In this paper, the absolute calibration of piezoelectric Acoustic Emission (AE) sensors is developed using multi-physics numerical and experimental models. In this process, two common excitation approaches including laser and pencil lead break (PLB) are used to generate the simulation sources because of their excellent reproducibility and well-established analytical expressions of their source functions. The numerical models include source function, steel plate and piezoelectric sensor model with the details including adhesive layer, wear plate, piezoelectric ceramic, and backing material. The experimental results of four types of AE sensors (true wideband sensor, low and high frequency conventional sensors and low frequency unpackaged sensor) are compared with the numerical results. The numerically obtained calibration curves show good agreement with the calibration curves provided by the manufacturer. The influences of adhesive layer, backing material and sensor size on the sensor response are studied. The uncoupled piezoelectric sensor models indicate that there is no single displacement history that the sensors can be used for calibration. It is shown that the quantitative AE analysis requires the coupled structural and electrical models of structural medium and piezoelectric sensor.

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Pipeline leak detection using an acoustic emission (AE) method requires highly sensitive transducers responding to less attenuative and dispersive wave motion in order to place the discrete transducer spacing in an acceptable approach. In this paper, a new piezoelectric transducer geometry made of PZT-5A is introduced to increase the transducer sensitivity to the tangential direction. The finite element analysis of the transducer geometry is modeled in the frequency domain to identify the resonant frequency, targeting 60 kHz, and the loss factor. The numerical results are compared with the electromechanical characterization tests. The transducer response to wave motion generated in different directions is studied using a multiphysics model that couples mechanical and electrical responses of structural and piezoelectric properties. The directional dependence and the sensitivity of the transducer response are identified using the laser-induced load function. The transducer response is compared with a conventional thickness mode AE transducer under simulations and leak localization in a laboratory scale steel pipe.