Failure of two aluminum sheets, AA5754 and AA6111, under stretching conditions is analyzed using a combined plane stress and plane strain approach. The sheet material is modeled by an elastic-viscoplastic constitutive relation that accounts for material plastic anisotropy, material rate sensitivity, and the softening due to the nucleation, growth, and coalescence of microvoids. Failure processes of sheet metals are modeled under plane strain tension. Also, failure strains are determined under bending conditions when the necking mode is suppressed. The results are consistent with experimental observations where the failure strain of the aluminum sheets increases significantly under bending conditions. The results indicate that when a considerable amount of necking is observed under stretching conditions, failure strains under bending conditions are higher.