Multifunctional phononic crystal filter for generating a nonlinear ultrasonic guided wave

Abstract Nonlinear guided waves have proven to be extremely sensitive to microscopic and mesoscopic damage in materials in recent years. However, many factors in measurement will bring non-damage-related interference signals into the nonlinear guided waves signal, which greatly restricts the detection accuracy in structural health monitor systems. In this paper, we propose a phononic crystal filter to purify the ultrasonic signal by filtering away both the needless mode of the primary wave and the second harmonic wave generated in the exciting stage. This method can guarantee the second harmonic signal is only generated by the S0 mode primary wave propagating in the inspection area. The design principle, theoretical analysis, and numerical simulations of the proposed filter are introduced, and the results demonstrate that our proposed filter can be applied in low-frequency S0 mode Lamb wave nonlinear harmonic wave testing. The research results promote the development of high-accuracy nonlinear damage location, imaging algorithm, and industrial applications.