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Professor Marco Amabili, Canada Research Chair, Department of Mechanical Engineering, McGill University, Montreal, Canada Born in Italy, he received his PhD in Bologna. Professor Amabili holds the Canada Research Chair in Vibrations at the Department of Mechanical Engineering, McGill University, Montreal, Canada. He received the Worcester Reed Warner Medal of the ASME (American Society of Mechanical Engineers) in 2020, the 2021 Raymond D. Mindlin Medal of the American Society of Civil Engineers, the 2021 International Gili-Agostinelli Prize of the “Lincei” National Academy of Sciences of Italy and the Guggenheim Fellowship in Engineering in 2022. He is the author of two monographs published by Cambridge University press and a plethora of scientific papers. Dr. Amabili is an elected Fellow of the Royal Society of Canada (Academy of Sciences), the Canadian Academy of Engineering, Foreign Member of Academia Europaea, Member the European Academy of Sciences and Arts, Member of the European Academy of Sciences and Fellow of the Engineering Institute of Canada. He is one of the five members of the Executive Committee of Applied Mechanics Division of the ASME. Amabili is also the chair of the Canadian National Committee for IUTAM (International Union of Theoretical and Applied Mechanics) and of the conference series ICoNSoM (Int. Conf. on Nonlinear Solid Mechanics). |
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Nonlinear Vibrations of Shells: From Classical Problems to Soft Biological Matter
This seminar will focus on nonlinear vibrations of shells made of traditional, composite, and soft biological materials. Starting from classical nonlinear shell theories, nonlinear dynamic phenomena that can be observed in circular cylindrical shells will be highlighted: from softening behavior to amplitude modulations, internal resonance and chaos. Then, in order to deal with thick walls and large strains associated to soft materials, the classical shell theories are modified by including shear and thickness deformations, as well as rotary inertia. Comparison of numerical simulations and experiments for large amplitude (geometrically nonlinear) vibrations of plates and shell structures will be presented and the very large increase of damping with the vibration amplitude will be discussed. This is a little-known phenomenon of fundamental importance in applications. The nonlinear damping will be derived in a very original way from viscoelasticity. The damping model obtained is geometrically nonlinear and the parameters are identified from experiments. Numerical results are compared to experimental forced vibration responses measured for large-amplitude vibrations of different structural elements.
Biological soft tissues are subjected to significant static and dynamic loading, yielding large strains that requires the introduction of hyperelastic and viscoelastic constitutive models. Results for human aortas will be shown and compared to experiments.
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Professor Alexander Shaw Senior Lecturer, Swansea University,Wales, UK Dr Alexander Shaw completed his PhD in the University of Bristol, considering how nonlinear shells could be exploited in vibration isolation problems. He then moved to Swansea University, and worked on morphing aircraft structures and further topics in nonlinear vibration, and was appointed Lecturer in the Department of Aerospace in 2016. In particular, he is interested in experimental methods for nonlinear structures and means of exploiting nonlinearity, and nonlinear phenomena arising in rotating machinery due to rotor stator contact. |
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Aperiodic Phenomena in Rotor Stator Contact Systems
Rotating machines form a huge part the engineered world, from aircraft engines to drilling operations. Possible contacts between the rotating shaft and some external stator are known to lead to some very rich, and potentially destructive, dynamic responses. There is a long history of academic studies demonstrating bifurcations, chaotic behaviour, and multiple and isolated solutions. Despite this, a framework that encompasses the diversity of phenomena that is observed seems to be lacking.
This talk shows how, in an isotropic rotor stator system, complex orbits are in fact periodic in the rotating frame, and initiate due to a form of internal resonance. It then shows how this insight can be used to derive an analytical method which can potentially reduce large systems to just a couple of resonant terms. The method is a harmonic balance approach augmented by the method of normal forms. It then discusses how the responses change as the initial assumptions are relaxed to include effects such as gravity and friction, and rigid impacts. It concludes with some ongoing experimental work.
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Professor Alper Erturk, Carl Ring Family Chair & Professor G. W. Woodruff School of Mechanical Engineering Georgia Institute of Technology Prof. Alper Erturk is the Carl Ring Family Chair in the Woodruff School of Mechanical Engineering at Georgia Tech, where he leads the Smart Structures & Dynamical Systems Lab. His theoretical and experimental research interests are in dynamics, vibration, and acoustics of passive and active (smart) structures for various engineering problems. He has published 120 journal papers, 130 conference proceeding papers, 5 book chapters, and 2 books (total citations > 19,000 and h-index: 60). He is a recipient of various awards including an NSF CAREER Award in Dynamical Systems, ASME C.D. Mote Jr. Early Career Award for “research excellence in the field of vibration and acoustics”, ASME Gary Anderson Early Achievement Award for “notable contributions to the field of adaptive structures and material systems”, SEM James Dally Young Investigator Award for “research excellence in the field of experimental mechanics”, and numerous best paper awards including the Philip E. Doak Award of the Journal of Sound and Vibration, and two ASME Energy Harvesting Best Paper Awards, among others. He is an Associate Editor for various journals such as Smart Materials & Structures and ASME Journal of Vibration & Acoustics. He holds Invited/Adjunct Professor positions at Politecnico di Milano (POLIMI) and at Korea Advanced Institute of Science and Technology (KAIST). He is a Fellow of ASME and SPIE. |
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Leveraging Vibration and Wave Phenomena in Dynamical Systems:
From Energy Harvesting and Bioinspired Robotics to Metamaterials and Transcranial Ultrasound
This talk will review our recent efforts on exploiting vibration and elastic/acoustic wave phenomena in emerging fields and across disciplines for various applications. The first part will discuss examples from the domain of vibration energy harvesting for small electronic components by using piezoelectric transduction in conjunction with concepts from nonlinear dynamics and fluid-structure interaction. Multifunctional scenarios will also be presented, such as combining energy harvesting and bio-inspired actuation in the same robotic platform, as well as concurrent energy harvesting and metamaterial-based vibration attenuation. In the second part, the focus will first be placed on phononic crystal-based manipulation of 2D elastic and 3D acoustic wave propagation. Specifically, in-air sound wave focusing and underwater ultrasonic wave focusing using 3D-printed phononic crystals with tailored microstructure will be summarized for applications including wireless power transfer. Then, ultrasonic power/data transfer to wireless components in metallic enclosures will be addressed along with the use of phononic crystals for crosstalk minimization via bandgap formation between the piezoelectric channels. Examples will also be given on programmable piezoelectric metamaterials with synthetic impedance circuits. Finally, the leveraging of vibrations and guided waves in the human skull will be discussed briefly for purposes ranging from high-fidelity modeling and parameter identification via vibroacoustic experiments to investigating the role and potential use of guided waves in cranial/transcranial ultrasound.
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Professor Jérôme Antoni Laboratoire Vibrations Acoustique University of Lyon, France Jerome Antoni (M.S. in Mechanical Engineering, 1995, Ph.D. in Signal Processing, 2000, University of Technology of Compiègne) joined the University of Technology of Compiègne in 2001, after completing his PhD at the University of Grenoble (France). He currently holds a full professor position at the University of Lyon, France, and leads the Laboratoire Vibrations Acoustique. The main direction of his research activity is concerned with the development of signal processing methods in mechanical applications, with a special interest in the resolution of inverse problems in acoustics and vibrations. This includes applications in machine and structural health monitoring (MHM & SHM), identification and imaging of acoustic and vibration sources. He has published about two hundred journal papers in these domains. Jerome Antoni is Associate Editor of Mechanical Systems and Signal Processing and with the editorial boards of Applied Sciences and Machines. |
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On the Representation of Sound Source Distributions in Inverse Acoustics
Inverse acoustics is concerned with the reconstruction of sound fields from remoted measurements. Of interest in this talk is acoustic imaging, an inverse acoustic problem that tries to map sound sources recovered from an array of microphones. This type of problem involves several mathematical and physical choices, which strongly determine the quality of the solution. A crucial question that readily arises is the proper definition of sound sources, the quantities of interest. Several theoretical results establish that the sound source distribution cannot be recovered uniquely, thus paving the way to different options. The talk will first review the most common choices used in the literature, such as expansions in eigenfunctions of the wave propagation operator, and will next concentrate on the Equivalent Source Method (ESM), which has become popular due to its flexibility. It will then introduce recent extensions of the ESM, such as solutions to account for diffraction, and theoretical cues for using equivalent dipoles instead of monopoles in 2D source representations. Finally, it will discuss some recent works for 3D source reconstructions in aeroacoustics.