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The New MFL Principle and Its Applications for Steel Pipes

Author: SunYanHua
Tutor: KangYiHua
School: Huazhong University of Science and Technology
Course: Measuring Technology and Instruments
Keywords: Steel Pipe High speed Magnetic Flux Leakage Testing Magnetic refraction Magnetic diffusion Magnetic compression Magnetic vacuum Magnetic disturbances
CLC: TG115.284
Type: PhD thesis
Year: 2010
Downloads: 476
Quote: 6
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Abstract


As an efficient method of non-destructive testing, magnetic flux leakage detection has been widely used in a variety of ferromagnetic material defect detection and assessment, special the automated steel pipe testing on a significant advantage. So far, the study of magnetic flux leakage testing has nearly 100 years, has important theoretical significance testing increased demand detection indicators improved in-depth study of the magnetic flux leakage testing methods, and the discovery of new principles, is also looking for steel pipe magnetic flux leakage nondestructive testing First one of the ways of the new method, the basic magnetic interaction electromagnetism and its physical characteristics as the starting point, combined with tainted combing and analysis of the magnetic detection methods and equipment operating characteristics, the formation mechanism of the defect leakage magnetic field is described as three main processes: magnetic refraction, magnetic diffusion and magnetic compression, the new mechanism for the formation of defects in the magnetic leakage causes; expand the parsing and argument by the mathematical derivation of finite element simulation and test these mechanisms; from which to know the background magnetic field will weaken the magnetic refraction enhanced magnetic compression, resulting in the reduction of the leakage magnetic field defect, and provides a theoretical basis for the magnetic flux leakage detection sensitivity. Further, the formation of a new the magnetic vacuum leaks principle and detection methods. A strong background magnetic field is cleared, to be tested in vivo magnetic flux in the defect occurred maximize deflection magnetic refraction, and the proliferation of smooth the reverse magnetic compression environment vitro magnetic vacuum region, the magnetic sensing element pickup most The strong magnetic flux leakage signal, while reducing noise of a signal caused by a background magnetic field. In the process of using the finite element simulation and experimental verification of the above methods, found the mutation and distortion of the magnetic field flux leakage phenomenon, to find the root cause for the leakage magnetic field detection signal interpretation. On the basis of the above study, for example, high-speed testing of steel pipe magnetic flux leakage testing method based on orthogonal magnetized steel pipe is non-rotating high-speed, successfully applied to the coiled tubing online testing. Furthermore, the invention of high-speed steel pipe non-rotating magnetic flux leakage detection method based on a single axial magnetization, successfully applied to the strip online testing. The two sets of equipment in the world's third China's first coiled tubing production line continuous operation for more than a year. A permanent disturbance in the process of looking for steel pipe inner trauma distinction proposed nondestructive detection principle, with a simple structure, the minimum cost to achieve the detection of the surface of the ferromagnetic member injury, and further the disturbance and the drain of the present invention a permanent magnet magnetic detection methods combined trauma detection signal distinction steel pipe method, solve 100% of the steel pipe trauma distinguish between issues, and to achieve a unified the steel pipe trauma injury equivalent evaluation. Finally, in order to tap the defect subtle features of magnetic flux leakage signal, using the finite element method of gradually refined the multilayer air layer modeling of the defect leakage magnetic field of the detailed calculation and analysis, the detection signal characteristics and formation causes of accurate explain, laid the foundation for quantitative magnetic flux leakage inspection.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallurgy ( Physical Metallurgy ) > Analytical tests of the metal (Metal Testing and Materials ) > Physical test method > NDT > Magnetic flaw detection
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