Remote Monitoring of Harsh Environments Using Acoustic Emissions: Fid-Bau Portal

Remote Monitoring of Harsh Environments Using Acoustic Emissions

Hurley, David / Huston, Dryver / Fletcher, Douglas

Abstract

This paper presents the results of studies assessing waveguided acoustic emission techniques for remotely sensing the condition of structures operating in extreme environments. A particularly acute challenge to sensing in extreme conditions is that the sensor and associated electronics are not sufficiently robust to withstand the structural test conditions. Instead, it is necessary to use signal transduction methods to carry the signal from the structure to a remote and more hospitable sensor location. In the studies reported here an inductively coupled plasma torch creates a simulated environment for the testing of hypervelocity vehicle heat shield materials. Stresses within the material generate acoustic emissions (AEs) that propagate as elastic waves. Waveguides coupled to the sample material and AE sensors allow sample material tests to be monitored remotely. The data were analyzed using multiple statistical methods. The results show that various testing conditions produce repeatable differences in the AE data set, providing evidence that AE testing is sensitive to changes in the thermal degradation of the sample material. AE testing currently offers the potential for real-time in situ monitoring of thermal degradation in laboratory testing conditions and represents progress toward a deployable diagnostic system for aerospace applications.