Determination of the bendability of ductile materials

Abstract

Understanding fracture in the bending of metal sheet is important but difficult especially for ductile materials were fracture is hard to quantify. New bend tests allow fracture analysis at higher bending strains, however, most of them are impractical for industrial application. This work investigates the link between material failure in bending of brittle and highly ductile materials and local tensile ductility which can be measured in a simple tensile test. For this, a 3-point bend test is developed based on the widely accepted VDA238-100, enabling the fracture of highly ductile aluminium alloys. The failure strain of brittle and ductile aluminium sheets in bending is determined. Uni-axial tensile tests are performed in combination with a digital image correlation (DIC) strain measurement system. Using the surface strain data, obtained from the DIC system during tensile testing and bend testing, a correlation between the local ductility in tensile testing and the fracture strain in bending was identified.