Structural health monitoring with an inductively coupled (wireless) Lamb wave transducer

Wafer-type PZT transducers are very effective as active sensors for Lamb wave studies in elastic plates and in steel bridge girders. It has been demonstrated that a single transducer can be used in pulse-echo mode, transmitting a transient waveform and then detecting return signals echoing from boundaries, irregularities, and flaws such as cracks. We describe here an inductively-coupled system consisting of a permanently attached transducer and a probe attached to the control electronics. When the probe is brought in proximity to the transducer an exciting pulse is coupled into the transducer and received reflections are coupled out of the transducer and recorded by the control electronics. We present experimental results establishing the effectiveness and practicality of the approach. Ample signal strength is obtained with excitation at less than 10 V.