Abstract: Selecting proper guided wave exciting frequency is of important practical significance in the engineering application of guided wave non-destructive testing (NDT). The characteristic of guided wave propagation in pipes that L(0, 1) and L(0, 2) have a cutoff frequency are respectively discussed, and the calculation formulas of their cutoff frequency are given. The varied relationship between the cutoff frequency of L(0, 1) and L(0, 2) mode guide waves, the outer diameter and wall thickness of pipes are discussed respectively. For a given steel pipe, experiments are carried out by selection of different exciting frequency. The results show that the “low-pass” type cutoff frequency of L(0, 1) and “high-pass” type cutoff frequency of L(0, 2) are reduced with the increase of outer diameter of pipes, and the “low-pass” type cutoff frequency of L(0, 1) and “high-pass” type cutoff frequency of L(0, 2) initially increase with the increase of wall thickness of pipes, but the increased amplitude decreases slowly. When the outer diameter of pipes attains a certain value, both of the cutoff frequencies are irrelevant to wall thickness of pipes. The experimental results are in agreement with theoretical computation of selected exciting frequency for guided wave NDT of pipes.

Key words: Dispersion, Guided wave, Magnetostrictive sensor, Non destructive testing, Pipe