Marco Amabili

• Nonlinear vibrations of shell structures.
• Derivation of nonlinear damping from viscoelasticity.
• Biomechanics of the human aorta and aortic grafts.
• Reduced-order models for nonlinear dynamics.
• Stability of shells and plates with fluid-structure interaction.
• Vibrations of laminated and FGM shells.
• Experimental nonlinear dynamic identification.

Research Selected Contributions

• Nonlinear vibrations and stability of shells interacting with fluids. This is an area of wide interest since shells are often associated to fluids and dynamic loads (rockets, storage tanks, fuselage of airplanes, …). Amabili applied the studies to nuclear engineering and soft biomaterials (arteries and grafts). His activity focused on integration of experiments and modelling.
  
  - Discovery of divergence instability of shells conveying flow. His water tunnel experiments and reduced-order modelling have shown, for the first time (1999), the subcritical divergence instability of circular shells conveying liquid flow. In this instability, instantaneous collapse arises before the stability limit under small perturbations, which is very dangerous in applications. This behavior was not known before his pioneering studies.
  -Nonlinear damping of shells. This was first ever reported by Amabili who identified it from experiments on shells in 2003. Nonlinear damping was later accurately modelled by Amabili using linear viscoelasticity introducing geometric nonlinearities. Before his studies, no model was available to describe the damping increase with the vibration amplitude which was compatible with experimental results.
   
• Mechanical characterization of the human aorta. This research is particularly significant to understand diseases (e.g. aneurysms) and develop innovative grafts. Amabili has been the first to characterize the quasi-static and dynamic mechanical behaviour of human aortic tissue with smooth muscle activation. This is a very challenging mechanical characterization which required the development of an innovative experimental protocol.

Impact

• Nonlinear vibrations and stability of shells interacting with fluids.
   
  - The experimental and numerical results of Amabili on instability and vibrations of shells coupled to fluids are largely used as a benchmark to validate numerical codes by industry and academia, and to improve safe design of nuclear components (Framatome Inc; Atomic Energy of Canada).
  - The experimental results and the models by Amabili on the damping increase with the vibration amplitude are relevant for safe design and certification. Framatome Inc (VA, USA) has used Amabili’s results to model the dynamic response of nuclear fuel rods supported by spacer grids - inside the core of nuclear reactors - under extreme events like earthquakes.
  - The book on nonlinear shell theories and large-amplitude vibrations of shells that Amabili wrote in 2008 (Cambridge Univ Press) is used by researchers in many countries (over 1,200 citations).
   
• Mechanical characterization of the human aorta
   
  - The experimental characterization of the active and passive dynamic properties of human aortic tissue developed by Amabili has been used to develop a new generation of mechanically-compatible aortic grafts, to overcome the unsatisfactory performance of presently used synthetic grafts which are too stiff and do not expand radially with consequential early failure.
   
• Former graduate students & collaborations in USA
   
  –Amabili supervised 63 graduate students and postdocs (Italy and Canada).
  –Collaborations include Framatome Inc and SANDIA National Labs, in addition to Academia.