Damage Identification in Cantilever Beams Based on High-Order Frequency Response Function with Improved Sensitivity

Abstract The damage indexes based on the modal frequency (DMF) have been widely used to identify damage and thus to warn about structural failure in advance. However, since the change of the DMF caused by damage is generally too small to be differentiated from environmental interference, the DMF cannot produce robust damage identification for in situ measurement. To improve the robustness of the DMF, a damage index, namely the difference of the frequency response function (DFRF), is developed in this article. Both numerical simulation and experiments are conducted to identify perpendicular notches in cantilever beams. Both the changes of the DMF and DFRF with respect to the notch depth are analyzed to investigate their sensitivities. Since the DFRF can sufficiently use the damage-related information reflected by all the frequencies rather than by modal frequencies only, the DFRF can produce obvious changes with respect to slight notch growth. Therefore, the change of the DFRF is hard to drown out with environmental interference and can robustly characterize damage for in situ measurement.