The use of pulsed Lamb waves for nondestructive testing of pipes

Abstract

For pipe diagnostics pulsed Lamb waves excited by omnidirectional emitter are usually used. Waves reflected from some unevenness and/or arrived from the emitter in the shortest way and spun around a number of times reach the point of reception. The latter pulses disturb the observation of the reflections from the defects in the wall and should be shortened as possible. From the other side, the information is extracted only from the rising edge of the received pulse. Therefore the further part of each received pulse is damped by randomizing. For this purpose some parameters of the excited pulse (the length or frequency of filling) are being changed. The received signal corresponding to some medium parameter is used as a reference. Other signals are multiplied by the reference one and summed. The product is maximal for the first wave of the signal, the other waves are damped. The experimental results, their analysis, and conclusions are presented in the paper.