Numerical modeling of existing acoustic emission sensor absolute calibration approaches

Within recent years, several alternative approaches to acoustic emission sensor calibration have been proposed. As some of these approaches make use of new geometries and materials, the aspect of absolute calibration in the context of these proposals is evaluated in this contribution. Validated numerical methods are applied to compare the expected acoustic emission sensor sensitivity in a variety of material and geometry configurations. The numerical approach uses a coupled structural and piezoelectric formulation in combination with electric circuit modeling. Established routines allow obtaining the sensitivity versus frequency curve as sensor response in electrical voltage per meters displacement. This study is performed for one previously used conical sensor design and one typical disc type sensor design to examine the impact of the investigated approaches for these different sensor dimensions and designs. Specific attention is paid to the influence of the propagation medium material properties, the chosen wave type and the geometry of the propagation medium. For use of plate-like propagation media further aspects, such as thickness, distance and formation of guided wave modes are evaluated. A primary result is that there is a significant influence to be expected for calibration attempts with different wave types for the same material, which can be of particular relevance when using sensor systems with extended aperture, such as common to most of the commercial sensors.