The transition from elastic behaviour to plastic ow of technical materials under the inuence of increasing mechanical load is obviously of major technical importance. Nevertheless it is a challenge to formalize this transition in terms of consistent eld theories. We adopt here the beautiful theoretical work of Kröner , Bilby , and Kunin , who have shown how this formalization can be done. We shall go beyond their results by assuming energy dissipation if dislocations are moved through surfaces as suggested earlier  due to the energy density contribution from inner curved surfaces. Sometimes the mutual movement of adhering planes is described in terms of a stick-slip movement, meaning that the solid switches between elastic and plastic, possibly (and in fact in most experimental cases) showing a hysteresis between the two. Earthquake shear waves, e.g., are a dramatic example. Classical eld theories can hardly account for this eect. We shall try to describe the solid deformations as dislocations in two dierent phases, allowing for transitions between these phases. The tool is the Ginzburg-Landau-formalism in the form Haken  used for selforganizing quantized systems. We are aware of the fact that this procedure is consequent only after the above mentioned classical eld theories have been quantized, a still open task for theoretical physicists, but we feel that the practical benet is worth the cavalier assumptions.