The Extended Stress-Based Forming Limit Curve (XSFLC) failure criterion has been shown to provide good qualitative and quantitative predictions of failure (necking) in straight tube hydroforming when the Keeler-Brazier (K-B) approximation is used to define the XSFLC failure curve. Depending on the level of end-feed (EF) used during hydroforming, the failure criterion has a tendency to over predict failure pressure at low EF and under predict failure pressure for high EF. The over/under predictions suggest that the strain-space εFLC, which the XSFLC is based on, has too high of a plane-strain intercept (FLC{sub}o), when it is obtained using the K-B approximation (developed for sheet metal).
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