Ductile Fracture Criterion in Cold Upsetting

Abstract

In this study, we aim to quantitatively evaluate ductile crack initiation with equivalent plastic strain and stress triaxiality on cold upsetting. An investigation into the behavior of cracking on the surface in the cold upsetting of typical cold-forged steels of S45C was carried out with a crank press. To apply various amounts of stress and strain histories, the shape of the test specimen was changed. The stress and strain histories were calculated by the finite element method (FEM). The result shows that ductile crack initiation was determined by equivalent plastic strain and stress triaxiality. The workability limit was predicted by comparing the criteria for ductile crack initiation to the history of the equivalent plastic strain and stress triaxiality to determine the final forging from the material by cold forging.