A method for measuring the initial tensor permeability of a plate-shaped sample

Abstract

The present application relates to the technical field of magnetic permeability measurement, and particularly relates to a kind of plate-shaped sample initial tensor magnetic permeability measurement method, the induced magnetic field of plate-shaped sample under the action of geomagnetic field is measured using magnetic sensor, and the 1:1 static magnetic field numerical model of plate-shaped sample is established, the induced magnetic field calculation value at probe is made equal to the measured value by adjusting model magnetic permeability parameter, to realize the measurement of plate-shaped sample initial tensor magnetic permeability.The present application can obtain the initial tensor magnetic permeability of material compared with standard magnetic permeability measurement method, and then more abundant magnetic parameter information can be established, which can provide important reference for ship degaussing, nondestructive testing and other fields.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic permeability measurement, and in particular to a method for measuring the initial tensor magnetic permeability of a plate-shaped sample. Background Art

[0002] Currently, there are two main standard methods for obtaining the magnetic permeability of ferromagnetic materials. One is the ring specimen method, in which an H-coil and a B-coil are wound around the ring specimen. Based on Ampere's circuit theorem, the magnetic field intensity H within the magnetic circuit can be accurately calculated from the magnetizing current i of the H-coil. The magnetic induction intensity B is determined using the B-coil and a flux integrator, and the magnetic permeability parameters are then extracted based on the BH curve. However, this method obtains the average magnetic permeability of the ring specimen in all directions. In reality, ferromagnetic materials can be anisotropic, and magnetic permeability is a tensor, requiring measurement of the permeability in different directions. The ring specimen method cannot obtain tensor permeability. The second is the permeometer method, which is suitable for specimens with an open magnetic circuit. The magnetic circuit is formed by setting a high-permeability magnetic yoke, and the H-coil and B-coil are wound around the specimen to measure the field intensity H and magnetic induction intensity B, respectively. However, this method can only obtain the magnetic permeability in a specific direction, and the magnetic field intensity measurement range is usually above 1 kA / m. It cannot obtain the initial magnetic permeability corresponding to weak magnetic fields (such as the Earth's magnetic field).

[0003] The present invention provides a method for measuring the initial tensor magnetic permeability of a plate-like sample. By measuring the induced magnetic field of the sample under the action of the geomagnetic field and inverting the initial magnetic permeability in different directions, the initial tensor magnetic permeability of the plate-like sample can be measured, thereby establishing richer magnetic parameter information, which can provide important reference for fields such as ship demagnetization and non-destructive testing. Summary of the Invention

[0004] In view of the above situation, in order to overcome the defects of the existing technology, this solution provides a method for measuring the initial tensor magnetic permeability of a plate sample, which can effectively obtain the initial tensor magnetic permeability of the material and make up for the shortcomings of the existing standard measurement method.

[0005] A method for measuring the initial tensor magnetic permeability of a plate-shaped sample comprises the following steps:

[0006] Step 1: Place the plate sample to be tested vertically on a horizontal non-magnetic platform, and keep the plate surface parallel to the geomagnetic vector;

[0007] Step 2: Place the magnetic sensor on one side of the sample. Support and fix the magnetic sensor with a smooth non-magnetic pad. Make the probe of the magnetic sensor pass through the center axis of the sample plate, and make the two axes of the probe parallel to the vertical direction and horizontal direction of the geomagnetic field respectively. Measure the actual distance L from the probe to the sample plate, and record the vertical component B of the magnetic sensor measurement value. mz1 and the horizontal component B parallel to the plate surface mx1 ;

[0008] Step 3: Rotate the sample 180° with the central axis of the sample plate as the rotation axis, while keeping the position of the magnetic sensor unchanged, and record the vertical component B of the magnetic sensor measurement value. mz2 and the horizontal component B parallel to the plate surface mx2 ;

[0009] Step 4: Keep the magnetic sensor in the same position, place the sample in an area away from the magnetic sensor, re-record the measurement value of the magnetic sensor, and obtain the vertical component B of the geomagnetic field. z and the horizontal component B x ;

[0010] Step 5: Replace B in step 2 mz1 and B mx1 Subtract B from step 4 respectively z and B x , and the vertical component magnetic field B of the sample is obtained respectively z1 and the horizontal component magnetic field B x1 , where B z1 Contains fixed magnetic field and induced magnetic field B iz1 +B pz1 , B x1 Contains fixed magnetic field and induced magnetic field B ix1 +B px1 ;

[0011] Step 6, replace B in step 3 mz2 and B mx2 Subtract B from step 4 respectively z and B x , and the vertical component magnetic field B of the sample is obtained respectively z2 and the horizontal component magnetic field B x2 , where B z2 Contains fixed magnetic field and induced magnetic field B iz1 -B pz1 , B x2 Contains fixed magnetic field and induced magnetic field B ix1 -B px1 ;

[0012] Step 7, replace B in step 5 z1 and B x1 Add B in step 6 respectively z2 and B x2 , and divided by 2, respectively, to obtain the sample in B z The induced magnetic field B under excitation iz and in B x The induced magnetic field B under excitation ix ;

[0013] Step 8: Establish a 1:1 static magnetic field numerical model of the plate specimen and set the vertical magnetic permeability μz , apply a vertical magnetic field B z As the excitation, calculate the vertical component B of the induced magnetic field at the probe jz , if B jz mz , then increase μ z , otherwise reduce μ z , until |B jz -B mz |<1nT, then the corresponding μ z It can be regarded as a measurement of the starting magnetic permeability in the vertical direction;

[0014] Step 9: In the 1:1 static magnetic field numerical model in step 8, set the horizontal magnetic permeability μ x , apply a horizontal magnetic field B x As the excitation, calculate the horizontal component B of the induced magnetic field at the probe jx , if B jx mx , then increase μ x , otherwise reduce μ x , until |B jz -B mz |<1nT, then the corresponding μ x It can be considered as a measurement of the starting magnetic permeability in the horizontal direction.

[0015] Preferred technical solution 1: The magnetic sensor is a dual-axis or tri-axis magnetic sensor.

[0016] Preferred technical solution 2: The width W of the sample should be greater than 5 times its thickness H.

[0017] Preferred technical solution three: the distance L between the probe and the sample plate surface is between 0.2 and 2 times the width W of the plate-shaped sample.

[0018] Preferred technical solution four: the sample can be a metal plate, preferably a steel plate.

[0019] The above structure enables this solution to have the following beneficial effects:

[0020] Compared with the standard magnetic permeability measurement method, the initial magnetic permeability of the sample in different directions can be obtained simultaneously, thereby more completely describing the magnetic anisotropy of the material and making up for the shortcomings of the existing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0022] Figure 1 This is the layout diagram of the magnetic sensors for this scheme.​​

[0023] Among them: 1-sample, 2-magnetic sensor, 3-probe, 4-non-magnetic pad. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0025] The magnetic sensors are arranged as follows Figure 1 As shown in the figure, the method for measuring the initial tensor permeability of a plate sample is as follows:

[0026] Step 1: Place the steel plate sample (1) to be tested with a side length of 150 mm and a thickness of 12 mm vertically on the horizontal ground, and keep the plate surface of the sample 1 parallel to the geomagnetic vector;

[0027] Step 2: Place the three-axis fluxgate magnetic sensor 2 on one side of the steel plate sample 1. The magnetic sensor 2 is supported and fixed by a smooth non-magnetic pad 4. The probe 3 of the magnetic sensor 2 passes through the center axis of the sample 1 plate surface, and the two axes of the probe 3 are parallel to the vertical direction Z and the horizontal direction X of the geomagnetic field. Measure the actual distance L from the probe 3 to the plate surface, and record the vertical component B of the measurement value of the magnetic sensor 2. mz1 and the horizontal component B parallel to the plate surface mx1 ;

[0028] Step 3: Rotate the sample 1 180° with the central axis of the sample 1 plate as the rotation axis, while keeping the position of the magnetic sensor 2 unchanged, and record the vertical component B of the measurement value of the magnetic sensor 2. mz2 and the horizontal component B parallel to the plate surface mx2 ;

[0029] Step 4: Keep the position of sensor 2 unchanged, place sample 1 in an area away from sensor 2, re-record the measurement value of magnetic sensor 2, and obtain the vertical component B of the geomagnetic field. z and the horizontal component B x ;

[0030] Step 5: Replace B in step 2 mz1 and B mx1 Subtract B from step 4 respectively z and B x , and the vertical component magnetic field B of sample 1 is obtained respectively z1 and the horizontal component magnetic field B x1 , where B z1 Contains fixed magnetic field and induced magnetic field Biz1 +B pz1 , B x1 contains the fixed magnetic field and the induced magnetic field B ix1 +B px1 ;

[0031] Step 6, B mz2 and B mx2 in step 3 are subtracted by B z and B x in step 4 respectively, to get the vertical component magnetic field B z2 and the horizontal component magnetic field B x2 of sample 1 respectively, where B z2 contains the fixed magnetic field and the induced magnetic field B iz1 -B pz1 , B x2 contains the fixed magnetic field and the induced magnetic field B ix1 -B px1 ;

[0032] Step 7, B z1 and B x1 in step 5 are added by B z2 and B x2 in step 6 respectively, and divided by 2, to get the induced magnetic field B z of sample 1 under B iz excitation and the induced magnetic field B x under B ix excitation respectively;

[0033] Step 8, a 1:1 finite element static magnetic field numerical model of sample 1 is built, the vertical permeability μ z is set, the vertical magnetic field B z is applied as excitation, the induced magnetic field vertical component B jz at probe 3 is calculated, if B jz <B mz , then μ z is increased, otherwise μ z is decreased, until |B jz -B mz |<1nT, then the corresponding μ z can be regarded as the measurement of the vertical initial permeability;

[0034] Step 9, in the finite element static magnetic field numerical model in step 8, the horizontal permeability μ x is set, the horizontal magnetic field B x is applied as excitation, the induced magnetic field horizontal component B jx at probe 3 is calculated, if B jx <B mx , then μ x is increased, otherwise μ x, until |B jz -B mz |<1nT, then the corresponding μ x It can be considered as a measurement of the starting magnetic permeability in the horizontal direction.

[0035] The above μ z and μ x That is, it constitutes the initial tensor permeability of the steel plate 1.

[0036] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for measuring the initial tensor magnetic permeability of a plate-like sample, characterized in that: The steps include: Step 1: Place the plate-shaped sample (1) to be tested vertically on a horizontal non-magnetic platform, and keep the plate surface parallel to the geomagnetic vector; Step 2: Place the magnetic sensor (2) on one side of the sample (1). The magnetic sensor (2) is supported and fixed by a smooth non-magnetic pad (4). The probe (3) of the magnetic sensor (2) passes through the central axis of the sample (1) plate surface, and the two axes of the probe (3) are parallel to the vertical direction and the horizontal direction of the geomagnetic field, respectively. Measure the actual distance L from the probe (3) to the sample (1) plate surface, and record the vertical component B of the measurement value of the magnetic sensor (2). mz1 and the horizontal component B parallel to the plate surface mx1 ; Step 3: Using the central axis of the sample (1) as the rotation axis, rotate the sample (1) 180° while keeping the position of the magnetic sensor (2) unchanged, and record the vertical component B of the measurement value of the magnetic sensor (2). mz2 and the horizontal component B parallel to the plate surface mx2 ; Step 4: Keep the position of the magnetic sensor (2) unchanged, place the sample (1) in an area away from the magnetic sensor (2), re-record the measurement value of the magnetic sensor (2), and obtain the vertical component B of the geomagnetic field. z and the horizontal component B x ; Step 5, replace B in step 2 mz1 and B mx1 Subtract B from step 4 respectively z and B x , and the vertical component magnetic field B of sample (1) is obtained respectively z1 and the horizontal component magnetic field B x1 , where B z1 Contains fixed magnetic field and induced magnetic field B iz1 +B pz1 , B x1 Contains fixed magnetic field and induced magnetic field B ix1 +B px1 ; Step 6, replace B in step 3 mz2 and B mx2 Subtract B from step 4 respectively z and B x , and the vertical component magnetic field B of sample (1) is obtained respectively z2 and the horizontal component magnetic field B x2 , where B z2 Contains fixed magnetic field and induced magnetic field B iz1 -B pz1 , B x2 Contains fixed magnetic field and induced magnetic field B ix1 -B px1 ; Step 7, replace B in step 5 z1 and B x1 Add B in step 6 respectively z2 and B x2 , and divided by 2, we can get the value of sample (1) in B z The induced magnetic field B under excitation iz and in B x The induced magnetic field B under excitation ix ; Step 8: Establish a 1:1 static magnetic field numerical model of the plate sample (1) and set the vertical magnetic permeability μ z , apply a vertical magnetic field B z As the excitation, calculate the vertical component B of the induced magnetic field at the probe (3) jz , if B jz mz , then increase μ z , otherwise reduce μ z , until |B jz -B mz |<1nT, then the corresponding μ z It can be regarded as a measurement of the starting magnetic permeability in the vertical direction;​ Step 9: In the 1:1 static magnetic field numerical model in step 8, set the horizontal magnetic permeability μ x , apply a horizontal magnetic field B x As the excitation, calculate the horizontal component B of the induced magnetic field at the probe (3) jx , if B jx mx , then increase μ x , otherwise reduce μ x , until |B jz -B mz |<1nT, then the corresponding μ x It can be considered as a measurement of the starting magnetic permeability in the horizontal direction.​ 2. The method for measuring the initial tensor magnetic permeability of a plate-like sample according to claim 1, wherein: The magnetic sensor (2) is a dual-axis or tri-axis magnetic sensor.

3. The method for measuring the initial tensor magnetic permeability of a plate-like sample according to claim 1, wherein: The width W of the test specimen (1) should be greater than 5 times its thickness H.

4. The method for measuring the initial tensor magnetic permeability of a plate-like sample according to claim 1, wherein: The distance L between the probe (3) and the plate surface of the sample (1) is between 0.2 and 2 times the width W of the plate-shaped sample (1).

Images