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SUMMARY:Strain gradient plasticity: Numerical modeling of size-effects in 
 porous metals - Prof Christian F. Niordson\, DTU
DTSTART:20190524T130000Z
DTEND:20190524T140000Z
UID:TALK119800@talks.cam.ac.uk
CONTACT:Hilde Hambro
DESCRIPTION:Micron scale size-effects in metals have been confirmed in num
 erous experiments\, exhibiting the general trend that smaller is stronger.
  For torsion of micron scale wires and bending of thin films\, it has been
  found that normalized twisting and bending resistance in the plastic defo
 rmation range increase with decreasing specimen size. In micro- and nano-i
 ndentation testing increased hardness for smaller indentations are measure
 d. It is generally accepted these size-effects in metals are due to so-cal
 led geometrically necessary dislocations that arise in the presence of ver
 y large plastic strain gradients. Such gradients may be imposed due to inh
 omogeneous overall deformation as in the examples above\, but they can als
 o arise under homogeneous deformation when boundaries are passivated\, suc
 h that plastic deformation is hindered due to blockage of dislocations.\n\
 nThe first part of this presentation presents a basis for numerical modeli
 ng of strain gradient plasticity\, both in the context visco-plastic mater
 ials and time-independent plasticity.\n\nThe second part treats size-effec
 ts in void growth\, with emphasis on extensions of conventional porous met
 al yield surfaces to include micron scale size-effects. \n
LOCATION:Oatley Seminar Room\, Department of Engineering
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