INFLUENCE OF THE NUMBER OF TENSILE/COMPRESSION CYCLES ON THE FITTING OF A MIXED HARDENING MATERIAL MODEL: ROLL LEVELLING PROCESS CASE STUDY

After rolling processes, metallic coils show several flatness imperfections and residual stresses that must be minimized when high quality components are manufactured by means of sheet metal forming processes. The equipments typically used for this purpose are roll levelling facilities. During this process, sheets are subjected to cyclic tension-compression deformations leading to a flat product. In order to know how a material behaves in this process, a cyclic reverse loading experiment is necessary. In the present work, a uniaxial cyclic tension-compression test has been used to determine the mechanical response of steel sheet under the different loading modes. After this, the Chaboche and Lemaitre nonlinear mixed hardening model has been fitted to the material behavior. This hardening model is able to reproduce some phenomena which occur during low cyclic deformation such as Bauschinger effect and workhardening. During the fitting of the model, the number of tension-compression cycles performed in the material characterization has been analyzed. Finally the influence of the material model in the roll leveling process results has been numerically analyzed. Different simulations have been performed with the objective of predicting residual stresses, residual curvatures, levelling force and torque at the end of the process.