plane plastic flow

Plastic flow, also known as plastic deformation, is the ability of a solid material to undergo permanent shape changes when subjected to stress. This occurs when the applied stress exceeds the material's yield strength, which is the minimum stress required to cause this permanent deformation without causing rupture. Below the yield point, a material exhibits elastic behavior, returning to its original shape once the stress is removed. Above the yield point, however, some deformation remains even after the stress is released.12

The theory of plane plastic flow, developed by Ludwig Prandtl in the early 20th century, analyzes the indentation of ductile solids and the resulting plastic slip lines. This concept is fundamental in understanding various metal-forming processes like rolling and forging, as well as geological phenomena such as rock folding.32