Ferromagnetic pipeline quantitative lossless evaluating method based on nonlinear magnetic saturation pulsed eddy current

Abstract

The invention discloses a ferromagnetic pipeline quantitative lossless evaluating method based on nonlinear magnetic saturation pulsed eddy current. An electromagnet coil is conducted with high direct current to form a strong static magnetic field so that a detected object can be magnetically saturated, pulse excitation and pulse signal detection are finished on a TR type pulsed eddy current probe when the detected object is in the magnetic saturation state, and quantitative lossless evaluating on the local thinning defect in a ferromagnetic pipeline is achieved based on a magnetic saturation pulsed eddy current nonlinear efficient direct problem signal simulation method and a defect reconstruction inverse problem algorithm. The method has the advantages of being free of contact, easy to achieve and operate, high in detecting efficiency and the like and can be widely applied to the quantitative lossless evaluating on the local thinning defect of a large number of ferromagnetic material pipeline containers used in a power station, chemical engineering and other structures.

Description

technical field [0001] The invention relates to the technical field of quantitative nondestructive testing of defects based on electromagnetic methods, in particular to a quantitative nondestructive evaluation method of ferromagnetic pipelines based on nonlinear magnetic saturation pulse eddy current. Background technique [0002] In order to ensure energy supply, adjust the energy structure and reduce greenhouse gas emissions, my country is vigorously developing nuclear power, which will soon reach more than 40 in recent years, entering the forefront of the world. The core meltdown accident of the Fukushima nuclear power plant in Japan highlights the importance of nuclear power structural safety. In addition to the loss of full power supply, which 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 leakage or even large r...

AI Technical Summary

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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