A method and apparatus for non-destructive testing based on pulsed eddy currents

Abstract

The application discloses a kind of based on pulse eddy current nondestructive testing method and device, belong to nondestructive testing field, it is rotated to the scanning of measurement point in turn by blade probe, obtains the feedback signal on different placement angle of single measurement point, and it is differentially processed to obtain corresponding difference signal, then according to the peak value of difference signal, judge whether the workpiece exists defect on the measurement point, finally according to the single or multiple difference signal collected, the direction, width, length and depth data of defect are obtained.The nondestructive testing method and device based on pulse eddy current of the application, by optimizing the shape of blade probe, and using unique rotating scanning mode, so that the blade probe can detect the length, width, depth and direction of micro crack and other parameters, while ensuring the detection efficiency, further improve the detection accuracy, improve the accuracy of detection result.

Description

Technical Field

[0001] This invention belongs to the field of nondestructive testing, specifically relating to a nondestructive testing method and apparatus based on pulsed eddy currents. Background Technology

[0002] With the advancement of science and technology, the demand for defect detection in machine parts in industrial production is constantly increasing. During use, micro-cracks caused by stress concentration can not only affect the service life of components but also threaten their safety.

[0003] Pulsed eddy current testing is a high-precision and high-sensitivity non-destructive testing method. Existing pulsed eddy current testing methods based on cylindrical or rectangular coils are ineffective at detecting micro-cracks and cannot fully and accurately determine data such as crack length, width, depth, and direction. Therefore, we designed a pulsed eddy current-based non-destructive testing method and apparatus to solve the above problems. Summary of the Invention

[0004] In response to one or more of the above-mentioned defects or improvement needs of the prior art, the present invention provides a non-destructive testing method and device based on pulsed eddy current, which utilizes the directional characteristics of the blade type and combines it with a rotary scanning method to collect feedback signals at multiple angles, thereby accurately obtaining various data of the crack.

[0005] To achieve the above objectives, the present invention provides a nondestructive testing method based on pulsed eddy currents, which includes the following steps:

[0006] S100: Calibrate the blade probe and obtain the calibration signal of the blade probe at a defect-free location;

[0007] S200: Select any measurement point on the workpiece, and use the blade probe to perform a rotational scan on the measurement point in sequence to obtain the feedback signal of a single measurement point at different placement angles;

[0008] S300: Sequentially acquires feedback signals from multiple measurement points on the workpiece;

[0009] S400: Extracts the peak values ​​of feedback signals from multiple measurement points and performs differential processing to obtain differential signals;

[0010] S500: Determine whether there is a defect in the workpiece at the measurement point based on the peak value of the differential signal;

[0011] S600: Based on the collected single or multiple differential signals, acquire data on the direction, width, length, and depth of the defect.

[0012] As a further improvement of the present invention, step S600 specifically includes the following steps:

[0013] S610: Obtain the maximum and minimum peak values ​​of the differential signal at the same measurement point;

[0014] S611: Obtain the angles corresponding to the maximum and minimum peak values ​​of the differential signal, and use this to determine the direction of the defect;

[0015] In step S611, the angle direction corresponding to the maximum peak value is parallel to the defect direction, and the angle direction corresponding to the minimum peak value is perpendicular to the defect direction.

[0016] As a further improvement of the present invention, step S600 further includes the following step:

[0017] S620: Obtain the width of the crack based on the direction of the defect and the distance between two adjacent detection points.

[0018] As a further improvement to the present invention, step S600 further includes the following step:

[0019] S630: Collects the maximum peak value of the differential signal at different measurement points to obtain depth data of multiple defects;

[0020] S631: Determine the depth change of a defect based on the depth data of multiple defects.

[0021] As a further improvement of the present invention, in step S600, obtaining the length of the defect includes the following steps:

[0022] S630: Obtain the number of measurement points that are identified as defects, and obtain the total length of the defects based on the number of measurement points and the length of the blade probe.

[0023] As a further improvement of the present invention, step S500 further includes the following step:

[0024] A threshold is set based on the calibration signal, and then the peak value of the differential signal is compared with the threshold. If the peak value exceeds the set threshold, it is determined that there is a crack; otherwise, it is determined that there is no defect.

[0025] As a further improvement of the present invention, the width of the defect is not greater than the length of the blade probe.

[0026] Based on this, the present invention also provides a non-destructive testing device for pulsed eddy currents, which includes a blade probe and a servo motor. The blade probe is mounted on the output shaft of the servo motor and rotates synchronously with the output shaft to achieve rotary scanning of the blade probe.

[0027] As a further improvement of the present invention, the blade probe includes an iron core, an excitation coil, and a receiving coil; the excitation coil and the receiving coil are respectively wound on the iron core.

[0028] As a further improvement of the present invention, the servo motor rotates by 10° each time.

[0029] The aforementioned improved technical features can be combined with each other as long as they do not conflict with each other.

[0030] In summary, the beneficial effects of the above-described technical solutions conceived by this invention compared with the prior art include:

[0031] The present invention relates to a pulsed eddy current-based nondestructive testing method and apparatus. By optimizing the shape of the blade probe and utilizing a unique rotating scanning method, the blade probe can detect parameters such as the length, width, depth, and direction of microcracks. This not only ensures testing efficiency but also further improves testing accuracy and the precision of the test results. Attached Figure Description

[0032] Figure 1 This is a flowchart of the nondestructive testing method based on pulsed eddy current in an embodiment of the present invention;

[0033] Figure 2 This is a logic block diagram of the nondestructive testing method based on pulsed eddy currents in an embodiment of the present invention;

[0034] Figure 3 This is a schematic diagram of the overall structure of the non-destructive testing device based on pulsed eddy current in an embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of the overall front view of the blade probe in the non-destructive testing device based on pulsed eddy current in an embodiment of the present invention;

[0036] Figure 5 This is a schematic diagram of the overall side view of the blade probe in the non-destructive testing device based on pulsed eddy current in an embodiment of the present invention;

[0037] Figure 6 This is a peak value diagram of differential signals at some measurement points in the non-destructive testing method based on pulsed eddy currents in this embodiment of the invention;

[0038] In all the accompanying drawings, the same reference numerals denote the same technical features, specifically: 1, servo motor; 2, blade probe; 21, iron core; 22, excitation coil; 23, receiving coil. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0040] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0042] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0043] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0044] Example:

[0045] Please see Figure 1 and Figure 2 The pulsed eddy current-based nondestructive testing method in the preferred embodiment of the present invention utilizes the directionality of the blade probe, combined with the blade probe's special rotational detection method, to obtain more complete and accurate crack information, thereby achieving rapid and accurate detection.

[0046] Specifically, the non-destructive testing method of the present invention includes the following steps:

[0047] S100: Calibrate the blade probe 2 and obtain the calibration signal of the blade probe 2 at a defect-free location.

[0048] Before actual use, the blade probe 2 needs to be calibrated to obtain the calibration signal of the blade probe 2 at the defect-free detection area, and use this as the standard data. The signal threshold is also set to facilitate subsequent comparison with the acquired signal to determine whether there are defects on the surface of the workpiece.

[0049] S200: Select any measurement point on the workpiece, and use the blade probe 2 to perform a rotational scan on the measurement point in sequence to obtain the feedback signal of a single measurement point at different placement angles.

[0050] Specifically, in step S200, after the blade probe 2 moves to the measurement point on the workpiece surface, it rotates via the servo motor 1 set on its top. The rotation method is to rotate around the measurement point as the center and acquire multiple sets of signals at the measurement point.

[0051] It is important to understand that during the entire process of the blade probe 2 rotating with the servo motor 1, the servo motor 1 preferably uses an intermittent rotation acquisition method, that is, it rotates a certain angle and then stops, and then acquires data through the blade probe 2 again. When the servo motor 1 adjusts the angle of the blade probe 2 for the same measurement point, the angle of rotation is preferably the same each time. Of course, in actual operation, the rotation of the blade probe 2 is often combined with linear motion, that is, the blade probe 2 rotates while moving along the surface of the workpiece.

[0052] S300: Sequentially collects feedback signals from multiple measurement points on the workpiece.

[0053] In the actual design process, measurement points can be set on the workpiece surface after observation. Alternatively, the operator can obtain the workpiece's dimensional information beforehand and then use the blade probe 2 to scan the workpiece according to its size and shape.

[0054] S400: Extracts the peak values ​​of feedback signals from multiple measurement points and performs differential processing to obtain differential signals.

[0055] As those skilled in the art would readily grasp the steps of differential processing the acquired feedback signal to obtain a differential signal, they will not be elaborated upon here.

[0056] S500: Based on the peak value of the differential signal, determine whether there is a defect in the workpiece at the measurement point.

[0057] Step S500 further includes the following steps:

[0058] A threshold is set based on the calibration signal, and then the peak value of the differential signal is compared with the threshold value obtained using the calibration signal in step S100 to determine whether there is a defect in the workpiece. If the peak value exceeds the set threshold, it is determined that there is a crack; otherwise, it is determined that there is no defect.

[0059] S600: Based on the collected single or multiple differential signals, acquire data on the direction, width, length, and depth of the defect.

[0060] The following provides further explanation regarding the direction, width, length, and depth data of the defects.

[0061] Firstly, when determining the direction of a defect, the following steps are included:

[0062] S610: Obtain the maximum and minimum peak values ​​of the differential signal at the same measurement point;

[0063] S611: Obtain the angles corresponding to the maximum and minimum peak values ​​of the differential signal, and use this to determine the direction of the defect.

[0064] In step S611, the angle direction corresponding to the maximum peak value is parallel to the defect direction, and the angle direction corresponding to the minimum peak value is perpendicular to the defect direction.

[0065] Understandably, given that the length of the blade probe 2 is greater than the crack width, due to the rotation of the blade probe 2, it will advance along the workpiece surface in a rotating manner. During this process, two extreme states occur: the blade probe 2 is parallel to the crack direction or perpendicular to the crack direction. When the blade probe 2 is perpendicular to the crack direction, it can only partially detect the crack, thus its corresponding detection peak is the minimum. After finding the position of the minimum peak, its angle information is obtained, and the crack direction can be deduced through orthogonal relationships and related angle information. Furthermore, when the blade probe 2 is parallel to the rectangular blade probe 2, the detection peak is the maximum; therefore, the angle of the maximum detected peak is the crack direction.

[0066] Furthermore, the acquisition of crack width data specifically includes the following steps:

[0067] S620: Obtain the width of the crack based on the direction of the defect and the distance between two adjacent detection points.

[0068] It is understandable that the width of the crack can be easily obtained through the waveform phase, a method that those skilled in the art can master and will not be elaborated upon here.

[0069] Furthermore, the acquisition of crack depth data includes the following steps:

[0070] S630: Collects the maximum peak value of the differential signal at different measurement points to obtain depth data of multiple defects;

[0071] S631: Determine the depth change of a defect based on the depth data of multiple defects.

[0072] In step S600, obtaining the crack length specifically includes the following steps:

[0073] S630: Obtain the number of measurement points identified as defects, and obtain the total length of the defects based on the number of measurement points and the length of the blade probe 2.

[0074] It is worth noting that the detection method in the preferred embodiment of the present invention can only be implemented in a rotating scanning manner when the width of the defect is not greater than the length of the blade probe 2. Therefore, the detection method of the present invention is mainly used for scanning and detecting fine cracks.

[0075] Based on this, please refer to Figures 3-5 The present invention also provides a non-destructive testing device for pulsed eddy currents, which includes a blade probe 2 and a servo motor 1. The blade probe 2 is mounted on the output shaft of the servo motor 1 and rotates synchronously with the output shaft to realize the rotational scanning of the blade probe 2.

[0076] Preferably, the blade probe 2 is a blade-type blade probe 2, which has a smaller width compared to the traditional rectangular blade probe 2, making it more suitable for detecting fine cracks and thus improving the sensitivity of the blade probe 2.

[0077] More specifically, the blade probe 2 includes an iron core 21, an excitation coil 22, and a receiving coil 23; the excitation coil 22 and the receiving coil 23 are respectively wound on the iron core 21.

[0078] In practical use, operators can mount the device onto a robotic arm or other drive mechanism, allowing the device to move along the surface of the workpiece to perform scanning and inspection. Preferably, the servo motor 1 rotates 10° at a time. It should be understood that the rotation angle of the servo motor 1 is related to factors such as the overall movement speed of the device and can be flexibly adjusted according to requirements such as detection rate and accuracy.

[0079] The present invention relates to a pulsed eddy current-based nondestructive testing method and apparatus. By optimizing the shape of the blade probe and utilizing a unique rotating scanning method, the blade probe can detect parameters such as the length, width, depth, and direction of microcracks. This not only ensures testing efficiency but also further improves testing accuracy and the precision of the test results.

[0080] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A nondestructive testing method based on pulsed eddy currents, characterized in that, It includes the following steps: S100: Calibrate the blade probe and obtain the calibration signal of the blade probe at a defect-free location; S200: Select any measurement point on the workpiece, and use the blade probe to perform a rotational scan on the measurement point in sequence to obtain the feedback signal of a single measurement point at different placement angles; wherein, the rotational scan is an intermittent rotational acquisition, that is, it stops after rotating a certain angle, and then the blade probe is used to acquire data again, and the rotation of the blade probe is combined with the linear motion. S300: Sequentially acquires feedback signals from multiple measurement points on the workpiece; S400: Extracts the peak values ​​of feedback signals from multiple measurement points and performs differential processing to obtain differential signals; S500: Determine whether there is a defect in the workpiece at the measurement point based on the peak value of the differential signal; Step S500 specifically includes the following steps: setting a threshold based on the calibration signal, then comparing the peak value of the differential signal with the threshold value; if the peak value exceeds the set threshold value, it is determined that there is a crack; otherwise, it is determined that there is no defect. S600: Based on the collected single or multiple differential signals, acquire data on the direction, width, length, and depth of the defect; Step S600 specifically includes the following steps: S610: Obtain the maximum and minimum peak values ​​of the differential signal at the same measurement point; S611: Obtain the angles corresponding to the maximum and minimum peak values ​​of the differential signal, and use this to determine the direction of the defect; In step S611, the angle direction corresponding to the maximum peak value is parallel to the defect direction, and the angle direction corresponding to the minimum peak value is perpendicular to the defect direction. S620: Obtain the width of the crack based on the direction of the defect and the distance between two adjacent detection points; S630: Collects the maximum peak value of the differential signal at different measurement points to obtain depth data of multiple defects; S631: Determine the depth change of a defect based on the depth data of multiple defects; In step S600, obtaining the length of the defect includes the following steps: The number of measurement points identified as defects is obtained, and the total length of the defects is obtained based on the number of measurement points and the length of the blade probe.

2. The nondestructive testing method based on pulsed eddy currents according to claim 1, characterized in that, The width of the defect is no greater than the length of the blade probe.

3. The nondestructive testing method based on pulsed eddy currents according to claim 1, characterized in that, The non-destructive testing is performed using a pulsed eddy current testing device, which includes a blade probe and a servo motor. The blade probe is mounted on the output shaft of the servo motor and rotates synchronously with the output shaft to achieve a rotary scanning of the blade probe.

4. The nondestructive testing method based on pulsed eddy currents according to claim 3, characterized in that, The blade probe includes an iron core, an excitation coil, and a receiving coil; the excitation coil and the receiving coil are respectively wound on the iron core.

5. The nondestructive testing method based on pulsed eddy currents according to claim 4, characterized in that, The servo motor rotates 10° each time.

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