Foil non-destructive stress magnetic measurement method and magnetic measurement system

Abstract

The application discloses a foil nondestructive stress magnetic measurement method and a magnetic measurement system, and comprises the following steps: S100, under different lift-off heights, test the curve relationship between magnetic induction voltage values V and excitation currents I 0i ; 0i S200, select an excitation current range I 0i ~I 0a with a V 0b change rate of 30% to 50%, and search for a lift-off height range h 0i ~h a with a V b change rate of 30% to 50%, and select I 0ab and h ab in the current range and the height range as test input conditions; S300, after a continuous pulling force is applied to a foil sample to be measured, test voltage values V 0ti and V 45ti in 0° and 45° directions; S400, increase at a rate of to obtain the relationship between the residual stress of the foil sample and the pulling force + and the sensitivity coefficient; S500, after the sensitivity coefficient is obtained, remove the continuous pulling force, and decompose to obtain the principal stress by using a known elastic analytic theory, so that the residual stress is obtained.

Description

Technical Field

[0001] This invention relates to the field of magnetic measurement methods, specifically to a non-destructive stress magnetic measurement method and system for foil, which tests the foil by utilizing its physical properties. Background Technology

[0002] The stress state of raw materials has always been a key factor affecting national economic sectors such as machining. Especially in the field of precision metal processing, the magnitude of material stress profoundly affects product quality, and the determination of material stress is of great economic significance. For example, in micron-level processing fields such as FMM using INVAR metal as raw material, tiny stress differences (<5 MPa) can lead to relatively large changes in product dimensions, and stress control will directly affect product yield. Currently, the industry mainly uses the warpage value after chemical semi-etching to characterize the stress level of raw materials, or uses X-ray diffraction, magnetic measurement, and ultrasound. Among them, magnetic measurement is widely used due to its high testing efficiency, wide detectable area, no radiation, and non-destructive properties.

[0003] In magnetic measurement, the magnetostrictive effect of ferromagnetic materials is generally used to determine residual stress. In a zero-stress state, ferromagnetic materials are magnetically isotropic, with permeability consistent in all directions. When stress exists in the material, the permeability of the ferromagnetic material becomes inconsistent in different directions, exhibiting magnetic anisotropy. The permeability is related to the stress state in that direction, known as stress-induced magnetic anisotropy (SMA). In other words, the presence of residual stress in the sample hinders the movement and orientation of magnetic domains, reducing magnetic susceptibility. Measuring the relative change in permeability allows for the determination of residual stress, also known as the magnetoelastic method. The relative change in permeability is often converted into an electrical signal (voltage or current) for measurement in magnetic measurements. Experiments and theory show that the current difference along the principal stress direction at a certain point in the material has an approximately linear relationship with the principal stress difference. Or the relationship between voltage and principal stress difference .

[0004] The current general practice for testing residual stress in specimens is to obtain a zero-stress sample of the specimen to be tested by means of annealing, and to calibrate the sensitivity coefficient α of the specimen by applying a certain tensile stress or compressive stress to the zero-stress sample.

[0005] Once α is known, a four-stage probe sensor containing an excitation coil and a magnetizing coil is generally used to measure the voltage and current signals of the test sample in the 0° and 45° directions, and the magnitude of the residual stress of the sample can be inferred.

[0006] The above-mentioned scheme for testing the residual stress of a sample using the stress-induced magnetotropic anisotropy detection method generally assumes that the residual stress of the sample is completely eliminated after full annealing. This leads to two main problems: firstly, full annealing is a qualitative method and may not necessarily guarantee that the sample stress is completely reduced to zero and magnetic isotropy is achieved; secondly, the sensitivity coefficient α of the test material is closely related to the microstructure of the material. The microstructure of the sample after full annealing is not consistent with that of the test sample. Both of these points will lead to excessively large errors in the calibrated sensitivity coefficient, thus making it impossible to determine the measurement error.

[0007] To ensure the accuracy of the sensitivity coefficient calibrated using the standard sample, the magnetic probe and the sample are kept at the same measurement lift height during normal testing and calibration. This means that the magnetic probe is usually in contact with the sample during calibration and testing. Such contact can easily cause damage and deformation to ultra-thin test samples, especially for 25µm INVAR thin strip materials used to manufacture FMM (Fine Metal Mask). This is not conducive to sample reuse and is even less conducive to online testing. Summary of the Invention

[0008] To address the above technical problems, this invention provides a non-destructive stress magnetic measurement method and system for foil materials. This method tests the foil materials by utilizing their physical properties. It eliminates the need for a stress magnetic measurement scheme that requires the preparation of zero-stress standard samples for calibration, and instead performs calibration and testing directly on the sample to be tested, completing both calibration and testing in one step.

[0009] The present invention adopts the following technical solution:

[0010] A non-destructive stress magnetic measurement method for foil includes the following steps:

[0011] S100: At different lift-off heights, the magnetic induction voltage V under different excitation currents was tested. 0i With excitation current I 0i The curve relationship;

[0012] S200: Select V 0i Excitation current range I with a change rate between 30% and 50% 0a ~ I 0b , and search V 0i Lift-off height range h with a change rate between 30% and 50% a ~h b Select I within the above current and height ranges. 0ab and h ab As test input conditions;

[0013] S300: Apply continuous tensile force to the foil sample to be tested. Then, the voltage values ​​V in the 0° and 45° directions were measured. 0ti and V 45ti The residual stress of the foil sample was obtained. With tension and sensitivity coefficient The relationship between them;

[0014] S400: The rate increases Similarly, the residual stress of the foil sample can be obtained. With tension + and sensitivity coefficient The relationship between these factors allows us to obtain the sensitivity coefficient. The average sensitivity coefficient of the foil sample can be expressed as a weighted integral as follows: ;

[0015] S500: Obtain the sensitivity coefficient Afterwards, remove the continuous tension. The unknown residual stress of the foil to be tested Given the angle θ between the maximum principal stress and the X-axis, the principal stresses are determined using known elastic analytical theory. , Thus, we can conclude .

[0016] Preferably, step S100 further includes: using a tensioning device to clamp both ends of the foil sample and flattening the foil sample under a certain tension.

[0017] Preferably, step S200 further includes: selecting V at the same lift-off height. 0i Excitation current range I with a change rate between 30% and 50% 0a ~ I 0b And search for V based on the excitation current range determined above. 0i Lift-off height range h with a change rate between 30% and 50% a ~h b .

[0018] Preferably, step S100 further includes: using a probe to test signals in any angle direction under the control of a rotary motor, so as to obtain the current value in the principal stress direction at different angles.

[0019] Preferably, the probe consists of two pairs of SN-level probes composed of two sets of U-shaped coils. One pair of SN-level probes generates an excitation magnetic field under the action of the excitation coil, and the other pair of SN-level probes generates an excitation magnetic field under the action of the excitation coil. The magnetic field is converted into an electrical signal through electromagnetic conversion, and the system obtains the magnitude of the electrical signal.

[0020] A non-destructive stress magnetic measurement system for foil materials, comprising:

[0021] frame;

[0022] The clamp is slidably fitted onto the frame, including an upper clamp and a lower clamp, and has a built-in tension sensing system;

[0023] The probe is located between the upper and lower clamps and has a built-in height sensing system.

[0024] The two ends of the foil sample are clamped on the upper and lower clamps, respectively, and the probe is positioned facing the foil sample.

[0025] Preferably, the frame is provided with a lead screw, and the upper and lower clamps are provided with lifting nuts that cooperate with the lead screw; the lead screw is also provided with a guide rod, and the left and right ends of the upper and lower clamps are provided with sliding holes that cooperate with the guide rod.

[0026] Preferably, the probe is slidably engaged with the sliding rod on the frame via a position adjustment crossbar.

[0027] Compared with the prior art, the present invention has the following advantages: The present invention provides a non-destructive stress magnetic measurement method and magnetic measurement system for foil materials. The method tests the foil materials by utilizing their physical properties. This method abandons the stress magnetic measurement scheme of making zero-stress standard samples for calibration, and directly performs calibration and testing on the sample to be tested, completing the calibration and testing in one go. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the probe setup method.

[0029] Figure 2 A schematic diagram of the decomposition of principal stresses.

[0030] Figure 3 This is a schematic diagram of the stress magnetic measurement system.

[0031] In the figure, there are: frame 1, lead screw 11, guide rod 12, sliding rod 13, position adjustment crossbar 14, clamp 2, upper clamp 21, lower clamp 22, and probe 3. Detailed Implementation

[0032] To facilitate understanding of the technical solution of the present invention, the following detailed description is provided in conjunction with the accompanying drawings and specific embodiments.

[0033] Example 1

[0034] like Figure 1-2 As shown, a non-destructive stress magnetic measurement method for foil includes the following steps:

[0035] S100: At different lift heights h1, h2, h3, ... h i The magnetic induction voltage V was tested under different excitation currents. 0i With excitation current I 0i The curve relationship;

[0036] Specifically, the probe is pointed towards the foil sample. Under alternating excitation current, the probe's coil generates an alternating excitation magnetic field. After the excitation magnetic field passes through the sample, the magnitude of the magnetic field generated by the excitation coil varies due to differences in residual stress, thus producing different excitation currents. In other words, different residual stresses generate different voltage difference signals (i.e., voltage values ​​V) within the probe. 0i This characterizes the residual stress of the foil.

[0037] S200: Select V 0i Excitation current range I with a change rate between 30% and 50% 0a ~ I 0b , and search V 0i Lift-off height range h with a change rate between 30% and 50% a ~h b Select I within the above current and height ranges. 0ab and h ab As test input conditions;

[0038] Among them, V 0i The rate of change refers to the change between two V values ​​under different excitation currents or different lift-off heights. 0i The relative rate of change, for example, V at height h1 0i Let V1 be the value of V at height h2. 0i If V2, then V 0i The rate of change is V 0i =(V2-V1) / V1;

[0039] In this embodiment, 30%~50% is selected because if the rate of change is too small, then within the range of large changes in excitation current and lift-off height, V 0i The change is too slight, which will result in too small a system resolution. If the rate of change is too large, it indicates that within a very small range of changes in excitation current and lift-off height, V... 0i Drastic changes can lead to larger system errors.

[0040] Based on the variation curves of different excitation currents and different lift-off heights obtained in S100, the lift-off height range h can be achieved through the built-in algorithm of the system program. a ~h bIn this embodiment, the current and height search algorithm built into the foil non-destructive stress testing system software (a prior art) is used to determine the value. Additionally, I within the aforementioned range is randomly selected. 0ab and h ab ;

[0041] S300: Apply continuous tensile force to the foil sample to be tested. Then, the voltage values ​​V in the 0° and 45° directions were measured. 0ti and V 45ti The residual stress of the foil sample was obtained. With tension and sensitivity coefficient The relationship between them, i.e., Formula 1: ,in The residual stress of the foil sample under no tensile force. This is the sensitivity coefficient;

[0042] Among them, the applied continuous tensile force 0~0.8σ s (Yield strength);

[0043] like Figure 1 The image shows the probe settings at 0° and 45°. Furthermore, when measuring voltage values ​​in both directions, the laser rangefinder continuously monitors the lift-off height h of the probe from the foil sample surface, providing feedback and adjustment to ensure the lift-off height h is maintained. ab It remains unchanged in the test;

[0044] S400: The rate increases The residual stress of foil samples is generally small relative to their yield stress (below 25 MPa). Under sufficiently large tensile loads, the influence of the residual stress of the foil sample itself on the sensitivity coefficient calibration can be ignored. That is, under large unidirectional tensile loads... The residual stress of the foil sample can be obtained below. With tension + and sensitivity coefficient The relationship between them, i.e., Formula 2: Subtracting Formula 1 from Formula 2 yields... The average sensitivity coefficient of the foil sample can be expressed as a weighted integral as follows: ;

[0045] S500: Obtain the sensitivity coefficient Afterwards, remove the continuous tension. The unknown residual stress of the foil to be tested Given the angle θ between the maximum principal stress and the X-axis, the principal stresses are determined using known elastic analytical theory. , Thus, we can conclude ;

[0046] Remove continuous tension (that is, when) When the value is 0, we get Formula 3: The angle between the direction of the maximum principal stress and the X-axis is... The principal stresses are obtained through elastic analytical decomposition. , , and thus ;

[0047] Among them, such as Figure 2 As shown, principal stress Principal stress refers to the maximum principal stress at the test point in a certain direction. It refers to the minimum principal stress at the test point in a certain direction, where θ is the angle. The angle with the X-axis direction. (This is achieved through calibration.) back, This is the calculated value.

[0048] This invention tests foil materials by utilizing their physical properties (electromagnetic induction). This method abandons the stress magnetic measurement scheme of making zero-stress standard samples for calibration in the prior art, and directly performs calibration and testing on the sample to be tested, completing the calibration and testing in one go. Calibration refers to calculating the coefficient factor in the calibration formula when the measured value of the sample is known. Testing refers to testing the measured value of the sample to be tested after knowing the above coefficient factor.

[0049] S100 further includes: using a tensioning device to clamp both ends of the foil sample and pulling the foil sample flat under a certain tension, wherein the tension in this embodiment is less than 1 MPa.

[0050] S100 further includes: using a probe to test signals in any angle direction under the control of a rotary motor, so as to obtain the current value in the principal stress direction at different angles.

[0051] The probe consists of two pairs of SN-level probes composed of two sets of U-shaped coils. One pair of SN-level probes generates an excitation magnetic field under the action of the excitation coil, and the other pair of SN-level probes generates an excitation magnetic field under the action of the excitation coil. The magnetic field is converted into an electrical signal through electromagnetic conversion, and the system obtains the magnitude of the electrical signal.

[0052] A non-destructive stress magnetic measurement system for foil materials, comprising:

[0053] Rack 1;

[0054] The clamp 2 is slidably fitted onto the frame 1, including an upper clamp 21 and a lower clamp 22, and has a built-in tension sensing system;

[0055] The probe 3 is located between the upper clamp 21 and the lower clamp 22, and has a built-in height sensing system that can obtain the probe lifting height in real time.

[0056] The two ends of the foil sample are clamped on the upper clamp 21 and the lower clamp 22 respectively, and the probe 3 is positioned facing the foil sample.

[0057] The frame 1 is provided with a lead screw 11, and the upper clamp 21 and the lower clamp 22 are provided with lifting nuts that cooperate with the lead screw 11; the lead screw 11 is also provided with a guide rod 12, and the upper clamp 21 and the lower clamp 22 are provided with sliding holes that cooperate with the guide rod 12 at both ends.

[0058] The probe 3 is slidably engaged with the sliding rod 13 on the frame 1 via the position adjustment crossbar 14.

[0059] The position adjustment crossbar 14 is also equipped with a rotary motor, which can adjust the angle of the probe 3 to obtain the current value in the direction of principal stress at different angles.

[0060] In use, the foil sample is held by the upper clamp 21 and the lower clamp 22, and a certain pulling force is applied to flatten the foil sample. The probe 3 does not directly contact the foil sample to obtain the voltage value of the foil sample; at different lift heights h1, h2, h3, ... h i The magnetic induction voltage V was tested under different excitation currents. 0i With excitation current I 0i The curve relationship; under the same lift-off height, select V 0i Excitation current range I with a change rate between 30% and 50% 0a ~ I 0b And search for V based on the excitation current range determined above. 0i Lift-off height range h with a change rate between 30% and 50% a ~h b Select I within the above range 0ab and h ab Apply continuous tensile force to the foil sample Test the voltage values ​​V at 0° and 45° directions. 0ti and V 45ti Increase After taking one measurement, the continuous tension was then removed. (that is, when) When the value is 0, the angle between the direction of the maximum principal stress and the X-axis is obtained. The principal stresses are obtained through elastic analytical decomposition. , , and thus .

[0061] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention shall be determined by the scope defined in the claims. Any improvements and modifications made by those skilled in the art without departing from the spirit and scope of the present invention shall also be considered as within the scope of protection of the present invention.

Claims

1. A non-destructive stress magnetic measurement method for foil materials, characterized in that, Includes the following steps: S100: At different lift-off heights, the magnetic induction voltage V under different excitation currents was tested. 0i With excitation current I 0i The curve relationship; S2 00: Select V 0i Excitation current range I with a change rate between 30% and 50% 0a ~ I 0b , and search V 0i Lift-off height range h with a change rate between 30% and 50% a ~h b Select I within the above-mentioned excitation current range and height range. 0ab and h ab As test input conditions; S300: Apply continuous tensile force to the foil sample to be tested. Then, the voltage values ​​V in the 0° and 45° directions were measured. 0ti and V 45ti The residual stress of the foil sample was obtained. With tension and sensitivity coefficient The relationship between them, i.e., Formula 1: ,in The residual stress of the foil sample under no tensile force. This is the sensitivity coefficient; S400: The rate increases The residual stress of the foil sample was obtained. With tension + and sensitivity coefficient The relationship between the two factors yields the sensitivity coefficient. The average sensitivity coefficient of the foil sample is expressed as a weighted integral as follows: ,in, ; S500: Obtain the sensitivity coefficient Afterwards, remove the continuous tension. The unknown residual stress of the foil to be tested Given the angle θ between the maximum principal stress and the X-axis, the principal stresses are determined using known elastic analytical theory. , Thus, we can conclude .

2. The non-destructive stress magnetic measurement method for foil according to claim 1, characterized in that, S100 further includes: using a tensioning device to clamp both ends of the foil sample and flattening the foil sample under a certain tension.

3. The non-destructive stress magnetic measurement method for foil according to claim 1, characterized in that, The S200 also includes: selecting V at the same lift-off height. 0i Excitation current range I with a change rate between 30% and 50% 0a ~ I 0b And search for V based on the excitation current range determined above. 0i Lift-off height range h with a change rate between 30% and 50% a ~h b .

4. The non-destructive stress magnetic measurement method for foil according to claim 1, characterized in that, S100 further includes: using a probe to test signals in any angle direction under the control of a rotary motor, so as to obtain the current value in the principal stress direction at different angles.

5. The non-destructive stress magnetic measurement method for foil according to claim 4, characterized in that, The probe consists of two pairs of SN-level probes composed of two sets of U-shaped coils. One pair of SN-level probes generates an excitation magnetic field under the action of the excitation coil, and the other pair of SN-level probes generates an excitation magnetic field under the action of the excitation coil. The magnetic field is converted into an electrical signal through electromagnetic conversion, and the system obtains the magnitude of the electrical signal.

6. A non-destructive stress magnetic measurement system for foil materials, characterized in that, Applied to the non-destructive stress magnetic measurement method for foil as described in any one of claims 1-4, and comprising: Rack (1); The clamp (2) is slidably fitted on the frame (1), including an upper clamp (21) and a lower clamp (22), and has a built-in tension sensing system; The probe (3) is located between the upper clamp (21) and the lower clamp (22) and has a built-in height sensing system; The two ends of the foil sample are clamped on the upper clamp (21) and the lower clamp (22) respectively, and the probe (3) is set towards the foil sample.

7. The foil non-destructive stress magnetic measurement system according to claim 6, characterized in that, The frame (1) is provided with a lead screw (11), and the upper clamp (21) and lower clamp (22) are provided with lifting nuts that cooperate with the lead screw (11); the lead screw (11) is also provided with a guide rod (12), and the upper clamp (21) and lower clamp (22) are provided with sliding holes that cooperate with the guide rod (12) at both ends.

8. The foil non-destructive stress magnetic measurement system according to claim 6, characterized in that, The probe (3) is slidably engaged with the sliding rod (13) on the frame (1) via the position adjustment crossbar (14).

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