2. Microscopic behavior

In crystalline materials, plastic deformation is achieved by microsliding (or possibly by macrosliding) of material elements relative to each other within each grain. Under the influence of a critical cission stress τ _c , sliding occurs through the movement of dislocations, in crystallographic directions notedb (for the Burgers vector) and on planes of normal n. According to Von Mises' rule, there must be as many slip systems as there are independent components of imposed deformation ( $⩽5$ ). In the case of plastic deformation typical of shaping, there are therefore several systems involved per grain. Plastic deformation then requires the creation, movement and interaction of dislocations from the different systems with barriers...