Monday  |  Salon 9  |  09:00 AM–09:20 AM

#15531, A Rapid Procedure to Re-construct S/N Curve by using Harmonic Components of Thermal Signal

The use of thermal indexes assessed by monitoring rapid fatigue tests (stepwised tests) with infrared detectors as reliable damage parameters to reconstruct the S/N curve is a topic still presenting open points. First of all, the selection of the proper thermal index representing damage is a topic to be explored and also the relationship between the damage from rapid stepwise tests and constant amplitude tests is another point of discussion.
In the present work, we deal with such an issue by investigating the First Amplitude Harmonic (FAH) of thermal signal related to thermoelastic phenomena and dissipative effects too. It has been demonstrated that FAH is related to stiffness degradation and stress-induced effects. Moreover, it provides a local analysis of specific effect related the material fatigue damage without artefacts.
The results show that due to the relationship between stiffness degradation and FAH, and specific material properties, it is possible to reconstruct the S/N curve by carrying out just one constant amplitude test and a stepwise rapid test. Moreover, the capability of temperature FAH to study fatigue behaviour and detect damage during any loading procedure is also presented.
By resuming the outputs of present research are related to the:
1. Capability of temperature first amplitude harmonic (FAH) to detect fatigue damage;
2. Capability of temperature FAH to study fatigue behaviour;
3. Correlation between FAH and stiffness degradation during any loading condition;
4. An innovative procedure to reconstruct the S/N curve from FAH data acquired during a stepwise loading.

Rosa De Finis   Politecnico di Bari
Davide Palumbo   politecnico di bari
Umberto Galietti   Politecnico di Bari