Multi-scale numerical simulation of fracture behavior of nickel-aluminum alloy by coupled molecular dynamics and cohesive finite element method (CFEM)

Abstract

In the current study, a multi-scale investigation on the crack propagation of B2-NiAl alloy was performed by using coupled molecular dynamics (MD) and the cohesive finite element method (CFEM). In particular, by using python programming, a FE model with a zero-thickness cohesive element for batch insertion was established. The T-S curve obtained from MD simulation was adopted as the material input parameter for the zero-thickness cohesive element to investigate the micro crack propagation mechanism and realize the macro crack random propagation simulation. The results showed that in micro-scale, the crack propagation behavior of single crystal B2-NiAl was primarily caused by continuous coalescence of the main cracks and microvoids generated from the stress concentration at the crack front. Furthermore, the single crystal B2-NiAl experienced phase transition and followed the Bain path. Moreover, the T-S curves at different temperatures were compared with Needleman classical theoretical models, demonstrating the properness of the Needleman model. Afterwards, the macroscopic fracture toughness values of B2-NiAl alloys at different temperatures were calculated and compared with those obtained from experiments. Such comparisons demonstrated good agreement with each other and indicated that the T-S curve obtained via MD can be applied to the FE method. These results validated the rationality of this multi-scale method, which offers an alternative approach for fracture behavior simulation across macro and micro scales.