Load effects on macroscopic scale fatigue crack growth path in 2324-T39 aluminium alloy thin plates

In the present paper, an experimental study is accomplished to characterise the load effects, including K-level, stress ratio, overloads and underloads, on fatigue crack growth path in aluminium alloy 2324-T39 thin plates under constant amplitude (CA) and simple variable amplitude (VA) loading conditions. Crack growth in L-T and T-L oriented specimens is also examined. The test results indicate that the crack path in the L-T oriented specimens under CA loading is remarkably meandering, but no significant crack branching is observed, compared with T-L oriented specimens; tension overloads produce macroscopic crack branching, and the K-level seems to be the principal factor on crack path deviation.