A novel reflection removal method for acoustic emission wave propagation in plate-like structures

Acoustic emission (AE) is defined as the transient elastic wave generation due to a rapid release of strain energy within or on the surface of a material, which is well known as a highly sensitive technique to detect various types of damage, such as crack propagation in structure. In order to obtain the propagation characterizations of AE signals, simulation based on finite element method (FEM) is effective method. This paper attempts to present a new modeling method of AE by investigating the removal of unwanted reflections from the boundaries of the waveguides including plate and thin-walled cylinder structures. The principles of these techniques are described based on the theory of the infinite element and Rayleigh damping. Then FEM is implemented to simulate the properties of AE source mechanism, propagation and reflection, and the finite element (FE) models are established with reflections removal condition proposed in this paper. To validate accuracy of the FE technique, the AE simulation of an isotropic plate is carried out then compared with the result of pencil lead broken test on a steel plate. By the Choi-Williams transformation the analysis result of the simulation and experiment AE signals indicate that the former is consistent with the latter. Then the removal effect is validated by AE simulations in a thin-walled cylinder and an anisotropic plate too. All of the results demonstrate that the Rayleigh damping has significant influence on the removal effect of infinite elements. The results of this study clearly illustrate the effectiveness of using the FE method to model AE wave propagation problems and high accuracy removal of unwanted reflection can be realized by the infinite elements with appropriate Rayleigh damping.