Characterizing ductile damage and failure: Application of the direct current potential drop method to uncracked tensile specimens

摘要

Modem high-strength steels exhibit excellent ductility properties but their application is hindered by traditional design rules. A characterization of necessary safety margins for the ductile failure of these steels is therefore required. Direct observation of ductile damage within tests is currently not possible, only limited measurements can be made with synchrotron or X-ray radiation facilities. The direct current potential drop (DCPD) method can determine ductile crack propagation with low effort in fracture mechanics. This study investigates the applicability of the DCPD method in notched round bar tensile specimens. The potential measurement is strongly influenced by continuous necking, which decreases the available cross section and thereby increases the specimen's electrical resistance. A possibility is presented to distinguish the geometrically induced potential rise from the one induced by damage to determine the onset of damage. The results help to develop an effective way to characterize the improved ductile failure behaviour of high-strength steels.