Interaction Between Circumferential Lamb Waves and Lamination in the Midplane of a Metallic Pipe

Abstract

Lamination is one of common defects in the manufacturing process of seamless metallic pipes. In this paper, the interaction between the circumferential Lamb waves and lamination in the midplane of an aluminum pipe is studied. The used circumferential Lamb waves are CL0 and CL1 modes generated with a finite element method code. Lamination along the circumferential direction is established by the demerging-node method. Numerical results of arrival time are compared with theoretical results in order to verify the accuracy of the excitation ways. The interaction between circumferential Lamb waves and lamination in a damaged full circular pipe is analyzed by composing the received waveforms of the corresponding receivers when CL0 and CL1 modes are excited at different excitation positions: the inner subpipe, the outer subpipe, and the main pipe. The composed waveforms fit well with the original waveforms. When CL0/CL1 mode reaches the entrance and exit of a lamination, it generates new mode and undergoes multiple reverberations, diffraction, and mode conversion between the two ends of the lamination. Based on the detailed analysis of the waveform in detail, some phenomena, which are different from those in a plate, are observed.