It was recalled that, although dislocation distributions were quite uniform at first, they usually became unstable when deformation occurred and underwent successive transitions towards various types of microstructure such as cells, deformation bands, persistent slip bands and labyrinth structures. This was well known but, in spite of a huge number of theoretical investigations, its modelling was still primative. An intermediate stage between micro- and macroscopic descriptions was suggested which consisted of the derivation of mesoscopic rate equations that described the dynamic evolution of dislocation densities. It was shown, using some classical examples, why this approach was useful for the description of mechanical systems undergoing plastic instabilities and how it could be used to determine the key physical processes involved in dislocation patterning. It was also shown that the localization of plastic deformation was a natural consequence of the collective behaviors which were caused by reaction and transport in dislocation populations.

Rate Equation Approach to Dislocation Dynamics and Plastic Deformation. D.Walgraef: Materials Science and Engineering A, 2002, 322[1-2], 167-75