isotropic hardening

Isotropic hardening refers to a material's increasing resistance to deformation as it undergoes plastic (permanent) deformation, regardless of the direction of applied forces. In this process, the material's yield surface—a boundary that defines the onset of plastic deformation—expands uniformly in all directions in stress space. This means the material "hardens" equally in all directions, making it more resistant to further deformation. Essentially, as the material is deformed, it becomes stronger and less likely to deform further, with this strengthening occurring uniformly no matter the type or direction of applied stress.