On a hybrid use of structural vibration signatures for damage identification: A virtual vibration deflection (VVD) method

A damage identification method named virtual vibration deflection (VVD) was developed, the principle of which was formulated based on the "weak" modality of the pseudo-excitation (PE) approach previously established. In essence, VVD is based on locating structural damage within a series of "sub-regions" divided from the entire structure under inspection, and each sub-region was considered as a "virtual" structure undergoing independent vibration. The corresponding vibration deflection of the "virtual" structure was then used to derive the damage index of VVD. Besides various advantages inheriting from the PE approach, for example, capability of detecting damage without baseline signals and pre-developed benchmark structures, VVD exhibits improved detection accuracy and particularly enhanced noise immunity compared with the PE approach, attributed to a hybrid use of multi-types of vibration signatures (MTVS). As a proof-of-concept investigation, a beam model was used in a numerical study to examine the philosophy of VVD. And the influences from different factors (i.e., level of measurement noise and measurement density) on the detection accuracy of VVD were discussed based on the numerical model. An experiment was carried out subsequently to identify the locations of multiple defects contained in an aluminum beam-like structure. Identification results constructed by the PE approach, VVD using single-type of vibration signatures, and VVD using MTVS, were presented, respectively, for the purpose of comparison.