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SUMMARY:Shock-Induced Pore Collapse in PMMA: Deformation Physics and Failu
 re Mechanics - Professor Guruswami Ravichandran\, Graduate Aerospace Labor
 atories\, California Institute of Technology
DTSTART:20260320T140000Z
DTEND:20260320T150000Z
UID:TALK236110@talks.cam.ac.uk
CONTACT:46601
DESCRIPTION:Porous materials play a central role in various engineering ap
 plications\, including the development of lightweight materials\, energy-a
 bsorbing structures\, and energetic solids. Porosity spans multiple scales
  and arises from manufacturing defects\, engineered foams\, and architecte
 d metamaterials. Under shock loading\, rapid pore collapse induces intense
  local deformation\, often leading to failure. However\, experimental insi
 ghts into this process remain limited to continuum-level measurements and 
 post-mortem analyses. This study introduces a novel technique for full-fie
 ld\, internal strain measurements during shock compression of transparent 
 materials\, applied to PMMA with embedded spherical pores. Using a normal 
 plate impact setup and high-speed imaging at 10 million frames per second\
 , we visualize pore collapse and extract time-resolved strain fields via d
 igital image correlation. Experiments reveal a critical shock stress at wh
 ich adiabatic shear bands (ASBs) initiate\, marking the first in-situ obse
 rvation of ASB formation during pore collapse. At higher stresses\, ASBs e
 volve into dominant shear bands\, culminating in dynamic shear fracture. W
 e also examine wave interactions between multiple pores using shadowgraphy
  and their influence on collapse and failure mechanisms. Complementary ela
 sticity theory and dynamic finite element simulations provide further insi
 ght into the physics governing pore collapse under extreme conditions.
LOCATION:Department of Engineering - LR4
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