Dynamic observation of localized strain pulsation generated in the plasticdeformation process by electronic speckle pattern interferometry

An electronic speckle pattern interferometry (ESPI) system, which makes it possible to observe dynamic phenomena, was applied to investigate the plast ic deformation process in tensile experiments of aluminum alloy samples. Th e dynamic behavior of a strain-localized band which propagated through a sp ecimen was thoroughly investigated. A pulsating fringe variation of the ord er of 1 Hz was discovered to be the fine structure of the propagating band. Fringe pulsation is caused by localized strain pulsation which suggests th at the stress relaxation process propagates periodically with a time consta nt which governs the dissipative characteristics of a heterogeneous materia l.