Design And Research Of Ultrasonic Guided Wave Detection System Based On Magnetostrictive Effect

Magnetostrictive guided wave detection technology not only has the advantages of fast detection distance with long propagation distance,but also can realize large lift-off and non-contact detection in high-temperature environment,so it has received more and more attention.In order to realize the development of magnetostrictive inspection equipment to low cost,miniaturization and portability,this paper design and studies the magnetostrictive guided wave detection system.This project was jointly funded by the National Natural Science Foundation of China(51675258,51261024,51075372),the Jiangxi Provincial Department of Education Science and Technology Research Project(GJJ150699)and the National Key R&D Project(2016YFF0203000).With the goal of finalizing the magnetostrictive ultrasonic guided wave detection system,the following aspects have been studied:Firstly,based on the parameters needed to determine the excitation end of the system,that is.The signal generator and the power amplifier circuit,the signal excitation module of the magnetostrictive guided wave detection system was designed in two different ways.One is to generate single-frequency narrow-band sinusoidal pulse signals with adjustable frequency and other parameters through the principle of programmable gate arrays.For power amplification devices,the ADA4870 chip is used to increase the relative voltage by means of power amplification.This method can generate 50 W excitation.Signal,this kind of excitation can only detect defects of small-diameter ferromagnetic specimens;in order to be able to detect larger diameter specimens,Then the signal excitation module was improved and it was designed in another way.The second method is to use a programmable gate array circuit board to generate two complementary square-wave pulse signals with dead time to control the on-off of the MOSFET in the bridge power amplifier circuit to generate amplitude,frequency,and the number of cycles is adjustable.The high-power square-wave pulse signal can generate a 1000 W power excitation signal.This type of excitation can detect defects in large-diameter ferromagnetic specimens,such as large-diameter pipes.At the same time,the pre-amplifier circuit and the hardware circuit of the band-pass filter circuit in the receiver are designed and studied,and relevant parameters are explained.Secondly,the software of the guided wave system was designed and researched.In order to make the programmable gate array output frequency and other parameters adjustable single frequency narrowband sinusoidal pulse signal,the author designed and programmed the relevant program code according to the DDS principle and verified it through experiments.The rationality of software design;In order to control the improved signal generator hardware circuit,a program for controlling the on-off of the field effect transistor in the bridge circuit was subsequently designed and programmed in the Quartus II software development platform.A flow chart of the design was drawn and the rationality of the software design was verified through experiments;in order to better receive and display the guided wave signal,a program for data acquisition and display was prepared using the LabVIEW software design platform,and it was proved in the actual test.This programming is reasonable and feasible.Thirdly,magnetostrictive torsional wave and longitudinal guided wave probes were designed and fabricated.The designed torsional wave probes were then applied to the developed guided wave detection system and verified experimentally to obtain the guided wave generated in the pipe.The wave velocity is 3300m/s.The guided wave velocity obtained in the experiment is in accordance with the theoretical wave velocity calculated by the dispersion curve.According to the principle of the longitudinal guided wave sensor,the longitudinal guided wave probe is designed using the bias magnet and the enameled wire.And through the theoretical analysis of the probe has been improved,using three-stage coil for winding;In addition,in order to minimize the reflected power of the power amplifier,the signal amplitude increases,the impedance matching module applied to the excitation end and the receiving end is designed and manufactured.Finally,using the magnetostrictive guided wave detection system.The related experimental research was conducted.The test pieces were subjected to ultrasonic test by transmitting different excitation voltage,excitation frequency,and excitation cycle number signals respectively,and the received signals were received by the receiving end.Guided wave characteristics were analyzed;cracks with a depth of 4mm and 6mm were also made along the circumference of the pipe and tested with a longitudinal guided wave probe.According to the experimental results,as the excitation voltage increases,the ultrasonic signal at the receiving end also increases.As the number of excitation signal cycles increases,the amplitude of the guided wave signal at the receiving end becomes larger,but the wave packet will correspond accordingly.The width of the widening is not that the number of cycles is better,2~8 are suitable.The experimental process shows that the design of the magnetostrictive guided wave detection system is reasonable.