Metamaterial-based frequency filter for nonlinear ultrasonic nondestructive evaluation

Nonlinear ultrasonic nondestructive evaluation is a technique for measuring the nonlinearity of a sample. Unlike the conventional ultrasonic nondestructive evaluation technique, nonlinear ultrasonic nondestructive evaluation can measure microcracks, material degradation, and fatigue. However, ultrasonic nondestructive evaluation has suffered from a critical problem in that the technique is affected by not only the sample's nonlinearity but also the measuring device's nonlinearity; owing to this, precise measurement is improbable. In this study, a new metamaterial filter is proposed that can effectively filter out the undesired nonlinear effect due to the measuring device's nonlinearity. Owing to the band gap of the metamaterial that can prevent wave propagation for a certain frequency range, a new metamaterial filter is designed. The basic theory of metamaterials is revisited and the metamaterial filter is designed using a periodic layer of aluminum and copper plate. Finally, finite element analyses are performed to check its filtering performance