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SUMMARY:Investigating plastic yielding across the strain rates - Dr Beñat
  Gurrutxaga Lerma\, Imperial College
DTSTART:20160520T130000Z
DTEND:20160520T140000Z
UID:TALK65520@talks.cam.ac.uk
CONTACT:Claire Whitaker
DESCRIPTION:The yield point of a material is often used in design applicat
 ions as the upper limit of acceptable mechanical stress within the materia
 l. Although sometimes regarded as a unique value\, the yield point is know
 n to be heavily dependent on the strain rate the material is loaded with. 
 In this talk\, dislocation dynamics will be employed to explore some of th
 e factors affecting this strain rate dependence of the yield point\, for s
 train rates ranging from 100/s to 10^ 9/s. This will set two fundamentally
  different regimes: a quasi-static\, low strain range regime (below ~10^ 6
 /s)  and a dynamic\, shock loading regime. In the quasi-static regime\, tr
 aditional dislocation dynamics and line dynamics are employed to explore t
 he impact the strain rate has on the bowing of dislocation segments leadin
 g to plastic yielding. For higher strain rates\, Dynamic Discrete Dislocat
 ion Plasticity (D3P) will be employed to simulates plasticity as a result 
 of the collective motion of individual dislocations. In D3P\, dislocations
  are modelled as discontinuities in a elastodynamic continuum\, so unlike 
 traditional discrete dislocation methods\, time is included as a true fiel
 d variable\, and dislocations are described as sources of elastodynamic wa
 velets emanating from their cores. This introduces a new dimension to the 
 classical study of dislocation-mediated phenomena. By studying the collect
 ive response of the dislocations in shocked systems under varied boundary 
 conditions we are able to study in detail the effect dislocations have on 
 phenomena ranging from the attenuation of the dynamic yield point to plast
 ic shielding of dynamic crack tips. 
LOCATION:Oatley Seminar Room\, Department of Engineering
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