Strain Hardening Behavior During Manufacturing of Tube Shapes by Hydroforming

다국어 초록 (Multilingual Abstract)

Safe and robust process design relies on knowledge of the evolution of the mechanical properties in a tube
during hydroforming. The manufacturing of tubular shapes generally consists of three main stages: bending,
preforming, and expansion. The latter is usually called hydroforming. As a result of these three steps, the
final product’s strain hardening history is nonlinear. In the present study, the strain hardening behavior during
hydroforming was experimentally investigated. The variation of local flow stress and/or local hardness was
used as an index of the strain hardening during the various steps and the local flow stress and/or local hardness
were used with respective correlations to determine the effective strain. The strain hardening behavior during
hydroforming after preforming has been successfully analyzed by using the relationships between hardness,
flow stress, and effective strain for variable pre-strains prior to hydroforming. The comparison of predicted
hardness with measured hardness confirms that the methodology used in this study is feasible, and that the
strain hardening behavior can be quantitatively estimated with good accuracy.

다국어 초록 (Multilingual Abstract)

Safe and robust process design relies on knowledge of the evolution of the mechanical properties in a tube
during hydroforming. The manufacturing of tubular shapes generally consists of three main stages: bending,
preforming, and expansion. The latter is usually called hydroforming. As a result of these three steps, the
final product’s strain hardening history is nonlinear. In the present study, the strain hardening behavior during
hydroforming was experimentally investigated. The variation of local flow stress and/or local hardness was
used as an index of the strain hardening during the various steps and the local flow stress and/or local hardness
were used with respective correlations to determine the effective strain. The strain hardening behavior during
hydroforming after preforming has been successfully analyzed by using the relationships between hardness,
flow stress, and effective strain for variable pre-strains prior to hydroforming. The comparison of predicted
hardness with measured hardness confirms that the methodology used in this study is feasible, and that the
strain hardening behavior can be quantitatively estimated with good accuracy.

참고문헌 (Reference)

1 W. J. Song, 368-, 2007

2 R. Hill, 281-, 1948

3 M. Koç, 41 : 761-, 2001

4 P. Ray, 47 : 1498-, 2005

5 E. Chu, 46 : 263-, 2004

6 B. S. Levy, 280-, 2004

7 P. Bortot, 381-, 2008

8 M. Nemat-Alla, 45 : 605-, 2003

9 M. Strano, 92-, 2004

10 Y. Xu, 413-, 2008

11 심호섭, "이차경화형 Co-Ni 합금강의 인장특성에 미치는 Co의 영향" 대한금속·재료학회 45 (45): 101-108, 2007

12 R. Hill, "The Mathematical Theory of Plasticity" Clarendon Press 1950

13 Heon Young Kim, "The Effect of Prebending on the Formability in the Tube Hydroforming Process of an Aluminum Rear Subframe" 대한금속·재료학회 13 (13): 87-92, 2007