Influence of internal pressure and axial compressive displacement on the formability of small-diameter ZM21 magnesium alloy tubes in warm tube hydroforming

Hajime Yasui, Taisuke Miyagawa, Shoichiro Yoshihara, Tsuyoshi Furushima, Ryuichi Yamada, Yasumi Ito

Research output: Contribution to journalArticle

Abstract

In this study, the influence of internal pressure and axial compressive displacement on the formability of small-diameter ZM21 magnesium alloy tubes in warm tube hydroforming (THF) was examined experimentally and numerically. The deformation behavior of ZM21 tubes, with a 2.0 mm outer diameter and 0.2 mm wall thickness, was evaluated in taper-cavity and cylinder-cavity dies. The simulation code used was the dynamic explicit finite element (FE) method (FEM) code, LS-DYNA 3D. The experiments were conducted at 250C. This paper elucidated the deformation characteristics, forming defects and forming limit of ZM21 tubes. Their deformation behavior in the taper-cavity die was affected by the axial compressive direction. Additionally, the occurrence of tube buckling could be inferred by changes of the axial compression force, which were measured by the load cell during the processing. In addition, grain with twin boundaries and refined grain were observed at the bended areas of tapered tubes. The hydroformed samples could have a high strength. Moreover, wrinkles, which are caused under a lower internal pressure condition, were employed to avoid tube fractures during the axial feeding. The tube with wrinkles was expanded by a straightening process after the axial feed. It was found that the process of warm THF of the tubes in the cylinder-cavity die was successful.

Original languageEnglish
Article number674
JournalMetals
Volume10
Issue number5
DOIs
Publication statusPublished - 2020 May

Keywords

  • Deformation characteristics
  • Forming defects
  • Forming limit
  • Magnesium alloy
  • Small-diameter tube
  • Tube hydroforming
  • Warm working

ASJC Scopus subject areas

  • Materials Science(all)

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