On Unusual Fractures Occurring under Testing Static Crack Resistance

The fractures of compact samples after static crack resistance testing, in which the crack on the addfracture site rotates at a right angle with respect to the plane of the initial (fatigue) crack. Possible reasons for the formation of this shape of fractures are analyzed. It is shown that one of the possible reasons for crack rotation consists in the presence of residual stresses in the sample body. To assess the magnitude of residual stresses, a template has been cut out from a part of a compact sample tested for static crack resistance subsequently examined by means of a double-sided layer removal technique. The presence of residual stresses in the direction parallel to the initial fatigue crack has been demonstrated, which confirms the conclusions made regarding a possible effect of residual stresses exerted on crack rotation in the course of addfracture.