Abstract: The stress intensity factor of the main crack in crack net can reflect the damage degree of components. However, it is difficult to calculate the stress intensity factor directly due to the shielding effect between cracks. It is supposed that the main crack cannot locate in the edge of the crack net, and the cracks in the net parallel to each other and perpendicular to constraint direction. The shielding residual percent s of main crack, the cracks’ space ratio n and the crack length radio f are defined. The rule of shielding effect between two same length cracks, two random cracks, three cracks and multi-cracks is studied. The relation of s-f-n is definitive, and it is independent of the boundary conditions, size of cracks and other factors. The stress intensity factor of main crack can be calculated by the factor of single crack by using this rule when shielding effect happens. The example shows that this method is accurate, simple, convenient and fast.

Key words: Crack net, Shielding effect, Stress intensity factor, Thermal fatigue