Using diffuse field interferometry for structural and material characterization in complex aircraft structures

Abstract

Structural health monitoring (SHM) systems often rely on propagating elastic waves through complex structures, which can result in the formation of diffuse-fields. Diffuse fields fill the whole structure with energy and are characterized by energy equi-partition among all propagation modes. Due to their apparent complexity, diffuse-fields are not commonly used by conventional SHM systems. However, recent theoretical and experimental studies have demonstrated that the local Green's functions (GF) can be estimated from the cross-correlation of diffuse wavefields recorded between points of a sensor grid and generated by sources located remotely from the monitoring area. The Diffuse Field Interferometry (DFI) concept yields the GF between all measured points (e.g. nominal response of the structure), effectively transforming each measurement point into a virtual source. The resulting local GFs provide detailed information on the dynamic behavior of the material/structure under investigation. In this work, Green's functions are estimated experimentally from DFI using full-field measurements obtained with a scanning laser vibrometer.