Advanced high-strength steels (AHSSs) exhibit large, and sometimes anisotropic, springback recovery after forming. Accurate description of the anisotropic elasto-plastic behaviour of sheet metals is critical for predicting their anisotropic springback behaviour. For some materials, the initial anisotropy is maintained while hardening progresses. However, for other materials, anisotropy changes with hardening. In this work, to account for the evolution of anisotropy of a dual-phase steel, an elastoplastic material constitutive model is developed. In particular, the combined isotropic-kinematic hardening model was modified. Tensile loading-unloading, uniaxial and biaxial tension, and tension-compression tests were conducted along the rolling, diagonal, and transverse directions to measure the anisotropic properties, and the parameters of the proposed constitutive model were determined. For validation, the proposed model was applied to a U-bending process, and the measured springback angles were compared to the predicted ones.

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Polyethylene terephthalate (PET) films produced by rolling and tentering have biaxial orientation and thus exhibit anisotropic mechanical properties such as yielding, hardening, and fracture. The anisotropy of film makes it difficult to analyze deformation and failures occurring during processing such as metal forming of polymer coated sheet metals. In this work, the anisotropic yielding and hardening of the PET film were measured and an anisotropic constitutive model is developed to represent the anisotropic behavior. In addition, fracture limits of the PET film were measured using the Nakajima test. To describe anisotropic fracture behavior of the film, an anisotropic fracture criterion based on the strain energy density and the theory of isotropic equivalent material was proposed. For validation of the developed constitutive model and the fracture criterion, a deep drawing test of the PET coated sheet metal was conducted. The film cracking predicted by the anisotropic fracture criterion agreed well with measurements.