Researchers at CEA-List have developed a novel method for the continuous, non-destructive monitoring of fatigue damage in metallic components using eddy-current testing. The technique, validated on an unnotched steel sample, successfully tracks the evolution of microstructural degradation throughout a fatigue test until final failure.

Traditional fatigue monitoring often relies on periodic inspections or post-mortem analysis, which can miss the progression of damage. This new approach embeds a miniature eddy-current sensor directly onto the specimen. By continuously measuring changes in the material's electromagnetic properties—specifically electrical conductivity and magnetic permeability—the system detects the accumulation of dislocations and microcracks long before macroscopic cracking occurs.

In the published study, the sensor data showed a clear correlation with the number of fatigue cycles. The measured signal evolved in three distinct phases: an initial stabilization period, a gradual linear degradation phase, and a final accelerated decline preceding rupture. This continuous data stream allows for the construction of real-time damage indicators and could enable predictive maintenance strategies, moving beyond simple cycle counting to actual condition-based monitoring.

The work demonstrates the potential for integrating such sensors into critical structures—like aerospace components or energy infrastructure—for lifelong structural health monitoring. By providing early warning of fatigue degradation, the method aims to improve safety, optimize inspection intervals, and extend the service life of metallic assets.

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