Geometrically necessary dislocations

Geometrically Necessary Dislocations (GNDs) are a specific type of dislocation that arise in crystalline materials when there is a gradient in the plastic deformation across the material. Unlike ordinary dislocations, which can move freely in a homogeneously deformed material, GNDs are required to accommodate the non-uniform strain fields that often occur during processes such as bending, stretching, or otherwise non-uniform deformation of materials.