Embedded sensitivity functions for characterizing structural damage

Abstract

The use of embedded sensitivities in vibration-based damage identification for structuralhealth monitoring is discussed. Embedded sensitivity functions are algebraic combinationsof measured frequency response function data that determine how the forced responses ofstructural systems change with perturbations in mass, damping, or stiffness. After thetheory of embedded sensitivity functions is reviewed, they are applied to characterizedamage in an analytical three-degree-of-freedom system, a bench top two-degree-of-freedomsystem, and a full-scale exhaust system. By comparing embedded sensitivity functions withfinite difference functions using undamaged and damaged frequency responsefunctions, damage is shown to be properly detected, located, and quantified intheory and practice assuming that structures are only damaged in one location.Demonstrations on the bench top system and exhaust system indicate that thetechnique is most effective when certain frequency ranges in the data are analyzed toavoid ranges of low signal-to-noise ratios and when changes to frequency responsefunctions are not excessive to avoid distortions in the estimated perturbations.