Time-dependent methods for limit strains determination of sheet metal

Currently, researchers can make strain measurements with digital image-correlation analysis (DIC). Data measured by DIC easily adapt to the traditional position-dependent method for evaluating limit strains, but this method is not applicable to materials that exhibit inhomogeneous deformation, like multiple necking.

DIC analysis allows for the application of time-dependent methods, which are based on analysis of the temporal evolution of strains to define the onset of necking. This article compares three recently proposed time-dependent techniques for determining limit strains: a thickness-control method, the strain-control method and an acceleration-correlation method. For experimental purposes, duplex 2205 stainless-steel sheet, 0.92mm thick, was tested in uniaxial tension.