Anisotropy and strain localization in steel foam

Steel foam fabricated by a powder metallurgical process was tested in uniaxial compression. The closed-cell foam samples exhibited anisotropy in compression, a phenomenon that was caused primarily by the ellipsoidal cell shapes within the foam. Yield strengths were 3× higher in the transverse direction than in the longitudinal direction. Yield strength also showed a power-law dependence on relative density (n≅1.8). Compressive strain was highly localized and occurred in discrete bands that extended transverse to the loading direction. The deformation bands were comprised of collapsed cells, and deformation occurred in a sequential manner with repeating cycles of yield, collapse and densification of cells. Foam densification commenced when all of the foam was converted into deformation bands.