A new fracture criterion for ductile materials based on a finite element aided testing method

The fracture criteria for ductile materials have been developed in numerous researches. However there are huge differences between them. Therefore, it's necessary to find a way to select or determine a ductile fracture criterion and identify its applicability and reliability. In this study, a finite element aided testing (FAT) method is proposed to obtain the uniaxial full-range constitutive relationship up to failure of A508-3 steel and SS316L. The fracture stress and strain are obtained based on finite element analysis. A series of tensile tests with different sample geometries and dimensions are carried out to find out the fracture threshold and the critical fracture stress triaxiality σ*. The experimental and simulation results showed that, the simulated load-displacement curves for all the different type of samples agree with experimental data by introducing the full range constitutive relationship obtained from the FAT method. The fracture threshold of ductile fracture is the first principle stress σ1. Stress triaxiality σ* of the specimens changes as the deformation continues. The critical fracture stress triaxiality σ*f has the most important influence on the fracture location and fracture threshold of the specimens. Critical fracture process in a wide range of stress triaxiality is investigated based on the finite element simulation process. Thus, a simple logarithmic-relationship between σ1f and σ*f has been constructed.