properties.  

CLEVER ARCHITECTURES, INTERFACES AND COMPETING MECHANISMS IN BIOLOGICAL MATERIALS

Nature uses modest constituents to synthesize composite materials with exceptional mechanical properties for structural and impact resistance purposes. In most cases, these materials achieved outstanding mechanical properties avoiding the typical trade-offs often attained by manmade materials. While these materials require modern microscopy techniques to characterize their complex hierarchical structures, most of our learnings come from the way these materials mitigate catastrophic damage, revealing the most important mechanisms and features of their inner structure that contribute to energy dissipation and toughening. Considering the current progress in material synthesis and manufacturing, these new concepts have converged to the field of architected materials.  In this talk, I will describe some interesting mechanics problems that we encountered as we studied some extraordinary species, and how we can translate these lessons learned to architected materials. In particular, I will focus on a few examples related to how the combination of clever architectures, interfaces, material properties and competing mechanisms can promote delocalization to mitigate catastrophic failure, hence, improving toughness and impact resistance without sacrificing other important mechanical properties. Most of this discussion is driven by how we can eventually translate these lessons learned to the development and manufacturing of architected materials.

Prof. Zavattieri is being hosted by Prof. Evgueni Flipov (CEE). If you would like to meet with him during his visit, please send an email to micde-events@umich.edu. If you are an MICDE or CEE student and would like to join Prof. Zavattieri for lunch please RSVP by Monday, November 4th. 

Bio: Sanjay Govindjee is the Horace, Dorothy, and Katherine Johnson Professor in Engineering.  His main interests are in theoretical and computational mechanics with an emphasis on micro-mechanics of nonlinear phenomena in solid materials.  He was the winner of the inaugural Zienkiewicz Prize and Medal in 1998 and more recently received a 2018 Alexander von Humboldt Foundation Research Prize in honor of his lifetime achievements.  For the last two and half years, he has been the PI and co-Director of the NSF NHERI SimCenter at Berkeley.

The NSF Natural Hazards Engineering Research Infrastructure (NHERI) Computation and Simulation Center (SimCenter) at Berkeley: An Overview

In October 2016, the National Science Foundation awarded the NHERI SimCenter to Berkeley.  The SimCenter is the computational satellite to the eight experimental sites of the NHERI constellation.  Its primary goal is to advance natural hazards engineering through the use of simulation.  The center develops and stands-up open-source software to simulate the effects of seismic, wind, and water loads on structures with a focus on regional assessments of damage at high resolution under uncertainty.  The SimCenter’s work includes both research and educational components.

The SimCenter has just completed Year 3 or its original mandate and now offers a wide selection of user friendly front end applications that permit local as well as HPC cloud based execution of simulations.  Simulations can be of single detailed structural models subjected to a variety of harzards using state-of-the-art and state-of-the-practice loading methodologies.  They can also be of a larger regional nature using simpler models and further coupled to forward uncertainty propogation with Monte Carlo methods with or without surrogating.  Engineering demands can be further propogated into damage and loss, downtime and recovery, using Hazus methodologies, FEMA P58 methods, or user provided techniques with our hazard-blind framework.  All elements of the SimCenter’s software are desgined in a plug-n-play fashion to promote detailed research into natural hazard effects with the ability to see impacts on a larger scale.

In this presentation, I will give an overview of the SimCenter’s recent activities and discuss research needs and how researchers can participate in the SimCenter’s activities, along with a preview of upcoming developments anticipated in Year 4

Prof. Govindjee is being hosted by Prof. Garikipati (ME).

Bio: Ramanathan Vishnampet is a Computational Data Scientist at the Global Business Lines Analytics & Optimization group at ExxonMobil Upstream Integrated Solutions. He graduated with a Ph.D. in Theoretical and Applied Mechanics from the University of Illinois at Urbana-Champaign, where his dissertation focused on an exact and consistent adjoint method for high-fidelity discretization of the compressible flow equations. Ramanathan started as a Senior Research Engineer at ExxonMobil in 2015, where he worked in the Process Stratigraphy team, an integrated team including Computational Scientists, Geoscientists, Seismic Interpreters, and Stratigraphers. He helped develop a physics-based stratigraphic model for studying deepwater stratigraphy and showed the emergence of chaotic dynamics and self-organization that limit the ability of traditional model inversion techniques to be applied to the forward model. In his current team, Ramanathan is working on a scheduling problem for ExxonMobil’s Unconventionals asset base using heuristics and discrete optimization. He is also leading his section’s efforts in adopting lean and agile software development practices, cloud-based deployment using a service architecture, and DevOps processes. Ramanathan’s hobbies include cooking, traveling, and spending time with his daughter.

Prediction under chaos using a depth-averaged model of turbidity currents

In this talk, I will demonstrate a forward stratigraphic model based on depth-averaged governing equations for the flow of submarine turbidity currents over an erodible bed. This model is being used with some success by the Process Stratigraphy team at ExxonMobil to generate stratigraphic models for deepwater environments of deposition. The mathematical model consists of a system of nonlinear hyperbolic PDEs, with an additional so-called Exner equation for modeling the flow-bed sediment exchange and their bedload transport. The Exner equation plays a key role since a (slow time scale) change in the gradient of the bed influences the (fast time scale) momentum of the flow. The transport equations, along with closure models for sediment transport, TKE balance, and water entrainment, are solved using a first-order finite-volume method with a HLLC approximate Riemann solver and integrated using an explicit Euler scheme. The model shows the emergence of self-organized patterns in the deposits, including the creation of bedforms, channel formation, and avulsions, consistent with observations of modern systems and lab experiments. These occur even with uniform boundary conditions and symmetric initial conditions. The initial disturbances that trigger these mechanisms are ostensibly sourced by floating-point roundoff errors. An ensemble of simulations with slightly different initial conditions are used to analyze statistics on shapes of geomorphic elements and grain size distributions. The objective is to assess whether and under what conditions such a numerical model can be predictive and quantify the uncertainty in the results arising due to the irreducible chaos in the dynamical system.

Dr. Vishnampet is being hosted by Prof. Capecelatro (ME). If you would like to meet with him during his visit, please send an email to micde-events@umich.edu.