Strain and strain rate measurement during the bulge test by electronic speckle pattern interferometry

This paper presents a new experimental method to measure the strain increment and the strain rate during the bulge of a copper sheet. The electronic speckle pattern interferometry (ESPI) is combined with the bulge test to measure the field of strain increment. The strain rate 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 strain rates in the region of the top of the specimen.