Effective ductile fracture characterization of 17-4PH and Ti6Al4V by shear–tension tests: experiments and damage models calibration

An experimental campaign based on multiaxial tests is carried out to characterize the ductile behavior of 17-4PH steel and a Ti6Al4V titanium alloy, and to calibrate numerical ductile damage models, accordingly. This study aimed to identify a minimal set of four specimen types to ensure the robust tuning of the damage models, using only a conventional uniaxial machine for testing. Two different shear–tension candidate geometries are identified, modified, and used together with cylindrical and notched bar specimens to evaluate material plastic strain at fracture under several stress states, characterized by different triaxialities and Lode angles. Finite element analysis and digital image correlation techniques are used to identify local data not directly measured from the tests. Three recent ductile damage models are calibrated using the experimental data. The accuracy of the proposed approach is validated and presented for the two alloys, by comparing the results with calibrations performed on the same materials using more conventional multiaxial tests. It is shown that the new methodology is effective, and how either one of the two shear–tension geometries in addition to tensile tests could replace, with the same level of accuracy, typical more complex calibration procedures involving tests that require dedicated facilities.