Effects of superimposed hydrostatic pressure on sheet metal formability

P. D. Wu*, J. D. Embury, D. J. Lloyd, Yonggang Huang, K. W. Neale

*Corresponding author for this work

Research output: Contribution to journalArticle

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Abstract

The effect of superimposed hydrostatic pressure on sheet metal formability is studied analytically and numerically. A tensile sample of power-law hardening material under superimposed hydrostatic pressure is first analyzed using the classical isotropic plasticity theory. It is demonstrated that the superimposed hydrostatic pressure p lowers the true tensile stress level at yielding by the amount of p, while material work-hardening is independent of p. It is showed, based on the Considère criterion, that the superimposed hydrostatic pressure increases the uniform strain. The effect of superimposed hydrostatic pressure on sheet metal formability is further assessed by constructing the Forming Limit Diagram (FLD) based on the M-K approach. It is found that the superimposed pressure delays the initiation of necking for any strain path. The difference in predicted FLDs between the superimposed hydrostatic pressure and the stress component normal to the sheet plane is demonstrated. Finally, the effect of superimposed hydrostatic pressure on fracture in round bars under tension is studied numerically using the finite element method, based on the Gurson damage model. The experimentally observed transition of the fracture surface, from the cup-cone mode under atmospheric pressure to a slant structure under high pressure, is numerically reproduced.

Original languageEnglish (US)
Pages (from-to)1711-1725
Number of pages15
JournalInternational Journal of Plasticity
Volume25
Issue number9
DOIs
StatePublished - Sep 1 2009

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Keywords

  • A. Ductility
  • B. Elastic-plastic material
  • C. Stability
  • Superimposed pressure

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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