In power plants, special concerns from the point of view of destruction are caused by parts rotating at high frequencies, especially metal-consuming and highly loaded shafts of turbo-machines. When analyzing data on the interaction of the most dangerous metallurgical defects -cracks -the concept of "relative size" of a defect (RDS) is used, which is the ratio of half of the total size of defects to the distance between their centers. The available recommendations for problems of various classes

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... are not always unambiguous, which leads to an overestimation of the stress intensity factor (SIF) by approximately 1.5 times. To assess the influence of interacting defects, it was proposed to use a specially obtained function, which is a correction function for determining the stress intensity factor and is determined experimentally using the photo-elasticity method. A special correction function (SPF) depends on the geometric parameters of the model, cracks and their location in the body of the model. In the case of pairs of defects of the same type and their identical sizes, the parameters of the SPF are a characteristic of the interaction between defects. The procedure for the photoelastic determination of the SIF is described in detail, and the experimental dependences of the SIF for the characteristic points of interacting defects are presented. Cases with the RDS from 0 to 0.77 were considered. The characteristic values are determined, which make it possible to obtain three ranges of RDS for internal and surface interacting defects. Experimental dependences of the SPF on the RDS are obtained for internal, surface, and surface-internal interacting defects.