A dual wave probe and electromagnetic ultrasonic transducer for bolt axial force measurement

Abstract

The application relates to the technical field of transducers, and discloses a double-wave probe and an electromagnetic ultrasonic transducer for bolt axial force measurement, the double-wave probe comprising a square coil and a permanent magnet array, the permanent magnet array comprising a first permanent magnet, a third permanent magnet and a fourth permanent magnet, the first permanent magnet being arranged above a first preset area of the square coil, the third permanent magnet and the fourth permanent magnet being arranged above a second preset area of the square coil, the first preset area corresponding to the side of one direction of the square coil, when the square coil is electrified, the current directions of various mass points 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, and the polarities of the third permanent magnet and the fourth permanent magnet are opposite, and the application can solve the technical problem of transverse wave form distortion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transducers, in particular to a double-wave probe and an electromagnetic ultrasonic transducer for bolt axial force measurement. BACKGROUND

[0002] In engineering such as construction, bridge, mechanical equipment, etc., 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 the bolt, the change of the connection state can be checked, and possible problems can be found and repaired in time, thereby prolonging the service life of the structure. The bolt can also be measured to withstand the expected load, thereby avoiding structural problems caused by insufficient or excessive axial force.

[0003] The ultrasonic method is a method for accurately measuring the axial force of the bolt. Common ultrasonic methods include piezoelectric ultrasonic and electromagnetic ultrasonic. Piezoelectric ultrasonic needs to use a coupling agent to propagate ultrasonic waves into the measured workpiece, and the surface of the measured workpiece needs to be polished smooth. Moreover, the piezoelectric wafer and the coupling agent cannot withstand high temperatures, and are generally applied in scenes below 80℃, which has a small detection temperature range and causes certain difficulties in construction. Electromagnetic ultrasonic does not need a coupling agent, has low requirements for the surface condition of the measured workpiece, does not require surface treatment, and has the advantage of high temperature resistance. Therefore, it is more practical and efficient to measure the axial force of the bolt using electromagnetic ultrasonic.

[0004] Currently, in the field of electromagnetic ultrasonic transducers, there are two methods for measuring the axial force of the bolt, namely single-wave method and double-wave method. The single-wave method for measuring the axial force of the bolt refers to that a single ultrasonic wave pulse is sent to the measured material by an ultrasonic sensor, usually only a transverse wave or only a longitudinal wave, the propagation time of the ultrasonic signal is recorded, the existing length of the bolt is obtained, and according to Hooke's law, the original length and the existing length of the bolt are known, so that the axial force of the bolt can be calculated. The original length of the bolt generally needs to be consulted from the original record, but in many cases, the original record is not available or has errors with the actual original length, at which time manual disassembly measurement is required. However, in some complex environments, it is difficult to disassemble the bolt, resulting in low overall measurement efficiency. When measuring the axial force of the bolt by the double-wave method, two single-wave probes can be used for measurement twice, or a double-wave probe capable of exciting two kinds of waves can be used. The double-wave probe is more efficient and has more advantages than the two single-wave probes measured twice.

[0005] The existing double-wave probe used by the ultrasonic transducer is as follows Figure 1As shown, the coil adopts a circular spiral structure, and a vertical magnetization cylindrical permanent magnet and a cylindrical permanent magnet are arranged above the spiral coil; when the spiral coil is supplied with alternating current, eddy current of corresponding frequency is induced in the skin depth of the surface of the bolt, the direction of the eddy current is opposite to the current direction in the spiral coil, then the eddy current generates force under the action of the magnetic field, i.e. Lorentz force, the direction of the force can be judged by the left-hand rule. Under the action of the cylindrical permanent magnet, the magnetic field is perpendicular to the coil, and the particles on the surface of the test piece move along the respective radial directions under the action of the Lorentz force, exciting a transverse wave. Since the coil in the existing double-wave probe adopts a circular spiral structure, there is a difference in the radial directions of the particles, therefore, when the magnetic field is perpendicular to the coil under the action of the cylindrical permanent magnet, the particles on the surface of the test piece move along the respective radial directions under the action of the Lorentz force, exciting a transverse wave, the vibration form at this time will cause mutual interference between the particles, thereby the phenomenon of transverse wave waveform distortion occurs, affecting the measurement accuracy of the axial force. SUMMARY

[0006] Therefore, the application 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 of the electromagnetic ultrasonic transducer in the prior art.

[0007] The application provides a double-wave probe for bolt axial force measurement, which comprises a square coil and a permanent magnet array.

[0008] In use, the square coil is arranged above the bolt, the first permanent magnet is arranged above the square coil, when the square coil is supplied with alternating current, eddy current of corresponding frequency is induced in the skin depth of the surface of the bolt, the first permanent magnet generates a magnetic field perpendicular to the square coil on the surface of the bolt in the first region and below the first region, the particles on the surface of the bolt move along the respective horizontal directions under the action of the Lorentz force, exciting a transverse wave, since the current directions of the particles in the square coil in the first preset region are the same, the current directions of the eddy currents generated by the particles on the surface of the bolt are also the same, therefore, the particles do not interfere with each other, linear polarization phenomenon occurs, and the transverse wave waveform is not distorted, in addition, the third permanent magnet and the fourth permanent magnet generate a magnetic field parallel to the square coil on the surface of the bolt in the second region and below the second region, the particles on the surface of the bolt move along the respective axial directions under the action of the Lorentz force, exciting a longitudinal wave, 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 2d to 3d, more magnetic field lines can pass through the bolt, the magnetic field strength on the surface of the bolt is increased, and a longitudinal wave with stronger excitation capability can be excited.

[0011] Optionally, the permanent magnet array further comprises a non-ferromagnetic material connecting block, a first side of the non-ferromagnetic material connecting block is connected with the first permanent magnet, and a second side of the non-ferromagnetic material connecting block is connected with the third permanent magnet, and the first side and the second side are both 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, and at the same time, since the third permanent magnet and the fourth permanent magnet are connected through the first non-ferromagnetic material interlayer, the first permanent magnet, the third permanent magnet, the first non-ferromagnetic material interlayer and the fourth permanent magnet form an integral whole, which is convenient to 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 in parallel with each side of the square coil.

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

[0015] Optionally, the permanent magnet array further comprises a second permanent magnet, the second permanent magnet is located above a 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 located on opposite sides of the square coil respectively, and 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, the current directions are opposite, according to the left-hand rule, the directions of the Lorentz forces are the same, the vibration directions of the particles are the same, transverse waves in the same direction are excited, and the area of the transverse wave excitation region can be increased.

[0017] Optionally, the permanent magnet array further comprises 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 arranged between the fifth permanent magnet and the sixth permanent magnet, the fifth permanent magnet and the sixth permanent magnet have opposite polarities, the fifth permanent magnet and the fourth permanent magnet have the same polarity, and the second preset area and the fourth preset area are located on opposite sides of the square coil.

[0018] In this mode, the polarities of the fifth permanent magnet and the sixth permanent magnet are in an axial symmetry relationship with the polarities of the third permanent magnet and the fourth permanent magnet, so that the same direction of the Lorentz force is ensured, the same direction of the longitudinal wave is excited, and the area of the transverse wave excitation region can be increased.

[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 mode, by limiting the distance between the fifth permanent magnet and the sixth permanent magnet to range from 2d to 3d, more magnetic induction lines can pass through the bolt closure, the magnetic field strength on the surface of the bolt is increased, and a longitudinal wave with stronger excitation capability can be excited.

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

[0022] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the following specific embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

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

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

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

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

[0027] Explanation of reference signs:

[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 DESCRIPTION

[0029] The technical solutions of the present application will be described clearly and completely below in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] In the description of the present application, it should be noted that the orientations or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third", "fourth" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0031] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

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

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

[0034] In addition, under the action of the cylindrical permanent magnet, the magnetic field is perpendicular to the coil, and the particles on the surface of the test piece move along the respective radial directions under the action of the Lorentz force, exciting the transverse wave. Under the joint action of the cylindrical permanent magnet and the cylindrical permanent magnet, the magnetic field parallel to the helical coil is formed on the surface of the bolt when the closed magnetic induction lines are formed between the air gaps in the annular region, the particles on the surface of the test piece move along the respective axial directions under the action of the Lorentz force, exciting the longitudinal wave, but since the magnetic field parallel to the helical coil is mostly located above the test piece, the signal strength of the longitudinal wave is far lower than that of the transverse wave.

[0035] Therefore, the embodiment of the present application provides a double-wave probe for bolt axial force measurement, which changes the radial vibration into linear polarization by changing the shape of the coil, and eliminates the problem of transverse wave form distortion. Meanwhile, the problem of weak longitudinal wave signal of the electromagnetic ultrasonic transducer is solved.

[0036] Please refer to Figure 2 The double-wave probe for bolt axial force measurement comprises a square coil 10 and a permanent magnet array.

[0037] The permanent magnet array comprises a first permanent magnet 1, a third permanent magnet 3 and a fourth permanent magnet 4. 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 corresponds to the side of one direction of the square coil 10. When the square coil 10 is energized, the current directions of the particles in the first preset area are the same. The first non-ferromagnetic material interlayer 8 is arranged 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 vertical magnetization 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 an example, the square coil 10 is divided into four areas according to the direction of the side, and the first preset area, the second preset area, the third preset area and the fourth preset area are divided according to the 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 non-ferromagnetic material, which can be copper, aluminum or ceramic, etc. 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] The double-wave probe for bolt axial force measurement of the embodiment of the present application, when in use, the square coil 10 is arranged above the bolt, the first permanent magnet 1 is arranged above the square coil 10, when the square coil 10 is supplied with alternating current, the skin depth on the surface of the bolt will induce eddy current of the corresponding frequency, the first permanent magnet 1 generates a magnetic field perpendicular to the square coil 10 on the bolt surface in the first area and below the first area, the particles on the bolt surface move along the horizontal direction of the respective positions under the action of the Lorentz force, and excite the transverse wave, because the current directions of the particles in the first preset area of the square coil 10 are the same, 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, and the linear polarization phenomenon occurs, and the transverse wave form is not distorted.

[0042] The paths of the magnetic fields generated by the third permanent magnet 3 and the fourth permanent magnet 4 are two, as shown in the figure, 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, and path two is that the fourth permanent magnet 4 generates closed magnetic induction lines through the square coil 10, the ultrasonic transducer shell, the inside of the bolt and the third permanent magnet 3, in this process, there is a magnetic field parallel to the square coil 10 in the inside of the bolt, the particles on the surface of the bolt move along the axial direction of the respective positions under the action of the Lorentz force, and excite the longitudinal wave. Figure 3

[0043] Therefore, the double-wave probe for bolt axial force measurement of the embodiment of the present application can excite the transverse wave and the longitudinal wave at the same time, and avoid the distortion of the transverse wave form.

[0044] In some embodiments, 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.

[0045] Specifically, it is known from the foregoing analysis that the longitudinal wave signal is mainly excited through path two, and therefore the relative strength of the magnetic fields of path one and path two directly affects the longitudinal wave intensity of the electromagnetic ultrasonic transducer. The relative strength of the magnetic fields of path one and path two depends on the distance between the third permanent magnet 3 and the fourth permanent magnet 4.

[0046] With the increase of the distance between the third permanent magnet 3 and the fourth permanent magnet 4, the area of the transduction region also increases accordingly. This helps to improve the coverage range of the magnetic field, thereby enhancing the overall strength of the magnetic field. However, the increase of the distance also brings new problems. When the distance is too large, the magnetic resistance of path one will be smaller than that of path two. The magnetic resistance refers to the degree of hindrance that the magnetic field lines suffer when passing through a certain path, and the size of the magnetic resistance is related to the length, cross-sectional area and magnetic permeability of the material of the path. The smaller magnetic resistance of path one means that the magnetic field lines are more likely to close through path one 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 is too weak to excite a longitudinal wave with a strong signal. Although increasing the distance can increase the area of the transduction region, the magnetic reluctance of path one is smaller than that of path two when the distance is too large, and the magnetic lines of force will preferentially select the magnetic field formed by path one, which cannot excite a longitudinal wave with a strong signal.

[0048] Suppose 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 reluctance of path two is smaller than that of path one, more magnetic lines of force pass through the bolt closure, the magnetic field strength on the surface of the bolt increases, and a longitudinal wave with stronger ability can be excited.

[0049] In this way, by limiting the distance between the third permanent magnet 3 and the fourth permanent magnet 4 to 2d to 3d, more magnetic lines of force pass through the bolt closure, the magnetic field strength on the surface of the bolt increases, and a longitudinal wave with stronger ability can be excited.

[0050] In some embodiments, the permanent magnet array further comprises a non-ferromagnetic material connecting block 7, a first side of the non-ferromagnetic material connecting block 7 is connected to the first permanent magnet 1, and a 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 being 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 non-ferromagnetic material, which can be copper, aluminum, or ceramic, etc. If the non-ferromagnetic material connecting block 7 is ferromagnetic material, the first permanent magnet 1 will directly form a closed magnetic line of force 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, and at the same time, the third permanent magnet 3 and the fourth permanent magnet 4 are connected through the first non-ferromagnetic material interlayer 8, so that the first permanent magnet 1, the third permanent magnet 3, the first non-ferromagnetic material interlayer 8, and the fourth permanent magnet 4 form an integral whole, which is convenient to use.

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

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

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

[0056] As shown in the figure, the second permanent magnet 2 is located above a 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, and the current direction of the square coil 10 in the first preset area and the third preset area is opposite when the square coil 10 is energized. Figure 4

[0057] 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 arranged between the fifth permanent magnet 5 and the sixth permanent magnet 6, the polarity of the fifth permanent magnet 5 and the sixth permanent magnet 6 is opposite, the polarity of the fifth permanent magnet 5 and the fourth permanent magnet 4 is the same, the second preset area and the fourth preset area are respectively located on opposite sides of the square coil 10, and the current direction of the square coil 10 in the second preset area and the fourth preset area is opposite when the square coil 10 is energized.

[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 vertical sides of the non-ferromagnetic material connecting block 7 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 in adjacent preset areas is rotated by 90°.

[0060] Among them, the magnetic field directions generated by the second permanent magnet 2 and the first permanent magnet 1 are opposite, the current directions are opposite, according to the left-hand rule, the directions of the Lorentz forces are the same, the vibration directions of the particles are the same, the same direction of the transverse wave is excited, and the area of the transverse wave excitation region can be increased.

[0061] The polarities of the fifth permanent magnet 5 and the sixth permanent magnet 6 are in an axial symmetric relationship with the polarities of the third permanent magnet 3 and the fourth permanent magnet 4, the same direction of the Lorentz force is ensured, the same direction of the longitudinal wave is excited, and the area of the transverse wave excitation region can be increased.

[0062] The various permanent magnets are connected into a cross-shaped structure through the non-ferromagnetic material connecting block 7, the test area can be increased, and the use is convenient.

[0063] Further, 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. ​

[0064] In the mode, by limiting the distance range of the fifth permanent magnet 5 and the sixth permanent magnet 6 to 2d-3d, more magnetic induction lines can pass through the bolt closure, the magnetic field intensity of the bolt surface is increased, and the longitudinal wave with stronger excitation capacity can be excited.

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

[0066] The dual-wave probe and the electromagnetic ultrasonic transducer for bolt axial force measurement according to the embodiment of the present application change the radial vibration into linear polarization by changing the shape of the coil, eliminate the problem of transverse wave waveform distortion, and reduce the axial force measurement error.

[0067] By limiting the distance range of the third permanent magnet 3 and the fourth permanent magnet 4 to 2d-3d and the distance range of the fifth permanent magnet 5 and the sixth permanent magnet 6 to 2d-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 the non-ferromagnetic material connecting block 7, the test area can be increased, and the use is facilitated.

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

[0070] Although the embodiments of the present application are described above with reference to the drawings, various modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the present application, and such modifications and changes fall within the scope defined by the appended claims.

Claims

1. A dual-wavelength probe for measuring bolt axial force, characterized in that, include: A square coil (10) is divided into four regions according to the direction of its sides, namely, a first preset region, a second preset region, a third preset region, and a fourth preset region, in a clockwise or counterclockwise direction. A 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 a first preset area of ​​the square coil (10). The third permanent magnet (3) and the fourth permanent magnet (4) are disposed above a second preset area of ​​the square coil (10). The first preset area is disposed on one side of the square coil (10). When the square coil (10) is energized, the current direction of each mass point of the square coil (10) in the first preset area is the same. A first non-ferromagnetic material interlayer (8) is provided between the third permanent magnet (3) and the fourth permanent magnet (4). The polarities of the third permanent magnet (3) and the fourth permanent magnet (4) are opposite. The distance between the third permanent magnet (3) and the fourth permanent magnet (4) is 2d to 3d, where d is the lift-off distance, which is the distance between the magnet and the nut.

2. The dual-wavelength probe for measuring bolt axial force according to claim 1, characterized in that, The permanent magnet array also 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), the second side of the non-ferromagnetic material connecting block (7) is connected to the third permanent magnet (3), and both the first side and the second side are perpendicular to the square coil (10).

3. A dual-wavelength probe for measuring bolt axial force according to claim 2, characterized in that, 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).

4. A dual-wavelength probe for measuring bolt axial force according to claim 1, characterized in that, The permanent magnet array also includes a second permanent magnet (2), which is located above the third preset region 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 region and the third preset region are located on opposite sides of the square coil (10). When the square coil (10) is energized, the current direction of the square coil (10) in the first preset region and the third preset region is opposite.

5. A dual-wavelength probe for measuring bolt axial force according to claim 1, characterized in that, The permanent magnet array also includes a fifth permanent magnet (5) and a sixth permanent magnet (6). The fifth permanent magnet (5) and the sixth permanent magnet (6) are located above the fourth preset region 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. The polarities of the fifth permanent magnet (5) and the fourth permanent magnet (4) are the same. The second preset region and the fourth preset region are located on opposite sides of the square coil (10). When the square coil (10) is energized, the current direction of the square coil (10) in the second preset region and the fourth preset region is opposite.

6. A dual-wavelength probe for measuring bolt axial force according to claim 5, characterized in that, The distance between the fifth permanent magnet (5) and the sixth permanent magnet (6) is 2d to 3d, where d is the lift-off distance.

7. An electromagnetic ultrasonic transducer for measuring bolt axial force, characterized in that, Including the dual-wavelength probe as described in any one of claims 1 to 6.

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