Quadrupole variable-angle magnetic measurement probe and plane vector stress measurement method

Abstract

The invention provides a quadrupole variable-angle magnetic measurement probe and a plane vector stress measurement method, and relates to the technical field of mechanical property detection. The quadrupole variable-angle magnetic measurement probe comprises a variable-angle probe excitation magnetic core, a variable-angle probe detection magnetic core and a variable-angle probe multi-layer coil, and a non-90-degree included angle is formed between the variable-angle probe excitation magnetic core and the variable-angle probe detection magnetic core. The method comprises the following steps: changing the ratio of magnetic circuit lengths in the directions of positive pressure sigma x and sigma y on the surface of a test piece through a variable-angle probe excitation magnetic core and a variable-angle probe detection magnetic core which form an included angle of non-90 degrees, changing coefficients of the positive pressure sigma x and sigma y, and performing vector stress measurement at a plane single point by using a first measurement method or a second measurement method, and obtaining vector stress values of the maximum principal stress sigma1 and the minimum principal stress sigma2 at a single point in the plane and a principal stress direction angle theta. According to the method, the plane stress state can be reflected more visually, and the problem that the absolute values of the maximum principal stress sigma 1 and the minimum principal stress sigma 2 at the plane single point cannot be obtained through an existing method is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of mechanical property detection, and more particularly, to a quadrupole variable-angle magnetic measurement probe and a planar vector stress measurement method. Background Art

[0002] With the development of production technology, the detection requirements for residual stress are getting higher and higher in many fields. Non-destructive testing is an essential tool for the development of modern industry, which can detect various defects of the object to be detected without damaging or basically not damaging the material or component. At present, China is in the stage of large-scale economic construction. Railway construction, bridge erection and other projects are based on various steels. During various mechanical processes, such as cold drawing, bending, casting, forging, welding, cutting, heat treatment and assembly, different degrees of residual stress will appear in the workpiece. Therefore, the demand for non-destructive testing of steel components is increasing day by day. Among the non-destructive testing technologies, the most remarkable development at present is the magnetic measurement method. For the magnetic measurement method of residual stress, foreign scholars have carried out many effective theoretical and experimental studies.

[0003] Scholars such as H. Yamada analyzed the magnetic circuit distribution of the quadrupole sensor, carried out relevant magnetic circuit calculations and first proposed that in all directions of the material, the magnetic permeability of the material is distributed in an ellipse, and the main magnetic permeability is linearly related to the main stress. There is a certain relationship between the change of magnetic permeability and the corresponding output. After derivation, the conclusion is obtained that when the connection line of the excitation magnetic poles is 45° with the main stress direction, there is a relationship of V = K(σ x -σ y ). The research group of Professor Wang Zhenshan of Xi'an Jiaotong University has carried out a large number of theoretical and practical application studies on magnetic measurement stress, and deduced the relationship between the magnetic flux change of the probe and the stress, and obtained many important conclusions: such as the conclusion that there is a linear relationship between the main stress difference and the magnetic flux change, and this conclusion is applied to actual detection. Based on the research theoretical results of the above scholars, it is found that all magnetic measurement methods can only measure the difference and direction angle between the maximum principal stress and the minimum principal stress at a single point on the plane. Although the main stress difference at a single point on the plane has been obtained, there are thousands of numerical combinations of the maximum principal stress σ1 and the minimum principal stress σ2. Therefore, the existing magnetic measurement methods cannot fully and intuitively represent the plane stress state. Summary of the Invention

[0004] In view of the above technical problems that the absolute values of the maximum principal stress σ1 and the minimum principal stress σ2 at a single point on the plane cannot be obtained by the existing methods, a quadrupole variable-angle magnetic measurement probe and a planar vector stress measurement method are provided.

[0005] The technical means adopted by the present invention are as follows:

[0006] A four-pole variable-angle magnetic measurement probe, comprising: a variable-angle probe excitation magnetic core, a variable-angle probe detection magnetic core, and a variable-angle probe multi-layer coil. The variable-angle probe multi-layer coil is sleeved on the variable-angle probe excitation magnetic core and the variable-angle probe detection magnetic core, and a non-90° included angle is formed between the variable-angle probe excitation magnetic core and the variable-angle probe detection magnetic core.

[0007] The present invention also provides a planar vector stress measurement method, which uses the above four-pole variable-angle magnetic measurement probe for measurement, and comprises the following steps:

[0008] By means of the variable-angle probe excitation magnetic core and the variable-angle probe detection magnetic core with a non-90° included angle in the four-pole variable-angle magnetic measurement probe, the ratio of the magnetic circuit lengths in the directions of the normal pressures σ x and σ y on the surface of the test piece is changed, the coefficients of the normal pressures σ x and σ y are changed, and the vector stress values of the maximum principal stress σ1 and the minimum principal stress σ2 and the principal stress direction angle θ at a single point in the plane are obtained by using the first measurement method or the second measurement method for vector stress measurement at a single point in the plane.

[0009] Further, the first measurement method comprises:

[0010] Obtaining the sensitivity coefficient K1 of the four-pole vertical probe, the sensitivity coefficient K2 of the four-pole variable-angle magnetic measurement probe, and the variable-angle ratio coefficient c;

[0011] Measuring two output voltage values in the 0° direction and the 45° direction at a single point in the plane by means of the four-pole vertical probe;

[0012] Measuring the output voltage value in the 0° direction at a single point in the plane by means of the four-pole variable-angle magnetic measurement probe;

[0013] According to the three obtained output voltage values, combining the sensitivity coefficient K1, the sensitivity coefficient K2, and the variable-angle ratio coefficient c, the vector stress values of the maximum principal stress σ1 and the minimum principal stress σ2 at a single point in the plane are obtained.

[0014] Further, the second measurement method comprises:

[0015] Obtaining the sensitivity coefficient K2 of the four-pole variable-angle magnetic measurement probe and the variable-angle ratio coefficient c;

[0016] The four-pole variable-angle magnetic measurement probe rotates coaxially at intervals of 45° by 4 angles with the 0° direction as the reference angle at a single point in the plane for measurement, and four output voltage values in the 0° direction, the 45° direction, the 90° direction, and the 135° direction are measured;

[0017] According to the four obtained output voltage values, combined with the sensitivity coefficient K2 of the four-pole variable-angle magnetic measurement probe and the variable-angle proportionality coefficient c, the vector stress values of the maximum principal stress σ1 and the minimum principal stress σ2 at a single point in the plane are obtained.

[0018] Further, the maximum principal stress σ1, the minimum principal stress σ2, and the principal stress direction angle θ at a single point in the plane satisfy the following formula:

[0019]

[0020] In the formula: σ1 is the maximum principal stress at a single point in the plane / Mpa; σ2 is the minimum principal stress at a single point in the plane / Mpa; θ is the principal stress direction angle of the specimen / radian; K1 is the sensitivity coefficient of the four-pole vertical probe / μV·Mpa -1 ; K2 is the sensitivity coefficient of the four-pole variable-angle magnetic measurement probe / μV·Mpa -1 ; is the output voltage value obtained by measuring along the X direction using the four-pole variable-angle magnetic measurement probe / μV; V0 is the output voltage value obtained by measuring along the X direction (0° direction) using the four-pole vertical probe / μV; c is the variable-angle proportionality coefficient; V 45 is the output voltage value obtained by measuring along the direction at 45° to the X direction using the four-pole vertical probe / μV.

[0021] Further, the maximum principal stress σ1, the minimum principal stress σ2, and the principal stress direction angle θ at a single point in the plane satisfy the following formula:

[0022]

[0023] Among them,

[0024]

[0025] In the formula: σ1 is the maximum principal stress at a single point in the plane / Mpa; σ2 is the minimum principal stress at a single point in the plane / Mpa; θ is the principal stress direction angle of the specimen / radian; K2 is the sensitivity coefficient of the four-pole variable-angle magnetic measurement probe / μV·Mpa -1 ; c is the four-pole variable-angle probe proportionality coefficient; and are the voltage values corresponding to the X direction and the Y direction at this point / μV; and are the voltage values corresponding to the directions at 45° to the X direction and the Y direction at this point / μV; σ 0° and σ 90° are the magnitudes of the normal stresses corresponding to the X direction and the Y direction (90° direction) at this point / Mpa; σ 45° and σ 135°The normal stress magnitudes corresponding to the directions at 45° to the X and Y directions at this point, respectively, in MPa.

[0026] Further, the sensitivity coefficient K1 is determined by a unidirectional tensile calibration test, in which the unidirectional tensile calibration test adopts a step-by-step stress loading method with a stress interval of 10 MPa. The sensitivity coefficient K1 satisfies the following formula:

[0027]

[0028] In the formula: K1 is the sensitivity coefficient of the quadrupole vertical probe in μV·MPa -1 ; K 1i is the sensitivity coefficient corresponding to the stress loaded in a single interval in μV·MPa -1 ; n is the number of loading times; V 0i is the output voltage value in the 0° direction corresponding to the stress loaded in a single interval in μV; σ i is the stress loaded in a single interval in MPa.

[0029] Further, the sensitivity coefficient K2 is determined by a unidirectional tensile calibration test, in which the unidirectional tensile calibration test adopts a step-by-step stress loading method with a stress interval of 10 MPa. The sensitivity coefficient K2 satisfies the following formula:

[0030]

[0031] In the formula: K2 is the sensitivity coefficient of the quadrupole variable-angle magnetic measurement probe in μV·MPa -1 ; K 2i is the sensitivity coefficient corresponding to the stress loaded in a single interval in μV·MPa -1 ; n is the number of loading times; is the output voltage value in the 90° direction corresponding to the stress loaded in a single interval in μV; σ i is the stress loaded in a single interval in MPa.

[0032] Further, the variable-angle proportionality coefficient c is determined by a unidirectional tensile calibration test and satisfies the following formula:

[0033]

[0034] In the formula: c is the variable-angle proportionality coefficient; c i is the proportionality coefficient corresponding to the stress loaded in a single interval; n is the number of loading times; is the output voltage value in the 90° direction corresponding to the stress loaded in a single interval in μV; is the output voltage value in the 0° direction corresponding to the stress loaded in a single interval in μV.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] 1. For the four-pole variable-angle magnetic measurement probe and the planar vector stress measurement method provided by the present invention, compared with the existing measurement methods, the vector stress values of the maximum principal stress σ1 and the minimum principal stress σ2 at a single point on the plane can be obtained. The two planar vector stress magnetic measurement methods with the four-pole variable-angle magnetic measurement probe as the core can more intuitively reflect the planar stress state, and at the same time avoid the cumulative error generated by the shear stress difference method in the process of data processing. It has a broad application prospect in the field of magnetic method for detecting residual stress.

[0037] 2. For the four-pole variable-angle magnetic measurement probe and the planar vector stress measurement method provided by the present invention, aiming at the measurement of vector stress at a single point on the plane, the present invention improves the existing four-pole vertical probe measurement method that cannot obtain the planar vector stress value, and proposes a four-pole variable-angle magnetic measurement probe. The main feature of the four-pole variable-angle magnetic measurement probe is that a non-90° angle can be formed between the excitation magnetic core of the variable-angle probe and the detection magnetic core of the variable-angle probe. The mathematical relationship between the output voltage value of the four-pole variable-angle magnetic measurement probe and the stress is summarized through experiments. At the same time, two calculation methods are proposed to solve the planar vector stress value, and different points selected in the plane are measured in turn, and finally the stress state of the plane can be obtained.

[0038] Based on the above reasons, the present invention can be widely promoted in the fields of mechanical property detection and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0040] Figure 1 It is a schematic structural diagram of an existing four-pole vertical probe.

[0041] Figure 2 It is a schematic structural diagram of the four-pole variable-angle magnetic measurement probe of the present invention.

[0042] Figure 3 It is an equivalent magnetic circuit schematic diagram of an existing four-pole vertical probe.

[0043] Figure 4 It is a variable coefficient equivalent magnetic circuit schematic diagram of the four-pole variable-angle magnetic measurement probe of the present invention.

[0044] Figure 5 It is a schematic diagram of establishing the X-axis and Y-axis directions of the present invention.

[0045] In the figure: 101 is the excitation core of the vertical probe; 102 is the detection core of the vertical probe; 103 is the multi-layer coil of the vertical probe; 104 is the measurement sample I; 201 is the excitation core of the variable-angle probe; 202 is the detection core of the variable-angle probe; 203 is the multi-layer coil of the variable-angle probe; 204 is the measurement sample II. Specific Embodiment

[0046] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The description of at least one exemplary embodiment below is actually only illustrative and in no way restricts the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0048] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, unless otherwise clearly specified in the context, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0049] Unless otherwise specifically stated, the relative arrangements of the components and steps, numerical expressions, and values described in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for the convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant fields may not be discussed in detail, but where appropriate, the said technologies, methods, and devices should be regarded as part of the specification. In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0050] Embodiment 1

[0051] The present invention provides a four-pole variable-angle magnetic measurement probe and a planar vector stress measurement method, which relate to the measurement of residual stress by magnetic measurement method, and particularly to a magnetic measurement method for the absolute value of planar biaxial stress, and can solve problems such as the inability to obtain the absolute values of the maximum principal stress σ1 and the minimum principal stress σ2 at a single point on a plane by existing methods.

[0052] Figure 1 Fig. 4 is a structural schematic diagram of an existing four-pole vertical probe (four-pole vertical magnetic core probe). The four-pole vertical probe is placed on a measurement specimen I 104. The four-pole vertical probe mainly consists of a vertical probe excitation magnetic core 101, a vertical probe detection magnetic core 102, and a vertical probe multi-layer coil 103.

[0053] Figure 2 Fig. 8 is a structural schematic diagram of the four-pole variable-angle magnetic measurement probe of the present invention. The four-pole variable-angle magnetic measurement probe is placed on a measurement specimen II 204. The four-pole variable-angle magnetic measurement probe mainly consists of a variable-angle probe excitation magnetic core 201, a variable-angle probe detection magnetic core 202, and a variable-angle probe multi-layer coil 203. The variable-angle probe multi-layer coil 203 is sleeved on the variable-angle probe excitation magnetic core 201 and the variable-angle probe detection magnetic core 202.

[0054] The principle of the present invention:

[0055] For the measurement of vector stress at a single point on a plane, as shown in the appendix, a mathematical model of the four-pole variable-angle magnetic measurement probe is established based on the existing four-pole vertical probe measurement method to improve the original measurement method. A four-pole variable-angle magnetic measurement probe is designed, and at the same time, two calculation methods are proposed to solve the planar vector stress value. Figure 1 As shown, based on the existing four-pole vertical probe measurement method, a mathematical model of the four-pole variable-angle magnetic measurement probe is established to improve the original measurement method. A four-pole variable-angle magnetic measurement probe is designed, and at the same time, two calculation methods are proposed to solve the planar vector stress value.

[0056] Among them, the four-pole variable-angle magnetic measurement probe of the present invention consists of three main parts: a variable-angle probe excitation magnetic core 201, a variable-angle probe detection magnetic core 202, and a variable-angle probe multi-layer coil 203. The characteristic of the four-pole variable-angle magnetic measurement probe is that a non-90° angle is formed between the variable-angle probe excitation magnetic core 201 and the variable-angle probe detection magnetic core 202. The four-pole variable-angle magnetic measurement probe changes the ratio of the magnetic path lengths in the directions of the normal stresses σ x and σ y to change the two normal stress coefficients for solving the value of cσ x -σ y , as shown in the appendix. The present invention takes changing the ratio of the magnetic path lengths in the directions of the normal stresses σ Figure 2 and σ x and σ y to change the two normal stress coefficients as the core, and proposes two calculation methods to obtain the planar vector stress value.

[0057] Method 1: The four-pole vertical probe measures the output voltage values in the 0° direction and the 45° direction at a single point on the plane, and the four-pole variable-angle magnetic measurement probe measures the output voltage value in the 0° direction at a single point on the plane. The vector stress values of the maximum principal stress σ1 and the minimum principal stress σ2 are solved by combining the three obtained output voltage values.

[0058] Method 2: The four-pole variable-angle magnetic measurement probe rotates coaxially by 4 angles with the 0° direction as the reference angle at a single point on the plane, with each angle separated by 45°. Four output voltage values are measured, and the vector stress values of the maximum principal stress σ1 and the minimum principal stress σ2 are solved by combining the four obtained output voltage values.

[0059] The specific principle and solution process are as follows:

[0060] (1) When measuring with a four-pole vertical probe, when the magnetic path lengths in the σ x and σ y directions are equal, the magnetic resistance difference between the two directions of the normal pressures σ x and σ y is:

[0061]

[0062] In the formula: R1 is the magnetic resistance of the surface material of the measured part between the magnetic poles ND1 when the magnetic path lengths are equal / Ω; R2 is the magnetic resistance of the surface material of the measured part between the magnetic poles D1 in the direction of the normal pressure σ y when the magnetic path lengths are equal / Ω; σ x is the normal stress in the X direction (0° direction) / Mpa; σ y is the normal stress in the Y direction (90° direction) / Mpa; σ1 is the maximum principal stress at a single point on the plane / Mpa; σ2 is the minimum principal stress at a single point on the plane / Mpa; θ is the principal stress direction angle of the specimen / radian; l is the magnetic path length of the magnetic pole / mm; λ S is the saturation magnetostriction coefficient; μ0 is the magnetic permeability of vacuum / (H / m); M S is the magnetization vector; S is the cross-sectional area of the magnetic path / m 2 .

[0063] Then, the effective value of the output voltage V1 of the detection coil of the four-pole vertical probe can be expressed as:

[0064]

[0065] In the formula: V1 is the output voltage of the detection coil of the four-pole vertical probe / μV; σ x is the normal stress in the X direction / Mpa; σ y is the normal stress in the Y direction / Mpa; ε is the induced electromotive force generated by the detection coil / μV; R D is the resistance value of the detection coil / Ω; XD where \(L\) is the inductive reactance value of the detection coil / \(\Omega\); \(\omega\) is the angular frequency / (rad / s), because the exciting current is an alternating current; \(I\) is the exciting current value / mA; \(K_1\) is the sensitivity coefficient of the four-pole vertical probe / \(\mu V\cdot Mpa\). -1

[0066] As shown in the appendix Figure 3 , due to the symmetry of the magnetic circuit on the surface of the test piece, the lengths of the four magnetic paths between the exciting magnetic pole and the detection magnetic pole are equal. Therefore, the magnetic resistances of the four magnetic paths \(R_1 = R_2 = R_3 = R_4\), so \(\sigma\) x and \(\sigma\) y coefficients are both 1.

[0067] (2) Measure using a four-pole variable-angle magnetic measurement probe. As shown in the appendix Figure 4 , change the magnetic path length between the exciting magnetic pole and the detection magnetic pole to change the equivalent magnetic circuit of the four-pole vertical probe. \(\sigma\) x and \(\sigma\) y coefficients change, and then the output voltage \(V_2\) is linearly related to \((c\sigma\) x - \(\sigma\) y ).

[0068] Therefore, the magnetic resistance difference in the two directions of \(\sigma\) x and \(\sigma\) y can be expressed as:

[0069]

[0070] In the formula: \(R_1'\) is the magnetic resistance in the direction of \(\sigma\) x / \(\Omega\) (magnetic resistance of the surface material of the test piece between the variable-angle magnetic poles \(ND_1\) / \(\Omega\)); \(R_2'\) is the magnetic resistance in the direction of \(\sigma\) y / \(\Omega\) (magnetic resistance of the surface material of the test piece between the variable-angle magnetic poles \(D_1S\) / \(\Omega\)); \(\sigma\) x is the normal stress in the X direction / Mpa; \(\sigma\) y is the normal stress in the Y direction / Mpa; \(\lambda\) S is the saturation magnetostriction coefficient; \(\mu_0\) is the vacuum permeability / (H / m); \(M\) S is the magnetization vector; \(l_1\) is the effective length of the magnetic path passing through the magnetic resistance \(R_1'\) / mm; \(l_2\) is the effective length of the magnetic path passing through the magnetic resistance \(R_2'\) / mm; \(S_1\) is the effective cross-sectional area of the magnetic path passing through the magnetic resistance \(R_1'\) / m 2 ; \(S_2\) is the effective cross-sectional area of the magnetic path passing through the magnetic resistance \(R_2'\) / m 2 .

[0071] Then, the effective value of the output voltage value \(V_2\) of the detection coil of the four-pole variable-angle magnetic measurement probe can be expressed as:

[0072] ​

[0073] Where: V2 is the output voltage value of the detection coil of the four-pole variable-angle magnetic measurement probe / μV; ε is the induced electromotive force generated by the detection coil / μV; R D is the resistance value of the detection coil / Ω; X D is the inductive reactance value of the detection coil / Ω; K2 is the sensitivity coefficient of the four-pole variable-angle magnetic measurement probe / μV·Mpa -1 ; σ x is the normal stress in the X direction / Mpa; σ y is the normal stress in the Y direction / Mpa; c is the variable-angle proportionality coefficient.

[0074] Since the effective cross-sectional area of the magnetic circuit is affected by the magnetic circuit length and the magnitude of the excitation current, and is also affected by the manufacturing error of the probe, the variable-angle proportionality coefficient c needs to be obtained through experimental tensile calibration. K1 is the sensitivity coefficient of the four-pole vertical probe, and K2 is the sensitivity coefficient of the four-pole variable-angle magnetic measurement probe.

[0075] (3) After obtaining the values of K1, K2, and c through the unidirectional tensile calibration test, the vector stress values of the maximum principal stress σ1 and the minimum principal stress σ2 can be obtained through two calculation methods.

[0076] The specific method is as follows:

[0077] Method 1: The four-pole vertical probe measures the output voltage values in the 0° direction and the 45° direction at a single point on the plane, and the four-pole variable-angle magnetic measurement probe measures the output voltage value in the 0° direction at a single point on the plane. Combining the three obtained output voltage values, the vector stress values of the maximum principal stress σ1 and the minimum principal stress σ2 are solved. σ x and σ y The specific expressions of the normal stress and the three output voltage values are:

[0078]

[0079] When performing vector stress measurement at the same point on the plane, V0 is the output voltage value obtained by using the four-pole vertical probe along the X direction (0° direction) / μV; V 45 is the output voltage value obtained by using the four-pole vertical probe along the direction at 45° to the X direction / μV; is the output voltage value obtained by using the four-pole variable-angle magnetic measurement probe along the X direction / μV; K1 is the sensitivity coefficient under the same parameters of the four-pole vertical probe / μV·Mpa -1 ; K2 is the sensitivity coefficient under the same parameters of the four-pole variable-angle magnetic measurement probe / μV·Mpa -1 ; σ 0° and σ 90° are the magnitudes of the normal stresses corresponding to the X direction and the Y direction (90° direction) at this point / Mpa; σ45° and σ 135° are respectively the magnitudes of the normal stresses corresponding to the directions at 45° to the X - direction and the Y - direction at this point / Mpa.

[0080] Among them, the difference in principal stresses and the principal stress direction angle at the measurement point can be obtained using a quadrupole vertical probe, that is, through the above - mentioned formula ① and formula ②, we can get:

[0081]

[0082] Combining the quadrupole vertical probe and the quadrupole variable - angle magnetic - measurement probe, the magnitudes of the two normal stresses in the 0° direction and the 90° direction at the measurement point can be obtained, that is, through the above - mentioned formula ① and formula ③, we can get:

[0083]

[0084] According to the fact that the sum of any two mutually - perpendicular normal stresses within a point in elasticity is equal, that is:

[0085] σ 0° +σ 90° = σ1 + σ2;

[0086] Therefore, after obtaining the principal stress difference and the principal stress sum at a point, according to the plane - stress relationship in elasticity, the maximum principal stress σ1, the minimum principal stress σ2, and the principal stress direction angle θ can be expressed as:

[0087]

[0088] In the formula: σ1 is the maximum principal stress at a single point on the plane / Mpa; σ2 is the minimum principal stress at a single point on the plane / Mpa; θ is the principal stress direction angle of the specimen / radian (rad); K1 is the sensitivity coefficient of the quadrupole vertical probe / μV·Mpa -1 ; K2 is the sensitivity coefficient of the quadrupole variable - angle magnetic - measurement probe / μV·Mpa -1 ; is the output voltage value measured along the X - direction using the quadrupole variable - angle magnetic - measurement probe / μV; V0 is the output voltage value measured along the X - direction (0° direction) using the quadrupole vertical probe / μV; c is the variable - angle proportionality coefficient; V 45 is the output voltage value measured along the direction at 45° to the X - direction using the quadrupole vertical probe / μV.

[0089] Method 2: The quadrupole variable - angle magnetic - measurement probe rotates coaxially by 4 angles with 0° as the reference angle at a single point on the plane, each angle being separated by 45°, measures four output voltage values, and combines the four obtained output voltage values to solve the vector stress values of the maximum principal stress σ1 and the minimum principal stress σ2. σ x and σ yThe specific expressions of the normal stress and the four output voltage values are as follows:

[0090]

[0091] When performing vector stress measurement on the same point in a plane, and are the output voltage values / μV obtained by using a variable-angle probe to measure along the X direction (0° direction), the direction perpendicular to the X direction (90° direction), the direction at 45° to the X direction, and the direction at 135° to the X direction respectively; K2 is the sensitivity coefficient / μV·Mpa under the same parameters of the four-pole variable-angle magnetic measurement probe. -1 ; σ 0° and σ 90° are the magnitudes of the normal stresses corresponding to the X direction and the Y direction (90° direction) at this point / Mpa respectively; σ 45° and σ 135° are the magnitudes of the normal stresses corresponding to the directions at 45° to the X direction and the Y direction at this point / Mpa respectively.

[0092] Among them, according to the specific expressions of the above four output voltage values, it can be obtained that:

[0093]

[0094] Therefore, according to the plane stress relationship in elasticity theory, the maximum principal stress σ1, the minimum principal stress σ2, and the principal stress direction angle θ can be expressed as:

[0095]

[0096] In the formula: σ1 is the maximum principal stress at a single point in the plane / Mpa; σ2 is the minimum principal stress at a single point in the plane / Mpa; θ is the principal stress direction angle of the specimen / radian (rad); σ 0° and σ 90° are the magnitudes of the normal stresses corresponding to the X direction and the Y direction (90° direction) at this point / Mpa respectively; σ 45° and σ 135° are the magnitudes of the normal stresses corresponding to the directions at 45° to the X direction and the Y direction at this point / Mpa respectively.

[0097] The two plane vector stress magnetic measurement methods with a four-pole variable-angle magnetic measurement probe as the core of the present invention have the characteristics of more intuitively understanding the plane stress state, and avoid the cumulative error generated by using the shear stress difference method in the existing magnetic measurement methods. It has broad application prospects in the field of magnetic method for detecting residual stress.

[0098] Example 2

[0099] The conditions of this embodiment are set as follows: the material of the tensile specimen is 45# steel, with a length of 120 mm, a width of 50 mm, and a thickness of 10 mm. After annealing treatment, for the calibration tests of the four-pole vertical probe and the four-pole variable-angle magnetic measurement probe, the excitation frequency is 1000 Hz, the excitation current is 40 mA, and the lift-off height is 0.5 mm.

[0100] The specific implementation steps are as follows:

[0101] (1) Determine the X-axis and Y-axis directions:

[0102] As shown in the appendix Figure 5 , under the condition of unidirectional loading, the center position of the tensile specimen is the origin O, the tensile direction is the X-axis (0° direction), and the Y-axis is perpendicular to the X-axis.

[0103] (2) Determine the sensitivity coefficient K1, the sensitivity coefficient K2, and the variable-angle proportionality coefficient c:

[0104] 1) Under the condition of unidirectional loading, the 0° direction of the four-pole vertical probe is parallel to the tensile direction. At this time, the output voltage value V0 and σ x -σ y are linearly related. The loading stress σ and the output voltage V0 form an approximate straight line passing through the origin, and the slope is the sensitivity coefficient K1. The specific expression of the sensitivity coefficient K1 is:

[0105]

[0106] In the formula: K1 is the sensitivity coefficient of the four-pole vertical probe / μV·Mpa -1 ; K 1i is the sensitivity coefficient corresponding to the loading stress under a single interval / μV·Mpa -1 ; n is the number of loading times; V 0i is the output voltage value in the 0° direction corresponding to the loading stress under a single interval / μV; σ i is the loading stress under a single interval / Mpa.

[0107] 2) Under the condition of unidirectional loading, the 0° direction of the four-pole variable-angle magnetic measurement probe is parallel to the tensile direction. At this time, the output voltage value and cσ x -σ y are linearly related. When the 90° direction of the four-pole variable-angle magnetic measurement probe is parallel to the tensile direction, the output voltage value and cσ x -σ y are linearly related, and the sensitivity coefficient K2 remains unchanged. The loading stress σ and the output voltage value form a straight line passing through the origin, and the slope is the sensitivity coefficient K2. The specific expression of the sensitivity coefficient K2 is:

[0108]

[0109] Where: K2 is the sensitivity coefficient of the four-pole variable-angle magnetic measurement probe / μV·Mpa -1 ; K 2i is the sensitivity coefficient corresponding to the applied stress under a single interval / μV·Mpa -1 ; n is the number of loadings; is the output voltage value in the 90° direction corresponding to the applied stress under a single interval / μV; σ i is the applied stress under a single interval / Mpa.

[0110] Therefore, the variable-angle proportionality coefficient c of the four-pole variable-angle magnetic measurement probe can be expressed as:

[0111]

[0112] Where: c is the variable-angle proportionality coefficient; c i is the variable-angle proportionality coefficient corresponding to the applied stress under a single interval; n is the number of loadings; is the output voltage value in the 90° direction corresponding to the applied stress under a single interval / μV; is the output voltage value in the 0° direction corresponding to the applied stress under a single interval / μV.

[0113] (3) Perform vector stress measurement at a single point on the plane:

[0114] Obtain the sensitivity coefficient K1 of the four-pole vertical probe, the sensitivity coefficient K2 of the four-pole variable-angle magnetic measurement probe, and the variable-angle proportionality coefficient c through a calibration test. Based on changing the ratio of the magnetic circuit lengths in the directions of the normal pressures σ x and σ y as the core, two calculation methods are proposed to solve the absolute values of the maximum principal stress σ1 and the minimum principal stress σ2 and the principal stress direction angle θ at a single point in the plane. The specific expressions are as follows:

[0115] The specific expression 1 for the absolute values of the maximum principal stress σ1 and the minimum principal stress σ2 and the principal stress direction angle θ obtained by the first calculation method is:

[0116]

[0117] Where: σ1 is the maximum principal stress at a single point on the plane / Mpa; σ2 is the minimum principal stress at a single point on the plane / Mpa; θ is the principal stress direction angle of the specimen / radian (rad); K1 is the sensitivity coefficient of the four-pole vertical probe / μV·Mpa -1 ; K2 is the sensitivity coefficient of the four-pole variable-angle magnetic measurement probe / μV·Mpa -1 ; V is the output voltage value / μV obtained by measuring along the X direction using a four-pole variable-angle magnetic probe; V0 is the output voltage value / μV obtained by measuring along the X direction (0° direction) using a four-pole vertical probe; c is the variable-angle proportionality coefficient; V 45 is the output voltage value / μV obtained by measuring along the direction at 45° to the X direction using a four-pole vertical probe.

[0118] The specific expressions two for the absolute values of the maximum principal stress σ1 and the minimum principal stress σ2 and the principal stress direction angle θ obtained by the second calculation method are as follows:

[0119]

[0120] In the formula: σ1 is the maximum principal stress at a single point on the plane / Mpa; σ2 is the minimum principal stress at a single point on the plane / Mpa; θ is the principal stress direction angle of the specimen / radian (rad); σ 0° and σ 90° are respectively the magnitudes of the normal stresses corresponding to the X direction and the Y direction (90° direction) at this point / Mpa; σ 45° and σ 135° are respectively the magnitudes of the normal stresses corresponding to the directions at 45° to the X direction and the Y direction at this point / Mpa.

[0121] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A quadrupole variable angle magnetic probe, characterized in that: include: A variable angle probe excitation magnetic core (201), a variable angle probe detection magnetic core (202) and a variable angle probe multilayer coil (203), wherein the variable angle probe multilayer coil (203) is sleeved on the variable angle probe excitation magnetic core (201) and the variable angle probe detection magnetic core (202), and a non-90° angle is formed between the variable angle probe excitation magnetic core (201) and the variable angle probe detection magnetic core (202).

2. A method for measuring plane vector stress, characterized in that: The method of measuring using the quadrupole variable angle magnetic probe as claimed in claim 1 comprises the following steps: By using a variable angle probe excitation core (201) and a variable angle probe detection core (202) in a quadrupole variable angle magnetic probe that form a non-90° angle, the normal pressure σ on the surface of the test piece is changed. x and σ y The ratio of the magnetic path length in the direction changes the normal pressure σ x and σ y The coefficient is obtained, and the vector stress measurement at a single point in the plane is performed using the first measurement method or the second measurement method to obtain the vector stress values ​​of the maximum principal stress σ1 and the minimum principal stress σ2 at the single point in the plane and the principal stress direction angle θ.

3. The method for measuring plane vector stress according to claim 2, characterized in that: The first measurement method comprises: Obtain the sensitivity coefficient K1 of the quadrupole vertical probe, the sensitivity coefficient K2 of the quadrupole variable angle magnetic probe and the variable angle proportional coefficient c; Two output voltage values ​​in the 0° and 45° directions are measured at a single point on the plane using a quadrupole vertical probe; The output voltage value in the 0° direction is measured at a single point on the plane by using a quadrupole variable angle magnetic probe; According to the three output voltage values ​​obtained, combined with the sensitivity coefficient K1, the sensitivity coefficient K2 and the variable angle proportional coefficient c, the vector stress values ​​of the maximum principal stress σ1 and the minimum principal stress σ2 at a single point in the plane are obtained.

4. The method for measuring plane vector stress according to claim 2, characterized in that: The second measurement method comprises: Obtain the sensitivity coefficient K2 and the variable angle proportional coefficient c of the quadrupole variable angle magnetic probe; The quadrupole variable angle magnetic probe is rotated coaxially at 45° intervals at 0° direction as the reference angle at a single point on the plane to measure four output voltage values ​​at 0°, 45°, 90° and 135° directions. According to the four output voltage values ​​obtained, combined with the sensitivity coefficient K2 and the variable angle proportional coefficient c of the quadrupole variable angle magnetic probe, the vector stress values ​​of the maximum principal stress σ1 and the minimum principal stress σ2 at a single point in the plane are obtained.

5. The method for measuring plane vector stress according to claim 3, characterized in that: The maximum principal stress σ1, minimum principal stress σ2 and principal stress direction angle θ at a single point in the plane satisfy the following formula: Where: σ1 is the maximum principal stress at a single point on the plane / Mpa; σ2 is the minimum principal stress at a single point on the plane / Mpa; θ is the principal stress direction angle of the specimen / radian; K1 is the sensitivity coefficient of the quadrupole vertical probe / μV·Mpa -1 ; K2 is the sensitivity coefficient of the quadrupole variable angle magnetic probe / μV·Mpa -1 ; is the output voltage value obtained by measuring along the X direction using a quadrupole variable angle magnetic probe / μV; V0 is the output voltage value obtained by measuring along the X direction using a quadrupole vertical probe / μV; c is the variable angle proportional coefficient; V 45 It is the output voltage value / μV measured by using a quadrupole vertical probe in a direction 45° to the X direction.

6. The method for measuring plane vector stress according to claim 4, characterized in that: The maximum principal stress σ1, minimum principal stress σ2 and principal stress direction angle θ at a single point in the plane satisfy the following formula: in, Where: σ1 is the maximum principal stress at a single point on the plane / Mpa; σ2 is the minimum principal stress at a single point on the plane / Mpa; θ is the principal stress direction angle of the specimen / radian; K2 is the sensitivity coefficient of the quadrupole variable angle magnetic probe / μV·Mpa -1 ; c is the proportional coefficient of the quadrupole variable angle probe; and are the voltage values ​​corresponding to the X and Y directions at the point / μV respectively; and are the voltage values ​​corresponding to the direction of 45° with the X direction and the Y direction at this point / μV; σ 0° and σ 90° are the normal stress magnitudes corresponding to the X and Y directions at the point / Mpa; σ 45° and σ 135° They are respectively the normal stress magnitude / Mpa corresponding to the direction at 45° to the X direction and the Y direction at this point.

7. The method for measuring plane vector stress according to claim 3 or 5, characterized in that: The sensitivity coefficient K1 is determined by a uniaxial tensile calibration test, in which the uniaxial tensile calibration test adopts a stepwise stress loading method with a stress interval of 10Mpa. The sensitivity coefficient K1 satisfies the following formula: Where: K1 is the sensitivity coefficient of the quadrupole vertical probe / μV·Mpa -1 ; K 1i is the sensitivity coefficient corresponding to the loading stress in a single interval / μV·Mpa -1 ; n is the number of loading times; V 0i is the output voltage value in the 0° direction corresponding to the loading stress under a single interval / μV; σ i is the loading stress in a single interval / Mpa.

8. The method for measuring plane vector stress according to claim 4, characterized in that: The sensitivity coefficient K2 is determined by a uniaxial tensile calibration test, in which the uniaxial tensile calibration test adopts a stepwise stress loading method with a stress interval of 10Mpa. The sensitivity coefficient K2 satisfies the following formula: Where: K2 is the sensitivity coefficient of the quadrupole variable angle magnetic probe / μV·Mpa -1 ; K 2i is the sensitivity coefficient corresponding to the loading stress in a single interval / μV·Mpa -1 ; n is the number of loading times; is the output voltage value at 90° corresponding to the loading stress under a single interval / μV; σ i is the loading stress in a single interval / Mpa.

9. The method for measuring plane vector stress according to claim 3, 4 or 5, characterized in that: The variable angle proportional coefficient c is determined by the uniaxial tensile calibration test and satisfies the following formula: Where: c is the variable angle proportional coefficient; c i is the proportional coefficient corresponding to the loading stress in a single interval; n is the number of loading times; It is the output voltage value in the 90° direction corresponding to the loading stress under a single interval / μV; It is the output voltage value in the 0° direction corresponding to the loading stress under a single interval / μV.

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