Ultrasonic Guided Wave Techniques And The Application To NDT In Pipes

Corrosion and pitting defects in pipe work are major problems in the oil, chemical, and other industries. These defects can occur at the outer or inner surface of the pipe and can lead to a serious loss of pipe wall thickness. Traditional Ultrasonic nondestructive testing techniques are single position measurements, therefore, they tend to be so slow that making long distance pipe inspection is almost impossible. An alternative to traditional pipe detection method is to excite stress waves, which can propagate along the pipe, and to monitor the response of the pipe for changes in the received signal at some remote positioa An ultrasonic inspection technique using guided waves was applied to detect and determine the exact location of flaws in long steel pipes. Since many modes of guided waves are generated due to guided waves' multi-modes characteristic in the inspected pipe, to select and excite only single mode to detect 1he pipe can obviously simplify the analysis complexity. The project just do research on using certain guided wave modes to detect the pipe flaw. First, the development in this field was introduced. And the relative theories and basis were explained. Finally, some important conclusions were drawn, that is, using distributed PZT transducers, ultrasonic guided waves are generated and received in a pipe. Usually, there are many different modes of guided wave propagating in the pipe and these modes are generally dispersive, the specific exciting signal of a Harming windowed toneburst with a central frequency of 70kHz for decreasing the effect of dispersion was selected. And guided wave are generated using 16 distributed PZT transducers in a circumferential direction for suppressing flexural modes. The experimental results greatly agreed with the theoretical ones. On this basis, the flaw of the pipe can be detected and located by analysing the data from the receiving waves.