Porous Plasticity & Damage era
Nikolai Kachanov's early damage mechanics introduced porosity evolution and void-mediated degradation as the basis for ductile failure. Ahmed Gurson formulated the porous plasticity model that embeds a void volume fraction into the yield surface, enabling predictions of ductile fracture in metals. James Needleman extended this continuum approach to explicit void nucleation and growth and implemented it within finite element analyses. Anastasios Aifantis introduced gradient plasticity concepts to regularize damage and connect microstructural porosity with the macroscopic continuum response.