Effect of crack deflection and branching on the R-curve behaviour of an Al-Li alloy 2090 sheet

Abstract

The methodology to predict the increase in crack growth resistance due to crack deflection and branching is described. These procedures are discussed with respect to an AI-Li alloy 2090 sheet in T6 condition, the R-curve tests on which revealed that the crack path in L T orientation was deflected and branched while it remained nominally straight in TL orientation. The resistance to slow stable crack extension in L-T orientation was found to be significantly higher as compared to that in T-L orientation. Such behaviour is rationalized in terms of crack deflection and branching. The observed variation in the crack path morphology and the resulting R-curves in L-T and T-L orientations can be understood in terms of the microstructural features of the alloy.