Micro- and Macroscale Damage Detection Using the Nonlinear Acoustic Vibro-Modulation Technique

TLDR

Structural components can develop microscopic damage under service and environmental loads that may progress to macroscopic cracks, and while macroscale cracking is reliably detected by existing NDE methods, there is a growing need for inspection technologies that assess damage across micro‑ to macro‑scales. This article explores the application of the nonlinear acoustic vibro‑modulation technique (VMT) to incipient damage detection and monitoring. The authors demonstrate VMT by inspecting cast aluminum automotive parts and aging aircraft fuselage for macroscopic damage, and by monitoring acoustic nonlinearity in a strain‑controlled three‑point‑bending fatigue test to assess microscale damage. The experiment showed a steady rise in nonlinear acoustic response during fatigue, indicating early damage accumulation before macroscopic fracture. Keywords: damage detection, micro‑scale damage, nondestructive nonlinear acoustics, prognosis, structural health monitoring; acknowledgments note NAVAIR support and assistance from Dr.

Abstract

Abstract Subjected to in-service and environmental loads, even relatively new structural components may reveal signs of microscopic deterioration. Very often, this initial damage further progresses into meso- and macroscales leading to development of one or several macrocracks that cause ultimate structural failure. Although the onset of macroscale cracking can be reliably detected by modern NDE methodologies, there is an increasing need for inspection technologies that may allow for assessing structural damage at a wide range of scales, i.e., from micro to macro. This article explores application of the nonlinear acoustic vibro-modulation technique (VMT) to incipient damage detection and monitoring. The nonlinear acoustic detection of the macroscopic damage is illustrated with examples: inspection of the cast aluminum automotive parts and testing of the aging aircraft fuselage. The microscale damage assessment is realized by real-time monitoring of the acoustic nonlinearity in the strain controlled three-point-bending fatigue test. In the experiment, a stable increase of the nonlinear response during specimen fatigue was observed indicating early damage accumulation before the macroscopic fracture. Keywords: damage detectionmicro-scale damagenondestructivenonlinear acousticsprognosisstructural health monitoring ACKNOWLEDGMENTS Authors would like to acknowledge financial support of NAVAIR (program manager Dr. Vinod S. Agarwala) and help of Dr. Hudson Wu and Mr. Stanislav Stoupin in experimental testing. Notes ∗Now at New Mexico Institute of Mining and Technology.