Elastic Wave Propagation in an Infinite Media

For most of the complicated geometries encountered in ultrasonic nondestructive evaluation (NDE) applications, finite element (FE) solutions [1–4] of the elastic wave equation are usually limited because of the spatial discretization required for accuracy. Artificial boundaries introduced to limit the spatial dimensions of a given problem can cause unwanted reflections which corrupt the desired response. The simplest approach to this problem is to ensure that the model is large enough for the unwanted reflections to be separated from the desired signal in the time domain. But this becomes very expensive for most applications, especially for full 3-D geometries. Models for infinite media, therefore, are very important for numerical modeling in 3-D and even in many 2-D practical applications.