Development of a hybrid finite element/finite integration model for the UK's National Physical Laboratory acoustic emission reference facility

Recent advances in computing power and signal processing techniques have highlighted the need for a greater understanding of acoustic emission (AE) wave propagation and the interactions with the sensor being used. Complex structures often lead to numerous wave modes being generated which arrive at a surface mounted sensor from different angles of incidence and in different planes. To fully understand the signals produced by the sensor, one requires intimate knowledge of the elastic wave propagation through the structure and understanding of the sensors response to the propagating elastic wave. This paper proposes a hybrid method for modelling acoustic emission reference systems in both the electrical and acoustical domain using the finite element (FE) method and the elastodynamic finite integration technique (EFIT). The method for validation of the FE and EFIT methods is detailed and the hybrid method has been tested using inputs to the EFIT code generated in a FE model of a conical piezoelectric transducer excited with an electric charge function. The agreement for both axial and radial displacement components at the opposite sensor loaded surface has been shown to be excellent and only shows small discrepancies after several reflections. The hybrid method shows excellent potential for modelling more complex acoustic emission structures in the future by combining the FE capabilities of modelling piezoelectric material in the electro-mechanical domain and the EFIT capabilities for rapid solutions to large scale linear and non-linear propagation problems.