A PC Simulation Of The Propagation Of The Lamb Waves In Pipes

Abstract

A new method of the simulating of the Lamb waves propagation in pipes was developed. The waves were excited and received by means of the point-form transducers of the longitudinal waves, contacting with the wall of the pipe. Such transducers radiate the antisymmetric Lamb waves of zero order. The wall is like an infinite plate for each direction of the wave propagation, when the diameter of the pipe is much greater than pipe's wall thickness. In this case, the use of beam model for simulating is possible. The wave reaches the receiving point not only directly by the shortest way, but also by rotating around of the circumference of the pipe 1,2,3,. . . times. The resulting wave is a superposition of all partial waves. A transient response corresponding the switching-on of the harmonic exciting voltage may be obtained as a sum of simple trigonometric functions or phasors. On the other hand, this signal and the transient response may be used as the test fbnction/response for calculating of the transient process by not point-form transducers or by modulating of exciting harmonic voltage with more complicated, as step-function, signal. Some interesting phenomena were simulated and tested experimentally. For example, interference was discovered and investigated by one point-form transducer and homogenous propagating media for each ray.