The Fatigue Crack Growth Under Variable Amplitude Loading In Built Up Structures PDF Download

Thirty three specimens were tested both at constant and variable amplitude loading. The specimens, cut from sheets of 7075-T6 aluminium alloy, coming from the same batch were both simple sheets and riveted stiffened panels. The constant amplitude tests on simple sheet specimens were carried out in order to obtain the average K-rate relationship and the relevant scatter of the batch of sheets. The constant amplitude tests on stiffened panel were aimed at obtaining information on rivet flexibility and friction forces. Variable amplitude tests were performed utilizing the FALSTAFF spectrum. The data on sheet specimens was used to assess the reliability of prediction methods such as those devised by Wheeler and Willenborg, and the stiffened panels test data to establish how these methods work in the case of built-up structures. The results, especially those concerning the spectrum tests on stiffened panels, are still preliminary, but significant in as far as they allow us to assess the reliability of crack grow prediction methods and to obtain a qualitative but deep insight into the phenomenon of crack growth in built-up structures.