METHOD FOR REFERENCE-FREE DAMAGE DETECTION IN PLATE-LIKE STRUCTURES USING IMPEDANCE INFORMATION

摘要

PURPOSE: A flat structure reference-free crack detecting method using impedance information is provided to accurately the existence of damages or cracks of a flat structure by utilizing the existence of mode modification signals separated from impedance signal itself. CONSTITUTION: A flat structure reference-free crack detecting method using impedance information is as follows. A signal measuring unit excites a first piezoelectric sensor or a second piezoelectric sensor attached to symmetrical positions on both surfaces of a flat plate structure(S110). Admittance signals between the first and second piezoelectric sensors being excited are measured(S120). A signal separating unit respectively separates the measured admittance signals into mode signals and mode modification signals according to relative amplitude and phase(S130). An error computation unit reconstructs the separated mode signals and mode modification signals as the admittance signals and calculates a signal difference between the reconstructed admittance signals and the admittance signals measured by signal separating unit(S140). A damage decision unit calculates an energy value generated by the calculated signal difference among the measured admittance signals and an energy value of the mode modification signals generated by mode modification among the mode signals. If the calculated energy value of the mode modification signal is larger than the energy value generated by the signal difference, damages are existed in the flat structure(S150).