neckingilmiö

The necking phenomenon, also known as localized plastic deformation, is a critical behavior observed in ductile materials subjected to tensile stress. It refers to the significant and localized reduction in the cross-sectional area of a specimen at a specific point before fracture. This occurs after the material has passed its ultimate tensile strength and entered the plastic deformation stage.

As the material elongates, the stress distribution becomes non-uniform. At a certain point, the material begins to yield and deform plastically. This plastic deformation causes a decrease in the cross-sectional area at that location. However, due to strain hardening, the material at the necked region becomes stronger, which temporarily counteracts further yielding. This leads to a concentration of stress in the already reduced cross-section, promoting further localized deformation.

The onset of necking is a clear indicator that the material is approaching fracture. The phenomenon is closely related to the material's ductility, with more ductile materials exhibiting more pronounced necking. It is a key consideration in material science and engineering for predicting the behavior of components under tensile load and for designing structures that can withstand such stresses. The study of necking helps in understanding fracture mechanics and in the development of materials with improved tensile properties.