Structural health monitoring experiments with a canonical element of an aerospace vehicle

Abstruct-This paper presents the results of structural health monitoring (SHM) experiments conducted on a canonical element of a conceptual aerospace vehicle. The canonical element. representing a portion of a thermal protection system, is a carbon-carbon panel attached to a steel backing structure with bolts and brackets. Vibration responses to swept-frequency sinusoid excitation are recorded for 16 different structural states. Statistical pattern recognition methods are used to construct classifiers. Two fundamental experiments are conducted. The objective of the fmt experiment is to determine whether or not one bolt at a time is missing from the structure. In this two-class problem, the average damage detection accuracy is 97.6%. The corresponding accuracy of correctly detecting a boltmissing condition is 99.1% at a false alarm rate of 3.1% . The objective of the second experiment is to determine which, if any, of the fastening bolts in a canonical element were missing. In this 16-class problem, the average localization accuracy is 80.1%.