Steel Plate Coupled Behavior of MEMS Transducers Developed for Acoustic Emission Testing

Multiple narrow-band MEMS transducers located on a single chip, which are sensitive to normal surface displacement, had been developed and characterized earlier for acoustic emission testing. The chip includes 18 separate transducers tuned to frequencies between 100 kHz and 1 MHz. The MEMS chip was mounted on a steel plate excited by pencil break with two experiment configurations. In the first experiment, a single chip was used and excited from four different locations. Arrival times were computed by a threshold technique and by time-frequency graphs obtained by wavelet transform. Then, flexural wave velocities corresponding to each device frequency were computed by averaging the results of four consecutive triggers. In the second experiment, three chips were mounted on the steel plate and excited from four different locations. Source locations were determined by using wave velocities computed in the first experiment. Four transducer outputs were collected simultaneously using a multi-channel oscilloscope during both experiments. In this paper, the performance of the MEMS chip coupled to steel plate is evaluated under the consequences of these experiments. New prospects on the source location determination that are gained by the developed MEMS chip are discussed.