Double-wave probe and electromagnetic ultrasonic transducer for bolt axial force measurement

Abstract

The invention relates to the technical field of transducers, and discloses a double-wave probe for bolt axial force measurement and an electromagnetic ultrasonic transducer, the double-wave probe comprises a square coil and a permanent magnet array, the permanent magnet array comprises a first permanent magnet, a third permanent magnet and a fourth permanent magnet, the first permanent magnet is arranged above a first preset area of the square coil, and the third permanent magnet is arranged above a second preset area of the square coil; the third permanent magnet and the fourth permanent magnet are arranged above the second preset area of the square coil, the first preset area is arranged corresponding to the edge of the square coil in one direction, and when the square coil is electrified, the current directions of all mass points of the square coil in the first preset area are the same; a first non-ferromagnetic material interlayer is arranged between the third permanent magnet and the fourth permanent magnet, the polarity of the third permanent magnet is opposite to that of the fourth permanent magnet, and the technical problem of transverse wave waveform distortion can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of transducers, and particularly to a dual-wave probe and an electromagnetic ultrasonic transducer for bolt axial force measurement. Background Art

[0002] In projects such as buildings, bridges, and mechanical equipment, bolt connection is a common connection method, and its axial force state directly affects the safety and stability of the structure. By regularly measuring the axial force of bolts, the change of the connection state can be checked, potential problems can be discovered and repaired in time, and the service life of the structure can be extended. It can also measure whether the bolt can withstand the expected load to avoid structural problems caused by insufficient or excessive axial force.

[0003] The ultrasonic method is a method for accurately measuring the axial force of bolts. The commonly used ultrasonic methods include piezoelectric ultrasound and electromagnetic ultrasound. Piezoelectric ultrasound needs to use a coupling agent to transmit ultrasonic waves to the workpiece to be measured, and the surface of the workpiece to be measured needs to be polished smoothly. Moreover, neither the piezoelectric wafer nor the coupling agent can withstand high temperatures, and it is generally applied in scenarios below 80°C, with a small detection temperature range, causing certain difficulties to construction. Electromagnetic ultrasound does not require a coupling agent, has low requirements for the surface condition of the workpiece to be measured, does not require surface treatment, and has the advantage of high temperature resistance. Therefore, it is more practical and efficient to use electromagnetic ultrasound to measure the axial force of bolts.

[0004] Currently, in the field of electromagnetic ultrasonic transducers, there are two methods for measuring bolt axial force: the single-wave method and the dual-wave method. Measuring the bolt axial force by the single-wave method means that an ultrasonic sensor sends a single ultrasonic pulse to the material to be measured, usually only using shear waves or only using longitudinal waves, records the propagation time of the ultrasonic signal, obtains the current length of the bolt, and according to Hooke's law, knowing the original length and the current length of the bolt, the bolt axial force can be calculated. The original length of the bolt generally needs to be checked in the original record, but in many cases, there is no original record or there is an error between the original record and the actual original length. At this time, manual disassembly measurement is required, but it is very difficult to disassemble the bolt in some complex environments, resulting in a very low overall measurement efficiency. When measuring the bolt axial force by the dual-wave method, two single-wave probes can be used to measure twice, or a dual-wave probe that can generate two types of waves can be used. The dual-wave probe is more efficient and has more advantages than using two single-wave probes to measure twice.

[0005] The existing dual-wave probes used in ultrasonic transducers are as Figure 1As shown in the figure, the coil adopts a circular spiral structure. There are a cylindrical permanent magnet and a cylindrical permanent magnet with vertical magnetization above the spiral coil. When an alternating current is passed through the spiral coil, eddy currents with corresponding frequencies will be induced within the skin depth of the bolt surface. The direction of these eddy currents is opposite to the direction of the current in the spiral coil. Then, under the action of the magnetic field, a force will be generated by the eddy currents, that is, the Lorentz force. The direction of the force can be determined by the left-hand rule. Under the action of the cylindrical permanent magnet, the magnetic field is perpendicular to the coil. The particles on the surface of the specimen move along their respective radial directions under the action of the Lorentz force, exciting transverse waves. Since the coils in the existing double-wave probes adopt a circular spiral structure and there are differences in the radial directions of each particle, when the magnetic field is perpendicular to the coil under the action of the cylindrical permanent magnet and the particles on the surface of the specimen move along their respective radial directions under the action of the Lorentz force, transverse waves are excited. At this time, the vibration form will cause interference between the particles, resulting in the phenomenon of transverse wave waveform distortion and affecting the axial force measurement accuracy. Summary of the Invention

[0006] In view of this, the present invention provides a double-wave probe and an electromagnetic ultrasonic transducer for bolt axial force measurement, which can overcome the technical problem of transverse wave waveform distortion in existing electromagnetic ultrasonic transducers.

[0007] The first aspect of the present invention provides a double-wave probe for bolt axial force measurement, including a square coil; a permanent magnet array, including a first permanent magnet, a third permanent magnet, and a fourth permanent magnet. The first permanent magnet is arranged above the first preset area of the square coil, and the third permanent magnet and the fourth permanent magnet are arranged above the second preset area of the square coil. The first preset area corresponds to the side of the square coil in one direction. When the square coil is energized, the current directions of the particles in the first preset area of the square coil are the same. There is a first non-ferromagnetic material interlayer between the third permanent magnet and the fourth permanent magnet, and the polarities of the third permanent magnet and the fourth permanent magnet are opposite.

[0008] When the double-wave probe for bolt axial force measurement of the present invention is in use, the square coil is arranged above the bolt. By arranging the first permanent magnet above the square coil, when an alternating current is passed through the square coil, eddy currents with corresponding frequencies will be induced within the skin depth of the bolt surface. The first permanent magnet generates a magnetic field perpendicular to the square coil on the bolt surface in the first area and below it. The particles on the bolt surface move along their respective horizontal directions under the action of the Lorentz force, exciting transverse waves. Since the current directions of the particles in the first preset area of the square coil are the same, the current directions of the eddy currents generated by the particles on the bolt surface are also the same. Therefore, there is no interference between the particles, and a linear polarization phenomenon occurs, and the transverse wave waveform will not be distorted. In addition, the third permanent magnet and the fourth permanent magnet generate a magnetic field parallel to the square coil on the bolt surface in the second area and below it. The particles on the bolt surface move along their respective axial directions under the action of the Lorentz force, exciting longitudinal waves, realizing double-wave measurement.

[0009] Optionally, the distance between the third permanent magnet and the fourth permanent magnet ranges from 2d to 3d, where d is the lift-off distance.

[0010] In this way, by limiting the distance between the third permanent magnet and the fourth permanent magnet to the range of 2d to 3d, more magnetic induction lines can be closed through the bolt, the magnetic field strength on the bolt surface increases, and longitudinal waves with stronger energy can be excited.

[0011] Optionally, the permanent magnet array further includes a non-ferromagnetic material connecting block. The first side of the non-ferromagnetic material connecting block is connected to the first permanent magnet, and the second side of the non-ferromagnetic material connecting block is connected to the third permanent magnet. Both the first side and the second side are perpendicular to the square coil.

[0012] In this way, the first permanent magnet and the third permanent magnet are connected through different sides of the non-ferromagnetic material connecting block. At the same time, since the third permanent magnet and the fourth permanent magnet are connected through the first non-ferromagnetic material interlayer, in this way, the first permanent magnet, the third permanent magnet, the first non-ferromagnetic material interlayer, and the fourth permanent magnet can be made into a whole, which is convenient for use.

[0013] Optionally, the non-ferromagnetic material connecting block is a square block, and each side of the non-ferromagnetic material connecting block is arranged parallel to each side of the square coil.

[0014] In this way, each side of the non-ferromagnetic material connecting block is arranged parallel to each side of the square coil, so that each preset area corresponds to a side in one direction of the square coil, and the eddy current directions generated by the bolts below each preset area are the same, thereby changing the radial vibration into linear polarization and solving the problem of transverse wave waveform distortion.

[0015] Optionally, the permanent magnet array further includes a second permanent magnet. The second permanent magnet is located above the third preset area of the square coil. The polarity of the second permanent magnet is opposite to that of the first permanent magnet. The first preset area and the third preset area are respectively located on opposite sides of the square coil. When the square coil is energized, the current directions in the first preset area and the third preset area of the square coil are opposite.

[0016] In this way, the magnetic field directions generated by the second permanent magnet and the first permanent magnet are opposite, and the current directions are opposite. According to the left-hand rule, it can be known that the directions of the Lorentz forces are the same, the vibration directions of the particles are the same, and transverse waves in the same direction are excited, and further, the area of the transverse wave excitation region can be increased.

[0017] Optionally, the permanent magnet array further includes a fifth permanent magnet and a sixth permanent magnet. The fifth permanent magnet and the sixth permanent magnet are located above the fourth preset area of the square coil. A second non-ferromagnetic material interlayer is provided between the fifth permanent magnet and the sixth permanent magnet. The polarities of the fifth permanent magnet and the sixth permanent magnet are opposite, and the polarities of the fifth permanent magnet and the fourth permanent magnet are the same. The second preset area and the fourth preset area are respectively located on opposite sides of the square coil. When the square coil is energized, the current directions in the second preset area and the fourth preset area of the square coil are opposite.

[0018] In this method, the polarities of the fifth permanent magnet and the sixth permanent magnet and the polarities of the third permanent magnet and the fourth permanent magnet are in an axisymmetric relationship, ensuring the Lorentz force in the same direction and exciting longitudinal waves in the same direction, which can increase the area of the shear wave excitation region.

[0019] Optionally, the distance between the fifth permanent magnet and the sixth permanent magnet ranges from 2d to 3d, where d is the lift-off distance.

[0020] In this method, by limiting the distance between the fifth permanent magnet and the sixth permanent magnet to the range of 2d to 3d, more magnetic induction lines can be closed through the bolt, increasing the magnetic field strength on the surface of the bolt and enabling the excitation of longitudinal waves with stronger energy.

[0021] The second aspect of the present invention provides an electromagnetic ultrasonic transducer for bolt axial force measurement, including the dual-wave probe in the first aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 It is a schematic structural diagram of a dual-wave probe in the related art;

[0024] Figure 2 It is a schematic structural diagram of the dual-wave probe for bolt axial force measurement in the embodiment of the present invention;

[0025] Figure 3 It is a schematic diagram of the magnetic induction line path of the third permanent magnet and the fourth permanent magnet in the embodiment of the present invention;

[0026] Figure 4 It is a schematic principle diagram of the dual-wave probe for bolt axial force measurement in the embodiment of the present invention.

[0027] Description of the reference numerals:

[0028] 1 - First permanent magnet; 2 - Second permanent magnet; 3 - Third permanent magnet; 4 - Fourth permanent magnet; 5 - Fifth permanent magnet; 6 - Sixth permanent magnet; 7 - Non - ferromagnetic material connecting block; 8 - First non - ferromagnetic material interlayer; 9 - Second non - ferromagnetic material interlayer; 10 - Square coil. Detailed implementation mode

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0030] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", "third", "fourth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0031] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0032] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] In a double - wave probe as Figure 1 shown, under the action of a cylindrical permanent magnet, the magnetic field is perpendicular to the coil, and the particles on the surface of the specimen move along their respective radial directions under the action of the Lorentz force, exciting transverse waves. Since the coils in the existing double - wave probes adopt a circular spiral structure and there are differences in the radial directions of each particle, when, under the action of a cylindrical permanent magnet, the magnetic field is perpendicular to the coil and the particles on the surface of the specimen move along their respective radial directions under the action of the Lorentz force, transverse waves are excited. At this time, the vibration form will cause interference between particles, resulting in the phenomenon of transverse - wave waveform distortion and affecting the axial - force measurement accuracy.

[0034] In addition, under the action of the cylindrical permanent magnet, the magnetic field is perpendicular to the coil. The particles on the surface of the specimen move along their respective radial directions under the action of the Lorentz force, exciting transverse waves. Under the combined action of the cylindrical permanent magnet and the cylindrical permanent magnet, when closed magnetic induction lines are formed between the air gaps in the circular ring region, a magnetic field parallel to the spiral coil is formed on the surface of the bolt. The particles on the surface of the specimen move along their respective axial directions under the action of the Lorentz force, exciting longitudinal waves. However, since most of the magnetic field parallel to the spiral coil is located above the specimen, the intensity of the longitudinal wave signal is much lower than that of the transverse wave.

[0035] In view of this, an embodiment of the present invention provides a dual-wave probe for measuring the axial force of a bolt. By changing the shape of the coil, the radial vibration is changed into linear polarization, eliminating the problem of transverse wave waveform distortion. At the same time, the problem of weak longitudinal wave signals of electromagnetic ultrasonic transducers is solved.

[0036] Please refer to Figure 2 , the dual-wave probe for measuring the axial force of a bolt according to the embodiment of the present invention includes a square coil 10 and a permanent magnet array.

[0037] The permanent magnet array includes a first permanent magnet 1, a third permanent magnet 3, and a fourth permanent magnet 4. The first permanent magnet 1 is disposed above the first preset area of the square coil 10. The third permanent magnet 3 and the fourth permanent magnet 4 are disposed above the second preset area of the square coil 10. The first preset area corresponds to the side of the square coil 10 in one direction. When the square coil 10 is energized, the current directions of the particles in the first preset area of the square coil 10 are the same. A first non-ferromagnetic material interlayer 8 is provided between the third permanent magnet 3 and the fourth permanent magnet 4, and the polarities of the third permanent magnet 3 and the fourth permanent magnet 4 are opposite.

[0038] Specifically, the first permanent magnet 1, the third permanent magnet 3, and the fourth permanent magnet 4 are all vertically magnetized permanent magnets with the same height.

[0039] The first preset area and the second preset area are different positions in the square coil 10, so that the first permanent magnet 1, the third permanent magnet 3, and the fourth permanent magnet 4 are located at different positions on the same horizontal plane. In one example, the square coil 10 is divided into four areas according to the direction of the sides, and the first preset area, the second preset area, the third preset area, and the fourth preset area are divided in a clockwise or counterclockwise direction. When the square coil 10 is energized, the current directions of the particles in the same preset area are the same.

[0040] The first non-ferromagnetic material interlayer 8 is made of a non-ferromagnetic material, and the non-ferromagnetic material can be copper, aluminum, or ceramic, etc. Because if the interlayer is a ferromagnetic material, the third permanent magnet 3 will directly form a closed magnetic induction line with the fourth permanent magnet 4 through the ferromagnetic material.

[0041] A dual-wave probe for bolt axial force measurement according to an embodiment of the present invention, when in use, a square coil 10 is arranged above the bolt. By arranging a first permanent magnet 1 above the square coil 10, when an alternating current is passed through the square coil 10, eddy currents of a corresponding frequency will be induced within the skin depth of the bolt surface. The first permanent magnet 1 generates a magnetic field perpendicular to the square coil 10 on the bolt surface in the first region and below it. The particles on the bolt surface move along their respective horizontal directions under the action of the Lorentz force, exciting shear waves. Since the current directions of the particles in the square coil 10 are the same in the first preset region, and the current directions of the eddy currents generated by the particles on the bolt surface are also the same, therefore, the particles do not interfere with each other, resulting in a linear polarization phenomenon and the shear wave waveform not being distorted.

[0042] There are two paths for the third permanent magnet 3 and the fourth permanent magnet 4 to generate a magnetic field, as Figure 3 shown. Path one is that the third permanent magnet 3 and the fourth permanent magnet 4 generate closed magnetic induction lines through the first non-ferromagnetic material interlayer 8. Path two is that the fourth permanent magnet 4 generates closed magnetic induction lines through the square coil 10, the ultrasonic transducer housing, and inside the bolt and the third permanent magnet 3. During this process, there is a magnetic field parallel to the square coil 10 inside the bolt, and the particles on the bolt surface move along their respective axial directions under the action of the Lorentz force, exciting longitudinal waves.

[0043] Therefore, the dual-wave probe for bolt axial force measurement according to the embodiment of the present invention can simultaneously excite shear waves and longitudinal waves and avoid shear wave waveform distortion.

[0044] In some embodiments, the distance range between the third permanent magnet 3 and the fourth permanent magnet 4 is 2d to 3d, where d is the lift-off distance.

[0045] Specifically, through the foregoing analysis, it is known that the longitudinal wave signal is mainly excited by the magnetic induction of path two. Therefore, the relative strengths of the magnetic fields of path one and path two directly affect the longitudinal wave intensity of the electromagnetic ultrasonic transducer. And the relative strengths of the magnetic fields of path one and path two depend on the distance between the third permanent magnet 3 and the fourth permanent magnet 4.

[0046] As the distance between the third permanent magnet 3 and the fourth permanent magnet 4 increases, the area of the transducer region will also increase accordingly. This helps to increase the coverage range of the magnetic field and thus enhance the overall intensity of the magnetic field. However, the increase in distance also brings new problems. When the distance is too large, the magnetic resistance of path one will be less than that of path two. Magnetic resistance refers to the degree of obstruction that the magnetic field lines encounter when passing through a certain path, and the size of the magnetic resistance is related to the length, cross-sectional area of the path, and the magnetic permeability of the material. A smaller magnetic resistance of path one means that the magnetic field lines are more likely to close through path one rather than through path two.

[0047] Therefore, if the distance between the third permanent magnet 3 and the fourth permanent magnet 4 is too small, the magnetic field parallel to the square coil 10 will be very weak and cannot excite longitudinal waves with strong signals. Although increasing the distance will increase the area of the transducer region, if it is too large, the magnetic resistance of path one will be less than that of path two, and the magnetic induction lines will preferentially choose the magnetic field formed by path one, and longitudinal waves with strong signals cannot be excited either.

[0048] Assume that the lift-off distance (the distance between the magnet and the nut) is d. When the distance between the third permanent magnet 3 and the fourth permanent magnet 4 is greater than twice the lift-off distance and less than three times the lift-off distance, the magnetic resistance of path two is less than that of path one, and more magnetic induction lines are closed through the bolt, increasing the magnetic field strength on the surface of the bolt and enabling the excitation of longitudinal waves with stronger energy.

[0049] In this way, by restricting the distance range between the third permanent magnet 3 and the fourth permanent magnet 4 to 2d to 3d, more magnetic induction lines can be closed through the bolt, increasing the magnetic field strength on the surface of the bolt and enabling the excitation of longitudinal waves with stronger energy.

[0050] In some embodiments, the permanent magnet array further includes a non-ferromagnetic material connecting block 7. The first side of the non-ferromagnetic material connecting block 7 is connected to the first permanent magnet 1, and the second side of the non-ferromagnetic material connecting block 7 is connected to the third permanent magnet 3. Both the first side and the second side are perpendicular to the square coil 10.

[0051] The non-ferromagnetic material connecting block 7 is mainly used to fix the surrounding permanent magnets. The non-ferromagnetic material connecting block 7 is made of a non-ferromagnetic material, which can be copper, aluminum, or ceramic, etc. Because if the non-ferromagnetic material connecting block 7 is a ferromagnetic material, the first permanent magnet 1 will directly form closed magnetic induction lines with the non-ferromagnetic material connecting block 7 through the ferromagnetic material.

[0052] In this way, the first permanent magnet 1 and the third permanent magnet 3 are connected through different sides of the non-ferromagnetic material connecting block 7. At the same time, since the third permanent magnet 3 and the fourth permanent magnet 4 are connected through the first non-ferromagnetic material interlayer 8, in this way, the first permanent magnet 1, the third permanent magnet 3, the first non-ferromagnetic material interlayer 8, and the fourth permanent magnet 4 can be made into a whole, which is convenient for use.

[0053] Furthermore, the non-ferromagnetic material connecting block 7 is a square block, and each side of the non-ferromagnetic material connecting block 7 is arranged parallel to each side of the square coil 10.

[0054] In this way, each side of the non-ferromagnetic material connecting block 7 is arranged parallel to each side of the square coil 10, so that each preset region corresponds to one side of the square coil 10 in one direction, and the eddy current directions generated by the bolts under each preset region are the same, thereby changing the radial vibration into linear polarization and solving the problem of transverse wave waveform distortion.

[0055] Furthermore, the permanent magnet array further includes a second permanent magnet 2, a fifth permanent magnet 5, and a sixth permanent magnet 6.

[0056] As Figure 4 shown, the second permanent magnet 2 is located above the third preset area of the square coil 10. The polarity of the second permanent magnet 2 is opposite to that of the first permanent magnet 1. The first preset area and the third preset area are respectively located on opposite sides of the square coil 10. When the square coil 10 is energized, the current directions in the first preset area and the third preset area of the square coil 10 are opposite.

[0057] The fifth permanent magnet 5 and the sixth permanent magnet 6 are located above the fourth preset area of the square coil 10. A second non-ferromagnetic material interlayer 9 is provided between the fifth permanent magnet 5 and the sixth permanent magnet 6. The polarities of the fifth permanent magnet 5 and the sixth permanent magnet 6 are opposite, and the polarities of the fifth permanent magnet 5 and the fourth permanent magnet 4 are the same. The second preset area and the fourth preset area are respectively located on opposite sides of the square coil 10. When the square coil 10 is energized, the current directions in the second preset area and the fourth preset area of the square coil 10 are opposite.

[0058] Exemplarily, the non-ferromagnetic material connecting block 7 is a square block. The first permanent magnet 1, the fourth permanent magnet 4, the second permanent magnet 2, and the fifth permanent magnet 5 are sequentially arranged on four side faces of the non-ferromagnetic material connecting block 7 perpendicular to the square coil 10 in a counterclockwise direction. The first permanent magnet 1 and the second permanent magnet 2 are oppositely arranged, and the fourth permanent magnet 4 and the fifth permanent magnet 5 are oppositely arranged.

[0059] Correspondingly, the first preset area, the second preset area, the third preset area, and the fourth preset area are also sequentially arranged in a counterclockwise direction, and the current direction rotates 90° in adjacent preset areas.

[0060] Among them, the magnetic field directions generated by the second permanent magnet 2 and the first permanent magnet 1 are opposite, and the current directions are opposite. According to the left-hand rule, it can be known that the directions of the Lorentz forces are the same, the vibration directions of the particles are the same, and transverse waves in the same direction are excited, thereby increasing the area of the transverse wave excitation region.

[0061] The polarities of the fifth permanent magnet 5 and the sixth permanent magnet 6 and the polarities of the third permanent magnet 3 and the fourth permanent magnet 4 are in an axisymmetric relationship, ensuring the Lorentz forces in the same direction, exciting longitudinal waves in the same direction, and increasing the area of the transverse wave excitation region.

[0062] By connecting each permanent magnet into a cross-shaped structure through the non-ferromagnetic material connecting block 7, the test area can be increased and it is convenient to use.

[0063] Furthermore, the distance range between the fifth permanent magnet 5 and the sixth permanent magnet 6 is 2d to 3d, where d is the lift-off distance.

[0064] In this method, by restricting the distance range between the fifth permanent magnet 5 and the sixth permanent magnet 6 to 2d to 3d, more magnetic induction lines can be closed through the bolt, the magnetic field strength on the bolt surface increases, and longitudinal waves with stronger energy can be excited.

[0065] The embodiment of the present invention also provides an electromagnetic ultrasonic transducer for bolt axial force measurement, including a dual-wave probe in any of the above embodiments.

[0066] For the dual-wave probe and electromagnetic ultrasonic transducer for bolt axial force measurement in the embodiment of the present invention, by changing the shape of the coil, the radial vibration is changed into linear polarization, the problem of transverse wave waveform distortion is eliminated, and the axial force measurement error is reduced.

[0067] By restricting the distance range between the third permanent magnet 3 and the fourth permanent magnet 4 to 2d to 3d, and the distance range between the fifth permanent magnet 5 and the sixth permanent magnet 6 to 2d to 3d, the longitudinal wave signal can be enhanced, and the problem that the longitudinal wave signal of the existing dual-wave probe is much smaller than the transverse wave signal can be solved.

[0068] By connecting each permanent magnet into a cross-shaped structure through a non-ferromagnetic material connecting block 7, the test area can be increased and it is convenient to use.

[0069] In addition, the dual-wave probe and electromagnetic ultrasonic transducer for bolt axial force measurement in the embodiment of the present invention can also avoid the problem of low detection efficiency caused by the need to measure the original length when measuring the bolt axial force by the single-wave method.

[0070] Although the embodiments of the present invention have been described above in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A dual-wave probe for bolt axial force measurement, characterized in that: include: Square coil (10); A permanent magnet array comprises a first permanent magnet (1), a third permanent magnet (3) and a fourth permanent magnet (4), wherein the first permanent magnet (1) is arranged above a first preset area of ​​the square coil (10), and the third permanent magnet (3) and the fourth permanent magnet (4) are arranged above a second preset area of ​​the square coil (10), the first preset area being arranged corresponding to an edge of the square coil (10) in one direction, when the square coil (10) is energized, the current directions of the various particles of the square coil (10) within the first preset area are the same, a first non-ferromagnetic material interlayer (8) is arranged between the third permanent magnet (3) and the fourth permanent magnet (4), and the third permanent magnet (3) and the fourth permanent magnet (4) have opposite polarities.

2. A dual-wave probe for bolt axial force measurement according to claim 1, characterized in that: The distance between the third permanent magnet (3) and the fourth permanent magnet (4) ranges from 2d to 3d, wherein d is the lift-off distance.

3. The dual-wave probe for bolt axial force measurement according to claim 1, characterized in that: The permanent magnet array further comprises a non-ferromagnetic material connecting block (7), a first side surface of the non-ferromagnetic material connecting block (7) being connected to the first permanent magnet (1), a second side surface of the non-ferromagnetic material connecting block (7) being connected to the third permanent magnet (3), and the first side surface and the second side surface being both perpendicular to the square coil (10).

4. A dual-wave probe for bolt axial force measurement according to claim 3, characterized in that: The non-ferromagnetic material connection block (7) is a square block, and the respective sides of the non-ferromagnetic material connection block (7) are arranged parallel to the respective sides of the square coil (10).

5. The dual-wave probe for bolt axial force measurement according to claim 1, characterized in that: The permanent magnet array further comprises a second permanent magnet (2), the second permanent magnet (2) being located above a third preset area of ​​the square coil (10), the polarity of the second permanent magnet (2) being opposite to the polarity of the first permanent magnet (1), the first preset area and the third preset area being respectively located on two opposite sides of the square coil (10), and when the square coil (10) is energized, the current directions of the square coil (10) in the first preset area and the third preset area are opposite.

6. The dual-wave probe for bolt axial force measurement according to claim 1, characterized in that: The permanent magnet array further comprises a fifth permanent magnet (5) and a sixth permanent magnet (6), wherein the fifth permanent magnet (5) and the sixth permanent magnet (6) are located above a fourth preset area of ​​the square coil (10), a second non-ferromagnetic material interlayer (9) is provided between the fifth permanent magnet (5) and the sixth permanent magnet (6), the fifth permanent magnet (5) and the sixth permanent magnet (6) have opposite polarities, the fifth permanent magnet (5) and the fourth permanent magnet (4) have the same polarity, the second preset area and the fourth preset area are respectively located on opposite sides of the square coil (10), and when the square coil (10) is energized, the current directions of the square coil (10) in the second preset area and the fourth preset area are opposite.

7. A dual-wave probe for bolt axial force measurement according to claim 6, characterized in that: The distance between the fifth permanent magnet (5) and the sixth permanent magnet (6) ranges from 2d to 3d, wherein d is the lift-off distance.

8. An electromagnetic ultrasonic transducer for bolt axial force measurement, characterized in that: Comprising a dual-wave probe as described in any one of claims 1 to 7.

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