Applications of the multiple damage location assurance criterion

The paper describes work on a correlation coefficient that compares changes in a structure's resonant frequencies with predictions based on a frequency-sensitivity model derived from finite element analysis. The approach can provide good predictions of both the location and absolute size of damage at one or more sites. It offers the practical attraction of only requiring measurements of the changes in a few of the structure's resonant frequencies between the undamaged and damaged states. A further advantage is that the initial modal survey to find the undamaged structure's frequencies and mode shapes need only be carried out in sufficient detail to provide a match with the FE model. Since only about ten modes are needed, the number of measurements required is modest and subsequent checks for damage would require even fewer measurements in order to establish the changes in the natural frequencies. A recent development shows that using changes in both the anti-resonant and resonant frequencies improves the detection capability without increasing the measurement frequency range.