The Bias Magnetic Field Test Method And Device For Longitudinal Mode Magnetostrictive Guided Wave Inspection

Magnetostrictive longitudinal guided wave technology can achieve 100% detection of non-reachable area cross section by single point excitation method.It is especially suitable for the detection of bridge cables and pipelines,which is a research hotspot of nondestructive testing.How to obtain the effect of bias magnetic field is an engineering problem that restricts the development of magnetostrictive guided wave.Aiming at the above problems,this dissertation is based on the mechanism of bias magnetic field.By studying the distribution characteristics of bias magnetic field,In addition,the test method and device of the bias magnetic field are developed.Firstly,aiming at the problems in the application of permanent magnet magnetizer,the characteristics of bias magnetic field are studied.Based on the principle of magnetostrictive longitudinal guided wave excitation and reception,the mechanism of the bias magnetic field is analyzed.The magnetic field distribution is obtained by magnetic circuit analysis and finite element numerical simulation.According to the conversion efficiency curve and the finite element simulation results,the influence of the uneven distribution of the bias magnetic field on the amplitude of the guided wave detection signal is obtained.Then,in order to solve the problem that permanent magnet bias magnetizer cannot be evaluated,the bias magnetic field test method is proposed based on the characteristics of the tangential continuity of the magnetic field.In this method,the relationship between the bias magnetic field intensity and the amplitude of the guided wave received signal is established.The magnetic field in the air is used to characterize the bias magnetic field.The effectiveness of the method is determined by finite element simulation and experiment,and it is applied in the laboratory.Finally,based on the bias magnetic field test method,the device for bias magnetic field of permanent magnetizer is developed.The design of the measurement module of the evaluation device was completed,and the corresponding evaluation software was developed.Moreover,the function of the measurement module and the evaluation device is verified by experiment.The experimental results show that the bias magnetic field evaluation device can realize the evaluation of the bias magnetic field.The development of the device provides guidance for the installation of field permanent magnet magnetizers.