Excitation Mechanism of Flexural-Guided Wave Modes F(1,2) and F(1,3) in Pipes

The L(0, 2) and T(0, 1) modes are the two most commonly used modes in a pipe inspection; however, they are insensitive to axial cracks in the pipe. Therefore, it is meaningful to explore the excitation and utilization of the guided wave modes, which are different from the L(0, 2) and T(0, 1) modes. In this study, the excitation mechanism of two kinds of flexural-guided wave modes, F(1, 2) and F(1, 3), in a pipe is discussed in detail. The discussion is based on the dynamic response solution, which is obtained by the eigen-function expansion method. Either mode can be excited by employing two transducer arrays. Each array is composed of sixteen elements. Moreover, the position, vibration direction, and phase of each element should be appropriately chosen. The validity of the excitation method is demonstrated by the numerical results obtained using the finite element method.