Strain and strain rate measurement during the bulge test by electronics speckle pattern interferometry. http://dx.doi.org/10.1016/j.jmatprotec.2006.12.013

Abstract

This paper presents a new experimental method to measure the strain increment and the strainrate during the bulge of a copper sheet. The electronic specklepatterninterferometry (ESPI) is combined with the bulgetest to measure the field of strain increment. The strainrate is used to detect heterogeneity in the strain distribution.
The main originality of this work is the application of an optical interferometer to determine the field of plastic strain increments and strainrates in the region of the top of the specimen.