In-situ fatigue damage monitoring of rolled Al-Zn-Mg alloy using an advanced acoustic emission technique

In the present study, damage evolution in rolled Al-Zn-Mg alloy and its welds is evaluated using the acoustic emission (AE) method and crack initiation is detected using digital imaging during fatigue tests. The AE characteristics and source mechanisms are analysed based on microstructural and fractographic observations. The experimental results show that AE energies are effective indicators for detecting fatigue crack initiation in Al-Zn-Mg alloys. The results obtained were verified through digital images of the notch tip region of the Al-Zn-Mg alloy samples. For small percentages of the applied load range close to the peak load, the AE count rates show a reasonable correlation with the crack propagation rates. These correlations can be applied to predict the remaining service life of fatigue-damaged structures. The analyses performed demonstrate that the AE technique is sensitive to variations in the fracture mode and could be applied to monitor fatigue damage evolution in welded structures.