Characterization of Damage Mechanisms During Bending of 6xxx Aluminum Automotive Sheets

Bendability is a key property of aluminum automotive panels. Previous work showed that the bendability may not be characterized by macroscopic parameters. In the present work, the kinetics of damage development during bending of 6016 sheet was first characterized experimentally. Then, a mechanical model analyzing independently the influence of the microstructure, the flow stress distribution, the hardening behavior of the material and the sheet thickness on the bendability was developed.The experimental analysis showed that suppressing surface roughness does not lead to an improvement in bendability and that through thickness strain localization controls damage development. Shear bands have been characterized thanks to EBSD map analysis. The observed shear bands extend over 2–3 grains and can concentrate strains of about unity. The mechanical model reproduced the experimental observations and allowed quantifying the influence of microstructure, material behavior and sheet thickness on the bendability. The spatial distribution of the flow stress and the strain hardening at large strains control the sheet bendability.