Modeling crack growth from pores under compressive loading with application to metallic glasses

The mechanism of the fatigue-crack growth is essential to understand the fatigue and fracture behavior of bulk metallic glasses (BMGs) and is thus critical to predict the service lifetime of BMGs as potential engineering structural materials. Experiments indicate that fracture under compressive loading exhibits distinct behaviors different from that under tensile loading. A typical compression failure may initiate from micro porosity where cracks propagate in a direction generally parallel to the loading axis. Micromechanical stress analysis shows that pores cause axial tensile microcracks emanating from the pore. A simplified computational model based on the linear elastic fracture mechanics (LEFM) is proposed to investigate crack initiation and subsequent propagation under compressive load, where the effect of crack closure on mode-I fracture is considered. The stable crack length is characterized by a dimensionless fracture-mechanics quantity required to attain the associated crack length. The behavior of crack growth is examined based on the stress-intensity-factor (SIF) calculation, and its dependence on the loading and lateral confinement conditions is discussed.