Mixed mode (I and II) fracture behavior of nanoglass and metallic glass

Abstract

Nanoglasses (NGs) have shown large tensile ductility and hardness than metallic glasses (MGs) used to synthesized them. The mixed mode (I and II) fracture experiments and complementary finite element (FE) simulations reported significant influence of applied mode mixity on the crack tip plasticity and fracture toughness of MGs. However, no such study has been under taken for NGs which are synthesized from MGs only. Therefore, two-dimensional, plane strain, FE analysis on the stationary crack in nanoglass (NG) and metallic glass (MG) subjected to mixed mode (I and II) loading conditions are performed under small scale yielding (SSY) conditions by employing the constitutive model for MGs. It is found that the crack tip plasticity is markedly affected by mode mixity in both NGs and MGs, and the shear bands ahead of crack tip appears to be more diffused in the former than the latter. Further, the plastic zone size ahead of the crack tip in NG is larger than that for MG for identical loading conditions. Also, FE simulations predict enhancement in fracture toughness of both the alloys with increase in the mode I contribution. In addition, the results suggest that the NGs may not exhibit larger fracture toughness than MGs with identical composition, although they exhibit larger tensile ductility.