The latest from flexLab: Mechanics of Slender Structures and Fluid-Structure Interactions
Event details
| Date | 24.05.2018 |
| Hour | 16:15 › 17:15 |
| Speaker | Matteo Pezzulla, Dong Yan and Paul Grandgeorge - EPFL STI IGM Flexible Structures Laboratory (flexLab) |
| Location | |
| Category | Conferences - Seminars |
Abstract
Deformation of perforated elastic sheets due to the hydrodynamic loading by a viscous fluid, by Matteo Pezzulla
From spider webs and insect wings, to wire fences and parachutes, Nature and technology provide us with vast examples of perforated flexible structures that undergo elastic deformation due to fluid flow. Whereas fluid flow through porous media has been studied extensively, the fluid-structure interactions of a perforated slender elastic object that undergoes large deformations due to the loading of a surrounding viscous fluid has received much less attention. I will talk about our ongoing research, where we use precision desktop experiments to focus on the prototypical problem of a perforated elastic plate moving through a viscous fluid, at low to moderate Reynolds number. Via a reduced theoretical model based on Kirchhoff-Euler beam theory coupled with a low Reynolds description for the fluid forcing, we seek to provide a predictive framework for the deformation of perforated plates due to hydrodynamic loading. We hope that our findings may lead to a better understanding of fluid-structure interactions between porous slender structures and viscous flows, across biological and technological applications.
Defect-controlled buckling of depressurized elastic spherical shells, by Dong Yan
Spherical shells are ubiquitous in nature and engineering structures, across a wide range of length-scales. Small geometric imperfections can substantially decrease the buckling strength of shells. In this talk, I will present our ongoing research on the buckling of spherical shells containing a thickness defect. Through a customizable coating technique, a thickness defect with controllable geometric properties is fabricated by blowing the polymer layer during curing. We vary the amplitude of thickness variation and study the buckling behavior of our spherical shells. We quantify the effect of a thickness defect on the buckling strength. The experimental results are then contrasted against finite element modeling (FEM) simulations. Upon validation of the numerics, we then use FEM to perform a broader exploration of the parameter space. Our results lead to a better understanding of imperfection sensitivity, which is a concrete foundation for accurately predicting the buckling pressure of shell structures in engineering.
Unravelling the tight interplay between geometry and mechanical response of elastic knots, by Paul Grandgeorge
May they be functional for shoelaces, undesirable when tangling up cables, or even aesthetically appealing in Celtic decoration art, knots are dealt with on a daily basis. Even for medical purposes, surgeons have employed knots to secure sutures for millennia. Even though they come across in such a wide variety of fields, the predictive understanding of knot topology and mechanics remains challenging. Past studies have primarily focused on mathematically ideal knots, discarding most physical properties of the knotted rod such as cross-section diameter, bending stiffness or frictional behavior along self-contact regions. In this talk, I will present our ongoing experimental research on elastic knots, performed in collaboration with Prof. John Maddocks. In particular, I will focus on the orthogonal clasp, a simple yet rich configuration (2 fibers crossing, see picture), to present our 3D-imaging and image-processing strategy. We hope the gained physical insight will pave the road for future material and configuration optimizations of functional knots in the areas of surgery and other engineering applications.
Bio
Matteo Pezzulla is a postdoc in the Flexible Structures Laboratory (flexLab) at EPFL. He is interested in the fluid-structure interactions (FSI) of perforated slender structures and viscous fluids, at low Reynolds numbers, and in the geometric mechanics of slender structures such as shells, possibly coupled with swelling.
Dong Yan is a postdoc in the Flexible Structures Laboratory (flexLab) at EPFL. He is interested in the mechanics of slender structures. He is currently working on the buckling of spherical shells.
Paul Grandgeorge is a postdoc in the Flexible Structures Laboratory (flexLab) at EPFL. He is interested in the mechanical behavior of slender structures undergoing non-linear deformations. More specifically, he is currently working on the mechanics of elastic knots.
Deformation of perforated elastic sheets due to the hydrodynamic loading by a viscous fluid, by Matteo Pezzulla
From spider webs and insect wings, to wire fences and parachutes, Nature and technology provide us with vast examples of perforated flexible structures that undergo elastic deformation due to fluid flow. Whereas fluid flow through porous media has been studied extensively, the fluid-structure interactions of a perforated slender elastic object that undergoes large deformations due to the loading of a surrounding viscous fluid has received much less attention. I will talk about our ongoing research, where we use precision desktop experiments to focus on the prototypical problem of a perforated elastic plate moving through a viscous fluid, at low to moderate Reynolds number. Via a reduced theoretical model based on Kirchhoff-Euler beam theory coupled with a low Reynolds description for the fluid forcing, we seek to provide a predictive framework for the deformation of perforated plates due to hydrodynamic loading. We hope that our findings may lead to a better understanding of fluid-structure interactions between porous slender structures and viscous flows, across biological and technological applications.
Defect-controlled buckling of depressurized elastic spherical shells, by Dong Yan
Spherical shells are ubiquitous in nature and engineering structures, across a wide range of length-scales. Small geometric imperfections can substantially decrease the buckling strength of shells. In this talk, I will present our ongoing research on the buckling of spherical shells containing a thickness defect. Through a customizable coating technique, a thickness defect with controllable geometric properties is fabricated by blowing the polymer layer during curing. We vary the amplitude of thickness variation and study the buckling behavior of our spherical shells. We quantify the effect of a thickness defect on the buckling strength. The experimental results are then contrasted against finite element modeling (FEM) simulations. Upon validation of the numerics, we then use FEM to perform a broader exploration of the parameter space. Our results lead to a better understanding of imperfection sensitivity, which is a concrete foundation for accurately predicting the buckling pressure of shell structures in engineering.
Unravelling the tight interplay between geometry and mechanical response of elastic knots, by Paul Grandgeorge
May they be functional for shoelaces, undesirable when tangling up cables, or even aesthetically appealing in Celtic decoration art, knots are dealt with on a daily basis. Even for medical purposes, surgeons have employed knots to secure sutures for millennia. Even though they come across in such a wide variety of fields, the predictive understanding of knot topology and mechanics remains challenging. Past studies have primarily focused on mathematically ideal knots, discarding most physical properties of the knotted rod such as cross-section diameter, bending stiffness or frictional behavior along self-contact regions. In this talk, I will present our ongoing experimental research on elastic knots, performed in collaboration with Prof. John Maddocks. In particular, I will focus on the orthogonal clasp, a simple yet rich configuration (2 fibers crossing, see picture), to present our 3D-imaging and image-processing strategy. We hope the gained physical insight will pave the road for future material and configuration optimizations of functional knots in the areas of surgery and other engineering applications.
Bio
Matteo Pezzulla is a postdoc in the Flexible Structures Laboratory (flexLab) at EPFL. He is interested in the fluid-structure interactions (FSI) of perforated slender structures and viscous fluids, at low Reynolds numbers, and in the geometric mechanics of slender structures such as shells, possibly coupled with swelling.
Dong Yan is a postdoc in the Flexible Structures Laboratory (flexLab) at EPFL. He is interested in the mechanics of slender structures. He is currently working on the buckling of spherical shells.
Paul Grandgeorge is a postdoc in the Flexible Structures Laboratory (flexLab) at EPFL. He is interested in the mechanical behavior of slender structures undergoing non-linear deformations. More specifically, he is currently working on the mechanics of elastic knots.
Practical information
- General public
- Free
Organizer
- MEGA.Seminar Organizing Committee (Anna Lee, Lorenzo Benedetti, Hervé Elettro, Till Junge, Francesco Maresca, Roozbeh Rezakhani, Dong Yan, Noelia Simone)