Analysis of ultrasonic wave propagation in metallic pipe structures using finite element modelling techniques

This paper describes the development of a FEM representing ultrasonic inspection in a metallic pipe. The model comprises two wedge transducer components, water coupled onto the inner wall of a steel pipe and configured to generate/receive ultrasonic shear waves. One device is used in pulse-echo mode to analyse any reflected components within the system, with the second transducer operating in a passive mode. A number of simple defect representations have been incorporated into the model and both the reflected and transmitted wave components acquired at each wedge. Both regular crack and lamination defects have been investigated, at 3 different locations to evaluate the relationship between propagation path length and defect response. These responses are analysed in both the time and frequency domains. Moreover, the FEM has produced visual interpretation, in the form of a movie simulation, of the interaction between the propagating pressure wave and the defect. A combination of these visual aids and the predicted temporal/spectral waveforms has demonstrated fundamental differences in the response from either a crack or lamination defect.