Surface effect induced thickness-dependent stress intensity factors of nano-thickness cracked metal plates

Fracture toughnesses of cracked plates strongly depend on their thicknesses at the macroscale in available experiments, where the main reason has been answered well using the threedimensional constraint theory. However, main factors dominating the thickness-effect fracture performance of nano-thickness cracked plates are still not clear. In this study, the surface effect addressed as a function of the bulk surface energy density and surface relaxation parameter is introduced into our theoretical model to characterize fracture properties of nano-thickness cracked metal plates. Equations of both stress intensity factors (SIFs) and crack-tip stress fields are derived by the principle of virtual work. By comparison with the results of molecular dynamics simulations, finite element method as well as the Gurtin and Murdoch surface model, our theoretical model exhibits better predictions with numerical simulations. Moreover, all results show that the effect of the surface property on SIFs is obvious only when the thickness of a plate is smaller than 10 nm. This study should be of great help for understanding the fracture mechanism of nano-thickness cracked metal plates.

Automated summary

In this study, the fracture properties of nano-thickness cracked metal plates were characterized by introducing the surface effect into a theoretical model. The theoretical model showed better predictions compared to numerical simulations, and the results indicated that the surface property only has a significant influence on the stress intensity factors when the plate thickness is smaller than 10 nm.