Mechanical damage assessment by means of thermo-electrical lock-in thermography

The present work deals with the nondestructive assessment of the metallic materials' mechanical damage. An innovative Nondestructive Evaluation (NDE) methodology based on two thermographic approaches was developed in order the state of fatigue damage to be assessed. The first approach allows the detection of heat waves generated by the thermomechanical coupling during the fatigue loading (online method). Specifically, both the thermo-elastic and intrinsic dissipated energy was correlated with the mechanical degradation and the remaining fatigue life. The second approach involves the monitoring of the materials' thermal behavior using a Peltier device for accurate thermal excitation (offline method). The correlation of the thermal behavior and the state of damage was achieved by the determination of the material's thermal response. The combination of these two approaches enables the rapid and accurate assessment of the cumulative damage