Electromagnetic ultrasonic sensor

Abstract

The application provides an electromagnetic ultrasonic sensor, which comprises a shell, a permanent magnet assembly and a first hollow coil arranged in the shell, the permanent magnet assembly comprises a first permanent magnet and a second permanent magnet, the second permanent magnet is coaxially arranged with the first permanent magnet and is sleeved outside the first permanent magnet, the magnetic field directions of the first permanent magnet and the second permanent magnet are opposite, the first hollow coil is arranged below the first permanent magnet and coaxially arranged with the permanent magnet assembly, the outer diameter of the first hollow coil is less than or equal to the outer diameter of the first permanent magnet, the shell is sleeved outside the permanent magnet assembly and the first hollow coil, the shell is provided with a plug-in interface, and the plug-in interface is electrically connected with the first hollow coil. The electromagnetic ultrasonic sensor provided by the application can avoid the phase difference caused by the opposite force source formed by the coil, and the waveform bifurcation distortion is easily caused when the sound wave propagates or reflects in the test piece.

Description

Technical Field

[0001] This invention relates to the field of industrial testing technology, and in particular to an electromagnetic ultrasonic sensor. Background Technology

[0002] Bolts are commonly used fasteners for connecting various mechanical parts. When using torque tightening, the axial force (or preload) control accuracy is typically within ±20% to 30%, making precise control of the tightening process difficult. Furthermore, the different tightening sequences of multiple fasteners and bolt flanges can cause significant changes in bolt axial force after tightening. For equipment already in operation, effective measurement of bolt tightening axial force is also challenging. These factors lead to considerable uncertainty and unmeasurability in bolt tightening, jeopardizing safe equipment operation.

[0003] The ultrasonic bolt axial force measurement method uses an ultrasonic sensor to excite ultrasonic waves in the bolt, and indirectly measures the bolt axial force by measuring the time it takes for the ultrasonic waves to travel through the bolt.

[0004] Electromagnetic ultrasound is a technology that eliminates the need for ultrasonic coupling agents, enabling convenient ultrasonic excitation and reception, and offers significant advantages in bolt axial force measurement. Electromagnetic ultrasonic methods for bolt axial force measurement are divided into single-wavelength and dual-wavelength methods.

[0005] The basic principle of the single-wave method is to utilize the linear relationship between the time offlight (TOF) of sound waves (either transverse or longitudinal waves) in the bolt and the bolt axial force. The axial force is indirectly characterized by pre-calibrating the linear relationship between TOF and axial force and by measuring the TOF. Since TOF is insensitive to axial force, the TOF variation caused by bolt length tolerances is much greater than the influence of axial force on TOF. Therefore, the initial state of each bolt needs to be determined before axial force measurement.

[0006] The dual-wave method simultaneously generates transverse and longitudinal waves within the bolt. It integrates information from both waves, overcoming the limitations of the single-wave method. Utilizing the different sensitivities of longitudinal and transverse wave velocities to axial force, the dual-wave method eliminates the bolt length variable in the calculation formula through comparison and subtraction. With a single calibration, the axial force of the bolt in its in-service state can be measured without needing to measure its initial state.

[0007] Electromagnetic ultrasound technology can easily generate strong transverse wave signals in ferromagnetic conductors, but it is difficult to generate longitudinal waves. Currently used electromagnetic ultrasound probes with cylindrical permanent magnets and helical coils produce relatively small longitudinal wave signals, making it difficult to accurately measure axial force. Existing technologies incorporate a magnetic circuit closure at the end of the permanent magnet furthest from the coil to enhance the magnetic field; however, this closure is ineffective and increases the sensor's height, affecting the height limitations during use. Summary of the Invention

[0008] The purpose of this invention is to provide an electromagnetic ultrasonic sensor that can simultaneously excite transverse waves and strong longitudinal waves, and ensure that the received echo signal is not distorted or bifurcated, thus solving the problem in the prior art that it is difficult to excite longitudinal waves and that the echo signal is prone to distortion and bifurcation.

[0009] To achieve one of the above-mentioned objectives, one embodiment of the present invention provides an electromagnetic ultrasonic sensor, comprising:

[0010] A permanent magnet assembly includes a first permanent magnet and a second permanent magnet, wherein the second permanent magnet is coaxially arranged with the first permanent magnet and sleeved on the first permanent magnet, and the magnetic field directions of the first permanent magnet and the second permanent magnet are opposite.

[0011] A first hollow coil is disposed below the first permanent magnet and is coaxially arranged with the permanent magnet assembly. The outer diameter of the first hollow coil is less than or equal to the outer diameter of the first permanent magnet.

[0012] The outer casing is fitted over the permanent magnet assembly and the first hollow coil. The outer casing is provided with a plug-in interface, which is electrically connected to the first hollow coil.

[0013] As a further improvement of one embodiment of the present invention, the ratio of the inner diameter to the outer diameter of the first hollow coil is 0.1 to 0.8.

[0014] As a further improvement of one embodiment of the present invention, for bolts made of steel, the ratio of the inner diameter to the outer diameter of the first hollow coil is 0.2 to 0.6.

[0015] As a further improvement of one embodiment of the present invention, a second hollow coil is also included, which is disposed below the permanent magnet assembly. The outer diameter of the second hollow coil is larger than the inner diameter of the second permanent magnet, and the inner diameter of the second hollow coil is smaller than the outer diameter of the first permanent magnet.

[0016] As a further improvement of one embodiment of the present invention, the first permanent magnet is a solid cylinder or a hollow cylinder along the length of the first permanent magnet.

[0017] As a further improvement of one embodiment of the present invention, when the shape of the first permanent magnet is a hollow cylinder along the length direction of the first permanent magnet, the inner diameter of the first hollow coil is greater than or equal to the inner diameter of the first permanent magnet.

[0018] As a further improvement of one embodiment of the present invention, a magnetic shielding component is also included, which is disposed between the permanent magnet assembly and the first hollow coil.

[0019] As a further improvement of one embodiment of the present invention, the magnetic shielding element is 1 to 6 layers of copper foil or magnetic sheet.

[0020] As a further improvement of one embodiment of the present invention, it also includes a wear-resistant sheet, which is disposed below the first hollow coil.

[0021] As a further improvement of one embodiment of the present invention, the insertion interface is disposed on the side wall of the housing along the length direction of the permanent magnet assembly.

[0022] One or more technical solutions provided by this invention have at least the following technical effects or advantages:

[0023] The electromagnetic ultrasonic sensor provided by this invention combines a permanent magnet assembly with a hollow coil to generate strong longitudinal waves. Furthermore, by setting the coil as a hollow coil, and wherein the outer diameter of the first hollow coil is less than or equal to the outer diameter of the first permanent magnet, in the height direction, the portion of the first hollow coil within the range of the first permanent magnet can avoid the formation of opposite force sources between the portion of the coil within the range of the first permanent magnet and the portion outside the range of the first permanent magnet, which would lead to a phase difference and cause waveform bifurcation and distortion when the sound wave propagates or is reflected in the specimen. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the electromagnetic ultrasonic sensor in an embodiment of the present invention.

[0025] Figure 2 yes Figure 1 A top view of a medium-sized electromagnetic ultrasonic sensor.

[0026] Figure 3 yes Figure 2 Schematic diagram of cross section along line AA.

[0027] Figure 4 It is the distribution of magnetic field intensity on the surface of the specimen without a closed-loop magnetic circuit.

[0028] Figure 5 It is the distribution of magnetic field intensity on the surface of a specimen with a closed-loop magnetic circuit.

[0029] Figure 6 It refers to the longitudinal and transverse waves when a first hollow coil and a second hollow coil are provided.

[0030] 1. Outer shell; 11. Housing; 12. Cover; 13. Socket; 14. Connector; 2. Permanent magnet assembly; 21. First permanent magnet; 22. Second permanent magnet; 3. First hollow coil; 4. Second hollow coil; 5. Magnetic shield; 6. Wear-resistant sheet. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The terms used in this document, such as “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” indicating spatial relative positions, are used for illustrative purposes to describe the relationship of one unit or feature relative to another unit or feature as shown in the accompanying drawings. The terms “spatial relative positions” may be intended to include different orientations of the equipment in use or operation other than those shown in the figures.

[0033] For example, if the device in the figure is flipped, a unit described as being "below" or "under" other units or features will be "above" other units or features. Therefore, the exemplary term "below" can encompass both above and below orientations. The device may be oriented in other ways (rotated 90 degrees or otherwise) and the spatially related descriptive terms used herein will be interpreted accordingly.

[0034] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0035] Furthermore, it should be understood that although the terms "first," "second," etc., may be used herein to describe various elements or structures, the objects described should not be limited by these terms. These terms are only used to distinguish these objects from one another. For example, a first permanent magnet may be referred to as a second permanent magnet, and similarly, a second permanent magnet may be referred to as a first permanent magnet, without departing from the scope of protection of this application.

[0036] This invention provides an electromagnetic ultrasonic sensor, such as... Figure 1As shown, the assembly includes: a housing 1, a permanent magnet assembly 2, and a first hollow coil 3. The permanent magnet assembly 2 includes a first permanent magnet 21 and a second permanent magnet 22. The second permanent magnet 22 is coaxially arranged with the first permanent magnet 21 and is sleeved on the outside of the first permanent magnet 21. The magnetic field directions of the first permanent magnet 21 and the second permanent magnet 22 are opposite. The first hollow coil 3 is disposed below the first permanent magnet 21 and is coaxial with the permanent magnet assembly 2. The outer diameter of the first hollow coil 3 is less than or equal to the outer diameter of the first permanent magnet 21. The housing 1 is sleeved on the permanent magnet assembly 2 and the first hollow coil 3. The housing 1 is provided with a plug-in interface 13, which is electrically connected to the first hollow coil 3.

[0037] The electromagnetic ultrasonic sensor provided in this embodiment of the invention uses a hollow coil, and the outer diameter of the first hollow coil 3 is less than or equal to the outer diameter of the first permanent magnet 21. That is, the first hollow coil 3 does not span two magnetic poles, which can prevent the vertical component of the magnetic field below the coil from reversing and forming a force source in the opposite direction. This eliminates or reduces the sound wave sidelobes, reduces the superposition of sound rays between the sidelobes and the main lobe, and avoids sound wave bifurcation and distortion. Using a hollow coil can greatly reduce the anti-phase magnetization force generated in the central region of the coil, thereby increasing the positive resultant force and enhancing the longitudinal wave signal. The inner diameter of the second permanent magnet matches the outer diameter of the first permanent magnet, which can ensure a strong longitudinal wave excitation while reducing the size of the electromagnetic ultrasonic sensor.

[0038] Specifically, the outer shell 1 has an upwardly opening shell 11 and a cover 12 that covers the upper opening of the shell 11. A detection port is opened at the bottom of the shell 11 away from the cover 12. The insertion interface 13 is provided on the side wall of the outer shell 1 along the length direction of the permanent magnet assembly 2. Specifically, a plug 14 is fixed at the insertion interface 13. The first hollow coil 3 is electrically connected to the plug 14 through the insertion interface 13.

[0039] During installation, the first hollow coil 3 and the permanent magnet assembly 2 are sequentially placed into the housing 11 through the opening, and then the cover 12 is closed to the housing 11. During measurement, the insertion interface 13 located on the side wall, compared to the conventional insertion interface 13 located on the top, offers less restriction on the height of the measurement application. The insertion interface 13 is electrically connected inward to the first hollow coil 3 and electrically connected outward to the wires on the host machine that provide the excitation source for the first hollow coil 3.

[0040] Furthermore, the ratio of the inner diameter to the outer diameter of the first hollow coil 3 is 0.1 to 0.8. When the ratio of the inner diameter to the outer diameter of the first hollow coil 3 is 0.1 to 0.8, the combination of the first hollow coil 3 and the permanent magnet assembly 2 can significantly improve the ability to excite longitudinal waves. Preferably, for bolts made of steel, the combination of the first hollow coil 3 and the permanent magnet assembly 2 with an inner diameter to outer diameter ratio of 0.2 to 0.6 provides even better ability to excite longitudinal waves.

[0041] Furthermore, a hollow coil, namely the second hollow coil 4 in Figure 3, is set below the permanent magnet assembly 2. The second hollow coil 4 is electrically connected to the connector 13, and its outer diameter is larger than the inner diameter of the second permanent magnet 22, while its inner diameter is smaller than the outer diameter of the first permanent magnet 21. The second hollow coil 4 can not only cooperate with the first permanent magnet 21 to generate longitudinal waves, but also cooperate with the second permanent magnet 22 to generate longitudinal waves. That is, the second hollow coil 4 can generate stronger longitudinal waves than the first hollow coil 3, but at the same time, there will be problems of transverse wave bifurcation and distortion. Therefore, the first hollow coil 3 and the second hollow coil 4 are connected to different excitation sources through the connector 13 to achieve the simultaneous generation of strong, unbifurated, and undistorted transverse and longitudinal waves, thereby better realizing the accurate measurement of bolt axial force.

[0042] In this embodiment, the first hollow coil 3 is disposed below the second hollow coil 4, but the vertical position of the first hollow coil 3 and the second hollow coil 4 is not restricted. The first hollow coil 3 can also be disposed above the second hollow coil 4 without affecting the transverse and longitudinal waves generated by the first hollow coil 3 and the second hollow coil 4.

[0043] Furthermore, the first permanent magnet 21 is either a solid cylinder or a hollow cylinder along its length. When the first permanent magnet 21 is a solid cylinder, the inner diameter of the first hollow coil 3 is affected by the material and diameter of the bolt being measured. When the first permanent magnet 21 is a hollow cylinder along its length, the inner diameter of the first hollow coil 3 is greater than or equal to the inner diameter of the first permanent magnet 21, so that the first hollow coil 3 is always within the range of the first permanent magnet 21 in the height direction of the electromagnetic ultrasonic sensor, thus preventing the vertical component of the magnetic field below the coil from reversing.

[0044] Preferably, the difference between the inner diameter of the second permanent magnet and the outer diameter of the first permanent magnet 21 does not exceed 1 mm. Since the outer diameter of the first hollow coil 3 does not exceed the outer diameter of the first permanent magnet 21, the difference between the inner diameter of the second permanent magnet and the outer diameter of the first permanent magnet 21 does not need to be particularly limited, and the purpose of the present invention can be achieved. Therefore, it is sufficient to make the second permanent magnet 22 fit over the first permanent magnet 21. However, making the difference between the inner diameter of the second permanent magnet and the outer diameter of the first permanent magnet 21 not exceed 1 mm can avoid errors that prevent the first permanent magnet 21 and the second permanent magnet 22 from being able to be combined.

[0045] Furthermore, the electromagnetic ultrasonic sensor also includes a magnetic shielding component 5 and a wear-resistant sheet 6. The magnetic shielding component 5 is disposed between the permanent magnet assembly 2 and the hollow coil, that is, the magnetic shielding component 5 separates the permanent magnet assembly 2 and the first hollow coil 3 and the second hollow coil 4 on both sides of the magnetic shielding component 5, which can isolate most of the magnetic field generated by the first hollow coil 3 and the second hollow coil 4 under alternating current, and reduce the influence of the magnetic field generated by the first hollow coil 3 and the second hollow coil 4 under alternating current on the static magnetic field generated by the permanent magnet assembly 2. Preferably, in the height direction of the permanent magnet assembly 2, the projections of the first hollow coil 3 and the second hollow coil 4 are on the magnetic shielding component 5. Preferably, the magnetic shielding component 5 can be 1 to 6 layers of copper foil or magnetic conductive sheet.

[0046] The wear-resistant plate 6 is positioned below the hollow coil, that is, the first hollow coil 3 and the second hollow coil 4 are positioned above the wear-resistant plate 6. This prevents the bolts from wearing down the hollow coil during repeated testing, thus protecting the hollow coil. The wear-resistant plate 6 is a ceramic or plastic sheet with low conductivity and low magnetic permeability. Two layers of the wear-resistant plate 6 can be provided. When the wear-resistant plate 6 near the detection port wears down and needs replacement, it can be directly removed from the detection port, extending the replacement interval of the wear-resistant plate 6 in the electromagnetic ultrasonic sensor and reducing the number of replacements.

[0047] Furthermore, the first hollow coil 3 and the second hollow coil 4 can be wound with enameled wire or processed using PCB technology, wherein the PCB can be a flexible PCB or a conventional PCB.

[0048] To further optimize the implementation effect of the present invention, this embodiment uses both a scheme without a closed magnetic circuit (the scheme of the present invention) and a scheme with a closed magnetic circuit for simulation experiments, and obtains the following results. Figure 4 , 5 The magnetic field strength distribution diagram on the surface of the specimen is shown. It can be seen from the diagram that the presence or absence of a closed magnetic circuit has almost no effect on the magnetic field strength.

[0049] In addition, this embodiment conducts experiments on the sensor of the present invention, which is equipped with a first hollow coil 3 and a second hollow coil 4, and obtains the following results: Figure 6 The intensity diagrams of longitudinal and transverse waves are shown in Table 1, with specific reference values ​​and measured values.

[0050]

[0051] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0052] The detailed descriptions listed above are merely specific descriptions of feasible embodiments of the present invention, and are not intended to limit the scope of protection of the present invention. All equivalent embodiments or modifications made without departing from the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electromagnetic ultrasonic sensor, characterized in that, include: A permanent magnet assembly includes a first permanent magnet and a second permanent magnet. The second permanent magnet is coaxially arranged with the first permanent magnet and sleeved on the outside of the first permanent magnet. The magnetic field directions of the first permanent magnet and the second permanent magnet are opposite. The difference between the inner diameter of the second permanent magnet and the outer diameter of the first permanent magnet does not exceed 1 mm. A first hollow coil is disposed below the first permanent magnet and is coaxially arranged with the permanent magnet assembly. The outer diameter of the first hollow coil is less than or equal to the outer diameter of the first permanent magnet. The outer casing is fitted over the permanent magnet assembly and the first hollow coil. The outer casing is provided with a plug-in interface, which is electrically connected to the first hollow coil.

2. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, The ratio of the inner diameter to the outer diameter of the first hollow coil is 0.1 to 0.

8.

3. The electromagnetic ultrasonic sensor according to claim 2, characterized in that, For bolts made of steel, the ratio of the inner diameter to the outer diameter of the first hollow coil is 0.2 to 0.

6.

4. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, It also includes a second hollow coil disposed below the permanent magnet assembly, wherein the outer diameter of the second hollow coil is larger than the inner diameter of the second permanent magnet, and the inner diameter of the second hollow coil is smaller than the outer diameter of the first permanent magnet.

5. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, The first permanent magnet is either a solid cylinder or a hollow cylinder along its length.

6. The electromagnetic ultrasonic sensor according to claim 5, characterized in that, When the first permanent magnet is a hollow cylinder along its length, the inner diameter of the first hollow coil is greater than or equal to the inner diameter of the first permanent magnet.

7. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, It also includes a magnetic shielding component, which is disposed between the permanent magnet assembly and the first hollow coil.

8. The electromagnetic ultrasonic sensor according to claim 7, characterized in that, The magnetic shielding component consists of 1 to 6 layers of copper foil or magnetic sheets.

9. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, It also includes a wear-resistant sheet, which is disposed below the first hollow coil.

10. The electromagnetic ultrasonic sensor according to claim 1, characterized in that, The insertion interface is located on the side wall of the housing along the length of the permanent magnet assembly.

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