A stress wave generator with active coil protection device

Abstract

The present invention discloses a stress wave generator with an active coil protection device, which belongs to the field of stress wave generating devices for testing the dynamic mechanical properties of materials. In view of the problem that the active coil and the insulating interlayer are damaged during the experiment of the existing stress wave generator due to the easy damage of the bolts connecting the insulating interlayer and the mass block and the low reliability of the axial limit of the insulating shell, the present invention designs a special wheel disc protection cover, and the wheel disc protection cover is provided with 20 countersunk holes along the axial direction around the wheel disc protection cover, and a rib converging inward is provided around one end of the wheel disc protection cover, and the other end is an open end. The wheel disc protection cover is mounted on the active coil and the insulating interlayer, the inner wall of the rib is against the active coil, and the end face of the open end is in contact with the first mass block. The wheel disc protection cover and the first mass block are fixedly connected by 20 screws, so as to realize mechanical protection of the active coil and the insulating interlayer, avoid damage to the active coil during the experiment, improve the experimental stability, and reduce the experimental cost.

Description

Technical Field

[0001] The invention belongs to the field of stress wave generating devices for dynamic mechanical property testing of materials, and in particular relates to a stress wave generator with an active coil protection device. Background Art

[0002] With the continuous development of modern science and technology, engineering materials are increasingly widely used in various fields such as civil facilities, military weapons, and aerospace. During service, materials are inevitably subjected to impact loads. Understanding the mechanical response of materials under impact loading is helpful for the engineering application and engineering design of various materials. At present, in the field of solid mechanics, the most widely used technology for measuring the mechanical properties of materials under high strain rates is the Hopkinson bar technology.

[0003] The basic principle of the Hopkinson bar test technology is: when the striking rod (bullet) in the gun barrel bounces into the input rod at a certain speed, an incident pulse is generated in the input rod, and the stress wave propagates to the sample through the waveguide, and the sample deforms at high speed under the action of the stress pulse.

[0004] Since the dynamic deformation and destruction of materials and structures occur under the action of stress waves, the way stress waves are generated is crucial. The Hopkinson bar driven by electromagnetic launch technology has advantages that ordinary launch technologies cannot match, such as high launch speed, simple energy, high efficiency, excellent performance, strong controllability and diverse structures (reference: [1] Wang Weibin, Suo Tao, Guo Yazhou, et al. Experimental technology and research progress of electromagnetic Hopkinson bar [J]. Advances in Mechanics, 2021, 51(04): 729-754.).

[0005] Li Yulong and others from Northwestern Polytechnical University used self-developed electromagnetic Hopkinson rods in patents ZL201410161610.X, ZL201410171963.8, ZL201420198611.7, ZL201510051071.9, and ZL201510956545.4 to generate tensile and compressive stress waves required for loading based on electromagnetic riveting technology, which can complete the test of dynamic mechanical properties of specimens under high strain rate.

[0006] The electromagnetic Hopkinson bar device consists of a charging circuit, a discharging circuit and a stress wave generator:

[0007] The charging circuit includes a high-power transformer and a bridge regulator to convert the industrial AC voltage into a preset high-voltage DC voltage. Four customized pulse capacitors form a capacitor bank for storing and releasing electrical energy. The capacitance of each pulse capacitor is 2mF and the rated voltage is 5000V. Different capacitance values ​​(0.5mF-0.8mF) can be obtained by connecting the four capacitors in series and in parallel.

[0008] The discharge circuit is an LC circuit consisting of a capacitor bank and an active coil. When the capacitor is fully charged, the electric energy stored in the capacitor bank is released through the connected active coil by sending a trigger signal to the discharge switch. The current design is: In order to withstand a discharge current of up to 25,000V, the active coil is designed to be made of a 2mm thick and 15mm wide copper strip, with an outer diameter of 90mm, an inner diameter of 20mm, and an inductance design of 3.3μH. The gaps between the turns are filled with an insulating layer formed by resin material and glass cloth, which, on the one hand, avoids short circuits between the turns, and on the other hand, helps the active coil to withstand the radial Lorentz force generated during the discharge process. The discharge period of the LC discharge circuit can be theoretically estimated by the following formula:

[0009]

[0010] Wherein, L is the inductance of the active coil, C is the capacitance, and T is the pulse width of the generated half-sine current pulse.

[0011] The stress wave generator is mainly composed of an active coil, an insulating barrier, an insulating shell, a U-shaped clamp, and a main mass block. The insulating layer wraps the active coil in a circumferential direction, leaving only a gap at the electrode. The insulating shell is fitted over the active coil and the insulating layer, with one end of the insulating shell converging inward to hold the active coil, and the other end in contact with the main mass block, and its axial position is limited by the U-shaped clamp. The active coil and the insulating layer in the insulating shell are fixed to the main mass block of the stress wave generator by screws to reduce the exposed area of ​​the energized part. The mass block of the stress wave generating device is the main part, which is supported by 45 steel and is used to withstand the recoil force generated by electromagnetic loading. Grooves are processed on both sides of the mass block for installing the discharge cable connector. The electrode of the active coil is clamped into the groove of the discharge cable connector in the horizontal direction, and the entire stress wave generator is fixed to the base by a U-shaped clamp. The U-shaped clamp also fixes the discharge cable connector of the cable. Such a structural design can avoid the end of the discharge cable being in a hanging state. On the one hand, it can effectively prevent the rotation of the discharge cable relative to the active coil electrode, which may cause the screws to loosen and spark discharge. On the other hand, it can prevent the discharge cable from generating excessive traction on the active coil to damage the active coil electrode.

[0012] The pulse discharge current in the active coil generates a changing magnetic field around it. The magnetic field strength vector The direction of is basically distributed along the radial direction on the surface of the induction coil. The induction coil will generate an induced current under the action of a changing magnetic field (Lenz's law). Let q and The decibel is the charge carried by the particle in the induction coil and the velocity vector of the charge, and the magnetic field generated by the active coil. The Lorentz magnetic field force on the particle is

[0013]

[0014] From the vector calculation law, we know that the Lorentz force The direction is mainly perpendicular to the cross section of the induction coil, generating an electromagnetic repulsive force between the induction coil and the active coil. When the current in the discharge circuit is a half-sinusoidal current pulse, the Lorentz force is a stress wave pulse with the same shape.

[0015] The stress wave generator needs to use high-voltage instantaneous discharge to work. The working voltage is generally 1000-4000V. It generates a large load in a short time and propagates in the form of high-energy stress waves. According to Newton's third law, after the tensile wave generated by the large load is transmitted to the Hopkinson bar, a series of compression waves with the same amplitude and pulse width will be generated and propagated again in the opposite direction into the stress wave generator. Similarly, after the compression wave generated by the larger load is transmitted to the Hopkinson bar, a series of tensile waves with the same amplitude and pulse width will also be generated and propagated again in the opposite direction into the stress wave generator. The most direct impact is that a large amount of energy is generated to act on the active coil and the insulating barrier. Due to the limitation of the electromagnetic induction principle, the active coil cannot use a metal with higher strength as the raw material. In addition, the overall structure of the active coil and the insulating barrier of the existing stress wave generator is fixedly connected to the mass block through three bolts, and the axial limiting stability of the insulating barrier to the active coil and the insulating barrier is insufficient. During the test, each loading is repeated due to the cyclic nature of stress wave propagation (in dynamic mechanical form, these materials are compressive but not tensile. After the high-energy compression package is transmitted to these three bolts, the smaller force area bears a larger load, resulting in stress concentration). In almost every experiment, the bolts connecting the mass block and the insulating barrier are damaged, resulting in a gap between the active coil and the insulating barrier. The gap causes a large load on the interface, causing damage to the active coil.

[0016] As for the test process, firstly, it consumes material resources. The current active coil costs about 2,000 yuan. Each time a voltage of 3,000 V is applied, irreversible damage will be caused to the active coil, and the next test cannot be carried out. Therefore, each test will incur additional costs due to the lack of an effective active coil protection device. Secondly, even under low voltage, the active coil still needs to be checked and replaced frequently, which slows down the progress of the experiment and affects the efficiency of the experiment. Thirdly, if the insulating barrier formed by the resin material and glass cloth filled in the active coil is damaged, it will cause a short circuit and high-voltage sparking, which poses a great safety hazard.

[0017] Therefore, it is necessary to improve the protection of the active coil of the stress wave generating device. Summary of the invention

[0018] Technical issues to be solved:

[0019] In order to avoid the shortcomings of the prior art, the present invention provides a stress wave generator with an active coil protection device. Based on the existing stress wave generator structure and its experimental method, it is improved, and a wheel disc protection cover is designed to be mounted on the active coil and the insulating barrier. The wheel disc protection cover is connected to the mass block through fasteners installed on the periphery of the wheel disc protection cover, thereby changing the connection method of the original active coil and the insulating barrier as a whole with the mass block, improving the installation stability and reliability, and providing mechanical protection for the active coil.

[0020] The technical scheme of the present invention is: a stress wave generator with an active coil protection device, comprising an induction coil, an active coil, an insulating barrier, a U-shaped clamp, a first mass block, and a second mass block, wherein the induction coil, the active coil, the insulating barrier, the first mass block, and the second mass block are coaxially fitted and connected in sequence, the U-shaped clamp is sleeved on the outer diameter of the first mass block, and is used to fix the stress wave generating device and the discharge cable connector, and the U-shaped clamp is fixedly connected to the mounting seat of the stress wave generator; the electrode of the active coil is inserted into the discharge cable connector to connect the discharge circuit; the waveguide runs through the stress wave generator, one end of which is fixedly connected to the induction coil, and the other end is connected to the test piece, and is used to transmit the stress wave; it is characterized in that it also includes a wheel protection cover;

[0021] The wheel disc protection cover is a cylindrical hollow shell, one end of which is provided with an inwardly converging rib, the inner diameter of which matches the outer diameter of the induction coil; the other end is an open end, which is provided with two radially arranged notches for avoiding the active coil electrodes on both sides of the active coil; a plurality of countersunk holes axially penetrating the wheel disc protection cover shell are provided on the same circumference of the outer side of the rib;

[0022] The wheel disc protection cover is sleeved on the active coil and the insulating barrier, the inner wall of the rib is against the active coil, the open end surface is in contact with the first mass block, and the wheel disc protection cover is fixedly connected to the first mass block by fasteners passing through the countersunk hole.

[0023] A further technical solution of the present invention is that the countersunk holes avoid the slot position and are symmetrically arranged on the wheel disc protection cover shell on both sides of the slot.

[0024] A further technical solution of the present invention is that the number of the countersunk holes is 20.

[0025] A further technical solution of the present invention is: a plurality of threaded holes are provided on the contact surface between the first mass block and the wheel disc protection cover, and the threaded holes correspond one-to-one to the countersunk holes of the wheel disc protection cover for threaded connection with fasteners.

[0026] A further technical solution of the present invention is: a plurality of threaded through holes are evenly distributed on the same circumference of the first mass block, and the second mass block is provided with threaded through holes corresponding one to one to the plurality of threaded through holes on the first mass block, and bolts are passed through the second mass block, the first mass block and the insulating barrier in sequence to fix them.

[0027] A further technical solution of the present invention is that the first mass block and the second mass block are both provided with three threaded through holes.

[0028] A further technical solution of the present invention is: the stress wave generator also includes a cable connector, which is a strip plate structure with a boss at one end, and a cable installation hole is provided at the end of the boss for installing a discharge cable, and two screw holes are provided on the boss to pass through the cable installation hole for fixing the discharge cable; one end of the cable connector away from the boss contacts the plug-in surface of the active coil electrode and is connected to the end of the active coil electrode through a stud; the active coil electrode carries the cable connector and is inserted into the corresponding discharge cable connector.

[0029] A further technical solution of the present invention is that the thickness of the boss of the cable connector is greater than the thickness of the active coil electrode.

[0030] A further technical solution of the present invention is that the inner diameter of the wheel disc protection cover rib is larger than the outer diameter of the induction coil.

[0031] A further technical solution of the present invention is that a planar transition section is provided at the outer diameter of the wheel disc protection cover at a circumferential interval of 90° from the center line of the notch for installation and positioning.

[0032] Beneficial Effects

[0033] The beneficial effects of the present invention are as follows: a stress wave generator with an active coil protection device described in the present invention is designed with a special wheel disc protection cover, 20 countersunk holes are arranged axially around the wheel disc protection cover, the wheel disc protection cover is sleeved on the active coil and the insulating barrier, and 20 screws are passed through the countersunk holes and fixedly connected to the first mass block from one side of the retaining edge, thereby realizing mechanical protection of the active coil and the insulating barrier; at the same time, 3 bolts are passed through the second mass block, the first mass block is connected to the insulating barrier, which plays a further fixing role.

[0034] Through this structural design, the overall mechanical protection of the active coil and the insulating interlayer is achieved through the wheel protective cover, avoiding the problem of failure caused by the gap between the active coil and the insulating interlayer due to the failure of the original structural connection bolts and the insufficient axial limit stability of the insulating shell on the active coil and the insulating interlayer during the experimental loading process, thereby improving the safety of the active coil. The first mass block is connected by 20 screws around the wheel protective cover, so that the installation flatness of the active coil is improved, and the reliability is improved. After the flatness is guaranteed by the left-hand screw rule, the component loss of the force on the Hopkinson rod waveguide is reduced, and the deflection of the Hopkinson rod waveguide is reduced, and the bending is reduced.

[0035] The present invention eliminates the insulating shell in the original stress wave generating device, and the wheel disc protection cover also plays the role of the insulating shell, thereby avoiding additional structural complexity of parts as much as possible.

[0036] The present invention installs a cable connector on the electrode ends on both sides of the active coil. The cable connector and the active coil electrode are connected by double-stud flat contact. The cable connector is inserted into the discharge cable connector and connected to the cable. This structure increases the contact area between the electrode and the cable, avoids high-voltage discharge sparks, and improves the connection strength. Since screws are provided on the boss of the cable connector to fix the cable, fatigue damage due to the cable's own weight or static friction when the cable is mounted for a long time is prevented.

[0037] After experimental testing, the stress wave generator with an active coil protection device of the present invention has been applied to a voltage as high as 5500V, exploring a new voltage height; and it is more stable and applicable at a voltage of 1000-4000V. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the structure of the existing stress wave generator described in the background technology;

[0039] Figure 2 It is a schematic diagram of the first-view structure explosion of the stress wave generator with an active coil protection device of the present invention;

[0040] Figure 3 A schematic diagram of a second-view structural explosion of a stress wave generator with an active coil protection device according to the present invention;

[0041] Figure 4 It is a schematic diagram of the structure of the wheel disc protection cover of the present invention;

[0042] Figure 5 It is a structural schematic diagram of the wheel disc protection cover of the present invention, which is mounted on the active coil and the insulating barrier and is provided with fasteners;

[0043] Figure 6The structure diagram of the active coil electrode installation cable connector and the discharge cable connector of the present invention Figure 1 ;

[0044] Figure 7 The structure diagram of the active coil electrode installation cable connector and the discharge cable connector of the present invention Figure 2 ;

[0045] Figure 8 It is a schematic diagram of the overall structure of the stress wave generator with an active coil protection device without a U-shaped clamp of the present invention.

[0046] Explanation of the reference numerals: 1. induction coil, 2. waveguide, 3. active coil, 31. active coil electrode, 4. insulating barrier, 5. insulating shell, 6. discharge cable connector, 7. U-shaped clamp, 8. first mass block, 9. second mass block, 10. wheel disc protection cover, 101. rib, 102, notch, 103. countersunk hole, 104. screw, 105. plane transition section, 11. bolt, 12. cable connector, 121. boss, 122. screw hole, 13. stud. DETAILED DESCRIPTION

[0047] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0048] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0049] See also Figure 1 In the existing stress wave generator, the active coil 3 and the insulating barrier 4 are externally covered with an insulating shell 5, and the axial position of the insulating shell 5 is limited by a U-shaped clamp 7, thereby limiting the axial position of the active coil 3 and the insulating barrier 4, and the active coil 3 and the insulating barrier 4 are fixed as a whole to the mass block of the stress wave generating device by three bolts. During the experiment, the bolts are easily damaged by impact, and the axial limiting freedom of the insulating shell 5 is large and the reliability is not high, so the active coil 3 and the insulating barrier 4 are easily damaged.

[0050] See also Figure 2-3The present invention proposes a stress wave generator with an active coil protection device, comprising an induction coil 1, an active coil 3, an insulating barrier 4, a U-shaped clamp 7, a first mass block 8, a second mass block 9, a wheel protection cover 10, and a cable connector 12, wherein the induction coil 1, the active coil 3, the insulating barrier 4, the first mass block 8, and the second mass block 9 are coaxially connected in sequence, and a waveguide 2 passes through the stress wave generator, one end of which is fixedly connected to the induction coil 1, and the other end passes through the center holes of the active coil 3, the insulating barrier 4, the first mass block 8, and the second mass block 9 in sequence to connect the test piece for transmitting stress waves. Both sides of the first mass block 8 and the second mass block 9 are provided with grooves for placing the discharge cable connector 6, and the electrode 31 of the active coil is inserted into the discharge cable connector 6 to connect the discharge circuit. The U-shaped clamp 7 is sleeved on the outer diameter of the first mass block 9, and is used to fix the stress wave generating device and the discharge cable connector 6, and the two ends of the U-shaped clamp 7 are fixedly connected to the mounting seat for installing the stress wave generator through bolts.

[0051] See also Figure 4 The wheel protection cover 10 is a cylindrical hollow shell. A rib 101 converging inward is provided around one end of the wheel protection cover 10. The inner diameter of the rib 101 is larger than the outer diameter of the induction coil 1, which does not affect the ejection of the induction coil 1. The other end of the wheel protection cover 10 is an open end, which is provided with two radially arranged notches 102 for avoiding the active coil electrodes 31 on both sides of the active coil 3. 20 countersunk holes 103 axially penetrating the shell of the wheel protection cover 10 are provided on the same circumference outside the rib 101. Figure 5 The wheel protection cover 10 is mounted on the active coil 3 and the insulating barrier 4. The inner wall of the flange 105 abuts against the end of the active coil 3, and the open end surface contacts the first mass block 8. The wheel protection cover 10 is fixedly connected to the first mass block 8 by screws 104 passing through the countersunk holes 103. In order to improve the installation flatness of the wheel protection cover 10 and the active coil 3, the countersunk holes 103 avoid the position of the notches 102. 20 countersunk holes 103 are symmetrically arranged on the housing of the wheel protection cover 10 on both sides of the two notches 102, with 10 holes arranged on one side. In this embodiment, the center lines of the two radial notches 102 pass through the axis of the wheel protection cover 10.

[0052] At the same time, in order to cooperate with the installation of screw 104, refer to Figure 3 20 threaded holes are provided on the contact surface between the first mass block 8 and the wheel disc protection cover 10 , and the threaded holes on the first mass block 8 correspond one to one with the countersunk holes 103 of the wheel disc protection cover 10 .

[0053] See also Figure 2-3, three threaded through holes are evenly distributed on the same circumference of the first mass block 8, the second mass block 9 is provided with threaded through holes corresponding to the three threaded through holes on the first mass block 8 one by one, and the insulating interlayer 4 is also provided with threaded holes corresponding to the three threaded holes on the first mass block 8 on the side facing the first mass block 8, and the bolts 11 are passed through the threaded holes of the second mass block 9, the first mass block 8 and the insulating interlayer 4 in sequence to fix them.

[0054] See also Figure 3 , 6 -7, in order to improve the safety of the stress wave generator and avoid high-voltage discharge sparking, which may cause danger to the operator, the present invention designs a cable connector 12 to increase the contact area between the active coil electrode 31 and the discharge cable, and at the same time improve the connection strength between the active coil 3 and the cable. The cable connector 12 is a strip plate structure with a boss 121 at one end. The end of the boss 121 is provided with a cable installation hole for installing the discharge cable. The boss 121 is provided with two screw holes that pass through the cable installation hole, which are used to fix the discharge cable by installing screws. The thickness of the boss 121 of the cable connector is greater than the thickness of the active coil electrode 31. The end of the cable connector 12 away from the boss 121 contacts the plug-in surface of the active coil electrode 31, and is connected to the end of the active coil electrode 31 through the stud 13. Specifically, the connection between the cable connector 12 and the active coil electrode 31 is provided with a corresponding stud 13 installation hole. The active coil electrode 31 carries the cable connector 12 and is inserted into the corresponding discharge cable connector 6. In this embodiment, the discharge cable connector 6 is fixed by a U-shaped clamp 7 to prevent the discharge cable connector 6 at the end of the discharge cable from being in a suspended state and generating torque. On the one hand, it can effectively prevent the rotation of the discharge cable relative to the active coil electrode 31, which may cause the loosening of the connecting screws and discharge and sparking. On the other hand, it can prevent the discharge cable from generating excessive traction on the active coil 3, which may cause damage to the active coil electrode 31.

[0055] When the stress wave generator is installed on the base, in order to maintain a safe distance from the base surface and maintain tolerance under a certain pitch moment, a planar transition section 105 is provided tangentially on the outer wall of the wheel protection cover 10 in this embodiment. Specifically, the planar transition section 105 is circumferentially spaced 90° from the center line of the slot 102. When installed, the planar transition section 105 faces the base surface. Figure 8 Shown is a schematic diagram of the overall structure of the stress wave generator with an active coil protection device without a U-shaped clamp of the present invention.

[0056] The present invention realizes the protection of the active coil 3 and the insulating barrier 4 of the stress wave generator, especially the protection of the active coil 3, avoids the damage to the active coil 3 during the experiment, improves the experimental stability, and reduces the experimental cost.

[0057] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A stress wave generator with an active coil protection device, comprising an induction coil (1), an active coil (3), an insulating barrier (4), a U-shaped clamp (7), a first mass block (8), and a second mass block (9), wherein the induction coil (1), the active coil (3), the insulating barrier (4), the first mass block (8), and the second mass block (9) are coaxially fitted and connected in sequence, the U-shaped clamp (7) is sleeved on the outer diameter of the first mass block (9) and is used to fix the stress wave generating device and the discharge cable connector (6), and the two ends of the U-shaped clamp (7) are fixedly connected to the mounting seat of the stress wave generator; the electrode (31) of the active coil is inserted into the discharge cable connector (6) to connect the discharge circuit; a waveguide (2) passes through the stress wave generator, one end of which is fixedly connected to the induction coil (1) and the other end is connected to the test piece, and is used to transmit the stress wave; the characteristics are: Also includes a wheel disc protection cover (10); The wheel disc protection cover (10) is a cylindrical hollow shell, one end of which is provided with an inwardly converging retaining edge (101), the inner diameter of which matches the outer diameter of the induction coil (1); the other end of the wheel disc protection cover (10) is an open end, the open end is provided with two radially arranged notches (102) for avoiding the active coil electrodes (31) on both sides of the active coil (3); a plurality of countersunk holes (103) axially penetrating the shell of the wheel disc protection cover (10) are provided on the same circumference of the outer side of the retaining edge (101); The wheel disc protection cover (10) is sleeved on the active coil (3) and the insulating barrier (4); the inner wall of the retaining edge (101) is against the active coil (3); the open end surface is in contact with the first mass block (8); and the wheel disc protection cover (10) is fixedly connected to the first mass block (8) by fasteners passing through the countersunk hole (103).

2. The stress wave generator with active coil protection device according to claim 1, characterized in that: The countersunk holes (103) avoid the positions of the two notches (102) and are symmetrically arranged on the housing of the wheel disc protection cover (10) on both sides of the notches (102).

3. The stress wave generator with active coil protection device according to claim 2, characterized in that: The number of the countersunk holes (103) is 20.

4. The stress wave generator with active coil protection device according to claim 1, characterized in that: The contact surface between the first mass block (8) and the wheel disc protection cover (10) is provided with a plurality of threaded holes, the threaded holes corresponding one-to-one to the countersunk holes (103) of the wheel disc protection cover (10) and being used for threaded connection with fasteners.

5. The stress wave generator with active coil protection device according to claim 1, characterized in that: The first mass block (8) has a plurality of threaded through holes evenly distributed on the same circumference, and the second mass block (9) is provided with threaded through holes corresponding one to one to the plurality of threaded through holes on the first mass block (8), and bolts are passed through the second mass block (9), the first mass block (8) and the insulating barrier (4) in sequence to fix them.

6. The stress wave generator with active coil protection device according to claim 5, characterized in that: The first mass block (8) and the second mass block (9) are both provided with three threaded through holes.

7. The stress wave generator with active coil protection device according to claim 1, characterized in that: The stress wave generator further comprises a cable connector (12), which is a strip plate-shaped structure with a boss (121) at one end, a cable installation hole being provided at the end of the boss (121) for installing a discharge cable, and two screw holes (122) being provided on the boss (121) and passing through the cable installation hole for fixing the discharge cable; an end of the cable connector (12) away from the boss (121) contacts the plug-in surface of the active coil electrode (31) and is connected to the end of the active coil electrode (31) via a stud (13); the active coil electrode (31) carries the cable connector (12) and is inserted into the corresponding discharge cable connector (6).

8. The stress wave generator with active coil protection device according to claim 7, characterized in that: The thickness of the cable connecting piece boss (121) is greater than the thickness of the active coil electrode (31).

9. The stress wave generator with active coil protection device according to claim 1, characterized in that: The inner diameter of the retaining edge (101) of the wheel disc protection cover (10) is greater than the outer diameter of the induction coil (1).

10. The stress wave generator with active coil protection device according to claim 1, characterized in that: The wheel disc protection cover (10) is provided with a plane transition section (105) at an outer diameter which is 90° circumferentially spaced from the center line of the notch (102) for installation and positioning.

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