Analysis of localization of strains by ESPI, in equibiaxial loading (bulge test) of copper sheet metals

In this paper, an original application of ESPI in materials engineering has been described. The technique was used to analyze a bulge test in order to study strain localization by following the strain rate progress. Results show that ESPI allows detecting clearly the two stages of localization, namely, the diffuse and localized necks. Using this technique, forming limit diagrams can thus be established accurately.