2. Yield strength of pure metals

2.1 Critical shear stress

The continuity of the crystal structure means that any dislocation must close on itself (dislocation loop) or terminate on another dislocation, on a free surface or on an internal interface of the microstructure (grain boundary, phase boundary, etc.). In an undeformed annealed metal crystal, there is a residual density of crystalline defects. The residual dislocation density ρ ₀ , expressed as the total length of dislocation lines per unit volume, is of the order of 10 ⁸ to 10 ¹⁰ m.m ^-3 . These dislocations arrange themselves in a three-dimensional, more or less complex configuration...