Evaluation of a Micromechanism-Inspired Ductile Fracture Criterion for Formability and Fracture Prediction in Single Point Incremental Forming of AA۱۰۵۰ Aluminum Sheet

This study presents an experimental and numerical investigation of ductile fracture prediction in the single-point incremental forming (SPIF) of AA۱۰۵۰ aluminum sheets. The mechanical properties of the material were determined using uniaxial tensile tests, and the combined Swift-Voce hardening law was employed to define the plastic behavior of the material at strains beyond the onset of necking. The micromechanism-inspired ductile fracture criterion DF۲۰۱۴ was calibrated using uniaxial, plane-strain, in-plane shear, and notched tensile tests through the curve fitting toolbox in MATLAB and implemented in ABAQUS/Explicit ۲۰۲۲ through a VUSDFLD user subroutine, incorporating both linear and nonlinear damage accumulation rules. SPIF simulations were performed for a straight groove, a truncated cone, and a truncated pyramid, both with variable wall angles, and validated against experimental measurements of in-plane principal strains and thickness variations. The results demonstrate that incorporating the nonlinear damage accumulation rule, which accounts for the non-proportional loading history and evolving stress state during SPIF, substantially improves fracture prediction compared with the linear rule. The resulting predicted fracture initiation depths for the truncated cone and truncated pyramid agreed well with the experimental results, with errors of ۶.۱% and ۴.۶%, respectively. On the other hand, the variable cut-off value for stress triaxiality in the DF۲۰۱۴ criterion and its ability to predict fracture under stress states with negative triaxiality did not have a significant effect on the results due to the predominance of tensile stress states during the forming of the truncated cone and truncated pyramid.

کلیدواژه ها:

Incremental Forming ، SPIF ، Ductile Fracture ، DF۲۰۱۴ ، Aluminum alloy