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SUMMARY:Advances in Shell Buckling: theory\, experiments\, localization an
 d shock-sensitivity - Professor Mike Thompson - Dept of Applied Maths
DTSTART:20150515T140000Z
DTEND:20150515T150000Z
UID:TALK59132@talks.cam.ac.uk
CONTACT:Lorna Everett
DESCRIPTION:This talk describes the static-dynamic analogy and its role in
  understanding the localized post-buckling of shell-like structures. We sh
 ow\, for example\, the true significance of the\nMaxwell energy criterion 
 load in predicting the sudden onset of “shock sensitivity” to lateral 
 disturbances. For technically ‘non-integrable’ systems\, such as thin 
 compressed shells\, we show how the emergence of spatial chaos generates a
  multiplicity of localized paths (and escape routes) with complex snaking 
 and laddering phenomena. These are illustrated in the response and energy 
 barriers of an axially compressed cylindrical shell.\n	After surveying NAS
 A’s current shell-testing programme\, we propose a new non-destructive t
 echnique to estimate the “shock sensitivity” of a laboratory specimen 
 that is in a compressed metastable state before buckling. This uses a prob
 e to measure the nonlinear load-deflection characteristic under a rigidly 
 applied lateral displacement. Sensing the passive resisting force\, it can
  be plotted in real time against the displacement\, displaying an equilibr
 ium path along which the force rises to a maximum and then decreases to ze
 ro: having reached the free state of the shell that forms a mountain-pass 
 in the potential energy. The area under this graph gives the energy barrie
 r against lateral shocks. The test is repeated at different levels of the 
 overall compression. A symmetry-breaking bifurcation can be encountered on
  this path\, and we show how this can be suppressed by a controlled second
 ary probe tuned to deliver zero force on the shell.\n
LOCATION:Cambridge University Engineering Department\, LR5
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