Discrete Element Simulations of Damage Evolution of NiAl-Based Material Reconstructed by Micro-CT Imaging

Sintered porous materials present challenges for any modeling approach applied to simulate their damage evolution because of their complex microstructure, which is crucial for the initialization and propagation of microcracks. This paper presents discrete element simulations of the damage evolution of a NiAl-based material reconstructed by micro-CT imaging. A novel geometry reconstruction procedure based on micro-CT images and the adapted advancing front algorithm fills the solid phase using well-connected irregular and highly dense sphere packing, which directly represents the microstructure of the porous material. Uniaxial compression experiments were performed to identify the behavior of the NiAl sample and validate the discrete element model. Discrete element simulations based on micro-CT imaging revealed a realistic representation of the damage evolution and stress–strain dependency. The stress and strain of the numerically obtained curve peak differed from the experimentally measured values by 0.1% and 4.2%, respectively. The analysis of damage evolution was performed according to the time variation rate of the broken bond count. Investigation of the stress–strain dependencies obtained by using different values of the compression strain rate showed that the performed simulations approached the quasi-static state and achieved the acceptable accuracy within the limits of the available computational resources. The proposed stress scaling technique allowed a seven times increase of the size of the time step, which reduced the computing time by seven times.