A plane stress anisotropic plastic flow theory for orthotropic sheet metals

A phenomenological theory is presented for describing the anisotropic plastic flow of orthotropic polycrystalline aluminum sheet metals under plane stress. The theory uses a stress exponent, a rate-dependent effective flow strength function, and five anisotropic material functions to specify a flowpotential, an associated flow rule of plastic strain rates, a flow rule of plastic spin, and an evolution lawof isotropic hardening of a sheetmetal. Eachof the five anisotropicmaterial functionsmay be represented by a truncatedFourier series based on the orthotropic symmetry of the sheetmetal and their Fourier coefficients canbe determinedusing experimental data obtained from uniaxial tension and equal biaxial tension tests. Depending on the number of uniaxial tension tests conducted, three models with various degrees of planar anisotropy are constructed based on the proposed plasticity theory for power-law strain hardening sheetmetals. Thesemodels are applied successfully to describe the anisotropic plastic flow behavior of 10 commercial aluminum alloy sheet metals reported in the literature. 2005 Elsevier Ltd. All rights reserved.