The residual strain measurement of thin conductive metal wire after electrical failure with SEM moiré

In this study, the residual strain of a thin conductive metal wire on a polymer substrate after electrical failure is measured with SEM moiré. Focused ion beam (FIB) milling is applied to fabricate micron moiré gratings on the surfaces of constantan wires and the random phase shifting technique is used to process moiré fringes. The virtual strain method is briefly introduced and used to calculate the real strain of specimens. In order to study the influence of a defect on the electrical failure of the constantan wire, experiments were conducted on two specimens, one with a crack, while the other one without any crack. By comparing the results, we found that the defect makes the critical beam current of electrical failure decrease. In addition, the specimens were subjected to compression after electrical failure, in agreement with the observed crack closure of the specimen. The successful results demonstrate that the moiré method is effective to characterize the full-field deformation of constantan wires on the polymer membrane, and has a good potential for further application to the deformation measurement of thin films.