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4 April 2006 Micro/meso scale fatigue damage accumulation monitoring using nonlinear acoustic vibro-modulation measurements
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Monitoring the incipient damage at the earliest possible stage is essential for predicting structural performance and remaining life of structural components. Existing prognostic methodologies incorporate conventional SHM and NDE techniques responsive to cracks and delaminations resulted from the irreversible material fracture and disintegration at the macro-scale. There is an increasing need for technologies that could allow for monitoring material degradation at the micro/meso scale before the onset of the macro-scale fracture. In this contribution, we report results of the real-time monitoring of the material micro/meso scale degradation using the nonlinear acoustic vibro-modulation technique. The technique explores nonlinear acoustic interaction of high frequency ultrasound and low frequency structural vibration at the site of the incipient damage. The indicator of the damage severity, nonlinear acoustic damage index (DI), was measured in real time during the strain-controlled three-point bending fatigue test of aluminum and steel specimens. Nondestructively, degradation of the specimen was revealed through the increase in the DI, which correlated well with the respective decrease in the specimen's stiffness. Destructive SEM examination confirmed sensitivity of the DI to the incipient micro/meso scale damage and advocated for utilizing the vibro-modulation approach for assessment of material degradation before fracture.
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Andrei Zagrai, Dimitri Donskoy, Alexander Chudnovsky, Edward Golovin, and Vinod S. Agarwala "Micro/meso scale fatigue damage accumulation monitoring using nonlinear acoustic vibro-modulation measurements", Proc. SPIE 6175, Testing, Reliability, and Application of Micro- and Nano-Material Systems IV, 617506 (4 April 2006);

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