Extended finite element method analysis for shielding and amplification effect of a main crack interacted with a group of nearby parallel microcracks

The shielding and amplification effects of transverse array of microcracks on a main crack are investigated using extended finite element method. The interaction between macrocracks and microcracks is quantitatively characterized in terms of the stress intensity factor which is calculated by the interaction integral method and the complete stress field in the entire domain could be given without remeshing. Various distributions of microcracks with different number, location, and density are considered. For a microcrack collinear to the main crack, the numerical results agree quite well with the analytical solution. Interestingly, the shielding and amplification effects display periodicity when the main crack is placed inside the microcrack rows. In particular, the minimum stress intensity factor of the main crack which refers to the maximum shielding effect is primarily determined by the nearest microcracks. However, the maximum stress intensity factor is largely affected by the distribution and density of microcracks and even could be turned from enhancement to shielding. The results are consistent with the microcrack-toughening phenomenon observed in the experiments and are meaningful for the design of new microstructure-toughening materials.