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Tea-Time Talks are organised by the Dynamics and Vibration Group and take place on Fridays (in term time) at 4pm James Dyson Building Seminar Room on the main Trumpington Street site. All visitors are welcome.
Updated: 55 min 15 sec ago

Fri 20 Jan 16:00: Title - tbc

Tue, 10/01/2023 - 16:30
Title - tbc

Abstract not available

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Fri 03 Feb 14:00: Phononics: Structural dynamics of materials and implications to fluid dynamics, heat transfer, and beyond

Tue, 10/01/2023 - 13:55
Phononics: Structural dynamics of materials and implications to fluid dynamics, heat transfer, and beyond

Abstract not available

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Fri 17 Feb 14:00: Modeling of Fibrous Tissues Considering the Microstructure

Wed, 28/12/2022 - 16:18
Modeling of Fibrous Tissues Considering the Microstructure

Nowadays, the 3D ultrastructure of a fibrous tissue can be reconstructed in order to visualize the complex nanoscale arrangement of collagen fibrils including neighboring proteoglycans even in the stretched loaded state [1]. In particular, experimental data of collagen fibers in human artery layers have shown that the fibers are not symmetrically dispersed [2]. In addition, it is known that collagen fibers are cross-linked and the density of cross-links in arterial tissues has a stiffening effect on the associated mechanical response. A first attempt to characterize this effect on the elastic response is presented and the influence of the cross-link density on the mechanical behavior in uniaxial tension is shown [3]. A recently developed extension of the model that accounts for dispersed fibers connected by randomly distributed cross-links is outlined [4]. A simple shear test focusing on the sign of the normal stress perpendicular to the shear planes (Poynting effect) is analyzed. In [5] it was experimentally observed that, in contrast to rubber, semi-flexible biopolymer gels show a tendency to approach the top and bottom faces under simple shear. This so-called negative Poynting effect and its connection with the cross-links as well as the fiber and cross-link dispersion is also examined.

References

[1] A. Pukaluk et al.: An ultrastructural 3D reconstruction method for observing the arrangement of collagen fibrils and proteoglycans in the human aortic wall under mechanical load. Acta Biomaterialia, 141:300-314, 2022.

[2] G.A. Holzapfel et al.: Modelling non-symmetric collagen fibre dispersion in arterial walls. Journal of the Royal Society Interface, 12:20150188, 2015.

[3] G.A. Holzapfel and R.W. Ogden: An arterial constitutive model accounting for collagen content and cross-linking. Journal of the Mechanics and Physics of Solids, 136:103682, 2020.

[4] S. Teichtmeister and G.A. Holzapfel: A constitutive model for fibrous tissues with cross-linked collagen fibers including dispersion – with an analysis of the Poynting effect. Journal of the Mechanics and Physics of Solids, 164:104911, 2022.

[5] P.A. Janmey et al.: Negative normal stress in semiflexible biopolymer gels. Nature Materials, 6:48–51, 2007.

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Fri 16 Jun 14:00: Title to be confirmed

Wed, 28/12/2022 - 12:24
Title to be confirmed

Abstract not available

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Fri 17 Feb 14:00: Modeling of Fibrous Tissues Considering the Microstructure

Wed, 28/12/2022 - 11:58
Modeling of Fibrous Tissues Considering the Microstructure

Nowadays, the 3D ultrastructure of a fibrous tissue can be reconstructed in order to visualize the complex nanoscale arrangement of collagen fibrils including neighboring proteoglycans even in the stretched loaded state [1]. In particular, experimental data of collagen fibers in human artery layers have shown that the fibers are not symmetrically dispersed [2]. In addition, it is known that collagen fibers are cross-linked and the density of cross-links in arterial tissues has a stiffening effect on the associated mechanical response. A first attempt to characterize this effect on the elastic response is presented and the influence of the cross-link density on the mechanical behavior in uniaxial tension is shown [3]. A recently developed extension of the model that accounts for dispersed fibers connected by randomly distributed cross-links is outlined [4]. A simple shear test focusing on the sign of the normal stress perpendicular to the shear planes (Poynting effect) is analyzed. In [5] it was experimentally observed that, in contrast to rubber, semi-flexible biopolymer gels show a tendency to approach the top and bottom faces under simple shear. This so-called negative Poynting effect and its connection with the cross-links as well as the fiber and cross-link dispersion is also examined. References [1] A. Pukaluk et al.: An ultrastructural 3D reconstruction method for observing the arrangement of collagen fibrils and proteoglycans in the human aortic wall under mechanical load. Acta Biomaterialia, 141:300-314, 2022. [2] G.A. Holzapfel et al.: Modelling non-symmetric collagen fibre dispersion in arterial walls. Journal of the Royal Society Interface, 12:20150188, 2015. [3] G.A. Holzapfel and R.W. Ogden: An arterial constitutive model accounting for collagen content and cross-linking. Journal of the Mechanics and Physics of Solids, 136:103682, 2020. [4] S. Teichtmeister and G.A. Holzapfel: A constitutive model for fibrous tissues with cross-linked collagen fibers including dispersion – with an analysis of the Poynting effect. Journal of the Mechanics and Physics of Solids, 164:104911, 2022. [5] P.A. Janmey

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Thu 16 Feb 11:00: Leveraging vibrations, nonlinear dynamics, and wave phenomena in emerging fields and across disciplines

Mon, 19/12/2022 - 09:52
Leveraging vibrations, nonlinear dynamics, and wave phenomena in emerging fields and across disciplines

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 .

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Fri 17 Feb 14:00: Title to be confirmed

Mon, 19/12/2022 - 08:52
Title to be confirmed

Abstract not available

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Latest news

PhD approved

12 March 2016

Amy Rimmer's PhD dissertation 'Autonomous Reversing of Multiply-Articulated Heavy Vehicles, PhD Dissertation, in Engineering Department' has been approved by the University.

PhD approved

12 March 2016

Graeme Morrison's PhD dissertation 'Combined Emergency Braking and Cornering of Articulated Heavy Vehicles' has been approved by the university.

PhD approved

3 February 2016

Qiheng (Matt) Miao's PhD dissertation 'Vision-based path-following control of articulated vehicles' has been approved by the university.