Fatigue Damage Monitoring by Means of Acoustic Emission and Thermography in Ti Grade 5 Specimens

In this paper the crack propagation process in Titanium grade 5 specimens subjected to uniaxial fatigue loading was studied by adopting two different non-destructive technique (NDT) namely Acoustic Emission (AE) and Thermography. A couple of sensors placed on the sample and acoustically coupled with the metal through a coupling gel allowed to detect elastic waves produced inside the sample as a consequence of activation of inner defects. Part of the overall acoustic activity can be directly referred to the crack propagation process. At the same time the superficial temperature of the specimens was continuously monitored during the whole test to detect variation in temperature in the sample. In particular the rise of temperature around the crack tip was monitored in order to evaluate the advancing of the crack during the test. Finally the two methods were compared in order to underline differences in capability of predicting incumbent catastrophic failure.