Strain measurement of nickel thin film by a digital image correlation method

Digital image correlation is a whole-field and non-contact strain-measuring method. It provides deformation information of a specimen by processing two digital images captured before and after the deformation. To search the deformed images, a hybrid genetic algorithm, in which a simulated annealing mutation process and adaptive mechanisms are combined with a real-parameter genetic algorithm, is adopted. This method is used to measure the strain during the microtensile testing of nickel thin film. In addition to the conventional single region, a double region in which the strain is inferred from the distance change of two regions is proposed to calculate the strain by digital image correlation. The results indicate that while the strain values obtained by single-region method are reasonable, those obtained by the double region method are more accurate. Moreover, the mechanical properties of nickel thin film could be obtained.