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SUMMARY:Anomalous dynamics of snap-through instabilities -  Dr Michael Gom
 ez\, DAMPT\, Cambridge
DTSTART:20181109T140000Z
DTEND:20181109T150000Z
UID:TALK110713@talks.cam.ac.uk
CONTACT:Hilde Hambro
DESCRIPTION:Snap-through buckling is a type of instability in which an ela
 stic object rapidly jumps from one state to another. Such instabilities ar
 e familiar from everyday life: children’s popper toys rapidly ‘pop’ 
 and jump after being turned inside-out\, while snap-through is harnessed t
 o generate fast motions in applications ranging from soft robotics to swit
 ches in micro-scale electronics and artificial heart valves. Despite the u
 biquity of snap-through in nature and engineering\, its dynamics is usuall
 y only understood qualitatively\, with many examples reported of delay phe
 nomena in which snap-through occurs much more slowly than would be expecte
 d for an elastic instability. To explain this discrepancy\, it is commonly
  assumed that some dissipation mechanism\, such as viscoelasticity in the 
 object\, must be causing the system to lose energy and slow down.\n\nWe fi
 rst demonstrate that anomalously slow dynamics are\, in fact\, possible in
  elastic systems with negligible dissipation. This time delay arises from 
 the remnant or ‘ghost’ of the snap-through bifurcation\, and is remini
 scent of the ‘critical slowing down’ observed in other areas of physic
 s such as phase transitions. However\, in many real systems (including the
  popper toy)\, viscoelastic effects are present to some degree. To gain in
 sight into the influence of viscoelasticity we then study a Mises truss as
  a simple model system that exhibits bistability and snap-through. Using a
  combination of asymptotic analysis and direct numerical solutions\, we el
 ucidate the role that viscoelastic effects play in obtaining anomalously s
 low snap-through dynamics\, as opposed to the purely elastic slowing down.
  Finally\, we show that our conclusions also extend to more complex viscoe
 lastic structures used in morphing devices.\n
LOCATION:Oatley Seminar Room\, Department of Engineering
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