Fatigue Crack Growth of Alloy 7050-T7451 Plate in L-S Orientation

Abstract

Experiments have been conducted to investigate the crack growth characteristics of 7050-T7451 aluminium plate in L-S orientation. Two loading conditions are selected, i.e. constant amplitude and constant stress intensity factor range (ΔK). The effects of ΔK-levels and stress ratios (R) on crack splitting are studied. Test data shows that crack splitting could result in the reverse of crack growth rate trend with the increasing R ratio at high ΔK-level. The appearance of crack splitting depends on both ΔK and R.

Damage Mechanisms and Anisotropy of an AA7010-T7452 Open-Die Forged Alloy: Fatigue Crack Propagation

“…Jian et al showed the contrary effect for ΔK > 14 MPa√m, i.e., smaller grains due to sheet thickness reduction increased the FCP resistance for an L-T oriented crack [ 33 ]. Other studies investigated the orientation of the specimen with respect to the rolling direction [ 34 , 35 ]. Schubbe et al showed that the FCP rate of AA7050-T7451 tested in L-S orientation is higher compared to T-L and L-T at low ΔK.…”

“…It is scientifically evident that all these metallurgical factors affect FCP behavior, while partly contradictory or inconclusive results show that the quantitative description of the underlying interrelations is still a major challenge among researchers and engineers. Moreover, most of these studies focus on thick plates [ 18 , 19 , 20 , 21 , 30 , 34 , 35 ], sheets [ 13 , 22 , 28 , 29 , 33 ], or on the comparison of both [ 31 ], which are generally produced by a rolling process. A different process to control the grain structure of 7xxx series aluminum alloys more flexibly, especially for thicker products, is forging [ 13 , 17 ]; however, the open literature currently lacks studies that quantitatively analyze the microstructure–property relationships during fatigue crack growth in high-strength aluminum alloy forgings.…”