Specimen Design and Characterization for Thin-Walled Components in Very-High-Cycle Fatigue Regime: Aluminium 6082 Case Study.

Rapid characterization of high-cycle fatigue behaviour is of great interest, since conventional methods for developing S-N curves for longer fatigue lives are both costly in time and financial resources. Ultrasonic fatigue testing offers a promising alternative by enabling S-N curve evaluation in a fraction of the time, often hundreds of times faster, due to its high testing frequencies. Nevertheless, this technique presents specific challenges, including material overheating and limitations in specimens' geometry. Most ultrasonic fatigue studies employ hourglass specimens; however, this geometry restricts the testing of sheets and thin-walled components, which are increasingly used for their reduced mass and high stiffness-to-mass ratio. To overcome this limitation, the present work introduces a methodology for designing and testing flat specimens and corresponding gripping systems tailored to such components. The procedure is demonstrated for an aluminium alloy (6082), and preliminary experimental fatigue results are presented and compared with literature.