Interval-adjustable stacked eddy current probe and quantitative evaluation method of multiple characteristic parameters of probe

Abstract

The present invention discloses an interval-adjustable stacked eddy current probe and a quantitative evaluation method for multiple characteristic parameters of the probe, which relate to the field of non-destructive testing technology. The probe includes a box body, a lower coil group, an upper coil group, a distance adjustment component, an excitation end and a receiving end, and the fixed interval between the lower coil group and the upper coil group is adjusted by the distance adjustment component. By measuring and calculating the part to be tested, the steady-state eddy current response signal under the corresponding multiple characteristic parameters is obtained and a probe lift-off / defect multiple characteristic parameter eddy current response signal database is established; the database is used to establish a rapid calculation model for the multiple characteristic parameter changes of the eddy current response signal, and combined with the improved particle swarm optimization algorithm to optimize and obtain accurate defect parameters. The present invention can effectively reduce the evaluation error caused by the lift-off value deviation, and compared with the traditional single-coil probe mapping method, the evaluation result of the defect parameter is more accurate.

Description

Technical Field

[0001] The present invention relates to the technical field of nondestructive testing, and in particular to a stacked eddy current probe with adjustable spacing and a quantitative evaluation method for probe lift-off / defect multi-characteristic parameters. Background Art

[0002] Non-destructive testing technology can use physical or chemical methods and instruments to inspect and test the defects, chemical and physical conditions of materials, parts and equipment without damaging or affecting the performance of the object being tested.

[0003] Eddy current testing technology is a non-destructive testing technology based on the principle of electromagnetic induction and is suitable for conductive materials. When a coil carrying an alternating current is placed near a conductive test piece, the alternating magnetic field around the coil will generate eddy currents in the workpiece. Similarly, the secondary magnetic field generated by the eddy current will generate a reaction current in the coil. When the internal state of the workpiece changes, the eddy current will be redistributed. The principle is as shown in the attached figure. Figure 1 By measuring the electromagnetic physical quantities caused by eddy current disturbances, it is possible to perform tests such as flaw detection on the test piece.

[0004] The effectiveness of eddy current testing technology is influenced by numerous factors, including the conductivity and magnetic permeability of the test object; the size and location of the defect; and the probe placement and lift-off value. In engineering applications, eddy current testing maintains an appropriate lift-off distance between the probe and the test object, collecting test signals to assess defects. However, in actual testing, precise control of the probe lift-off value is difficult, directly impacting the final defect assessment results.

[0005] The traditional method of eddy current testing is to conduct multiple experiments on standard test parts at a calibrated lift-off value to obtain the test signal values ​​under different defect parameters, establish a mapping relationship between the defect parameters and the test signal based on the raw data obtained from the experiment, and then reversely calculate the corresponding defect parameters under the calibrated lift-off value based on the actual measured test signal. However, in the actual test process, due to factors such as the surface condition of the test part and the installation error of the test device, there will be a deviation between the lift-off value during the actual test and the lift-off reference value used in the calibration. This deviation is recorded as the lift-off value deviation δ, which represents the difference between the actual lift-off value t1 of the test probe and the calibrated lift-off value t * The difference between δ and t1 is t * The deviation of the lift-off value will interfere with the quantitative evaluation of defect parameters and affect the detection effect.

[0006] The traditional eddy current detection probe uses a single coil probe to detect the eddy current field signal, which cannot avoid the influence of the probe lift-off value deviation, and the evaluation results are difficult to guarantee the accuracy. When the traditional eddy current detection probe is used to collect signals for defect depth evaluation, the attached Figure 2 The error Δd in depth evaluation of defects with different depths d is given when there is a lift-off value deviation δ. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a stacked eddy current probe with adjustable spacing and a quantitative evaluation method for multiple characteristic parameters of the probe, so as to effectively eliminate the adverse effects caused by the deviation of the lift-off value and improve the accuracy of the evaluation effect.

[0008] To solve the above technical problems, according to one aspect of the present invention, a stacked eddy current probe with adjustable spacing is provided, comprising:

[0009] The box body has a columnar hollow fixing groove vertically arranged inside the box body;

[0010] The lower coil group and the upper coil group are spaced apart and arranged inside the fixed groove, wherein the lower coil group is fixed to the bottom of the fixed groove, and the upper coil group is slidably connected inside the fixed groove; the upper coil group and the lower coil group have the same structure, both consisting of a receiving coil and an excitation coil nested together, and both the receiving coil and the excitation coil include a coil skeleton and a coil;

[0011] The pitch adjustment assembly includes a fixed sleeve, a movable sleeve and a screw; the fixed sleeve is fixedly connected to the upper part of the box body, the movable sleeve is threadedly connected to the fixed sleeve, the screw is fixedly connected to the bottom of the movable sleeve, and the screw passes downward through the fixed sleeve and is connected to the upper coil assembly;

[0012] The excitation end and the receiving end, one group of the excitation end and the receiving end are connected to the upper coil group, and the other group of the excitation end and the receiving end are connected to the lower coil group.

[0013] Furthermore, the box body includes an upper box body and a lower box body, and the fixing groove is installed in the middle of the lower box body.

[0014] Furthermore, the fixed sleeve is fixedly connected to the top center of the upper box body.

[0015] Furthermore, the pitch of the thread connecting the movable sleeve and the fixed sleeve is 0.5 mm, the wall of the fixed sleeve is vertically processed with a fixed scale, and the periphery of the movable sleeve is divided into 50 equal grids and processed into movable scales.

[0016] Furthermore, a receiving slot is provided on the outer side edge of the coil frame of the receiving coil, and the receiving coil connects the wire to the receiving end through the receiving slot; an excitation slot is provided on the outer side edge of the coil frame of the excitation coil, and the excitation coil connects the wire to the excitation end through the excitation slot.

[0017] Furthermore, a positioning groove is provided on the side edge of the coil frame of the receiving coil, and a positioning block is provided on the inner side edge of the coil frame of the exciting coil, and the positioning block is embedded in the positioning groove for positioning cooperation.

[0018] According to another aspect of the present invention, a method for quantitatively evaluating multiple characteristic parameters of a probe is provided, comprising the following steps:

[0019] Step 1: Use the above-mentioned adjustable-interval stacked eddy current probe to measure and calculate the same material to be tested with different defect parameters at different lift-off values, obtain the steady-state eddy current response signal under the corresponding multiple characteristic parameters, and build a database;

[0020] Step 2: Using the database obtained in the above steps to establish a fast calculation model for multiple characteristic parameters of eddy current response signals using spline interpolation method;

[0021] Step 3: Use the adjustable interval stacked eddy current probe to obtain the signal values ​​to be detected of the lower coil group receiving coil and the upper coil group receiving coil respectively. And initialize the defect parameters;

[0022] Step 4: Substitute the initialization parameters of the defect into the fast calculation model to obtain the lower coil group receiving coil prediction signal V1(G, t1) and the upper coil group receiving coil prediction signal V2(G, t1+t0), where G is a vector composed of multiple defect characteristic parameters, t0 is the fixed interval maintained by the upper coil group and the lower coil group, and t1 is the constant lift-off value t1; and based on the eddy current response signal value to be detected, the improved particle swarm optimization algorithm is used to calculate the initial fitness value of the defect particle:

[0023] Step 5: Introduce random decision number P for probability control to determine whether to enter the crossover mutation operation: Among them, n is the current iteration number, n max is the maximum number of iterations; if rand(0,1)≥P, then the defective particles are sorted in ascending order according to the fitness value, the first 50% of the defective particles are used as the optimal solution group for crossover operation, and the rest are used as the inferior solution group for mutation operation, and a new population is generated and merged with the initial population under the current number of iterations to form an expanded population, and the first half of the defective particles with the highest fitness are selected as the elite population for update iteration until rand(0,1) is satisfied. <P;

[0024] Step 6: Calculate the fitness value. If it does not meet the preset minimum precision error requirement ε, update the speed and position of the defective particles of the improved particle swarm optimization algorithm, and return to step 4 for multiple iterations. If the minimum precision error is met, end the iteration and output the optimal solution of the defect parameters after the current optimization update.

[0025] In step 1, the signal values ​​of different lift-off values ​​t1 under the current defect characteristic parameters are collected to obtain the data set in t1=0,0.1,0.2,…tmax , t max The maximum lift-off value allowed for the probe was set, defect characteristic parameters were changed, multiple data sets were obtained, and a database was constructed.

[0026] Furthermore, the vector G formed by the multiple characteristic parameters of the defect includes defect depth d, defect length a, defect width w, defect angle θ, and plane position (x, y) of the defect.

[0027] Furthermore, the fast calculation model is:

[0028] Based on the discrete sample data of the database, the spline interpolation method is used to establish three-dimensional response surfaces of each defect characteristic parameter, lift-off value and eddy current response signal. Multiple response surfaces together constitute a rapid calculation model for multiple characteristic parameters of eddy current response signals.

[0029] The quantitative evaluation method for multiple characteristic parameters of probe lift-off / defects proposed in the present invention obtains steady-state eddy current response signals under different parameter conditions based on the designed interval-adjustable stacked eddy current probe, and establishes a fast calculation model through interpolation method to optimize the evaluation results by improving the particle swarm optimization algorithm.

[0030] The present invention can effectively reduce the evaluation error caused by the deviation of the lift-off value. Compared with the traditional single-coil probe mapping method, the evaluation results of the defect parameters are more accurate.

[0031] The present invention is applicable to the quantitative evaluation of defect conditions in the case of actual existence of lift-off value deviation, and can meet the requirements of engineering measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the principle diagram of eddy current detection.

[0033] Figure 2 It is an error diagram for depth evaluation of defects at different depths when there is a deviation in the lift-off value.

[0034] Figure 3 Schematic diagram of the structure of the adjustable interval stacked eddy current probe of the present invention, wherein: Figure 3 (a) is the main structure diagram of the probe. Figure 3 (b) is the specific structure diagram of the spiral pitch head. Figure 3 (c) is a schematic diagram of the lower coil group structure.

[0035] Figure 4 The present invention is based on the steady-state eddy current response signal acquisition process of the interval-adjustable stacked eddy current probe.

[0036] Figure 5 This is a comparison chart of the evaluation effects of the probe lift-off / defect multi-feature parameter quantitative evaluation method of the present invention and the traditional method under the influence of lift-off value deviation, where: Figure 5 (a) is the evaluation effect diagram of the traditional method. Figure 5 (b) is an evaluation effect diagram of the method of the present invention.

[0037] Figure 6 This is a comparison chart of the evaluation effects of the probe lift-off / defect multi-feature parameter quantitative evaluation method of the present invention and the traditional method under the influence of defect depth, where: Figure 6 (a) is the evaluation effect diagram of the traditional method. Figure 6 (b) is an evaluation effect diagram of the method of the present invention.

[0038] Figure 7 This is a flow chart for quantitative evaluation of defect parameters based on the steady-state eddy current response signal of stacked eddy current probes with adjustable spacing, where: Figure 7 (a) is the algorithm flow chart, Figure 7 (b) is the flow chart of the overall evaluation method.

[0039] Figure 8 is a schematic diagram of rectangular defects and parameters, where Figure 8 (a) is a schematic diagram of a three-dimensional coordinate system. Figure 8 (b) is the main view of the rectangular defect and its parameters. Figure 8 (c) is a top view showing the rectangular defect and its parameters.

[0040] In the figure: 1-upper box body; 2-lower box body; 3-lower coil group; 4-upper coil group; 5-pitch adjustment component; 6-fixed slot; 7-excitation end; 8-receiving end; 3A-receiving coil; 3B-excitation coil; 3C-positioning slot; 3D-receiving slot; 3E-excitation slot; 5A-fixed sleeve; 5B-fixed scale; 5C-movable sleeve; 5D-movable scale; 5E-screw; 5F-pitch adjustment knob, 9-signal generator, 10-power amplifier, 11-part to be tested, 12-oscilloscope, 13-data acquisition card. DETAILED DESCRIPTION

[0041] A typical embodiment of the present invention provides an adjustable-interval stacked eddy current probe, which includes a box body, a lower coil group 3, an upper coil group 4, a distance adjustment component 5, an excitation end 7 and a receiving end 8.

[0042] like Figure 3 (a) Figure 3 As shown in Figure (b), the box body comprises an upper box body 1 and a lower box body 2. The upper box body 1 and the lower box body 2 can be installed and fastened with screws, and can be disassembled and installed multiple times, making it convenient for testers to adjust and replace coil parameter configurations. A cylindrical hollow fixing slot 6 is vertically provided in the middle of the lower box body 2.

[0043] like Figure 3As shown in (b), the lower coil assembly 3 and the upper coil assembly 4 are spaced apart and arranged inside the fixing groove 6, and the fixing groove 6 limits the upper coil assembly 4 and the lower coil assembly 3. Among them, the lower coil assembly 3 is fixed to the bottom of the fixing groove 6, and the upper coil assembly 3 is slidably connected inside the fixing groove 6.

[0044] The upper coil group 4 and the lower coil group 3 have the same structure, both consisting of a receiving coil and an excitation coil nested together, both the receiving coil and the excitation coil include a coil skeleton and a coil, and both coils are wound with thin copper wire. Figure 3 As shown in (c), the lower coil group 3 is composed of a receiving coil 3A and an exciting coil 3B nested together, and the receiving coil 3A is nested inside the exciting coil 3B.

[0045] The distance adjustment component 5 is used to adjust the fixed distance between the lower coil group 3 and the upper coil group 4. Figure 3 As shown in (b), the pitch adjustment assembly 5 includes a fixed sleeve 5A, a movable sleeve 5C and a screw 5E.

[0046] The fixed sleeve 5A is fixedly connected to the upper portion of the box body. Specifically, the fixed sleeve 5A is fixedly connected to the top center of the upper box body 1 .

[0047] The movable sleeve 5C is threadedly connected to the fixed sleeve 5A. Figure 3 As shown in (b), an external thread is machined on the upper end of the fixed sleeve 5A, and an internal thread matching the external thread is machined on the inner upper portion of the movable sleeve 5C. The movable sleeve 5C is sleeved onto the outside of the fixed sleeve 5A.

[0048] Screw 5E is fixedly connected to the bottom of movable sleeve 5C. Screw 5E passes downward through fixed sleeve 5A and connects to upper coil assembly 4. The circumferential rotation of movable sleeve 5C around fixed sleeve 5A controls the axial movement of screw 5E, thereby driving the movement of upper coil assembly 4 and achieving quantitative control of the fixed spacing between lower coil assembly 3 and upper coil assembly 4.

[0049] In order to facilitate the rotation of the movable sleeve 5C, the outer diameter of the upper portion of the movable sleeve 5C is enlarged to form a pitch adjustment knob 5F.

[0050] like Figure 3 (a) Figure 3 As shown in Figure (b), a straight-head, straight-foot antenna mount is mounted at each corner of the upper housing 1. Two antenna mounts form a group, with one antenna mount in each group serving as the probe's excitation terminal 7 and the other antenna mount serving as the receiving terminal 8. The excitation and receiving terminals of one group are connected to the excitation coil and receiving coil of the upper coil assembly, respectively, while the excitation and receiving terminals of the other group are connected to the excitation coil and receiving coil of the lower coil assembly, respectively.

[0051] like Figure 4As shown, when the interval-adjustable stacked eddy current probe provided in the above embodiment is used for detection, a sinusoidal low-frequency AC signal is input by the signal generator 9, the gain of the power amplifier 10 is adjusted, and the voltage signal is amplified and output to the two excitation ends 7 of the probe. After the test piece 11 is tested, the oscilloscope 12 or the data acquisition card 13 collects the voltage response signals of the two receiving coils, and finally post-processes them through a computer to obtain the voltage amplitude under the current parameters.

[0052] In a preferred embodiment, the pitch of the thread connecting the movable sleeve 5C and the fixed sleeve 5A is 0.5 mm. Figure 3 As shown in Figure (b), the wall of fixed sleeve 5A is machined with fixed scale 5B vertically. The circumference of movable sleeve 5C is divided into 50 equally spaced grids, forming movable scale 5D. By reading the scale lines, quantitative control of the fixed spacing between lower coil assembly 3 and upper coil assembly 4 is easily achieved. The spacing can be varied from 0 mm to 5 mm, with an accuracy of 0.01 mm.

[0053] In another preferred embodiment, in order to facilitate the lead-out of the wire, a receiving slot is opened on the outer side edge of the coil frame of the receiving coil, and the receiving coil connects the wire to the receiving end through the receiving slot; an excitation slot is opened on the outer side edge of the coil frame of the excitation coil, and the excitation coil connects the wire to the excitation end through the excitation slot.

[0054] To ensure the coaxiality of the receiving coil and the exciting coil, a positioning groove is provided on the side edge of the coil frame of the receiving coil, and a positioning block is provided on the inner side edge of the coil frame of the exciting coil. The positioning block is embedded in the positioning groove for positioning.

[0055] Take coil group 3 as an example. Figure 3 As shown in Figure (c), the coil bobbin of the receiving coil 3A inside the lower coil assembly 3 has a positioning slot 3C. During installation, the positioning slot 3C aligns with the coil bobbin of the external excitation coil 3B. The receiving coil 3A is connected to the antenna pedestal 8 at the receiving end through a side receiving slot 3D, while the excitation coil 3B is connected to the antenna pedestal 7 at the excitation end through an excitation slot 3E.

[0056] Another typical embodiment of the present invention provides a method for quantitatively evaluating multiple characteristic parameters of probe lift-off / defects based on the above-mentioned adjustable interval stacked eddy current probe. Figure 7 、 Figure 8 As shown in the figure, the basic concept is to measure and calculate the test piece, obtain the steady-state eddy current response signal corresponding to multiple characteristic parameters, and establish a database of eddy current response signals with multiple characteristic parameters for probe lift-off and defects. This database is used to establish a rapid calculation model for the changes in multiple characteristic parameters of the eddy current response signal, and then, combined with an improved particle swarm optimization algorithm, optimize the model to obtain accurate defect parameters. The following uses the detection of rectangular defects as an example to illustrate the specific detection principle.

[0057] Step 1: Use an adjustable-interval stacked eddy current probe to measure and calculate the test piece of the same material with different defect parameters at different lift-off values, obtain the steady-state eddy current response signal under the corresponding multi-characteristic parameters, and build a database.

[0058] As attached Figure 8 As shown, a coordinate system is established as shown in the figure. The length, width and height of the part to be tested are expressed as L×W×H respectively. The rectangular defect is taken at the center of the part to be tested. The angle between the long side of the defect and the x-axis of the coordinate system is recorded as the defect angle θ, and the range of θ is 0° to 180°. The vector composed of multiple characteristic parameters of the defect is recorded as G, including the defect depth d, defect length a, defect width w, defect angle θ, and the plane position of the defect (x, y). The upper and lower coil groups of the detection probe maintain a fixed interval t0, and the defects are detected at a constant speed with a constant lift-off value t1. The voltage amplitude is recorded as the lower receiving coil signal value V1 and the upper receiving coil signal value V2. The signal values ​​of different lift-off values ​​t1 under the current defect characteristic parameters are collected to obtain a data set. Get the dataset in t1=0,0.1,0.2,…t max , t max Allow the maximum lift-off value for the probe. Change the defect characteristic parameters, obtain multiple data sets and build a database.

[0059] Step 2: Use the spline interpolation method to build a fast calculation model for multiple characteristic parameters of eddy current response signals using the database obtained in the above steps.

[0060] Based on the discrete sample data of the database, the spline interpolation method is used to establish three-dimensional response surfaces of each defect characteristic parameter, lift-off value and eddy current response signal. Multiple response surfaces together constitute a rapid calculation model for multiple characteristic parameters of eddy current response signals.

[0061] Step 3: Use the adjustable interval stacked eddy current probe to obtain the signal values ​​to be detected from the lower receiving coil and the upper receiving coil respectively. And initialize the defect parameters.

[0062] Step 4: Substitute the initialization parameters of the defect into the fast calculation model to obtain the lower receiving coil prediction signal V1(G, t1) and the upper receiving coil prediction signal V2(G, t1+t0); and based on the eddy current response signal value to be detected, use the improved particle swarm optimization algorithm to calculate the initial fitness value of the defect particle:

[0063] Step 5: Introduce the random decision number P for probability control to determine whether to enter the crossover mutation operation: Where n is the current iteration number, n maxis the maximum number of iterations; if rand(0,1)≥P, then the defective particles are sorted in ascending order according to the fitness value, the first 50% of the defective particles are used as the optimal solution group for crossover operation, and the rest are used as the inferior solution group for mutation operation, and a new population is generated and merged with the initial population under the current number of iterations to form an expanded population, and the first half of the defective particles with the highest fitness are selected as the elite population for update iteration until rand(0,1) is satisfied. <P。

[0064] Step 6: Calculate the fitness value. If it does not meet the preset minimum precision error requirement ε, update the speed and position of the defective particles of the improved particle swarm optimization algorithm and return to step 4 for multiple iterations. If the minimum precision error is met, end the iteration and output the optimal solution of the defect parameters after the current optimization update.

[0065] Taking the evaluation error of defect depth as an example, the probe lift-off / defect multi-characteristic parameter quantitative evaluation method provided by the present invention is compared with the traditional method.

[0066] As attached Figure 5 As shown, As the evaluation error value, d * The defect depth is evaluated, d is the actual defect depth, and δ is the lift-off value deviation. 0.6mm is taken as the calibration lift-off value t * , the steady-state eddy current response signals obtained under different lift-off values ​​are substituted into the two evaluation methods, and the evaluation errors of the two methods are calculated as the vertical coordinates. Figure 5 (a) It can be seen that in actual engineering tests, a small deviation in the lift-off value of the single-coil probe mapping method will significantly affect the evaluation results. In the evaluation of the three selected groups of defect depths, the maximum error can reach -85.458%. Therefore, the single-coil probe mapping method cannot accurately reflect the actual defect depth. Figure 5 (b) shows the evaluation error analysis of the method of the present invention, where the maximum evaluation error is only 8.6%, proving that the dual-coil-based evaluation method effectively eliminates the negative impact of the lift-off value deviation.

[0067] Attachment Figure 6 The influence of the defect depth on the two evaluation methods. At this time, the calibration lift-off value t * The voltage signals obtained at different actual defect depths d are substituted into the two evaluation methods to obtain the defect depth d after evaluation. * , the evaluation errors of the two methods are calculated as the vertical coordinate. Figure 6(a) It can be seen that the single-coil probe mapping method has a large evaluation error at any defect depth. In particular, when the defect depth d is 0.2mm, the evaluation error can reach -85.43% when the lift-off deviation δ is -0.4mm. Therefore, it is difficult to determine the actual defect depth based on the traditional method in actual measurement. Figure 6 As shown in Figure (b), the evaluation error remains virtually unchanged with changes in defect depth. Under the influence of liftoff deviation, the maximum error does not exceed 6.85%—for a defect depth d of 0.4 mm and a liftoff deviation δ of 0.2 mm. This demonstrates that the dual-coil evaluation method is virtually unaffected by defect depth in actual testing.

[0068] In summary, it is proved that the evaluation method based on the stacked eddy current probe with adjustable intervals proposed in the present invention effectively reduces the negative impact caused by the deviation of the lift-off value, meets the requirements of engineering measurement, and is suitable for quantitative evaluation of defect conditions when there is actually a deviation of the lift-off value.

Claims

1. A stacked eddy current probe with adjustable spacing, comprising: The box body has a columnar hollow fixing groove vertically arranged inside the box body; The lower coil group and the upper coil group are spaced apart and arranged inside the fixed groove, wherein the lower coil group is fixed to the bottom of the fixed groove, and the upper coil group is slidably connected inside the fixed groove; the upper coil group and the lower coil group have the same structure, both consisting of a receiving coil and an excitation coil nested together, and both the receiving coil and the excitation coil include a coil skeleton and a coil; The pitch adjustment assembly includes a fixed sleeve, a movable sleeve and a screw; the fixed sleeve is fixedly connected to the upper part of the box body, the movable sleeve is threadedly connected to the fixed sleeve, the screw is fixedly connected to the bottom of the movable sleeve, and the screw passes downward through the fixed sleeve and is connected to the upper coil assembly; The excitation end and the receiving end, one group of the excitation end and the receiving end are connected to the upper coil group, and the other group of the excitation end and the receiving end are connected to the lower coil group.

2. The adjustable interval stacked eddy current probe according to claim 1, characterized in that: The box body comprises an upper box body and a lower box body, and the fixing groove is installed in the middle of the lower box body.

3. The adjustable interval stacked eddy current probe according to claim 2, characterized in that: The fixed sleeve is fixedly connected to the top center of the upper box body.

4. The adjustable interval stacked eddy current probe according to claim 1, 2 or 3, characterized in that: The pitch of the thread connecting the movable sleeve and the fixed sleeve is 0.5mm. The wall of the fixed sleeve is vertically processed with a fixed scale, and the periphery of the movable sleeve is divided into 50 equal grids to form a movable scale.

5. The adjustable interval stacked eddy current probe according to claim 4, characterized in that: The outer side edge of the coil frame of the receiving coil is provided with a receiving notch, and the receiving coil connects the wire to the receiving end through the receiving notch; the outer side edge of the coil frame of the excitation coil is provided with an excitation notch, and the excitation coil connects the wire to the excitation end through the excitation notch.

6. The adjustable interval stacked eddy current probe according to claim 5, characterized in that: A positioning groove is provided on the side edge of the coil frame of the receiving coil, and a positioning block is provided on the inner side edge of the coil frame of the exciting coil. The positioning block is embedded in the positioning groove for positioning cooperation.

7. A method for quantitatively evaluating multiple characteristic parameters of a probe, characterized in that: The following steps are involved: Step 1: Using the adjustable-interval stacked eddy current probe according to any one of claims 1 to 6, measurement and calculation are performed on the test piece of the same material with different defect parameters at different lift-off values ​​to obtain steady-state eddy current response signals corresponding to multiple characteristic parameters, and construct a database; Step 2: Using the database obtained in the above steps to establish a fast calculation model for multiple characteristic parameters of eddy current response signals using spline interpolation method; Step 3: Use the adjustable interval stacked eddy current probe to obtain the signal values ​​to be detected of the lower coil group receiving coil and the upper coil group receiving coil respectively. And initialize the defect parameters; Step 4: Substitute the initialization parameters of the defect into the fast calculation model to obtain the lower coil group receiving coil prediction signal V1(G, t1) and the upper coil group receiving coil prediction signal V2(G, t1+t0), where G is a vector composed of multiple defect characteristic parameters, t0 is the fixed interval maintained by the upper coil group and the lower coil group, and t1 is the constant lift-off value t1; and based on the eddy current response signal value to be detected, the improved particle swarm optimization algorithm is used to calculate the initial fitness value of the defect particle: Step 5: Introduce random decision number P for probability control to determine whether to enter the crossover mutation operation: Among them, n is the current iteration number, n max is the maximum number of iterations; if rand(0,1)≥P, then the defective particles are sorted in ascending order according to the fitness value, the first 50% of the defective particles are used as the optimal solution group for crossover operation, and the rest are used as the inferior solution group for mutation operation, and a new population is generated and merged with the initial population under the current number of iterations to form an expanded population, and the first half of the defective particles with the highest fitness are selected as the elite population for update iteration until rand(0,1) is satisfied. <P; Step 6: Calculate the fitness value. If it does not meet the preset minimum precision error requirement ε, update the speed and position of the defective particles of the improved particle swarm optimization algorithm, and return to step 4 for multiple iterations. If the minimum precision error is met, end the iteration and output the optimal solution of the defect parameters after the current optimization update.

8. The method for quantitatively evaluating multiple characteristic parameters of a probe according to claim 7, wherein: In step 1, the signal values ​​of different lift-off values ​​t1 under the current defect characteristic parameters are collected to obtain the data set in t max The maximum lift-off value allowed for the probe was set, defect characteristic parameters were changed, multiple data sets were obtained, and a database was constructed.

9. The method for quantitatively evaluating multiple characteristic parameters of a probe according to claim 8, characterized in that: The vector G formed by the multiple characteristic parameters of the defect includes defect depth d, defect length a, defect width w, defect angle θ, and plane position (x, y) of the defect.

10. The method for quantitatively evaluating multiple characteristic parameters of a probe according to claim 8, wherein: The fast calculation model is: based on the discrete sample data of the database, the spline interpolation method is used to establish three-dimensional response surfaces of each defect characteristic parameter, lift-off value and eddy current response signal. Multiple response surfaces together constitute a fast calculation model of multiple characteristic parameters of the eddy current response signal.

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