Development Of The Pipe Ultrasonic Guided-wave Excitation Transducer Based On Terfenol-D

With the development of social economics, the pipeline transportation has become more and more important. However, the current pipes which are always worked in the wild for a long time have been severe corrosive and hard to control. Now, the damage to the pipeline has become a big problem. The traditional NDT technologies are always inefficient by detecting the pipelines with points. A new technology called ultrasonic guided wave testing has come true which test the pipes by guided wave. When there is a flaw, there will be a wave packet for the change of acoustic impedance of the pipe which is propagating via the guided wave. The length range of the pipe in several decameters can be tested in one time. By this technology, the testing range is limited by the energy of the acoustic transmission transducer. Nowadays the acoustic transmission transducers are made by a kind of material called PZT. However, this material has poor energy conversion efficiency for its low electromechanical coupling factor. It means the test range is not wide and it needs high load voltage which may cause potential safety hazard. Different from PZT, the giant magnetostrictive material has high magnetostriction coefficient which means it has high energy conversion rate. The material also only needs low load voltage for it is inspired by the coil. Now there are few reports about the development of the GMM material for the pipeline guided wave transducer. Therefore, this paper focuses on developing high performance pipeline ultrasonic guided wave excitation transducer based on the material Terfenol-D.(1)The theory of ultrasonic guided wave technology and the vibration principle of the giant magnetostrictive material should be studied to lay a foundation for developing the new kind transducer.(2)The study of the sensor should be started from four aspects which are size deviation of Terfenol-D, the design of the bias magnetic field, the design of alternating soil and the jig and fixture.(3)The testing system including hardware and software should be set up to send, amplify and receive signal. This system will test the factors which will influence the performance of the acoustic emission sensor.Now, the best sensor has been invented use three ? 8mm × 1mm NdFe B permanent magnet to provide bias magnetic field, it also uses enameled wire whose diameter is 0.2mm to wind the coil. The coil whose length is 13 mm and the number of the windings is 150 is used to be provided the alternating magnetic field. The result of the test shows the new sensor has larger power than the old one. The amplitude of echo signal provided by the new one of every weld and the end face is 2.8 multiple to the sensor made by PZT. The higher power of Terfenol-D let the new transducer can detect wider range; the detection error of the defect location is less than 0.04 mm which can basically meet the requirement of finding the place of the flaws.