"Dislocation avalanches, strain bursts, and the problem of plastic forming"
Relatore: Stefano Zapperi- CNR - Modena
09 Dicembre 2008 ore 15.30
|Under stress many crystalline materials exhibit irreversible plastic
deformation caused by the motion of lattice dislocations. In plastically
deformed microcrystals, internal dislocation avalanches lead to jumps in
the stress-strain curves (strain bursts) whereas in macroscopic samples
plasticity appears as a smooth process. By combining three-dimensional
simulations of the dynamics of interacting dislocations with statistical
analysis of the corresponding deformation behavior, it is possible to
determine the distribution of strain changes during dislocation avalanches
and establish its dependence on microcrystal size. Our results suggest
that for sample dimensions on the micron and sub-micron scale large strain
fluctuations may cause problems in controlling the resulting shape in a
plastic forming process.