Determination of the fatigue crack-growth rate from the fractographic analysis of a specimen representing the aircraft wing skin

This paper presents an example of the fractographic analysis of a typical riveted joint after fatigue testing. The loading used in the tests was derived from a load spectrum representing the real operational conditions of the PZL I-22 Iryda aircraft. The fatigue crack-growth rates derived from macroscopic and microscopic analyses of the fatigue fracture surfaces have been compared. It seems that for practical purposes, like the fracture analysis of parts or components, results of the macroscopic method are closer to the observed crack-growth rates. The presented results refer to the propagation of cracks in the wing skin under stable crack-growth conditions.