Edge and screw dislocations — defects that control plastic deformation
An edge dislocation is an extra half-plane of atoms. The Burgers vector b is perpendicular to the dislocation line.
Stress field: σxx = −Gb/2π(1−ν) · y(3x²+y²)/(x²+y²)².
A screw dislocation has b parallel to the line — helical atomic paths around the core.
Dislocations enable plastic flow far below the theoretical yield stress (Peierls-Nabarro).