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SUMMARY:Puncture mechanics of soft solids: A theoretical perspective - Pro
 f. Mattia Bacca\, UBC
DTSTART:20241103T130000Z
DTEND:20241103T140000Z
UID:TALK224197@talks.cam.ac.uk
CONTACT:Raymond E. Goldstein
DESCRIPTION:The determination of the critical puncture force required to p
 ierce a soft material is key to improve surgical technology (e.g. robotic 
 surgery)\, manufacturing (e.g. food processing) and in-situ material chara
 cterization. This seminar discusses a mechanical theory able to calculate 
 the critical depth  and force  required to insert a cylindrical needle w
 ith a spherical tip into a hyper elastic material. Needle insertion occurs
  as a mechanical instability\, by which the needle-specimen system snaps b
 etween the ‘indentation’ configuration and the ‘penetration’ one\,
  which then becomes energetically favoured. The model considers quasi-stat
 ic indentation\, thus neglects rate-dependent behaviour in the material. I
 t also considers frictionless contact\, and the cut material is assumed to
  be incompressible. Both  and  are functions of the toughness and shear 
 modulus of the cut material\, and of the radius of the needle. The scaling
  relations obtained from the model are then compared against experiments\,
  giving good agreement. To account for frictional and adhesive contact bet
 ween needle and specimen\, the model is extended to correlate interfacial 
 properties with the evolution of the puncture force with penetration depth
 . The extended model is again compared against experiments to provide vali
 dation\, and shows that the penetration of tough and soft materials is con
 trolled by friction\, while for brittle and stiff materials adhesion preva
 ils. Finally\, we analyse the role of volumetric compressibility in punctu
 re\, and discover that tough and soft materials develop higher puncture re
 sistance when compressible (lower bulk modulus).
LOCATION:MR14\,  Centre for Mathematical Sciences\, Wilberforce Road\, Cam
 bridge
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