DefinePK

Abstract

The surface bonded PZT transducers are employed to generate high frequency guided waves to detect damages in Structural Health Monitoring and non-destructive evaluation schemes. These sensors may undergo different operational loadings, which can cause damages to them. Hence, in the present work, a methodology is proposed to detect the sensor debonding using fundamental anti-symmetric Lamb wave mode. The PZT sensor when subjected to a propagating Lamb wave field, exhibits a unique maximum peak voltage, which depends on the sensor dimension and wavelength of the propagating Lamb wave. Sensor debonding changes the effective bonding surface, resulting in the shift of the peak voltage response in the frequency scale. Therefore, this shift in the frequency due to debond has been identified as a parameter to detect damage in the sensor. The procedure involves computing the Maximum Amplitude Spectra (MAS) of each sensor and changes in peak amplitude and its corresponding frequency. Further, debonded sensor output is found to be reduced, which is also a parameter to assess the damage in the sensor. However, reduction in sensor output may also occur due to the presence of damage in structure; hence it is difficult to make damage prediction based on sensor voltage alone. It has been noticed that the time of flight (TOF) between emitter and receivers (PZT sensors) is also affected by sensor debonding. Therefore, by monitoring MAS of each PZT sensor for a given frequency band of excitation and computing TOF, one can find the presence of damage in sensor and its integrity with respect to the host structure.