Structural Damage Identification in Homogeneous and Heterogeneous Structures Using Beamforming

In this study, beamformers consisting of phased sensor or actuator arrays are used in the nondestructive evaluation of homogeneous and heterogeneous structural components. Beamforming can be used to detect, locate, and quantify damage by suitably applying weights and time or phase delays to the tapped signals from a sensor array and/or actuator array in a narrow frequency band to obtain the desired directional sensitivities and optimal array gains. Some aspects about beamforming and wave propagation are discussed as a prelude to the experimental investigation. Design considerations for the phased arrays are also examined. The advantages of using adaptive over conventional beamforming are demonstrated with Frost constraint- and pilot signal-based adaptive techniques. Data from steel and composite plates are analyzed using propagating elastic waves and phased arrays of sensors and/or actuators. Damage, which can be characterized as a local change in impedance, is diagnosed by using propagating elastic waves as they are sensitive to small changes in impedance and do not require a large number of input/output transducers. Beamforming of sensor and/or actuator arrays is carried out to characterize damage in steel and composite plates by comparing the directivity patterns associated with the damage and baseline data.