A direct analytical methodology for the assessment of ductile fracture in metals based on multiaxial tests

The prediction accuracy of ductile damage models is subject to a sound calibration strategy which normally involves the execution of complex multiaxial tests and requires dedicated facilities. In addition, Finite Element (FE) analysis is mandatory to retrieve the stress and strain states at the critical point, which cannot be directly measured from experiments. To overcome this complexity, a minimal set of simple multiaxial tests is selected, and an analytical-numerical approach is proposed to evaluate, without resorting to FE, both the stress evolution with plastic deformation and the fracture strain, under any different loading condition of each test. This is achieved from the sole knowledge of the material bilinear stress-strain relation and of the applied test displacement at fracture. The obtained results are compared with a traditional testing and calibration methodology, and the robustness of the approach is proved on a 17-4PH steel, an X65 steel, and a Ti6Al4V alloy.