Abstract
The forming limits of austenitic stainless steel sheets were studied. It was found that the observed limit of straining in stretch forming, when both of the principal stresses are positive, is not set by localized necking, but instead by shearing fracture in the through thickness direction. Thus, the Marciniak-Kuczynski type of analysis, which has recently been successfully applied to both low-carbon steels and aluminum, may not apply to austenitic stainless steels. 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 fracture criterion of Ritchie and Thompson seems to overestimate the fracture limit. Better models are needed for the work hardening and to develop better limit strain criteria, since the work hardening seems to depend strongly on both strain rate and temperature. The formability of austenitic stainless steels appears to remain good even when coated with hard TiN, although unavoidable cracks will appear with continuing straining.