Piezoelectric, tapered acoustic emission transducer design and modeling method for high-precision damage detection in mechanical structures

Acoustic emission (AE) technology is suitable for early damage detection and location of mechanical structures owing to its high-frequency and high-sensitivity characteristics. However, as the core component for signal sensing, common cylindrical AE transducers have a large contact area, which makes the signal time of arrival (ToA) to exhibit a systematic deviation, thereby reducing the damage location accuracy. Further, a complete model of tapered AE transducers with a small contact area is lacking, and there is no study on a design theory for tapered matching layers considering wave attenuation. To overcome these drawbacks, this paper proposes a piezoelectric, tapered AE transducer design and modeling method. First, based on the structural features of tapered AE transducers, an energy radiation model and a thickness design model considering wave attenuation of the tapered matching layer were established, with the optimum thickness of matching layer determined. Second, a dimensional model considering aperture effects and an electromechanical coupling model of piezoelectric ceramics were established. On this basis, a complete dynamic simulation model for the electroacoustic characteristics of tapered AE transducers was developed. The multiphysical field coupling and transmission process of AE waves was resolved, and the correctness of above models was verified. Tapered AE transducers with different matching layer thicknesses were tailored. The correctness of the tapered matching layer design model and the accuracy of signal ToA for tapered AE transducers were verified by lead-breaking tests, where the tapered transducers exhibited better ToA accuracy than cylindrical ones. Finally, tomography and bearing damage tests were conducted to verify the effectiveness and superiority of the tapered AE transducer in damage detection and location. The proposed method can provide a valuable theoretical framework for transducer design in structural health monitoring in complex environments.