Effect of Periodic Rough Surface on Ultrasonic Pulse-echo Signal

Fluid flowing through a pipe not only reduces the pipe thickness but also creates a rough surface. In the inspection of pipes in the plant system, the pulse-echo method is used for thickness measurement. This study aims at the extension of the ultrasonic inspection and focuses on the reflected wave from a rough surface. In this paper, a simultaneous generation of plane and spherical waves by an ultrasonic probe is described. A computational simulation calculated the propagation of the ultrasonic waves in specimens with periodic flaws by the finite difference time domain method. In an experiment, a broadband frequency probe obtained ultrasonic signals in the same condition as the simulation. The simulation results were a good agreement with the experimental results. The frequency spectrum of the reflected wave depends on the periodic flaw parameters of the rough surface. This indicates a potential to predict the flaw parameters from the pulse-echo signal.