PROPAGATION OF GUIDED WAVES IN A HOLLOW CIRCULAR CYLINDER APPLICATION TO NON DESTRUCTIVE TESTING

In this paper, we study the propagation of guided waves in a tube and their interaction with surface defects. Axisymmetric (longitudinal and torsional) modes and nonaxisymmetric (flexural) modes are found and represented in phase and group velocity dispersion diagrams. The mode chosen to be generated is the second longitudinal mode L (0, 2), for the frequency-thickness product equal to 1 MHz. mm, at this product, the radial component of displacement is very small with regard to the axial component so, the attenuation is less important. According to our experimental results the L (0, 2) mode is sensitive to the depth variation and to the defect circumference. A relation of proportionality between the amplitude of the signal reflected by the defect and its depth was established. The results of the modal decomposition method, concerning the amplitude of the modes diffracted by circumferential defects according to the circumference of the defect, were presented and compared with the experimental measures results.