Investigation of novel embedded piezoelectric ultrasonic transducers on crack and corrosion monitoring of steel bar

Abstract A novel embedded piezoelectric ultrasonic transducers suitable for damage monitoring of steel bar were developed, and the crack and corrosion damages of the steel bar were investigated based on the ultrasonic pitch-catch technique. The experimental results of crack damages show that there exist series of wave packets in the ultrasonic time domain spectra, and some characteristic wave packets can be determined based on relationship of the length of the steel bar, crack location and acoustic velocity. With increasing the crack depth, the ultrasonic amplitudes in time domain spectra decrease gradually, and some individual peaks couple together. The location of crack on the steel bar can be calculated based on propagation time and acoustic velocity of the longitudinal mode wave. Different corrosion experiments were carried out to verify the corrosion monitoring ability of the proposed ultrasonic transducer, and the local corrosion monitoring results show that the head wave amplitude and the peak to peak value decrease with increasing the corrosion time, and a new wave packet related to corrosion damage appears in the spectra. The peak amplitude in the frequency domain spectra decreases with increasing the corrosion rate accompanying with disappearance of some frequency components. The proposed annular piezoelectric ultrasonic transducer was experimentally proved to be efficient in different damage monitoring of the steel bar.