Developing a fracture locus for predicting ductile fracture in stainless steel 316L additively manufactured using laser powder bed fusion

• Tailored specimen geometries enabled uniaxial tension tests over a wide range of stress triaxialities. • A fracture locus was built using stress state and equivalent plastic strain at fracture obtained from the experiments. • Symbolic regression using PySR was employed to develop interpretable closed-form equations for fracture prediction. • HIP-treated AM SS316L exhibits stress-state-dependent ductile fracture behavior. The ductile fracture behavior of additively manufactured hot-isostatically pressed stainless steel 316L was investigated using a combined experimental, numerical, and data-driven modeling approach. Plate-shaped and cylindrical geometries were designed to investigate three distinct stress states: shear-dominated, combined shear-tension, and high stress triaxiality. Finite element simulations were used to extract the stress state and equivalent plastic strain at fracture. The resulting data revealed a non-monotonic dependence of equivalent plastic strain at fracture on stress triaxiality. A fracture locus was constructed from data across seven calibration geometries, and closed-form analytical expressions were developed using symbolic regression. In addition, a stress-reduction factor, dependent on stress triaxiality and equivalent plastic strain, was introduced to account for material softening, enabling the accurate prediction of fracture initiation in the specimens. The proposed fracture locus and softening formulation provide an interpretable and computationally efficient framework for predicting ductile fracture in additively manufactured stainless steel 316L, and the framework can be extended to other ductile metals exhibiting similar stress-state dependence under complex stress states.