Improved binarization based method for local formability characterization of modern steels

True fracture strains obtained from the fracture surface area measurement of tensile test specimens allow for gauge-length independent characterization of the local formability. It is difficult and error prone to use the norm method (ASTM-E8) for fracture area measurement on modern advanced high strength steels (AHSS) owing to the irregular fracture surface and excessive necking, as this makes the accurate identification/measurement difficult and leads to high scattering. The presented work aims to solve this problem in local formability measurement and make the measurement process more robust. The results of the proposed approach, which involves specimen masking and image binarization show that through this method it is possible to improve the repeatability of the measurements, reduce the scattering due to operator influence and significantly reduce the time required for the measurements.