A. Zagrai, Stevens Institute of Technology, Hoboken, NJ; D. Donskoy, Intelligent Sensing Technologies, LLC, Fair Haven,, NJ; A. Chudnovsky, H. Wu, University of Illinois at Chicago, Chicago, IL; W. Hassan, Rolls-Royce Corporation, Indianapolis, IN; M. Gorelik, Honeywell Engines, Phoenix, AZ

Summary:

The majority of current NDE methodologies aim for detecting small scale cracks, delaminations or debonds that resulted from already irreversible materials fracture. New tools for assessing material degradation at the early stage before fracture only begin to emerge. Availability of these new technologies is crucial for predicting components performance and structural life, i.e. prognosis, as they provide information on structural health before the irreversible fracture occurred. In this contribution, we describe a vibro-modulation approach that utilizes nonlinear interaction of ultrasound and vibrations in the presence of materials imperfections. High nonlinearity of the degraded material causes modulation of the ultrasonic wave by low frequency vibrations resulting in additional side-band components in the spectrum of the measured signal. Amplitudes of these spectral components correlate with the severity of damage. Capabilities of the nonlinear acoustic vibro-modulation techniques for detecting of both materials damage before and after fracture are emphasized. We provide illustrative examples of monitoring the macro-scale damage (i.e. cracks) in the variety of structures, present new results for monitoring the fatigue damage in aircraft-grade materials, and discuss a phenomenological model that utilizes nonlinear acoustic data for predicting remaining fatigue life.