Study on Phononic Crystal-Based Waveguides for Ultrasonic Transducers

Ultrasonic transducers can transmit acoustic waves into the object under test and then receive the reflected signals. The processed reflected signals reveal the properties inside the object at the tested point. This test was often used in the fields of industrial, medical, and agriculture. Waveguides attached to transducers were used in some high temperature and corrosive environment. In these tests, ultrasonic signal from transducers were distorted to guided modes in waveguides. Thus the reflection became noisy signals and transducer array cannot manipulate the beam pattern with a conventional waveguide. Phononic crystals (PnCs) are artificial periodic materials, in which acoustic waves show band gaps and anisotropic propagation. PnCs were then applied as filters, resonant cavities, and super lens. Self-collimation of propagating waves were also observed in some PnCs. Therefore PnC was proposed to be a waveguide attached to transducers to control the mode conversion inside waveguides. In this project, PnC-based waveguides will be studied. PnCs for longitudinal and transverse waves will be designed to show self-collimation. By controlling the wave mode inside waveguides, the beam steering through the PnC-based waveguide can be achieved. The work included numerical simulation, design and fabrication of specimens, and experimental measurements. The study is expected to be valuable for the nondestructive test in industry and medical applications.

Project ID:PB10607-1030
External Project ID:MOST106-2221-E182-032