Monitoring of Metal Fatigue Damage Using Acoustic Emission and Thermography

Acoustic emission (AE) supplies information on the fracture behavior of different materials. In this study, AE activity was recorded in metal coupons with a V-shape notch, which were loaded in fatigue until final failure. AE parameters exhibit a sharp increase approximately 1000 cycles before final failure. The use of AE parameters is discussed both in terms of characterization of the damage mechanisms and as a tool for the prediction of ultimate fatigue life. Additionally, a nondestructive methodology based on lock-in thermography is applied to determine the crack growth rate using thermographic mapping of the material undergoing fatigue. The thermographic results on the crack growth rate of aluminum alloys were then correlated with measurements obtained by the conventional compliance method, and found to be in agreement.