Frequency-based damage detection method for excitation signals above work frequencies: theoretical aspects and experimental results

This work presents a cost-effective methodology to determine small damages using frequency response functions (FRFs) in the high-frequency range. The main objective is to determine a failure in its initial stage, allowing it to be analyzed and tracked. A theoretical analysis is performed, relating changes in the structural frequency response to small damages. In the analytic study, the strain modal energy change is estimated when the modal wavelength is similar to the damage rift dimension. The frequency change magnitude and its observability are analyzed based on practical FRF parameters. To demonstrate that a small damage can be noticeable in a high-frequency spectrum, an experimental procedure is performed to confirm it. Using a robust singular value decomposition algorithm a failure identification at approximately 0.16% and 0.34% of structural mass change is achieved. Employing measurement datasets composed of reference and damage sets obtained from a single measurement point, these results show the effectiveness and possibilities of the presented method.