Research On Modeling Method And Influence Factors Of Magnetostrictive Guided Waves In Pipelines

With the rapid development of China's economy and the urgent demand for energy transportation,the process of pipeline laying in China has also accelerated.It is necessary to develop the pipeline safety assessment capability and on-line detection technology to ensure the normal work of the pipeline.This paper is supported by the National Natural Science Foundation(51261024,51675258),the national key research and development project(2016YFF0203000)and the science and technology research project of the Jiangxi Provincial Education Department(GJJ150699).When using the traditional NDT method to detect the pipeline,it usually needs to remove the coating layer and insulation layer.The piezoelectric ultrasonic guided wave is not good for the high temperature detection,but the magnetostrictive guided wave does not need to treat the surface of the detection pipe for special treatment and can detect the object on line under the high temperature environment.When the pipeline is at high temperature,the sound velocity and sound pressure of ultrasonic guided waves will change.The propagation speed of ultrasonic will decrease with the increase of temperature,which makes it difficult to locate pipelines under high temperature.The quantitative evaluation of pipe defects is usually determined by the percentage of the section of the pipe which is lost by the area of the metal on a section of the pipe,and is determined by the reflection coefficient of the defect.In the oil and gas pipeline,there are not only the defects of the circumferential and axial,but also a lot of random angles,and the signals of the different modes are different to the defect detection.The ultrasonic guided wave detection process can be simulated by numerical simulation,and the load under different conditions can be set.It can be run repeatedly.It can simulate some difficult experiments,not only provide guidance for actual industrial testing,but also save the cost of the experiment.Therefore,it is of great significance to study the modeling method of magnetostrictive guided wave and its influence factors to improve the efficiency of guided wave detection,and can improve the help and reference for the quantitative of the guided wave defect and the influence of the signal in the high temperature.In view of the above problems,the main contents of this paper are as follows:1.On the basis of fully understanding the magnetostrictive guided wave detection technology,a guided wave excitation sensor equation is established.Through the synthesis of magnetostrictive force magnetic coupling equation,electromagnetic field theoretical equation,sensor excitation equation,and the multi physical field finite element software COMSOL Multiphysics,the working process of the magnetostrictive longitudinal guided wave sensor is used.Numerical simulation is carried out and the influence of lift off on longitudinal magnetostrictive guided wave signal is analyzed.2.After analyzing the structure of the magnetostrictive torsional guided wave sensor,a numerical model of the force and magnetic coupling of the torsion mode magnetostrictive guided wave sensor is set up,and the distribution of the magnetic field on the surface of the tube to be measured is analyzed and studied.At the same time,through the analysis of the displacement at a certain point in the position of the coil on the tube wall,the type of guided wave excited by the sensor is determined by comparing the vibration law of the particle in the circumferential and axial direction,and the effect of the excitation frequency on the magnetostrictive guided wave signal is discussed.3.the influence of the defect angle on the detection signal of the pipeline guided wave is put forward.The ferromagnetic pipeline is used as the research object.The influence of the axial direction of the defect and the circumferential direction of the defect on the guided wave detection is analyzed,and the sensitivity of the different mode guided waves to the axial and circumferential defects is analyzed.4.Based on the principle of magnetostrictive high temperature detection and the theoretical analysis of temperature field,a high temperature detection model for guided wave is established.The change of the detection signal of the longitudinal and torsional guided waves at different temperatures is studied,and the change curve of the amplitude and wave velocity at high temperature is obtained by post-processing.The feasibility and the signal influence of the magnetostrictive guided wave detection at high temperature are discussed.