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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:TALK58915@talks.cam.ac.uk
CONTACT:Lorna Everett
DESCRIPTION:Department of Applied Mathematics & Theoretical Physics\, Univ
 ersity of Cambridge\n \nThis talk describes the static-dynamic analogy and
  its role in understanding the localized post-buckling of shell-like struc
 tures. We show\, for example\, the true significance of the Maxwell energy
  criterion load in predicting the sudden onset of “shock sensitivity” 
 to lateral disturbances. For technically ‘non-integrable’ systems\, su
 ch as thin compressed shells\, we show how the emergence of spatial chaos 
 generates a multiplicity of localized paths (and escape routes) with compl
 ex snaking and laddering phenomena. These are illustrated in the response 
 and energy barriers of an axially compressed cylindrical shell.\n\n​Afte
 r surveying NASA’s current shell-testing programme\, we propose a new no
 n-destructive technique to estimate the “shock sensitivity” of a labor
 atory specimen that is in a compressed metastable state before buckling. T
 his uses a probe to measure the nonlinear load-deflection characteristic u
 nder a rigidly applied lateral displacement. Sensing the passive resisting
  force\, it can be plotted in real time against the displacement\, display
 ing an equilibrium path along which the force rises to a maximum and then 
 decreases to zero: having reached the free state of the shell that forms a
  mountain-pass in the potential energy. The area under this graph gives th
 e energy barrier 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 co
 ntrolled secondary probe tuned to deliver zero force on the shell.
LOCATION:Cambridge University Engineering Department\, LR5
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