Dynamic ESPI system for spatio-temporal strain analysis of a deforming solid object

In Dynamic Electronic Speckle Pattern Interferometry (DESPI), deformation analysis could be done for successively acquired frame data of interfering speckle patterns with no additional frames like phase shifting speckle patterns. Our final goal is to obtain a temporally varying process of two-dimensional strain field. Two normal strains and shearing strain are derived by numerical derivatives of two components of in-plane deformation. Analyzed results of tensile experiments of an Al-alloy sample will be shown. In the experiments, propagation of a strain localization band accompanied by serration of a stress curve was clearly observed quantitatively analyzed.