Flow localization in sheet specimens with pairs of holes

The deformation localization behavior of sheet specimens containing geometric perturbations in the form of pairs of through-thickness holes is examined. Both experiments and computational modeling are performed in either uniaxial or equal-biaxial tension in order to examine the effect of applied loading path on the far-field strain needed to initiate localized necking in the ligament between the hole pairs, The models also examine the influence of hole spacing and matrix strain hardening on ligament localization. The far-field strain needed to cause the localization of the ligament is shown to increase as the biaxiality of the loading path increases, the hole spacing increases, and the strain-hardening exponent increases. The present study also indicates that the onset of localized necking can be predicted by employing the Hill criterion, if the local strain states within the ligament are taken into account.