Micro-indentation based study on steel sheet degradation through forming and flattening: Toward a predictive model to assess cold recyclability

In Cold Roll Forming (CRF) process sheet material undergo a complex set of deformation that entail complicated through thickness residual deformation. This paper, focuses on material behaviour in CRF processes, with regarding damage and material degradation. A roll forming process is taken as case study and experimental investigation using extensive microhardness mapping alongside FE simulation of the process are the basis of material damage study. Indentation on different cross-sectional cutting angles -45, 0, 45 has been performed to study the sensitivity to orientation and crystallographic texture. A 3D Finite Element simulation with emphasis on through-thickness variation of the plastic deformation was carried out, using multiple layers of solid elements representing the sheet. A smart approach to reduce computational cost was employed in MSC.Marc by implementing simulation of a master model of complete material with shell elements, followed by partial sub-modelling comprising solid elements in regions of interest. This cross-sectional hardness map was then converted to the corresponding equivalent plastic strain in the cross section for validation. The correlation factor between Hardness and yield stress was discussed.