Method for monitoring fatigue damage using ferromagnetic materials surface stray magnetic field signal

A stray magnetic field and fatigue damage technology, applied in the size/direction of the magnetic field, material magnetic variables, magnetic properties measurement, etc., can solve the problem of no mapping relationship, and achieve the degree of fatigue damage, good repeatability, and high precision. Effect

Inactive Publication Date: 2008-02-20
ACADEMY OF ARMORED FORCES ENG PLA
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Problems solved by technology

For ferromagnetic components subjected to fatigue loads during service, because the fatigue load is usually lower than the yield limit of the material, especially in the early service stage, there will be no measurable strain in the dangerous parts of the ferrom...

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  • Method for monitoring fatigue damage using ferromagnetic materials surface stray magnetic field signal

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Embodiment Construction

[0023] The present invention is realized by following measures:

[0024] The material of the tested component is 18CrNiWAVA steel, and the metal magnetic memory testing instrument is EMS-2003.

[0025] First of all, the ferromagnetic material 18CrNiWAVA steel, which is the same as the material of the tested component, is selected, and the plate-shaped smooth fatigue test piece is made according to the national standard. Carry out final heat treatment on the standard sample according to the heat treatment specification of the tested component, in a vacuum of 8×10 -1 Heat it to 860°C in Pa WZC-30 type vacuum heat treatment furnace, keep it warm for 30 minutes, oil quench, then temper at 180°C, and water cool to room temperature to obtain a pure initial magnetic state.

[0026] Secondly, mark two parallel detection lines on the surface of the test piece with a length of 240mm, the length of the detection line is 100mm, and the vertical distance between the two lines is 10mm, as ...

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Abstract

The utility model discloses a method utilizing a stray magnetic field signal monitoring the damage of ferromagnetic, which belongs to the magnetic nondestructive inspection field. Ferromagnetic components do not have measurable strain in early stages of service, with difficulty to evaluate damage. The utility model, inspected material and smooth plantlike standard fatigue specimens have the same heat treatment state, and are demagnetized through high temperature, so as to get the pure initial magnetic state. And then a constant rate is imposed to pull the tension fatigue load, every stray magnetic field normal component of the surface inspecting components is unloaded corresponding to scheduled cycles, the slope Ks of different magnetic cycle curves is extracted, the critical value of the slope Ksc is determined, and the mapping relationship between the slope Ks before fatigue crack and fatigue cycles N is established. The measured components by the same value are inspected, and the measured slope Ks of the magnetic curve is compared with the critical value of the slope Ksc, and then the fatigue damage can be determined. The utility model has the advantages that the utility model has simple operation and accurate inspecting results, and dynamic monitoring the early fatigue damage of the ferromagnetic components in the unloaded state can be achieved.

Description

technical field [0001] The invention relates to a method for evaluating the fatigue damage degree of a ferromagnetic part bearing a fatigue load by using a spontaneous surface stray magnetic field signal, and belongs to the technical field of magnetic nondestructive testing. Background technique [0002] As a strong magnetic substance, ferromagnetic material has good strength, hardness, plasticity, toughness and other characteristics, and is widely used in various fields of industrial production. Many key components in mechanical equipment are made of ferromagnetic materials. Many of these components are in the working environment of repeated alternating loads, and fatigue failure is their main form of damage. [0003] Fatigue failure is a slow delayed failure process, which usually occurs under the action of alternating stress below the yield limit. There is no obvious plastic deformation in the macroscopic view, and the failure is concealed, often causing catastrophic cons...

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Application Information

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IPC IPC(8): G01R33/12G01R33/14G01R33/02
CPCG01N27/83
Inventor 徐滨士董世运董丽虹王丹
Owner ACADEMY OF ARMORED FORCES ENG PLA
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