A new fracture area method for predicting the growth of a newly coalesced crack in AA7050-T7451 aluminium alloy

A period of crack growth “retardation” after coalescence of a pair of cracks, propagating under constant amplitude cyclic loading, has been found in previous studies. In this study, quantitative fractography has been used to examine the evolving shapes and sizes of the fracture area of a newly coalesced crack. The size of the “remaining” area required for two coalesced cracks to form a single semi elliptical crack was found to be associated with the period of crack growth “retardation”. Based on this relationship, a new fracture area method has been formulated in which accounts for the period of crack growth “retardation” of a coalesced crack. The crack growth of the newly coalesced crack predicted using the new method agreed well with experimental data.