6. Global properties of tool-induced plastic flow

We have already pointed out that the two fundamental laws :

• the notion of plastic flow threshold ;

• the flow law verifying the principle of maximum work,

that govern the plastic behavior of the volume element derive directly from the fact that the elementary mechanisms of plastic deformation, at the atomic scale, also verify these two laws. These are laws which, verified on one scale, are also verified on the next.

If we consider plastic flow as a whole, we find the same type of laws, with the proviso that mechanical loads and velocity responses can be described by a finite number of quantities, i.e. two vectors: the loading vector Q