Forming and fracture limits of austenitic stainless steel sheets

The limit of straining of austenitic stainless steels in ordinary stretch forming, when both of the principal strains are positive, is usually not set by localized necking, but instead by inclined shearing fracture in the through thickness direction. It appears that the forming limits of austenitic stainless steels may be predicted fairly well by using the classical localized and diffuse necking criteria developed by Hill. The strain path-dependence may be accounted for by integrating the effective strain along the strain path. The modified Rice-Tracey fracture criterion seems to give a reasonable estimate for fracture limit strains. The Cockcroft, Latham and Oh criterion, however, underestimates the fracture limit. Necking limit strains are strongly dependent on the strain path. The fracture limit strains calculated using the modified Rice-Tracey criterion, however, did not depend as much on the strain path as the necking limit strains. (C) 2007 Elsevier B.V. All rights reserved.