THE DEFINITION OF INCIPIENT NECKING AND ITS IMPACT ON EXPERIMENTALLY OR THEORETICALLY DETERMINED FORMING LIMIT CURVES

In the current paper various methods for Forming Limit Curve (FLC)evaluation are presented and discussed. The capabilities of modern optical systems for strain measurement are demonstrated. A method for limit strain evaluation, based on the onset of instability, is described in detail. The method can be applied for the evaluation of experimental strains, as well as of strains from Finite Element (FE) simulations. Three different approaches have been applied for the determination of FLCs for a DP600 steel. The method used for limit strain evaluation is shown to have a considerable influence on the level of the resulting FLC. Also results from FE-simulations of the same tests are presented. Theimportance of always questioning how a certain FLC has been evaluated is emphasized