Description of heterogeneous dislocations distributions

Different approximations for the description of the internal stress field due to dislocations walls are given and discussed. The influence of disorder and the edge effects due to incomplete walls are particularly discussed. Finally the relationship between the internal stress and the flow stress are discussed in these particular cases. It is shown that identifying the flow stress with the internal stress averaged in the volume of the crystal may be misleading. Consequences on the propagation of glide bands are also examined. (orig.)