Magnetic eddy current sensor and detection method

Abstract

The present invention discloses a magnetic eddy current sensor, which belongs to the field of eddy current detection technology. It includes a cross four-column yoke, which includes a first column, a second column, a third column and a fourth column; excitation coils are arranged on the four columns; an eddy current sensor is arranged at the center position formed by the intersection of the Y axis of the cross four-column yoke and the X axis of the cross four-column yoke, that is, the Z axis of the cross four-column yoke; a three-axis magnetic sensitive element is arranged at the center position of the eddy current sensor; the eddy current sensor and the three-axis magnetic sensitive element are separated by a preset lift-off value from the test piece; the defects of the test piece are detected by eddy current tomography scanning and / or multi-directional excitation. The detection of cracks and internal defects of the test piece can be realized by eddy current tomography scanning, which is a method that is not available at present, and multi-directional excitation significantly reduces the situation of missed defect detection.

Description

Technical Field

[0001] The present invention relates to the technical field of eddy current detection, and in particular to a magnetic eddy current sensor and a detection method. Background Art

[0002] Magnetic flux leakage testing can detect defects, eddy current testing is sensitive to cracks, and magnetic flux leakage testing is prone to miss defects parallel to the excitation magnetic field due to different excitation directions. At present, there is a certain amount of missed defects in the axial / circumferential single excitation mode. Non-destructive testing refers to the method of inspecting and testing the structure, state and type, quantity, shape, nature, location, size, distribution and changes of defects inside and on the surface of the test piece by using physical or chemical methods, with the help of modern technology and equipment, without damaging or affecting the performance of the object being tested and the internal organization of the object being tested, under the premise of inspecting the inside of the mechanical material without damaging or affecting the performance of the object being tested and the internal organization of the object being tested. There are five main types of non-destructive testing: radiographic testing (RT), ultrasonic testing (UT), liquid penetrant testing (PT), magnetic particle testing (MT) and eddy current testing (ECT).

[0003] The existing technology has the following problems: the existing magnetic flux leakage detection cannot locate the specific internal position of the defect; the traditional eddy current detection can only detect surface and near-surface defects, and cannot accurately locate the depth of near-surface defects; the traditional magnetic flux leakage detection has a single excitation direction, and when the defect is parallel to the mileage direction, it will be missed; the simple magnetic flux leakage detection cannot distinguish whether the defect is located on the inner wall or the outer wall of the specimen. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a magnetic eddy current sensor.

[0005] The objective of the present invention is achieved through the following technical solutions: a magnetic eddy current sensor, comprising a cross four-column yoke, the cross four-column yoke comprising a first column, a second column, a third column and a fourth column; the first column and the third column are arranged at both ends of the Y axis of the cross four-column yoke, and the second column and the fourth column are arranged at both ends of the X axis of the cross four-column yoke; a first excitation coil is arranged on the first column, a second excitation coil is arranged on the second column, a third excitation coil is arranged on the third column, and a fourth excitation coil is arranged on the fourth column; an eddy current sensor is arranged at the center position formed by the intersection of the Y axis of the cross four-column yoke and the X axis of the cross four-column yoke, that is, the Z axis of the cross four-column yoke; a three-axis magnetic sensitive element is arranged at the center position of the eddy current sensor; the eddy current sensor and the three-axis magnetic sensitive element are preset with a lift-off value from the test piece; defects of the test piece are detected by eddy current tomography scanning and / or multi-directional excitation.

[0006] Preferably, the Y-axis and X-axis of the cross four-pillar magnetic yoke are rotated by preset angles to obtain the X1 direction and the Y1 direction; the working modes of the magnetic eddy current sensor include a magnetic eddy current tomography scanning mode, a Y-axis direction excitation detection mode, an X-axis direction excitation detection mode, an X1 direction excitation detection mode, a Y1 direction excitation detection mode, and a combined working mode; the combined working mode simultaneously uses at least two of the magnetic eddy current tomography scanning mode, the Y-axis direction excitation detection mode, the X-axis direction excitation detection mode, the X1 direction excitation detection mode, and the Y1 direction excitation detection mode, to detect surface defects and internal defects of the test piece, and to distinguish whether they are located on the inner wall or the outer wall of the test piece.

[0007] Preferably, the magnetic eddy current tomography scanning mode comprises the following steps:

[0008] The first excitation coil and the third excitation coil are used as a group of excitation coils, and the second excitation coil and the fourth excitation coil are used as another group of excitation coils. The excitation current in any group of excitation coils is changed multiple times to change the magnetic field in the test piece, thereby changing the magnetic permeability and further changing the detection depth; the position of the internal defect in the test piece is determined by comparing the eddy current signals under different excitation currents.

[0009] Preferably, the Y-axis direction excitation detection mode comprises the following steps:

[0010] A DC excitation current is passed through the first excitation coil and the third excitation coil, and the directions of the DC excitation currents in the first excitation coil and the third excitation coil are opposite. At this time, the first column, the third column and the test piece form a magnetic circuit; the spatial magnetic field changes are collected by a three-axis magnetic sensitive element to detect grooves, grooves in the X-axis direction and defects on the back side of the test piece.

[0011] Preferably, the X-axis direction excitation detection mode comprises the following steps:

[0012] A DC excitation current is passed through the second excitation coil and the fourth excitation coil, and the directions of the DC excitation currents in the second excitation coil and the fourth excitation coil are opposite. At this time, the second column, the fourth column and the test piece form a magnetic circuit; the spatial magnetic field changes are collected by a three-axis magnetic sensitive element to detect grooves and grooves in the Y-axis direction and defects on the back side of the test piece.

[0013] Preferably, the X1 direction excitation detection mode comprises the following steps:

[0014] A DC excitation current is passed through the first excitation coil, the second excitation coil, the third excitation coil and the fourth excitation coil, and the directions of the DC excitation currents in the first excitation coil and the third excitation coil are opposite, and the directions of the DC excitation currents in the second excitation coil and the fourth excitation coil are opposite, the directions of the DC excitation currents in the first excitation coil and the second excitation coil are the same, and the directions of the DC excitation currents in the third excitation coil and the fourth excitation coil are the same; at this time, the first column, the third column and the test piece form a magnetic loop, the second column, the fourth column and the test piece form a magnetic loop, and the magnetic field runs in the X1 direction; the spatial magnetic field changes are collected by a three-axis magnetic sensitive element to detect grooves and grooves in the Y1 direction and defects on the back of the test piece.

[0015] Preferably, the Y1 direction excitation detection mode comprises the following steps:

[0016] A DC excitation current is passed through the first excitation coil, the second excitation coil, the third excitation coil and the fourth excitation coil, and the directions of the DC excitation currents in the first excitation coil and the fourth excitation coil are opposite, the directions of the DC excitation currents in the second excitation coil and the third excitation coil are opposite, the directions of the DC excitation currents in the first excitation coil and the fourth excitation coil are the same, and the directions of the DC excitation currents in the second excitation coil and the third excitation coil are the same; at this time, the first column, the fourth column and the test piece form a magnetic loop, the second column, the third column and the test piece form a magnetic loop, and the magnetic field direction is in the Y1 direction; the spatial magnetic field changes are collected by a three-axis magnetic sensitive element to detect grooves and grooves in the X1 direction and defects on the back side of the test piece.

[0017] Preferably, the preset lift-off value is 3 mm.

[0018] The beneficial effects of the present invention are:

[0019] 1) Eddy current tomography can detect cracks and internal defects of the specimen, which is currently unavailable, and multi-directional excitation significantly reduces the number of missed defects.

[0020] 2) The mileage field and eddy current detection are introduced to realize the tomographic scanning of eddy current, and the specific position distribution of defects in the specimen can be located in combination with the detection method.

[0021] 3) The introduction of four-directional excitation magnetic fields can significantly reduce the occurrence of missed detections.

[0022] 4) The introduced eddy current detection can locate the defects inside, outside and in the middle of the specimen through eddy current tomography scanning method. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the overall structural layout diagram of the eddy current sensor;

[0024] Figure 2 This is the structural diagram of the cross four-column yoke;

[0025] Figure 3 It is a schematic diagram of the layout of eddy current sensor and three-axis magnetic sensitive element;

[0026] Figure 4 It is a schematic diagram of magnetic permeability curve;

[0027] Figure 5 A side view of the eddy current sensor with the test piece added;

[0028] Figure 6 It is a schematic diagram of the magnetic field when the first excitation coil and the third excitation coil are energized;

[0029] Figure 7 This is a simulation diagram of the magnetic field trend when the first excitation coil and the third excitation coil are energized;

[0030] Figure 8 It is a schematic diagram of the magnetic field when the second excitation coil and the fourth excitation coil are energized;

[0031] Fig. 9 This is a simulation diagram of the magnetic field trend when the second excitation coil and the fourth excitation coil are energized;

[0032] Fig.10 It is a schematic diagram of the penetration depth of eddy current in the tested piece when the current of the exciting coil is 100A;

[0033] Fig.11 It is a schematic diagram of the penetration depth of eddy current in the tested piece when the current of the exciting coil is 200A;

[0034] Fig.12 Schematic diagram of the eddy current penetration depth in the test piece when the excitation coil current is 300A. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0036] See also Figure 1-Figure 12The present invention provides a technical solution: a magnetic eddy current sensor, comprising a cross four-column yoke, the cross four-column yoke comprising a first column, a second column, a third column and a fourth column; the first column and the third column are arranged at both ends of the Y axis of the cross four-column yoke, and the second column and the fourth column are arranged at both ends of the X axis of the cross four-column yoke; a first excitation coil is arranged on the first column, a second excitation coil is arranged on the second column, a third excitation coil is arranged on the third column, and a fourth excitation coil is arranged on the fourth column; an eddy current sensor is arranged at the center position formed by the intersection of the Y axis of the cross four-column yoke and the X axis of the cross four-column yoke, that is, the Z axis of the cross four-column yoke; a three-axis magnetic sensitive element is arranged at the center position of the eddy current sensor; the eddy current sensor and the three-axis magnetic sensitive element are separated by a preset lift-off value from the test piece; defects of the test piece are detected by eddy current tomography scanning and / or multi-directional excitation.

[0037] In this embodiment, when eddy current detection is performed under a background magnetic field, the background magnetic field causes the magnetic permeability of the specimen to change, which will change the penetration depth of the eddy current detection, which is beneficial to enhancing the eddy current detection effect. The present invention introduces four-directional excitation magnetic fields through a specially designed magnetic yoke. The introduction of multi-directional excitation can greatly reduce the missed detection of grooves and furrows. At the same time, the size of the excitation magnetic field can be adjusted. When used in conjunction with an eddy current sensor, the eddy current detection depth can be changed to achieve internal defect detection of the specimen and to locate the defects in the depth direction of the specimen. When magnetic information and eddy current information are detected simultaneously, the defects can also be located on the inner and outer walls of the specimen.

[0038] In some embodiments, the Y-axis and X-axis of the cross four-pillar magnetic yoke are rotated by preset angles to obtain the X1 direction and the Y1 direction; the working modes of the magnetic eddy current sensor include a magnetic eddy current tomography scanning mode, a Y-axis direction excitation detection mode, an X-axis direction excitation detection mode, an X1 direction excitation detection mode, a Y1 direction excitation detection mode, and a combined working mode; the combined working mode simultaneously uses at least two of the magnetic eddy current tomography scanning mode, the Y-axis direction excitation detection mode, the X-axis direction excitation detection mode, the X1 direction excitation detection mode, and the Y1 direction excitation detection mode to detect surface defects and internal defects of the test piece, and distinguish whether they are on the inner wall or the outer wall of the test piece.

[0039] In this embodiment, the combined working mode combines the magnetic eddy current tomography scanning mode, the Y-axis direction excitation detection mode, the X-axis direction excitation detection mode, the X1 direction excitation detection mode, and the Y1 direction excitation detection mode. The magnetic eddy current sensor can detect surface and internal defects of the tested piece during the movement of the surface of the tested piece, and find internal defects of the test piece by changing the eddy current penetration depth. At the same time, the defects detected by the Y-axis direction excitation detection mode, the X-axis direction excitation detection mode, the X1 direction excitation detection mode, and the Y1 direction excitation detection mode, combined with the eddy current signal response, can distinguish whether the defects are on the inner wall or the outer wall. In the detection process, the eddy current signal and the magnetic signal are extracted by extracting the AC and DC signals in the three-axis magnetic sensitive sensor, thereby realizing the extraction of defect information.

[0040] In some embodiments, the magnetic eddy current tomography scanning mode comprises the following steps:

[0041] The first excitation coil and the third excitation coil are used as a group of excitation coils, and the second excitation coil and the fourth excitation coil are used as another group of excitation coils. The excitation current in any group of excitation coils is changed multiple times to change the magnetic field in the test piece, thereby changing the magnetic permeability and further changing the detection depth; the position of the internal defect in the test piece is determined by comparing the eddy current signals under different excitation currents.

[0042] In this embodiment, due to the existence of the skin effect, the skin depth calculation formula is as follows:

[0043]

[0044] Where: is the skin depth; f is the electromagnetic field frequency; is the magnetic permeability; is the conductivity.

[0045] The penetration depth of the magnetic field can be changed by changing the magnetic permeability of the material. The relationship between the magnetic permeability and the magnetic field is shown in FIG4. The present invention increases the magnetic field in the tested object by increasing the current in the excitation coil, thereby changing the magnetic permeability and then changing the detection depth, thereby realizing the tomographic scanning detection function at different depths. The eddy current penetration depth caused by the coil being energized is shown in FIG4. Fig.10, as shown in Figures 11 and 12. Since the eddy current sensor is fed with alternating current, the AC component of the three-axis magnetic sensitive element signal is extracted, and the signal of eddy current change can be extracted. Magnetic eddy current tomography scanning process: when the excitation current is A1, the eddy current penetration depth is Z1, and the eddy current signal B1 is obtained; when the current is increased to A2, the eddy current penetration depth is Z2, and the eddy current signal B2 is obtained... When the current is increased to Ax, the penetration depth is Zx, and the eddy current signal Bx is obtained. By comparing the eddy current signal B, the penetration depth when any eddy current signal Bi fluctuates is the specific position of the internal defect in the specimen.

[0046] In some embodiments, the Y-axis direction excitation detection mode includes the following steps:

[0047] A DC excitation current is passed through the first excitation coil and the third excitation coil, and the directions of the DC excitation currents in the first excitation coil and the third excitation coil are opposite. At this time, the first column, the third column and the test piece form a magnetic circuit; the spatial magnetic field changes are collected by a three-axis magnetic sensitive element to detect grooves, grooves in the X-axis direction and defects on the back side of the test piece.

[0048] In this embodiment, in the Y-axis direction excitation detection mode, the magnetic field direction is as follows Figure 6 , Figure 7 shown.

[0049] In some embodiments, the X-axis direction excitation detection mode includes the following steps:

[0050] A DC excitation current is passed through the second excitation coil and the fourth excitation coil, and the directions of the DC excitation currents in the second excitation coil and the fourth excitation coil are opposite. At this time, the second column, the fourth column and the test piece form a magnetic circuit; the spatial magnetic field changes are collected by a three-axis magnetic sensitive element to detect grooves and grooves in the Y-axis direction and defects on the back side of the test piece.

[0051] In this embodiment, in the X-axis direction excitation detection mode, the magnetic field direction is as follows Figure 8 , Fig. 9 shown.

[0052] In some embodiments, the X1 direction excitation detection mode includes the following steps:

[0053] A DC excitation current is passed through the first excitation coil, the second excitation coil, the third excitation coil and the fourth excitation coil, and the directions of the DC excitation currents in the first excitation coil and the third excitation coil are opposite, and the directions of the DC excitation currents in the second excitation coil and the fourth excitation coil are opposite, the directions of the DC excitation currents in the first excitation coil and the second excitation coil are the same, and the directions of the DC excitation currents in the third excitation coil and the fourth excitation coil are the same; at this time, the first column, the third column and the test piece form a magnetic loop, the second column, the fourth column and the test piece form a magnetic loop, and the magnetic field runs in the X1 direction; the spatial magnetic field changes are collected by a three-axis magnetic sensitive element to detect grooves and grooves in the Y1 direction and defects on the back of the test piece.

[0054] In some embodiments, the Y1 direction excitation detection mode includes the following steps:

[0055] A DC excitation current is passed through the first excitation coil, the second excitation coil, the third excitation coil and the fourth excitation coil, and the directions of the DC excitation currents in the first excitation coil and the fourth excitation coil are opposite, the directions of the DC excitation currents in the second excitation coil and the third excitation coil are opposite, the directions of the DC excitation currents in the first excitation coil and the fourth excitation coil are the same, and the directions of the DC excitation currents in the second excitation coil and the third excitation coil are the same; at this time, the first column, the fourth column and the test piece form a magnetic loop, the second column, the third column and the test piece form a magnetic loop, and the magnetic field direction is in the Y1 direction; the spatial magnetic field changes are collected by a three-axis magnetic sensitive element to detect grooves and grooves in the X1 direction and defects on the back side of the test piece.

[0056] In some embodiments, the preset lift-off value is 3 mm.

[0057] In this embodiment, 3 mm is only an example value, and other values ​​that can also achieve the purpose of the invention may also be used.

[0058] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A magnetic eddy current sensor detection method, Features: The magnetic eddy current sensor comprises a cross four-column yoke, and the cross four-column yoke comprises a first column, a second column, a third column and a fourth column; the first column and the third column are arranged at both ends of the Y axis of the cross four-column yoke, and the second column and the fourth column are arranged at both ends of the X axis of the cross four-column yoke; a first excitation coil is arranged on the first column, a second excitation coil is arranged on the second column, a third excitation coil is arranged on the third column, and a fourth excitation coil is arranged on the fourth column; an eddy current sensor is arranged at the center position formed by the intersection of the Y axis of the cross four-column yoke and the X axis of the cross four-column yoke, that is, the Z axis of the cross four-column yoke; a three-axis magnetic sensitive element is arranged at the center position of the eddy current sensor; the eddy current sensor and the three-axis magnetic sensitive element are set at a preset lift-off value from the test piece; The detection method comprises the following steps: detecting defects of the tested piece by eddy current tomography scanning and / or multi-directional excitation; The cross four-column magnetic yoke Y-axis and the cross four-column magnetic yoke X-axis rotate at a preset angle to obtain the X1 direction and the Y1 direction; the working modes of the magnetic eddy current sensor include a magnetic eddy current tomography scanning mode, a Y-axis direction excitation detection mode, an X-axis direction excitation detection mode, an X1 direction excitation detection mode, a Y1 direction excitation detection mode, and a combined working mode; the combined working mode simultaneously uses at least two of the magnetic eddy current tomography scanning mode, the Y-axis direction excitation detection mode, the X-axis direction excitation detection mode, the X1 direction excitation detection mode, and the Y1 direction excitation detection mode, to detect surface defects and internal defects of the tested piece, and distinguish whether they are located on the inner wall or the outer wall of the tested piece; The magnetic eddy current tomography scanning mode comprises the following steps: The first excitation coil and the third excitation coil are used as one group of excitation coils, and the second excitation coil and the fourth excitation coil are used as another group of excitation coils. The excitation current in any group of excitation coils is changed multiple times to change the magnetic field in the test piece, thereby changing the magnetic permeability and further changing the detection depth; the position of the internal defect in the test piece is determined by comparing the eddy current signals under different excitation currents; The Y-axis direction excitation detection mode comprises the following steps: A DC excitation current is passed through the first excitation coil and the third excitation coil, and the directions of the DC excitation currents in the first excitation coil and the third excitation coil are opposite. At this time, the first column, the third column and the tested object form a magnetic loop; the spatial magnetic field change is collected by a three-axis magnetic sensitive element to detect grooves, grooves in the X-axis direction and back defects of the tested object; The X-axis direction excitation detection mode comprises the following steps: A DC excitation current is passed through the second excitation coil and the fourth excitation coil, and the directions of the DC excitation currents in the second excitation coil and the fourth excitation coil are opposite. At this time, the second column, the fourth column and the tested object form a magnetic loop; the spatial magnetic field change is collected by a three-axis magnetic sensitive element to detect grooves and grooves in the Y-axis direction and back defects of the tested object; The X1 direction excitation detection mode includes the following steps: A DC excitation current is passed through the first excitation coil, the second excitation coil, the third excitation coil, and the fourth excitation coil, and the directions of the DC excitation currents in the first excitation coil and the third excitation coil are opposite, the directions of the DC excitation currents in the second excitation coil and the fourth excitation coil are opposite, the directions of the DC excitation currents in the first excitation coil and the second excitation coil are the same, and the directions of the DC excitation currents in the third excitation coil and the fourth excitation coil are the same; at this time, the first column, the third column and the test piece form a magnetic loop, the second column, the fourth column and the test piece form a magnetic loop, and the magnetic field is oriented in the X1 direction; the spatial magnetic field changes are collected by a three-axis magnetic sensitive element to detect grooves and grooves in the Y1 direction and defects on the back of the test piece; The Y1 direction excitation detection mode comprises the following steps: A DC excitation current is passed through the first excitation coil, the second excitation coil, the third excitation coil and the fourth excitation coil, and the directions of the DC excitation currents in the first excitation coil and the fourth excitation coil are opposite, the directions of the DC excitation currents in the second excitation coil and the third excitation coil are opposite, the directions of the DC excitation currents in the first excitation coil and the fourth excitation coil are the same, and the directions of the DC excitation currents in the second excitation coil and the third excitation coil are the same; at this time, the first column, the fourth column and the test piece form a magnetic loop, the second column, the third column and the test piece form a magnetic loop, and the magnetic field direction is in the Y1 direction; the spatial magnetic field changes are collected by a three-axis magnetic sensitive element to detect grooves and grooves in the X1 direction and defects on the back side of the test piece.

2. The eddy current sensor detection method according to claim 1, Features: The preset lift-off value is 3 mm.

Images