Quantitative non-destructive evaluation method for ferromagnetic pipelines based on nonlinear magnetic saturation pulsed eddy current
A pulsed eddy current, nonlinear technology, applied in the fields of material magnetic variables, measuring devices, material analysis by electromagnetic means, etc., can solve the problem of reducing material magnetic permeability, reducing eddy current skin depth, and cannot be directly applied to thick-walled pipeline detection, etc. problem, to achieve the effect of quantitative reconstruction, easy implementation and simple operation
Active Publication Date: 2017-09-12
XI AN JIAOTONG UNIV
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Problems solved by technology
However, for strong magnetic carbon steel pipelines, due to the influence of magnetic permeability, the skin depth of eddy currents is greatly reduced, so the PECT method cannot be directly applied to the detection of thick-walled pipelines, and new methods need to be developed
[0005] The phenomenon of magnetic saturation can reduce the magnetic permeability of materials. Magnetic saturation eddy current testing has been widely used in magnetic material testing, but it cannot detect defects on the inner surface of thick plates.
Combining the characteristics of pulsed eddy current and magnetic saturation eddy current, magnetic saturation pulsed eddy current detection is expected to overcome the above difficulties and realize the quantitative detection of inner surface thinning defects of carbon steel nuclear grade pipelines. There is no relevant research report at home and abroad.
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[0051] Such as figure 1 , figure 2 and image 3 As shown, the detection steps of the method of the present invention are as follows: a strong direct current is passed into the yoke coil 2 to form a strong static magnetic field, so that the detected ferromagnetic material 5 is in a state of magnetic saturation, reducing its magnetic permeability, and enhancing the skin tendency of the eddy current. depth. When the ferromagnetic material 5 to be detected is in a state of magnetic saturation, the excitation probe of the TR-type pulsed eddy current probe, that is, the excitation coil 3, is excited by a pulse signal through the pulse eddy current device. According to the law of electromagnetic induction, a Transient eddy current, the existence of defects will affect the distribution of eddy current, thereby affecting the distribution of the transient secondary magnetic field generated by eddy current, and the detection probe, that is, the voltage at both ends of the detection co...
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Abstract
The quantitative non-destructive evaluation method of ferromagnetic pipeline based on nonlinear magnetic saturation pulsed eddy current, firstly, a strong direct current is passed into the electromagnet coil to form a strong static magnetic field to magnetically saturate the detected object, and then the detected object is in a state of magnetic saturation. The TR-type pulsed eddy current probe completes the pulse excitation and pulse signal detection, and secondly, based on the magnetic saturation pulsed eddy current nonlinear high-efficiency forward problem signal simulation method and the defect reconstruction inverse problem algorithm, the quantitative non-destructive evaluation of local thinning defects in ferromagnetic pipelines is realized; The method has the advantages of non-contact, easy realization, easy operation, and high detection efficiency, and can be widely used in the quantitative nondestructive evaluation of local thinning defects of ferromagnetic material pipeline containers widely used in power stations, chemical industry and other structures.
Description
technical field [0001] The invention relates to the technical field of quantitative nondestructive detection of defects based on electromagnetic methods, in particular to a method for quantitative nondestructive evaluation of ferromagnetic pipelines based on nonlinear magnetic saturation pulsed eddy currents. Background technique [0002] In order to ensure energy supply, adjust energy structure and reduce greenhouse gas emissions, my country is vigorously developing nuclear power. In recent years, there will be more than 40 nuclear power plants, and it will enter the forefront of the world. The core meltdown accident of the Fukushima nuclear power plant in Japan highlights the importance of nuclear power structure safety. In addition to the loss of full power supply that may cause the core to fail to cool and cause a core accident, the occurrence and development of defects such as local thinning of a large number of nuclear-grade pipes necessary for cooling may also lead to...
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IPC IPC(8): G01N27/90G01N27/904
Inventor 解社娟陈振茂吴磊陈洪恩蔡文路田明明方倍培
Owner XI AN JIAOTONG UNIV