How to take the Lüders Plateau into Account in the Formability Prediction of Steel Sheets

Some steels exhibit the Lüders effect. This phenomenon depends on the material and structure (test piece geometry, loading speed, etc.). Most work hardening laws do not take this phenomenon into account. The objective of this work is to define the most appropriate hardening law to highlight the characteristics of Lüders effects. First, the various aspects of the Lüders effect are presented. Several local hardening laws are proposed to describe the plateau or not, some of which are taken from the bibliography. Simulations of uniaxial tensile testing and forming of stamped parts are performed to compare these different hardening laws in predicting the Lüders effect. The Exp_Swift hardening law is recommended for forming cards because it is fully compatible with all software dedicated to steel sheet formability analysis and does not require inverse calibration during identification to accurately predict the plateau length.