Definition - What does Plane Strain mean?
Plane strain refers to the physical deformation of a body that is characterized by the displacement of material in a direction that is parallel to a given plane. The occurrence of plane strain acts as a source of stress corrosion in metals.
Corrosionpedia explains Plane Strain
Plane strain is often observed in very thick materials. It is noticeably absent in long wires with stresses usually acting perpendicular to its length. Therefore the parallel strain or displacement along the length is zero.
Microscopic material a far distance from the surface of a thick component is not free to deform laterally because is constrained by the surrounding material. The stress state under these conditions is triaxial, resulting in zero strain perpendicular to both the stress axis and the direction of crack propagation when tension forces are present. Under plane-strain conditions, metals behave elastically until the fracture stress is reached.