Abstract
Freestanding nano-films generally fracture at a small strain less than 1%. It is due to the high yield strength and the localized fracture by inevitable defects. Since the localized fracture such as crack propagation is accompanied with large plastic deformation, the evaluation of large strain plasticity is important to explore the mechanics of fracture in nano-films. The purpose of the study is to develop a method for evaluating the plastic properties of nano-films in the large strain range. In this study, a stress concentrated region is intentionally created in a freestanding 500 nm-thick Cu film by introducing a notch having an appropriate radius of curvature. The local plastic deformation near the notch root is then qualitatively evaluated by a digital image correlation (DIC) method. The results show that the method can evaluate the local strain field ahead of the notch root in the large strain range up to about 4%.
