Method of determining the failure parameters of structural members with edge cracks

The theoretical-experimental method of determining the fracture parameters of structural members has been generalized for edge cracks on the basis of a solution for a half-plane with an edge crack. The error of determining the stress-intensity factors K_I and K_II does not exceed 2-3%. In many cases, the method makes it possible to determine, with the accuracy sufficient for practice, the stresses acting along the crack-line prior to crack appearance. The results show that the polynomials (7) can be used to approximate the load function. The number of terms, retained in the expansion (7), can be selected on the basis of the criterion (8). The approximation (9) is more suitable for solving the contact problems. Using this approximation, it is possible to have on average the error of determining the SIF and restore the loads applied to the panel. To apply the method, it is sufficient to measure the relative displacement of the edges in 1-3 points at a large distance from the tip. For the cracks extending to the curvilinear boundary the accuracy of restoration of the stresses by the proposed method depends on the b/R ratio, whereas there is no such dependence for a straight boundary.