Dynamic perturbation characteristics for non-baseline structural damage diagnosis

A damage identification method was proposed recently, the essence of which resided in locally examining the dynamic equilibrium condition of different structural components under inspection. The singularities of the constructed damage indices were considered to provide effective indication of the location and size of damaged zones. The accuracy of the method, however, suffers from significant interference by measurement noise due to the involvement of high-order derivatives of structural dynamic deflection. Moreover, the applicability of the technique is largely limited, because a variety of baseline parameters of the tested structures, e.g., Young's modulus and vibration frequencies, must be acquired as prior knowledge. In the present study, continuous wavelet transform (CWT) is first conducted based on the original damage index, yielding enhanced detection results capable of indicating multiple cracks in a beam component. The reliance of the method on the baseline parameters of the tested structure is effectively circumvented by developing a statistical estimation method in the spatial and scale domain, according to which the baseline information can be inversely estimated using only the measured data of structural vibration displacements. As a proof-of-concept investigation, the effectiveness of the newly established damage identification strategy is examined experimentally by identifying multiple cracks in an aluminum beam-like structure.