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SUMMARY:Scale effects induced by strain-gradient plasticity and interfacia
 l resistance in randomly heterogeneous media - John Willis\, DAMTP
DTSTART:20060213T130000Z
DTEND:20060213T140000Z
UID:TALK4648@talks.cam.ac.uk
CONTACT:Paul Metcalfe
DESCRIPTION:The theory and physical origin of strain-gradient plasticity w
 ill be briefly outlined\, and a "deformation theory" (as opposed to "flow 
 theory") version will be developed. A distinctive aspect of the theory is 
 that it requires an additional boundary condition\, or condition across an
 y interface. This may be turned to advantage by introducing an "interfacia
 l potential" that penalises the development of plastic flow at an interfac
 e\, by impeding the motion of dislocations. A scale-dependent hardening ef
 fect in any material such as a composite or a polycrystal is generated the
 reby.  Treatment of such materials as having random microgeometry renders 
 exact solution intractable but approximations (which in some cases are bou
 nds) can be developed via a variational formulation.  This will be illustr
 ated with simple examples.
LOCATION:MR4\, DAMTP
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