Research On The Design Of Guided Wave NDT Systems For Pipeline Based On Magnetostrictive Effect

Pipeline transportation has played a significant role in industry. However, the defects in the pipe easily lead to leaks and even explosion which will not only cause huge economic losses, but also pollute the environment and threaten people’s lives. Recently, the technology of magnetostrictive guided wave has been applied to nondestructive testing (NDT) of pipelines by many researchers, because the technology can inspect not only over long distance from a single position but also can realize inspect without touch and with a big lift-off distance. The sensors are the basic and key part of guided wave NDT systems, the longitudinal guided wave has good test sensitivity on the radial defects, and thus it is significant to promote the magnetostrictive guided wave NDT of pipes by improving the performance of magnetostrictive longitudinal guided wave sensors.Aiming at improving the performance of magnetostrictive longitudinal guided wave sensors and NDT system, researched the theory of magnetostrictive longitudinal guided wave sensors, then made the optimization design of the sensor, and designed the guided wave NDT system, then carried out the experiment research on magnetostrictive longitudinal guided wave sensors and NDT system. The major content and chapter arrangement of this thesis are as follows:Chapter one introduced the important significance of the research on the pipe magnetostrictive longitudinal guided wave sensors, analyzed the importance of the sensors in pipeline guided wave NDT, summarized the current domestic and international situation and developing tendency of magnetostrictive guided wave sensors on the principle, the implementation and the instrument developments, finally presented the major content and main framework of this thesis.Chapter two described the theory of magnetostrictive effect and ultrasonic guided wave, analyzed the principles of the sensors’energy transformation process, and then modeled the generating and receiving processes of sensors, got the relationship between the guided amplitude and the input current and the bias magnetic field. This chapter provided the theoretical basis of this thesis. Chapter three gave out the proposal of magnetostrictive longitudinal guided wave sensors, researched the influence of magnetic circuit’s parameters on the magnitude and uniformity of bias magnetic field, then made the optimization design of magnetic field, and then made the optimization design of generating and receiving coils, finally completed the impedance matching design.Chapter four designed the NDT system, developed the intelligent sweep frequency burst signal source to improve the efficiency and stability of the system. Since the characteristics of the excitation signals, designed the high pressure power amplifier with broadband, and then designed a piezoelectric array sensor, used for the test of magnetostrictive sensors.Chapter five had carried out the experimental study, researched the performance of the optical designed sensors both in incentive and receiving guided wave processes, and verified the effectiveness of the system by experiments, finally tested the pipe with crack defects used the sensors and NDT system. The results show that the optical designed sensors can effectively motivate and receive L(0,2) mode longitudinal guided wave.Chapter six concludes all the research and development work of this thesis and raised prospects and suggestions on further research as well.