Identification of elastic-plastic behavior in AHSS using the isotropic hardening model by the finite element method and EBSD

Abstract

The aim of this work is to analyze the maximum potential for use of isotropic hardening model in the determination of elastoplastic behavior in an advanced high strength steel (AHSS) known as dual phase steel, with yield stress of 780 MPa. This material belongs to a class of steels currently used the feedstock in the production of vehicles. This material was chosen because it has a high elastic return or spring back effect, which commits the mass production of components, causing dimensional failures in projects. Consequently, it is a steel that presents a complex microstructural behavior during deformation. Mechanical properties of the material were evaluated by tensile tests. Mechanical characterization of spring back effect was carried out by means of sheet metal forming, called three-point air bending. These results were compared with results obtained by the Finite Element Analysis, using the isotropic hardening model. Microstructures were analyzed by means of EBSD technique and the structural fractions resulting from mechanical bending processes were identified, as well as, one of the main mechanisms of reorganization of the crystalline reticulum, measured by CSL boundaries, was identified. The 2D simulation and the isotropic hardening model used in ABAQUS was efficient to identify the mechanical response of steel in relation to its plastic deformation, concluding that it has a kinematic type hardening. However, such a model used in ABAQUS was not totally satisfactory to predict the degree of spring back, since such a model does not take into account reduction in the Young's modulus present in the AHSS.