A DCAMM seminar will be presented by
Dr., PhD Daniel S. Balint
Dept. of Mechanical Engineering
Imperial College London
United Kingdom
Abstract:
Traditionally, the study of plastic relaxation processes under weak shock loading and high strain rates in crystalline materials has been
based on direct experimental measurement of the macroscopic response of the material. Using this data, well-known macroscopic constitutive laws and equations of state have been formulated. However, direct simulation of dislocations as the dynamic agents of plastic relaxation in those circumstances remains a challenge.
Current Discrete Dislocation Plasticity (DDP) methods, where dislocations are modeled as discrete line singularities in an elastic
continuum, are unable to adequately simulate plastic relaxation because they treat dislocation motion quasi-statically, thus neglecting the time-dependent nature of the elastic fields and assuming that they instantaneously acquire the shape and magnitude predicted by
elastostatics. Under shock loading, this assumption leads to artifacts that can only be overcome with a fully time-dependent formulation
of the elastic fields. The first part of this talk will be an overview of planar discrete dislocation plasticity, including a brief summary of
quasi-static studies on size effects conducted over the last ten years.
It will then be shown that the quasi-static approximation is unsuitable for very high strain rates (~10^6 and higher). Finally, a truly
dynamic formulation for the creation, annihilation and arbitrary motion of straight edge dislocations will be presented. The Dynamic
Discrete Dislocation Plasticity (D3P) method will be applied in a two-dimensional model of time-dependent plastic relaxation under shock loading, and some relevant results on the decay of the elastic precursor will be presented.
Danish pastry, coffee and tea will be served 15 minutes before the seminar starts.
All interested persons are invited.