The Study And Application Of Metal Pipeline Defect Magnetic Field Tomography

Magnetic field tomographic (MFT) detection of metal pipeline defects is an advanced pipe nondestructive testing technique, and on the basis of the development of the principle of electromagnetic induction and electromagnetic tomography (EMT). Its main advantage is that the interaction between dielectric and magnetic field during the process of testing does not affect all kinds of physical and chemical nature of the detecting objects. Moreover, it can avoid the energy consumption in the process of nondestructive testing measurement, and can achieve real-time important basic characteristics. Process uses magnetic field effect tube and it is so safe that there aren’t hazards to operators. Besides, there is low cost, high efficiency and accurate results as well as good portability. Therefore, EMT imaging technology in the field of nondestructive testing in the future has great potential applications at home and abroad.Fristly, based on the basic principle of electromagnetic induction, often for the metal pipe nondestructive testing using the basic theory of electromagnetic imaging techno fogy, analysis and deduction has been carried out, the various methods under the characteristics of the electromagnetic method for nondestructive testing are also compared. According to problems found in the process of imaging, magnetic field tomography is developed and proposed for metal pipe nondestructive testing.Secondly, we designed some MFT hardwares to improve the system and analyzed the nondestructive testing device from various aspects theoretically. Especially for the incentive to detect the magnetic field generator, an optimal approach is presented using Helmholtz coil to provide a controlled excitation source of magnetic field. COMSOL Multiphysics, a finite element simulation software for physical field coupling was used on metal pipeline magnetic field tomography imaging, the simulation experiment on the magnetic field tomography was done for the final image contrast analysis, where a variety of magnetic field intensity was applied with external excitations on different relative permeabilities of medium and different background conditions. After that, magnetic sensors, the flaw detection device to collect magnetic signals in magnetic field tomographie system was analyzed theoretically, and contrast was made for two traditional kinds of magnetic sensors in combination with the characteristics of magnetic field tomography.Finally, applications and advantages of the genetic algorithm (GA) used in the MFT images were briefly introduced, since GA guarantees the accuracy and clarity of imaging, so as to improve subsequent works.