Dynamics and Vibrations Group Tea-Time Talks

Abstract not available

• Speaker: Prof Zdenek Bazant
• Friday 16 June 2023, 14:00-15:00
• Venue: Oatley 1 Seminar Room.
• Series: Engineering Department - Mechanics Colloquia Research Seminars; organiser: Hilde Hambro.

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This talk will review our efforts on exploiting nonlinear dynamics, as well as vibration and elastic/acoustic wave phenomena, in engineering problems. First, we will discuss vibration energy harvesting using piezoelectricity for low-power electricity generation, with a focus on electroelastic dynamics and leveraging designed nonlinearities for bandwidth enhancement, followed by a brief account of inherent material, dissipative, and circuit nonlinearities. Experimental results will be compared against model simulations using the method of harmonic balance. Multiphysics problems of energy harvesting from fluid-structure interaction, and multifunctional concepts such as energy-harvesting bioinspired robotic fish will also be presented. After that, we will discuss mechanical and electromechanical metamaterials and metastructures for vibration/wave attenuation, including a recently introduced general theory, followed by piezoelectric metamaterials with digital programming enabled by synthetic impedance circuits. Bandgap (attenuation frequency range) tuning, rainbow phenomenon, wave compression, wave mode conversion, and reciprocity breaking will be demonstrated for elastic waves through spatial and spatiotemporal programming. Nonlinear metastructures exploiting chaotic vibrations will also be introduced. Our recent efforts on using analog and digital piezoelectric shunt circuits will then be shown for vibration attenuation in structures via concepts like nonlinear energy sink and basic Duffing-type nonlinear circuits. Finally, we will discuss examples on higher frequency problems including gradient-index phononic crystals lens designs for elastic and bulk acoustic/ultrasonic waves, wireless ultrasonic power and data transfer, and leveraging vibrations/vibroacoustics and guided waves in the human skull-brain system.

Bio: Prof. Alper Erturk is the Carl Ring Family Chair in the Woodruff School of Mechanical Engineering at Georgia Tech. His theoretical and experimental research interests are in dynamics, vibration, and acoustics of passive and active structures for various engineering problems. His publication/presentation record includes more than 130 journal papers, 220 conference papers/abstracts, 5 book chapters, and 2 books (total citations > 20,000 and h-index: 63). He is a recipient of various awards including the 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, among others. He is an Associate Editor for various journals such as Smart Materials & Structures (IOP) and Journal of Vibration & Acoustics (ASME) – and he was recently named the next Editor-in-Chief of Smart Materials & Structures, effective January 2023. 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 .

• Speaker: Prof Alper Erturk, Carl Ring Family Chair & Professor of Mechanical Engineering, Georgia Institute of Technology
• Thursday 16 February 2023, 12:00-13:00
• Venue: Department of Engineering - LR6.
• Series: Engineering Department - Mechanics Colloquia Research Seminars; organiser: Hilde Hambro.

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Abstract not available

• Speaker: Dr Ole Nielsen, BOSE
• Friday 10 March 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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In this talk I will make an attempt to follow the idea of regarding vibrations and dynamics, in systems of engineering and technology, as symptoms and indicators of complexity. Here the term complexity seems rather loosely defined at first. Still, I will try to make a case to use it for pointing to some of the key limitations of how vibrations and dynamics are viewed in present engineering, and how different and potentially more powerful perspectives might emerge or be developed.

• Speaker: Professor Norbert Hoffmann, Hamburg University of Technology (TUHH)
• Friday 10 February 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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In this talk I will make an attempt to follow the idea of regarding vibrations and dynamics, in systems of engineering and technology, as symptoms and indicators of complexity. Here the term complexity seems rather loosely defined at first. Still, I will try to make a case to use it for pointing to some of the key limitations of how vibrations and dynamics are viewed in present engineering, and how different and potentially more powerful perspectives might emerge or be developed.

• Speaker: Norbert Hoffmann, Professor for Structural Dynamics at TUHH
• Friday 10 February 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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Phononics is an emerging field that seeks to elucidate the nature of intrinsic mechanical motion in both conventional and artificially structured materials, and uses this knowledge to extend the boundaries of physical response at either the material or structural/device level or both. The field bridges multiple disciplines across applied physics and engineering, and spans multiple scales reaching the atomic scale where a rigorous definition of phonons originates–quanta of lattice vibrations. In this talk, I will present two distinct contributions of phononics, one to the classical field of fluid dynamics and the other to the emerging field of nanoscale heat transfer. In both cases, intervention that causes critical changes in fundamental physical behaviour is demonstrated.

In fluid dynamics, I will show that phonon motion underneath a surface interacting with a flow may be engineered to cause the flow to stabilize, or destabilize, as desired [Hussein et al., Proc. R. Soc. A, 2015]. The underlying control mechanism utilizes the principle of destructive or constructive interferences and the notion of symmetry breaking, core concepts in phononics. This is realized by installing a “phononic subsurface” (PSub), which is an architectured periodic structure placed in the subsurface region and configured to extend all the way such that its edge is exposed to the flow, forming an elastic fluid-structure interface. I will present results showcasing perfectly synchronized, passive, and responsive, phased response and energy exchange between the elastic domain of a PSub and the perturbation (instability) field within an interfacing flow. One outcome of this state of response is delay of laminar-to-turbulent transition.

In heat transfer, I will present the concept of a locally resonant nanophononic metamaterial (NPM) [Davis and Hussein, Phys. Rev. Lett., 2014], of which one realization is a freestanding silicon membrane (thin film) with a periodic array of nanoscale pillars extruding out of one or both free surfaces. Heat is transported along the membrane portion of this nanostructured material as a succession of wavenumber-dependent propagating vibrational waves, phonons. The atoms making up the minuscule pillars, on their part, generate wavenumber-independent resonant vibrational waves, which we describe as vibrons. These two types of waves interact causing a mode coupling for each pair leading to (1) the generation of new modes localized in the nanopillar portion(s) and (2) the reduction of the base membrane phonon group velocities around the coupling regions. These effects take place across the full spectrum and bring rise to a unique form of heat conduction, namely, resonant thermal transport. The outcome is an inherent reduction in the in-plane thermal conductivity of the base membrane material.

PSubs provide a new paradigm of flow control for drag reduction in air, sea, and land vehicles, and NPMs offer a new route for high-efficiency solid-state thermoelectric energy conversion.

———————————————————-

Bio: Mahmoud I. Hussein is the Alvah and Harriet Hovlid Professor at the Smead Department of Aerospace Engineering Sciences at the University of Colorado Boulder. He holds a courtesy faculty appointment in the Department of Physics and an affiliate faculty appointment in the Department of Applied Mathematics, and he has formally served as the Engineering Faculty Director of the Pre-Engineering Program and the Program of Exploratory Studies. He received a BS degree from the American University in Cairo (1994) and MS degrees from Imperial College London (1995) and the University of Michigan‒Ann Arbor (1999, 2002). In 2004, he received a PhD degree from the University of Michigan‒Ann Arbor, after which he spent two years at the University of Cambridge as a postdoctoral research associate.

Dr. Hussein’s research focuses on the dynamics of materials and structures, especially phononic crystals and metamaterials, at both the continuum and atomistic scales. His research considers areas that range from vibrations and acoustics of engineering materials and structures and passive flow control to lattice dynamics and thermal transport in semiconductor-based nanostructured materials. His studies are concerned with physical phenomena governing these systems, associated theoretical and computational treatments, and analysis of relevant mechanisms such as dispersion, resonance, dissipation, and nonlinearity. His team also conducts experiments to support some aspects of the theoretical work.

Dr. Hussein received a DARPA Young Faculty Award in 2011, an NSF CAREER award in 2013, and in 2017 was honored with a Provost’s Faculty Achievement Award for Tenured Faculty at CU Boulder. He has co-edited a book titled Dynamics of Lattice Materials published by Wiley. He is a Fellow of ASME and has served as an associate editor for the ASME Journal of Vibration and Acoustics. In addition, he is the founding vice president of the International Phononics Society and has co-established the Phononics 20xx conference series which is widely viewed as the world’s premier event in the emerging field of phononics.

• Speaker: Prof Mahmoud I. Hussein, Alvah and Harriet Hovlid Professor of Aerospace Engineering Sciences, University of Colorado Boulder
• Friday 03 February 2023, 14:00-15:00
• Venue: Department of Engineering - LR4.
• Series: Engineering Department - Mechanics Colloquia Research Seminars; organiser: Hilde Hambro.

Add to your calendar or Include in your list

Phononics is an emerging field that seeks to elucidate the nature of intrinsic mechanical motion in both conventional and artificially structured materials, and uses this knowledge to extend the boundaries of physical response at either the material or structural/device level or both. The field bridges multiple disciplines across applied physics and engineering, and spans multiple scales reaching the atomic scale where a rigorous definition of phonons originates–quanta of lattice vibrations. In this talk, I will present two distinct contributions of phononics, one to the classical field of fluid dynamics and the other to the emerging field of nanoscale heat transfer. In both cases, intervention that causes critical changes in fundamental physical behaviour is demonstrated.

In fluid dynamics, I will show that phonon motion underneath a surface interacting with a flow may be engineered to cause the flow to stabilize, or destabilize, as desired [Hussein et al., Proc. R. Soc. A, 2015]. The underlying control mechanism utilizes the principle of destructive or constructive interferences and the notion of symmetry breaking, core concepts in phononics. This is realized by installing a “phononic subsurface” (PSub), which is an architectured periodic structure placed in the subsurface region and configured to extend all the way such that its edge is exposed to the flow, forming an elastic fluid-structure interface. I will present results showcasing perfectly synchronized, passive, and responsive, phased response and energy exchange between the elastic domain of a PSub and the perturbation (instability) field within an interfacing flow. One outcome of this state of response is delay of laminar-to-turbulent transition.

In heat transfer, I will present the concept of a locally resonant nanophononic metamaterial (NPM) [Davis and Hussein, Phys. Rev. Lett., 2014], of which one realization is a freestanding silicon membrane (thin film) with a periodic array of nanoscale pillars extruding out of one or both free surfaces. Heat is transported along the membrane portion of this nanostructured material as a succession of wavenumber-dependent propagating vibrational waves, phonons. The atoms making up the minuscule pillars, on their part, generate wavenumber-independent resonant vibrational waves, which we describe as vibrons. These two types of waves interact causing a mode coupling for each pair leading (1) to the generation of new modes localized in the nanopillar portion(s) and (2) to the reduction of the base membrane phonon group velocities around the coupling regions. These effects take place across the full spectrum and bring rise to a unique form of heat conduction, namely, resonant thermal transport. The outcome is an inherent reduction in the in-plane thermal conductivity of the base membrane material.

PSubs provide a new paradigm of flow control for drag reduction in air, sea, and land vehicles, and NPMs present a new route for high-efficiency solid-state thermoelectric energy conversion.

———————————————————-

Bio: Mahmoud I. Hussein is the Alvah and Harriet Hovlid Professor at the Smead Department of Aerospace Engineering Sciences at the University of Colorado Boulder. He holds a courtesy faculty appointment in the Department of Physics and an affiliate faculty appointment in the Department of Applied Mathematics, and he has formally served as the Engineering Faculty Director of the Pre-Engineering Program and the Program of Exploratory Studies. He received a BS degree from the American University in Cairo (1994) and MS degrees from Imperial College London (1995) and the University of Michigan‒Ann Arbor (1999, 2002). In 2004, he received a PhD degree from the University of Michigan‒Ann Arbor, after which he spent two years at the University of Cambridge as a postdoctoral research associate.

Dr. Hussein’s research focuses on the dynamics of materials and structures, especially phononic crystals and metamaterials, at both the continuum and atomistic scales. His research considers areas that range from vibrations and acoustics of engineering materials and structures and passive flow control to lattice dynamics and thermal transport in semiconductor-based nanostructured materials. His studies are concerned with physical phenomena governing these systems, associated theoretical and computational treatments, and analysis of relevant mechanisms such as dispersion, resonance, dissipation, and nonlinearity. His team also conducts experiments to support some aspects of the theoretical work.

Dr. Hussein received a DARPA Young Faculty Award in 2011, an NSF CAREER award in 2013, and in 2017 was honored with a Provost’s Faculty Achievement Award for Tenured Faculty at CU Boulder. He has co-edited a book titled Dynamics of Lattice Materials published by Wiley. He is a Fellow of ASME and has served as an associate editor for the ASME Journal of Vibration and Acoustics. In addition, he is the founding vice president of the International Phononics Society and has co-established the Phononics 20xx conference series which is widely viewed as the world’s premier event in the emerging field of phononics.

• Speaker: Prof Mahmoud I. Hussein, Alvah and Harriet Hovlid Professor of Aerospace Engineering Sciences, University of Colorado Boulder
• Friday 03 February 2023, 14:00-15:00
• Venue: Department of Engineering - LR4.
• Series: Engineering Department - Mechanics Colloquia Research Seminars; organiser: Hilde Hambro.

Add to your calendar or Include in your list

This talk will review our efforts on exploiting nonlinear dynamics, as well as vibration and elastic/acoustic wave phenomena, in engineering problems. First, we will discuss vibration energy harvesting using piezoelectricity for low-power electricity generation, with a focus on electroelastic dynamics and leveraging designed nonlinearities for bandwidth enhancement, followed by a brief account of inherent material, dissipative, and circuit nonlinearities. Experimental results will be compared against model simulations using the method of harmonic balance. Multiphysics problems of energy harvesting from fluid-structure interaction, and multifunctional concepts such as energy-harvesting bioinspired robotic fish will also be presented. After that, we will discuss mechanical and electromechanical metamaterials and metastructures for vibration/wave attenuation, including a recently introduced general theory, followed by piezoelectric metamaterials with digital programming enabled by synthetic impedance circuits. Bandgap (attenuation frequency range) tuning, rainbow phenomenon, wave compression, wave mode conversion, and reciprocity breaking will be demonstrated for elastic waves through spatial and spatiotemporal programming. Nonlinear metastructures exploiting chaotic vibrations will also be introduced. Our recent efforts on using analog and digital piezoelectric shunt circuits will then be shown for vibration attenuation in structures via concepts like nonlinear energy sink and basic Duffing-type nonlinear circuits. Finally, we will discuss examples on higher frequency problems including gradient-index phononic crystals lens designs for elastic and bulk acoustic/ultrasonic waves, wireless ultrasonic power and data transfer, and leveraging vibrations/vibroacoustics and guided waves in the human skull-brain system.

Bio: Prof. Alper Erturk is the Carl Ring Family Chair in the Woodruff School of Mechanical Engineering at Georgia Tech. His theoretical and experimental research interests are in dynamics, vibration, and acoustics of passive and active structures for various engineering problems. His publication/presentation record includes more than 130 journal papers, 220 conference papers/abstracts, 5 book chapters, and 2 books (total citations > 20,000 and h-index: 63). He is a recipient of various awards including the 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, among others. He is an Associate Editor for various journals such as Smart Materials & Structures (IOP) and Journal of Vibration & Acoustics (ASME) – and he was recently named the next Editor-in-Chief of Smart Materials & Structures, effective January 2023. 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 .

• Speaker: Prof Alper Erturk, Carl Ring Family Chair & Professor of Mechanical Engineering, Georgia Institute of Technology
• Thursday 16 February 2023, 11:00-12:00
• Venue: Department of Engineering - LR6.
• Series: Engineering Department - Mechanics Colloquia Research Seminars; organiser: Hilde Hambro.

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Abstract not available

• Speaker: Prof Mahmoud I. Hussein, Alvah and Harriet Hovlid Professor of Aerospace Engineering Sciences, University of Colorado Boulder
• Friday 03 February 2023, 14:00-15:00
• Venue: Department of Engineering - LR4.
• Series: Engineering Department - Mechanics Colloquia Research Seminars; organiser: Hilde Hambro.

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Abstract not available

• Speaker: Samer Abdelmoeti, CUED
• Friday 24 February 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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Abstract not available

• Speaker: Professor David Sharp, The Open University
• Friday 03 March 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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Abstract not available

• Speaker: Dr Ole Nielsen, CUED
• Friday 10 March 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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Abstract not available

• Speaker: David Sharp
• Friday 03 March 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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Abstract not available

• Speaker: Samer Abdelmoeti, CUED
• Friday 24 February 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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As monitoring data from our critical systems and structures become more abundant, engineers (should) naturally wish to benefit from the learning available from them. Indeed, many elements of structural assessment and, in particular, those relying on a dynamic signature, are now evolving to take advantage of this, leading to the creation and adoption of a wealth of data-driven approaches. The use of machine learning in structural health monitoring, for example, is common, as many of the inherent tasks (such as regression and classification) in developing condition-based assessment fall naturally into its remit.

A significant challenge here, that is not often acknowledged, however, is that we commonly lack representative data from across the range of environmental and operational conditions structures will undergo, limiting the usability of an entirely data-based approach.

This talk will present a number of ways of incorporating the physical insight an engineer will often have of the structure they are attempting to model or assess into a machine learning approach through a Gaussian process regression framework. The talk will demonstrate how grey-box models, that combine simple physics-based models with data-driven ones, can improve predictive capability for structural assessment and system identification tasks. A particular strength of the approaches demonstrated here is the capacity of the models to generalise, with enhanced predictive capability in different regimes, increasing applicability in light of the aforementioned challenge.

• Speaker: Professor Lizzy Cross, University of Sheffield
• Friday 20 January 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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Abstract not available

• Speaker: Professor Lizzy Cross, University of Sheffield
• Friday 20 January 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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Abstract not available

• Speaker: Emeritus Professor Jim Woodhouse, CUED
• Friday 27 January 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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Abstract not available

• Speaker: Dr Matt de Brett
• Friday 24 February 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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Abstract not available

• Speaker: Professor Norbert Hoffmann
• Friday 10 February 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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Abstract not available

• Speaker: Emeritus Professor Jim Woodhouse, CUED
• Friday 27 January 2023, 16:00-17:00
• Venue: JDB Seminar Room, CUED.
• Series: Engineering Department Dynamics and Vibration Tea Time Talks; organiser: div-c.

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