Locating structural damage using frequency response reference functions

A technique for monitoring vibration measurements to detect structural damage is presented. Frequency response functions from a healthy structure are measured for reference data, then cross-spectral densities between pairs of combined damage and external forces are computed to detect any occurring damage. The excitation forces are not measured, and can be uniform, random, and uncorrelated, or applied at a single point on the structure. The technique bounds the damage location between the closest sensors on the structure, only a small number of sensors are needed, the damage force is approximated, and no model of the structure is used. For bending vibrations, rotations must also be measured which in practice is often difficult. In a finite-element simulation, the method located small damage and approximated the damage force for a beam structure.