Effect of Hardening Rule for Spring Back Behavior of Forging

Shinobu Narita, Kunio Hayakawa, Yoshihiro Kubota, Takafumi Harada, Takeshi Uemori

Research output: Contribution to journalConference articlepeer-review

12 Citations (Scopus)


Geometrical discrepancy between formed part and designed one is one of the major problems for metal forming processes. Spring back behavior is one of the most important factors on the discrepancy, in not only sheet metal forming but also cold forging process. For cold forging process, it is difficult to observe the change in geometry of forgings before and after release of tools/dies, since the workpiece during forging is covered by tools/dies in most cases. Uncertainty remains for the precision on geometrical prediction after spring back of the cold forged part. In the present research, the diameters of extruded shaft at the bottom dead center and after the release of tools/dies were measured to investigate the spring back behavior in the cold forging process. As a result of experiment, the diameter of extruded shaft was increased at the bottom dead center by spring back and decreased after the release by re-extrusion. For these series of change in diameter, FE analyses using isotropic and kinematic hardening models were performed in order to evaluate influence of spring back on the material hardening models in forging process. For kinematic hardening model, Yoshida-Uemori model modified for large strain region was employed. As a result of calculation, both the isotropic and kinematic hardening models showed the similar tendency on the change in diameter with the experimental one.

Original languageEnglish
Pages (from-to)167-172
Number of pages6
JournalProcedia Engineering
Publication statusPublished - 2017
EventInternational Conference on the Technology of Plasticity, ICTP 2017 - Hucisko, United Kingdom
Duration: Sept 17 2017Sept 22 2017


  • Bauschinger effect
  • FEM
  • cold forging
  • kinematic hardening model
  • stainless steel

ASJC Scopus subject areas

  • General Engineering


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