Events
Past Event
CANCELLED - TAM Seminar Series- Nicholas Triantafyllidis
McCormick - Mechanical Engineering
11:00 AM
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A230, Technological Institute
Details
FROM WRINKLES TO CREASES - ON STABLE LOCALIZED DEFORMATION SOLUTIONS IN HIGH SYMMETRY STRUCTURES USING GROUP THEORY
Nicolas Triantafyllidis 1,2
1Solid Mechanics Laboratory (CNRS-UMR 7649) & Department of Mechanics,
École Polytechnique, Palaiseau 91128, France
2Aerospace Engineering Department & Mechanical Engineering Department,
The University of Michigan, Ann Arbor, MI 48109-2140, USA (emeritus)
We are motivated by the celebrated Biot problem of surface instability in a hyperelastic half-space under axial compression and in particular the evolution, from an initially unstable bifurcated short wavelength, periodic deformation pattern to a stable solution involving a localized deformation. This feature is shared by other problems in mechanics, where a high initial symmetry (due to translational invariance) leads to a complex bifurcation pattern. Understanding the evolution of bifurcated solutions from a periodic pattern (wrinkling) to a highly localized one (crease) is the goal of this work.
Due to the complex structure of these nonlinear problems, we first study the behavior of an inextensible infinite Euler-Bernoulli beam subjected to a compressive axial force and connected to a nonlinear (polynomial) elastic foundation. We use group-theory methods to follow all bifurcated equilibrium paths in a systematic way and explore the emergence of stable localized solutions.
We next proceed with the analysis of the nonlinear hyperelastic half-space problem under axial compression, using different energy densities. To avoid the arbitrariness of the critical wavelength associated with the homogeneous half-space, we consider a half-space with functionally graded properties as well as a finite thickness layer bonded atop a half-space. The same group-theoretic approach is used to find the bifurcated solutions, from the initial unstable periodic wrinkles to a stable crease. A continuation method using the layer/half-space initial shear moduli ratio is also proposed as an alternative to seek the creased solution of the homogeneous half-space problem.
Work is collaboration with: S. Pandurangi, T. Healey (Cornell), and R. Elliott (U. Minnesota)
Seminar to be presented at Northwestern University, Evanston IL, USA on April 2, 2020
Short Bio of N. Triantafyllidis:
Prof. Triantafyllidis has obtained his Ph.D. in Engineering from Brown University in 1980. The same year he joined the faculty of the Aerospace Engineering Department at the University of Michigan in Ann Arbor, MI, USA starting as an Assistant Professor and reaching the rank of Full Professor in the Departments of Aerospace Engineering and Mechanical Engineering & Applied Mechanics. He is currently an emeritus Professor of the University of Michigan. In 2009 he moved to France to become CNRS Director of Research in the Solid Mechanics Laboratory (LMS) and a Professor of Mechanics at the Ecole Polytechnique.
Prof. Triantafyllidis’ research is in the areas of stability in solids and structures, structural mechanics and nonlinear continuum mechanics. Over the years he has worked in sheet metal forming problems, large flexible space structures, composites and cellular materials, the geomechanics of the earth’s crust and stability issues in homogenization problems. More recently he worked on the thermomechanical stability of shape memory crystals. His recent interests are in multiphysics – i.e. problems involving interactions between mechanical, electromagnetic and electronic effects in solids – with applications in magneto-elasticity, electromagnetic forming electric motors, strain effects in semiconductors, flexible photovoltaics and thin film electronics.
Time
Thursday, April 2, 2020 at 11:00 AM - 12:00 PM
Location
A230, Technological Institute Map
Contact
Calendar
McCormick - Mechanical Engineering
ME Alumni Seminar Series- Apostolos Karafillis
McCormick - Mechanical Engineering (ME)
2:00 PM
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1.350, Ford Motor Company Engineering Design Center
Details
On the Design and Manufacture of Structures for Flightworthy Gas Turbines
by Apostolos Karafillis
Chief Consulting Engineer
Structures and Additive Design
GE Aerospace
Abstract
The design and manufacture of gas turbine components presents unique technical challenges that highlight the relevance and importance of the disciplines of mechanical and aerospace engineering. In this presentation, we will focus on describing the fundamental technical requirements for parts of flightworthy gas turbines and will then share examples of designs and innovations to meet these requirements. The talk will include the description of typical loading conditions and operating environments, and the description of how these requirements guide the selection of design features, materials, and manufacturing methods. We will discuss three specific examples: The selection of features and architecture of a bearing housing, the design of a turbine frame with a mix of metallic and composite materials, and the development of methods for characterizing the performance of components manufactured with non-traditional methods. Through these examples, it will be shown that successful hardware design requires the combination of robust design methods, rigorous implementation of the principles of mechanics of materials, and the development of design and manufacturing innovation.
Time
Tuesday, April 30, 2024 at 2:00 PM - 3:00 PM
Location
1.350, Ford Motor Company Engineering Design Center Map
Contact
Calendar
McCormick - Mechanical Engineering (ME)
Russ Tedrake, MIT and Toyota Research Institute, "Dexterous Manipulation with Diffusion Policies"
Center for Robotics and Biosystems (CRB)
11:30 AM
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M416, Technological Institute
Details
Speaker: Russ Tedrake, Toyota Professor of EECS, Aero/Astro, ME at Massachusetts Institute of Technology and VP of Research at Toyota Research Institute
Title: Dexterous Manipulation with Diffusion Policies
Date and Time: Friday, May 3 at 11:30 AM CT
Location: Tech ESAM M416 and Zoom
Zoom Link: https://tinyurl.com/CRBSeminar
• NU-authenticated attendees will be automatically admitted. Others, please email amy.nedoss@northwestern.edu to be admitted from the waiting room.
Abstract:
At the Toyota Research Institute (TRI), we've been working on behavior cloning for dexterous manipulation. Building on the Diffusion Policy framework that we've recently developed in collaboration with Shuran Song, we now have a very solid pipeline for taking ~50-100 bimanual haptic teleop demonstrations and turning that into a surprisingly effective visuomotor (+tactile) policy. Because there is no explicit state representation required, these skills work equally well manipulating deformable, liquid, or other difficult to model tasks as they do for more traditional rigid-object manipulation. We're actively scaling this up into the multi-task setting and now see a plausible path towards "Large Behavior Models". This behavior cloning pipeline is working incredibly well, and must be understood deeply in the broader context of output-feedback control. Time permitting, I'll also tell you a bit about some new results in optimization-based planning and control, and where they might fit in the age of foundation models.
Bio:
Russ Tedrake is the Toyota Professor at the Massachusetts Institute of Technology (MIT) in the Department of Electrical Engineering and Computer Science, Mechanical Engineering, and Aero/Astro, and he is a member of MIT’s Computer Science and Artificial Intelligence Lab (CSAIL). He is also the Vice President of Robotics Research at Toyota Research Institute (TRI). He received a B.S.E. in Computer Engineering from the University of Michigan in 1999, and a Ph.D. in Electrical Engineering and Computer Science from MIT in 2004. Dr. Tedrake is the Director of the MIT CSAIL Center for Robotics and was the leader of MIT’s entry in the DARPA Robotics Challenge. He is a recipient of the NSF CAREER Award, the MIT Jerome Saltzer Award for undergraduate teaching, the DARPA Young Faculty Award in Mathematics, the 2012 Ruth and Joel Spira Teaching Award, and was named a Microsoft Research New Faculty Fellow. His research has been recognized with numerous conference best paper awards, including ICRA, Robotics: Science and Systems, Humanoids, Hybrid Systems: Computation and Control, as well as the inaugural best paper award from the IEEE RAS Technical Committee on Whole-Body Control.
Time
Friday, May 3, 2024 at 11:30 AM - 12:30 PM
Location
M416, Technological Institute Map
Contact
Calendar
Center for Robotics and Biosystems (CRB)