As for the calculation of the stress intensity factor of casting defects, scholars have made a lot of efforts and explored a variety of methods to calculate the stress intensity factor of casting defects, such as introducing “equivalent ellipse” to calculate the stress intensity factor of defects. The research results of many scholars show that the size and location of casting defects are important parameters that affect the fatigue performance of structures with casting defects. When calculating the stress intensity factor, it is necessary to comprehensively consider the comprehensive impact of casting defect area, location, load and other factors. Among them, Y. Murakami’s stress intensity factor calculation model is widely used, as shown in the formula:
Where: α Is the defect location coefficient, for internal defects α = 0.5, for surface defects α= 0．65; Ad is the defect area.
For cast structures, in addition to the location and shape of casting defects, which have a significant impact on the stress distribution of the structure, since inclusions and oxides absorb very little energy under the action of alternating loads, these casting defects usually act as fatigue sources in the fatigue behavior of the structure, and at the same time provide an easier path for crack propagation. Therefore, inclusions Casting defects such as oxides are also important factors affecting the fatigue performance of structures.