Workpiece curved surface micro-crack detection device and method

Abstract

The application discloses a workpiece curved surface micro-crack detection device and method. The device comprises a magnetizer placed above the curved surface of a workpiece to be detected, a flexible double-layer wire, and a sensor array. The double-layer wire comprises a lower layer wire and an upper layer wire, the lower layer wire is placed below the upper layer wire in coincidence, and the lower layer wire and the upper layer wire can independently form a closed loop for applying an alternating magnetic field to the curved surface of the workpiece to be detected when the side of the magnetizer close to the curved surface is parallel to the curved surface. The sensor array is clamped and arranged at a target position between the lower layer wire and the upper layer wire and on the side of the magnetizer close to the curved surface. The sensor array is used for detecting the magnetic induction intensity of the target position alternating magnetic field to identify the micro-crack on the curved surface of the workpiece to be detected according to the magnetic induction intensity of the target position alternating magnetic field. The device can improve the detection accuracy of the micro-crack.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of non-destructive testing, and more particularly to a device and method for detecting micro-cracks on a curved surface of a workpiece. BACKGROUND

[0002] In order to ensure the normal use of infrastructure and mechanical equipment, it is necessary to periodically conduct non-destructive testing on the ferromagnetic components thereof. Ferromagnetic components such as cold and hot rolling rolls, aircraft blades, bearing rollers, etc. not only have to withstand severe vibrations during operation, but also have to directly withstand huge alternating loads, so that vibration cracks and fatigue cracks are easily generated on the surface of these workpieces. The main features of these cracks are small depth (tens of microns), short length, easy expansion, various directions, and small detection space. The non-destructive testing of surface defects on workpieces with curved surfaces is currently an engineering difficulty and research hotspot, and therefore, there is an urgent need for a non-destructive testing method for micron-level cracks on the curved surface of a workpiece.

[0003] Electromagnetic non-destructive testing is a non-destructive testing technology that applies electromagnetic fields to interact with workpieces, and has many advantages such as non-contact, fast response, high sensitivity, and easy automation. Traditional electromagnetic non-destructive testing for micron-level cracks on the curved surface of a workpiece includes magnetic powder testing, eddy current testing, and magnetic flux leakage testing. Among them, magnetic powder testing has high precision, but is not easy to realize automation and pollutes the environment; eddy current testing is greatly affected by the environment and has a high false alarm rate; and magnetic flux leakage testing has a high degree of automation, but has a large background magnetic field and it is difficult to magnetize the curved surface of a workpiece. It can be seen that the traditional electromagnetic non-destructive testing for micron-level cracks on the curved surface of a workpiece still has problems such as low detection precision of micro-cracks and inability to be applied to complex curved surfaces. SUMMARY

[0004] In view of at least one defect or improvement demand of the prior art, the present application provides a device and method for detecting micro-cracks on the curved surface of a workpiece, which will help to improve the detection precision of micro-cracks and can be applied to the detection of micro-cracks on curved surfaces with various curvatures.

[0005] To achieve the above-mentioned purpose, according to a first aspect of the present application, a device for detecting micro-cracks on the curved surface of a workpiece is provided, which comprises:

[0006] A magnetizer is placed above the curved surface of the workpiece to be tested, and comprises a flexible double-layer wire, which comprises a lower layer of wire and an upper layer of wire. The lower layer of wire is placed below the upper layer of wire in a superimposed manner, and both the lower layer of wire and the upper layer of wire can independently form a closed loop to apply an alternating magnetic field to the curved surface of the workpiece to be tested when the magnetizer is close to the curved surface and the curved surface is parallel to each other.

[0007] A sensor array is clamped and positioned at a target location, which is between the lower and upper cabling and on the side of the magnetizer closest to the curved surface. The sensor array is used to detect the magnetic induction intensity of the AC magnetic field at the target location, so as to identify microcracks on the curved surface of the workpiece under test based on the magnetic induction intensity of the AC magnetic field at the target location.

[0008] Furthermore, the sensor array includes multiple sensing elements. The sensor array is used to detect the magnetic induction intensity of the AC magnetic field at the target location, so as to identify microcracks on the curved surface of the workpiece under test based on the magnetic induction intensity of the AC magnetic field at the target location. The sensor array is used to detect the magnetic induction intensity of the AC magnetic field at the target location when the tangential component of the background magnetic field in the spatial region where any sensing element is located is close to zero, so as to identify microcracks on the curved surface of the workpiece under test based on the magnetic induction intensity of the AC magnetic field at the target location. The tangential component is the tangential direction of the curved surface of the workpiece under test.

[0009] Furthermore, both the upper and lower layer cabling use flexible printed circuit boards and have the same structure.

[0010] Furthermore, the sensing element employs a TMR (tunneling magnetoresistance) element.

[0011] Furthermore, the sensor array is formed by arranging multiple TMR elements along the transverse direction of the workpiece to be measured.

[0012] Furthermore, the magnetizer is also used to apply an induced current field to the surface of the workpiece under test when it is parallel to the surface on the side closest to the surface. The induced current field is used to generate a secondary magnetic field. The sensor array is also used to detect the magnetic induction intensity of the secondary magnetic field at the target position, so as to identify microcracks on the surface of the workpiece under test based on the magnetic induction intensity of the secondary magnetic field at the target position.

[0013] According to a second aspect of the present invention, a method for detecting microcracks on curved surfaces of workpieces is also provided, applied to the aforementioned workpiece curved surface microcrack detection device, the method comprising:

[0014] Generate a detection excitation source. The excitation intensity of the detection excitation source is the vector sum of the excitation intensity of the lower layer cabling and the excitation intensity of the upper layer cabling.

[0015] The sensor array is set to operate in a near-zero tangential background magnetic field.

[0016] When the working environment of the sensor array is a near-zero tangential background magnetic field and the workpiece under test moves longitudinally in the detection excitation source, the output signal of the sensor array is acquired. The output signal of the sensor array includes the output signals of multiple sensing elements, which are used to characterize the magnetic induction intensity at the target position, so as to identify microcracks on the curved surface of the workpiece under test based on the magnetic induction intensity at the target position. The output signal of each sensing element is used to characterize the tangential component of the background magnetic field in its spatial region.

[0017] Furthermore, before generating the detection excitation source, the above-mentioned workpiece surface microcrack detection method also includes adjusting the side of the workpiece surface microcrack detection device close to the surface of the workpiece to be tested to be parallel to the surface of the workpiece by means of a contour control mechanism.

[0018] Furthermore, before generating the detection excitation source, the above-mentioned workpiece surface microcrack detection method also includes generating an AC first excitation current and a second excitation current through a programmable signal generator, inputting the first excitation current to the lower layer of the magnetizer and inputting the second excitation current to the upper layer of the magnetizer, wherein the first excitation current and the second excitation current have the same amplitude, the same frequency and the same phase.

[0019] Furthermore, the near-zero tangential background magnetic field indicates that the output signal of any sensing element is close to zero. Setting the working environment of the sensor array to a near-zero tangential background magnetic field includes adjusting the amplitude of the second excitation current by using a programmable signal generator while keeping the amplitude of the first excitation current constant, until the adjustment stops when the output signal of one sensing element is close to zero.

[0020] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0021] (1) The workpiece curved surface microcrack detection device provided by the present invention, by adopting a flexible double-layer wire structure magnetizer, can perform contour magnetization on the workpiece curved surface, thereby greatly overcoming the problem of signal instability caused by lift-off changes and avoiding the influence of lift-off changes on the detection accuracy of microcracks; it is also applicable to the detection of microcracks on curved surfaces of various curvatures, especially complex curved surfaces, and has a wide range of applications. Furthermore, by performing crack detection under near-zero tangential background magnetic field conditions with the sensor array, the detection accuracy of microcracks can be improved.

[0022] (2) By using a high-precision TMR element array as a sensor array, it is possible to detect micron-level cracks on curved surfaces. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of a workpiece curved surface microcrack detection device provided in an embodiment of this application;

[0025] Figure 2 A schematic flowchart illustrating a method for detecting microcracks on a workpiece curved surface, provided in an embodiment of this application;

[0026] Figure 3 A longitudinal cross-sectional schematic diagram of the spatial distribution of magnetic field lines formed above the workpiece to be tested during the detection process of the workpiece surface microcrack detection device provided in the embodiments of this application.

[0027] Figure 4 A schematic diagram illustrating the output voltage variation of a TMR element array for detecting transverse cracks on a workpiece surface with large curvature, as provided in an embodiment of this application.

[0028] Figure 5 A schematic diagram illustrating the output voltage variation of a single TMR element detecting cracks on a workpiece surface with different curvatures, as provided in an embodiment of this application.

[0029] Figure 6 This is a schematic diagram illustrating the output voltage variation of a single TMR element detecting cracks of different depths on a magnetic particle test piece, as provided in an embodiment of this application.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1 – Magnetizer, 2 – Sensor array, 3 – Workpiece to be measured, 4 – Magnetic field lines. Detailed Implementation

[0032] 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.

[0033] This application provides a device for detecting microcracks on curved surfaces of workpieces. Based on AC magnetic flux leakage detection technology, it detects microcracks on the surface of curved workpieces. These microcracks are tiny cracks with a depth on the micrometer scale (e.g., tens of micrometers). The workpiece to be tested can be a ferromagnetic component, including drill pipes, steel pipes, square steel, train rails, aircraft blades, etc.

[0034] It should be noted that the embodiments of this application are illustrated using the surface of the workpiece to be tested as a curved surface. The workpiece curved surface microcrack detection device provided in the embodiments of this application is also applicable to workpieces to be tested with a flat surface, and can detect microcracks on the flat surface of the workpiece to be tested; in addition to detecting microcracks, it can also detect cracks with a depth greater than tens of micrometers and larger, and can also detect workpiece surface defects such as pores and inclusions.

[0035] like Figure 1 As shown, the workpiece curved surface microcrack detection device includes a magnetizer 1 and a sensor array 2. The magnetizer 1 is placed above the curved surface of the workpiece 3 to be tested and includes a flexible double-layer cable, which consists of a lower cable and an upper cable. The lower cable is placed below the upper cable, and both the lower and upper cables can independently form a closed loop to apply an alternating magnetizing field to the curved surface of the workpiece 3 when the side of the magnetizer closest to the curved surface is parallel to the curved surface.

[0036] like Figure 1 As shown, the magnetizer has a tubular structure, with the lower layer of cabling positioned inside the upper layer of cabling. In other embodiments, since the double-layer cabling is flexible, the magnetizer can also be a flat plate structure or other structures, as long as the lower and upper layers of cabling can independently form a closed loop, and the lower layer of cabling is placed overlapping below the upper layer of cabling.

[0037] Specifically, since the upper and lower cabling layers are placed in an overlapping manner, the magnetizer applies an AC magnetizing field to the curved surface of the workpiece under test in a parallel superposition manner.

[0038] Furthermore, both the upper and lower ribbon cables use flexible printed circuit boards (FPCBs), and the upper and lower ribbon cables have the same structure. That is, the FPCBs used in the upper and lower ribbon cables have the same length and width, and the coils in the two FPCBs are parallel to each other and have the same number of turns.

[0039] Magnetizers employing a double-layer ribbon cable structure based on FPCB offer advantages such as high structural consistency, good flexibility, numerous turns, and small thickness. Due to the magnetizer's flexibility, when detecting microcracks on curved surfaces of workpieces, a contour-following control mechanism can be used to ensure that the shape of the microcrack detection device and the workpiece is consistent or nearly identical. Specifically, the side of the double-layer ribbon cable closest to the curved surface of the workpiece is parallel to the workpiece's surface, allowing the magnetizer to perform contour-following magnetization of the workpiece surface. This significantly overcomes the signal instability caused by lift-off variations and avoids the impact of lift-off variations on the detection accuracy of microcracks.

[0040] By employing a magnetizer with flexible characteristics, the workpiece surface microcrack detection device provided in this application embodiment can be applied to the detection of microcracks on surfaces with various curvatures, especially complex surfaces, such as surfaces with large curvature (large degree of bending) or surfaces with varying curvature (i.e., at least two curvatures exist on the surface).

[0041] like Figure 1 As shown, the sensor array 2 is clamped and positioned at the target location, which is between the lower and upper cabling and on the side of the magnetizer 1 closest to the curved surface of the workpiece 3 to be measured (i.e., Figure 1 The sensor array 2 (located between the double-layer cabling below the magnetizer 1) includes multiple sensing elements. These sensing elements are arranged in a matrix to form the sensor array 2, and each sensing element is independent and does not interfere with others. The width of the sensor array 2 is smaller than the width of the upper (or lower) cabling, and because both the upper and lower cablings are flexible, the sensor array can be sandwiched between the double-layer cabling.

[0042] Preferably, the sensor array is disposed in the middle region of a single layer of wiring (upper or lower layer) on the side of the magnetizer near the curved surface of the workpiece to be measured, thereby ensuring that the number of first and second magnetic field lines passing through each sensing element is the same. Since the first and second magnetic field lines passing through each sensing element are opposite in direction in the tangential direction, when there is a region without microcracks on the curved surface of the workpiece, the tangential components of the magnetic field generated by the lower and upper layer wiring in the space region where the sensing element is located above the region cancel each other out, that is, the tangential component of the background magnetic field in the space region where the sensing element is located is close to zero.

[0043] Among them, the first magnetic field line is the magnetic field line of the magnetic field generated by the lower layer of cabling, the second magnetic field line is the magnetic field line of the magnetic field generated by the upper layer of cabling, and the tangent is the tangential direction of the curved surface of the workpiece under test. The tangent here and the tangent mentioned elsewhere in this specification all refer to... Figure 1The x-axis and y-axis directions in the xyz spatial coordinate system are shown. The near-zero tangential background magnetic field means that the magnetic induction intensity of the tangential component of the background magnetic field in the spatial region where a sensing element in the sensor array is located is close to zero.

[0044] The sensor array is used to detect the magnetic induction intensity of the alternating magnetic field at the target location when the magnetic induction intensity of the tangential component of the background magnetic field in the spatial region where any sensing element is located is close to zero, so as to identify microcracks on the curved surface of the workpiece under test based on the magnetic induction intensity of the alternating magnetic field at the target location.

[0045] Preferably, the sensing element is a TMR (Tunnel Magnetoresistance) element. The sensor array is a TMR element array, which is formed by arranging multiple TMR elements along the transverse direction of the workpiece to be measured.

[0046] The output signal of a TMR element is either current or voltage. It detects the magnetic field strength in its surrounding space, converts the magnetic field strength into current or voltage through internal calculations, and outputs this as a signal. The larger the output signal, the stronger the magnetic field strength in its surrounding space. Compared to other sensing elements such as Hall effect sensors, TMR elements have the advantages of high precision, high accuracy, and high reliability in magnetic field detection.

[0047] It should be noted that the horizontal direction mentioned here, as well as the horizontal direction mentioned elsewhere in this specification, refers to... Figure 1 The y-axis direction in the xyz spatial coordinate system shown.

[0048] The sensor array is formed by arranging multiple TMR elements along the transverse direction of the workpiece under test. Therefore, it has the maximum sensitivity to the tangential component of the magnetic field generated by the workpiece under test.

[0049] In this embodiment, by setting the TMR element array at the target position, the larger the TMR output signal, the greater the depth of the microcracks on the curved surface of the workpiece under test; the closer the output signal is to 0, the less likely there are microcracks. By using a high-precision TMR element array as the sensor array, the workpiece curved surface microcrack detection device provided in this application embodiment has the ability to detect micron-level cracks on the curved surface of the workpiece.

[0050] Based on the characteristics of TMR elements: the lower the magnetic flux density of the background magnetic field, the higher the sensitivity of the TMR element. The sensitivity of the TMR element is highest when the magnetic flux density of the background magnetic field is close to zero; however, when the magnetic flux density of the background magnetic field exceeds a certain threshold, the sensitivity of the TMR element approaches zero, meaning the TMR element fails. Therefore, by using TMR elements as sensing elements and ensuring that the TMR element array operates in a near-zero tangential background magnetic field environment, the sensitivity of the sensor array can be improved, thereby achieving the goal of improving the detection accuracy of microcracks on the curved surface of the workpiece.

[0051] In one embodiment, the magnetizer is further configured to apply an induced current field to the surface of the workpiece under test when it is parallel to the surface on the side closest to the surface. The induced current field is used to generate a secondary magnetic field. The sensor array is further configured to detect the magnetic induction intensity of the secondary magnetic field at the target position when the tangential component of the background magnetic field in the spatial region where any sensing element is located is close to zero, so as to identify microcracks on the surface of the workpiece under test based on the magnetic induction intensity of the secondary magnetic field at the target position.

[0052] In this embodiment, an induced current field can be generated by a magnetizer, and the magnetic induction intensity of the secondary magnetic field at the target position can be detected by a sensor array. Thus, based on the magnetic induction intensity of the secondary magnetic field at the target position, minute signals such as longitudinal cracks on the curved surface of the workpiece under test can be identified, thereby realizing the detection of multi-directional cracks such as transverse cracks and longitudinal cracks.

[0053] like Figure 2 As shown, a method for detecting microcracks on curved surfaces of workpieces is provided, which is applied to the aforementioned workpiece curved surface microcrack detection device. The method includes the following steps:

[0054] Step 201: Using the contour control mechanism, adjust the side of the workpiece surface microcrack detection device that is close to the surface of the workpiece to be tested so that it is parallel to the surface of the workpiece.

[0055] The contour control mechanism can be a gripper, a robotic arm, or the like, used to adjust the shape of the workpiece surface microcrack detection device.

[0056] The shape-adaptive control mechanism enables the workpiece surface microcrack detection device to adapt to the shape of the workpiece under test, that is, to adjust the shape of the workpiece surface microcrack detection device to be consistent with or close to the shape of the surface of the workpiece under test, thereby ensuring the stable separation of the workpiece surface microcrack detection device and the workpiece under test during the detection process.

[0057] Step 202: A first excitation current and a second excitation current are generated by a programmable signal generator. The first excitation current is input to the lower layer of the magnetizer, and the second excitation current is input to the upper layer of the magnetizer. The first excitation current and the second excitation current have the same amplitude, the same frequency, and the same phase.

[0058] Among them, a programmable signal generator is a commonly used signal source used to provide AC excitation current. The excitation current it provides can be adjusted manually or automatically by a program. The first excitation current is used to input the excitation current to the lower layer cabling, and the second excitation current is used to input the excitation current to the upper layer cabling.

[0059] At the start of the test, a programmable signal generator is used to apply excitation currents of the same amplitude, frequency and phase to the lower and upper layers of the magnetizer.

[0060] Step 203: Generate a detection excitation source. The excitation intensity of the detection excitation source is the vector sum of the excitation intensity of the lower layer cabling and the excitation intensity of the upper layer cabling.

[0061] The excitation source for detection is the magnetic field applied to the workpiece by the magnetizer, including the magnetic field generated by the lower layer cabling and the magnetic field generated by the upper layer cabling. The excitation intensity is the magnetic induction intensity, used to describe the strength and direction of the magnetic field.

[0062] Since the excitation current of the magnetizer is alternating current, the workpiece surface microcrack detection device provided in this application is based on AC leakage magnetic field detection technology. According to the skin effect of AC leakage magnetic field detection technology, the magnetic field generated by the double-layer cable of the magnetizer is constrained to the skin layer of the workpiece surface to be tested. Thus, the magnetizer can deeply magnetize the skin layer of the workpiece surface to be tested, which is beneficial for the detection of microcracks on curved surfaces.

[0063] For example, after the magnetizer connects the first excitation current and the second excitation current, it generates a detection excitation source. The excitation intensity of the detection excitation source is the vector sum of the excitation intensity of the lower layer cable and the excitation intensity of the upper layer cable.

[0064] refer to Figure 3 , Figure 3 This is a schematic diagram of the longitudinal cross-section showing the spatial distribution of magnetic field lines formed above the curved surface of the workpiece during the detection process using a workpiece surface microcrack detection device. (Example:) Figure 3 As shown, with Figure 1 The x-axis direction is used for explanation, and the tangential component of the background magnetic field at the target location is mainly composed of the tangential component B of the excitation intensity of the lower layer of wiring. x下 The tangential component B of the excitation intensity of the upper layer cabling x上 It consists of two parts, B x下 Greater than Bx上 And B x下 and B x上 If the directions are opposite, the tangential component of the background magnetic field at the target location can be expressed as:

[0065] .

[0066] During the testing process, because the lower layer cabling is closer to the surface of the workpiece under test, the workpiece experiences a stronger compressive effect on the magnetic field generated by the lower layer cabling, thus causing B... x下 Greater than B x上 This ultimately results in the tangential component of the background magnetic field at the target location not being zero when the same amplitude, frequency, and phase excitation current is applied to the lower and upper layers of the cabling.

[0067] Step 204: Set the working environment of the sensor array to near-zero tangential background magnetic field.

[0068] Here, the near-zero tangential background magnetic field indicates that the output signal of any sensing element is close to zero. If the output signal of any sensing element is close to zero, it indicates that the sensor array is operating in a near-zero tangential background magnetic field environment.

[0069] For example, by using a programmable signal generator, while keeping the amplitude of the first excitation current constant, the amplitude of the second excitation current is adjusted until the output signal of one of the sensing elements approaches zero and the adjustment stops.

[0070] Taking a TMR element array as an example, the following explanation is provided. A specific TMR element in the TMR element array is used as a sensor to measure the tangential component of the background magnetic field in the spatial region where the TMR element array is located. By continuously acquiring the output signal of this TMR element, the magnitude of the current tangential component of the background magnetic field is obtained. Furthermore, the amplitude of the second excitation current is dynamically adjusted by a programmable signal generator until the output voltage of the TMR element approaches zero, that is, the tangential component of the background magnetic field at the target location approaches zero. This allows the TMR element array to operate in a near-zero tangential background magnetic field environment, thus ensuring that the TMR element array has high sensitivity.

[0071] By adjusting the excitation current of the upper layer cable, a near-zero tangential background magnetic field is provided for the sensor array, while avoiding the over-range saturation problem of the TMR element. By setting the operating environment of the sensor array to a near-zero tangential background magnetic field, the sensor array has high sensitivity during the detection process, thereby improving the detection accuracy of microcracks.

[0072] Step 205: When the working environment of the sensor array is a near-zero tangential background magnetic field and the workpiece under test moves longitudinally in the detection excitation source, the output signal of the sensor array is acquired. The output signal of the sensor array includes the output signals of multiple sensing elements, which are used to characterize the magnetic induction intensity at the target position, so as to identify the microcracks on the curved surface of the workpiece under test according to the magnetic induction intensity at the target position. The output signal of each sensing element is used to characterize the tangential component of the background magnetic field in its spatial region.

[0073] The sensor array output signal includes the output signals of multiple sensing elements, used to characterize the magnetic induction intensity at the target location. This magnetic induction intensity at the target location includes both the magnetic induction intensity of the alternating magnetic field and the magnetic induction intensity of the secondary magnetic field. By measuring the magnetic induction intensity of the alternating magnetic field and the secondary magnetic field at the target location, multi-directional microcracks, such as longitudinal and transverse cracks, on the curved surface of the workpiece can be detected.

[0074] It should be noted that the "vertical" direction here, as well as the "vertical" direction mentioned elsewhere in this specification, refers to... Figure 1 The x-axis direction in the xyz spatial coordinate system shown.

[0075] For example, a TMR element array is used as the sensor array for illustration. During the detection process, when the amplitude of the second excitation current is adjusted so that the TMR element array operates in a near-zero tangential background magnetic field environment, the workpiece surface microcrack detection device and the surface of the workpiece under test are stably lifted apart by the contour control mechanism. The workpiece under test begins to move along the longitudinal direction. Furthermore, during the movement of the workpiece under test along the longitudinal direction, it is still necessary to ensure that the working environment of the sensor array is near-zero tangential background magnetic field. If the output signal of no sensing element in the sensor array is close to zero, the amplitude of the second excitation current is adjusted while the amplitude of the first excitation current remains unchanged until the output signal of one sensing element is close to zero, at which point the adjustment stops. This ensures that the sensor array always operates under a near-zero tangential background magnetic field throughout the entire detection process. Because the TMR element array is densely arranged in the transverse direction, full coverage scanning of the surface of the workpiece under test can be achieved.

[0076] refer to Figures 4-6 During the inspection process, the workpiece surface microcrack detection device acquires the voltage signal of the TMR element array in real time. After processing through multi-stage AC / DC amplification and detection circuits, the defect signal is reconstructed according to a preset scanning speed. This allows for the detection of transverse cracks on the curved surface of a workpiece with high curvature, resulting in... Figure 4 The output voltage variation of the TMR element array is shown; during the detection of cracks on workpiece surfaces with different curvatures, the following results were obtained: Figure 5The output voltage variation of a single TMR element is shown; during the detection of cracks of different sizes on a magnetic particle sample, the following results were obtained: Figure 6 The output voltage variation of a single TMR element is shown.

[0077] Step 206: The output signal of the sensor array is amplified by an amplification circuit to identify microcracks based on the amplified output signal.

[0078] The amplification circuit can be a multi-stage AC / DC amplification circuit, which is not limited in this embodiment. The output signal of the TMR element array is amplified by the multi-stage AC / DC amplification circuit to ensure that the weak signals of micron-deep defects and longitudinal cracks can be further processed and identified.

[0079] In the above-mentioned method for detecting microcracks on curved surfaces of workpieces, a detection excitation source is generated by a magnetizer, and the working environment of the sensor array is set to a near-zero tangential background magnetic field. When the workpiece to be tested moves longitudinally in the detection excitation source, the magnetic induction intensity at the target position is detected by the sensor array. Based on the magnetic induction intensity at the target position, microcracks on the curved surface of the workpiece to be tested are identified. Since the magnetizer is flexible, it can achieve conformal magnetization, and the sensor array can work in a near-zero tangential background magnetic field. Therefore, it can improve the detection accuracy of microcracks and is applicable to the detection of microcracks on curved surfaces with various curvatures.

[0080] In one embodiment, a method for detecting microcracks on a workpiece surface is provided, which is jointly executed by a programmable signal generator, a contour control mechanism, a magnetizer positioned above the surface of the workpiece to be tested, and a TMR element array. The method includes the following steps:

[0081] 1) The magnetizer uses the magnetic field generated by the simultaneous excitation of the double-layer ribbon cable as the detection excitation source. It superimposes the excitation intensity of the upper ribbon cable on the excitation intensity of the lower ribbon cable. At the same time, the detection excitation source is confined within the skin layer of the workpiece surface, thus enabling deep magnetization of the skin layer of the workpiece surface, which is beneficial for the detection of microcracks.

[0082] 2) The magnetizer can adjust the amplitude of the excitation current of the upper layer ribbon cable through a programmable signal generator. With the amplitude of the excitation current of the lower layer ribbon cable kept constant, the amplitude of the excitation current of the upper layer ribbon cable is adjusted by the programmable signal generator, so that the magnetic fields generated by the double-layer ribbon cables in the defect-free area between them cancel each other out, thereby providing a near-zero tangential background magnetic field environment for the TMR element array;

[0083] 3) The TMR element array consists of highly sensitive TMR elements densely arranged along the transverse direction of the workpiece under test, which has the maximum sensitivity to the tangential component of the magnetic field generated by the workpiece under test.

[0084] 4) During operation, the TMR element array ensures that each TMR element is independent and does not interfere with each other. The TMR element array is stably lifted using a contour control mechanism. The output signal of a single TMR element represents the absolute value of the tangential component of the magnetic field at its location.

[0085] 5) The output signal of the TMR element array is amplified by a multi-stage AC / DC amplifier circuit to ensure that the weak signals of micron-level defects and longitudinal cracks can be further processed and identified.

[0086] In this embodiment, the flexible characteristics of the double-layer wire magnetizer and the contour control mechanism apply a stable AC magnetizing field and induced current field to the surface of complex workpieces, eliminating the weakening effect of large curvature workpiece surfaces on excitation and signal strength. This overcomes the problem of signal instability caused by lift-off variations and is applicable to defect detection of various curvature surfaces and complex surfaces. Furthermore, by using the tangential component of the magnetic field near the defect to characterize the defect, a near-zero tangential background magnetic field can be achieved using the double-layer wire magnetizer, and multi-directional cracks can be detected and distinguished under a single scanning direction.

[0087] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that this application is not limited to the described order of actions, as some steps may be performed in other orders or simultaneously according to this application. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0088] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0089] The above description is merely an exemplary embodiment of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of embodiments of this disclosure upon considering the specification and practicing the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described herein. The specification and embodiments are to be considered exemplary only, and the scope and spirit of this disclosure are defined by the claims.

[0090] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0091] 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 device for detecting microcracks on curved surfaces of workpieces, characterized in that, include: A magnetizer, placed above the curved surface of the workpiece under test, includes an upper layer ribbon cable and a lower layer ribbon cable. Both the upper and lower layer ribbon cables are made of flexible printed circuit boards (PCBs), and the lengths and widths of the PCBs used for the upper and lower layer ribbon cables are the same. The coils in the two PCBs are parallel to each other and have the same number of turns. The lower layer ribbon cable is placed below the upper layer ribbon cable. Both the lower and upper layer ribbon cables can independently form closed loops to apply an alternating magnetizing field to the curved surface of the workpiece under test when the side of the magnetizer closest to the curved surface is parallel to the curved surface. A sensor array is clampedly disposed at a target position, which is between the lower layer cabling and the upper layer cabling and on the side of the magnetizer closer to the curved surface. The sensor array is used to detect the magnetic induction intensity of the alternating magnetic field at the target position, so as to identify microcracks on the curved surface of the workpiece under test based on the magnetic induction intensity of the alternating magnetic field at the target position.

2. The apparatus as claimed in claim 1, characterized in that, The sensor array includes multiple sensing elements, which are used to detect the magnetic induction intensity of the alternating magnetic field at the target location, so as to identify microcracks on the curved surface of the workpiece under test based on the magnetic induction intensity of the alternating magnetic field at the target location, including: The sensor array is used to detect the magnetic induction intensity of the AC magnetic field at the target location when the tangential component of the background magnetic field in the spatial region where any sensing element is located is close to zero, so as to identify microcracks on the curved surface of the workpiece under test based on the magnetic induction intensity of the AC magnetic field at the target location, wherein the tangential direction is the tangential direction of the curved surface of the workpiece under test.

3. The apparatus as described in claim 2, characterized in that, The sensing element is a TMR element.

4. The apparatus as described in claim 3, characterized in that, The sensor array is formed by arranging multiple TMR elements along the lateral direction of the workpiece to be tested.

5. The apparatus according to any one of claims 1 to 4, characterized in that, The magnetizer is also used to apply an induced current field to the surface of the workpiece under test when it is parallel to the surface on the side closest to the surface. The induced current field is used to generate a secondary magnetic field. The sensor array is also used to detect the magnetic induction intensity of the secondary magnetic field at the target position, so as to identify microcracks on the surface of the workpiece under test based on the magnetic induction intensity of the secondary magnetic field at the target position.

6. A method for detecting microcracks on the curved surface of a workpiece, characterized in that, The method, applied to the workpiece surface microcrack detection device as described in claim 1, comprises: The workpiece surface microcrack detection device is placed above the curved surface of the workpiece to be tested; A programmable signal generator generates an AC first excitation current and a second excitation current. The first excitation current is input to the lower layer of the magnetizer, and the second excitation current is input to the upper layer of the magnetizer. The first excitation current and the second excitation current have the same amplitude, the same frequency, and the same phase. After the first excitation current and the second excitation current are turned on by the magnetizer, a detection excitation source is generated. The excitation intensity of the detection excitation source is the vector sum of the excitation intensity of the lower layer cable and the excitation intensity of the upper layer cable. The operating environment of the sensor array is set to near-zero tangential background magnetic field using the programmable signal generator. When the working environment of the sensor array is a near-zero tangential background magnetic field and the workpiece under test moves longitudinally in the detection excitation source, the output signal of the sensor array is acquired. The output signal of the sensor array includes the output signals of multiple sensing elements, which are used to characterize the magnetic induction intensity at the target position, so as to identify microcracks on the curved surface of the workpiece under test based on the magnetic induction intensity at the target position. The output signal of each sensing element is used to characterize the tangential component of the background magnetic field of its spatial region.

7. The method as described in claim 6, characterized in that, The step of placing the workpiece surface microcrack detection device above the surface of the workpiece to be tested includes: The workpiece surface microcrack detection device is placed above the curved surface of the workpiece to be tested; By using a contour control mechanism, the side of the workpiece surface microcrack detection device that is close to the surface of the workpiece to be tested is adjusted to be parallel to the surface of the workpiece to be tested.

8. The method as described in claim 6, characterized in that, A near-zero tangential background magnetic field indicates that the output signal of any sensing element is close to zero. Setting the operating environment of the sensor array to a near-zero tangential background magnetic field via the programmable signal generator includes: Using the programmable signal generator, while keeping the amplitude of the first excitation current constant, the amplitude of the second excitation current is adjusted until the output signal of one of the sensing elements approaches zero, at which point the adjustment stops.

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