Hollow rivet for connecting composite material and metal

Abstract

According to the hollow rivet for connecting the composite material and the metal, a plurality of wedge-shaped structures are arranged on a rivet cap, and a rivet body is of a hollow structure; the center of the wedge-shaped structure is provided with a counterbore used for containing chippings and being connected with a vacuum system. The hollow structure comprises a uniform cross-section part located on the upper portion and a variable cross-section part located on the lower portion. Drilling-rivet welding integration of the composite material and the metal can be achieved, the technological process is remarkably simplified, the production efficiency is improved, and the joint connection strength is high.

Description

Technical Field

[0001] The invention relates to a technology in the field of mechanical processing, in particular to a hollow rivet used for connecting composite materials and metals. Background Art

[0002] The defects faced by existing composite material and metal connection technologies include: when using pier riveting connection technology, there are problems such as large riveting force, easy damage to the surface around the hole, large riveting noise, and low efficiency; when using pier riveting and pull riveting and other connection technologies that require prefabricated through holes, it is often difficult to fully guarantee their sealing, and in environments such as humid or corrosive media, it is easy to cause joint performance to deteriorate; in addition, prefabricated through-hole debris enters the profile structure and cannot be discharged, which may cause safety and noise problems during service. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the present invention proposes a hollow rivet for connecting composite materials and metals, which can realize the integrated drilling-riveting and welding of composite materials and metals, significantly simplify the process flow, improve production efficiency and increase the joint connection strength.

[0004] The present invention is achieved through the following technical solutions:

[0005] The invention relates to a hollow rivet for connecting composite materials and metals. The rivet cap is provided with a plurality of wedge-shaped structures, and the rivet body is a hollow structure.

[0006] The center of the wedge-shaped structure is provided with a countersunk hole for accommodating debris and connecting a vacuum system.

[0007] The hollow structure is used to discharge debris generated during the process, and specifically includes: a uniform cross-section portion located at the top and a variable cross-section portion located at the bottom.

[0008] The cross section of the equal cross-section part is circular or cross-shaped.

[0009] The variable cross-section portion is in the shape of a cone which gradually expands outwards.

[0010] The rivet tail is provided with a cross-shaped groove structure.

[0011] The present invention relates to a riveting welding device based on the above-mentioned hollow rivet, comprising: a rivet driving device and a negative pressure device for in-situ suction and removal of debris, wherein: the rivet driving device is in contact with the wedge-shaped structure of the hollow rivet, and the negative pressure device is connected with the inside of the rivet driving device, the inside of the hollow rivet and the cavity formed by the plate to be processed, so that the debris is sucked out of the riveting joint by generating negative pressure.

[0012] The negative pressure device is realized by a vacuum pump, a filter or a hollow motor integrated with a rivet driving device. Technical Effects

[0013] The present invention adopts rivets with circumferential distribution and bottom cross-shaped groove structure, which reduces the axial riveting force while cutting and drilling the composite material plate during friction riveting and welding; the hollow rivet structure is used to connect the composite material and metal, which is convenient for the debris to be discharged from the joint structure, and avoids it from adhering to the rivet / metal plate solid-state interface during riveting and welding, resulting in a decrease in joint strength. At the same time, the hollow structure rivet structure is conducive to the collection and cleaning of debris, avoiding it from remaining in the joint structure and causing abrasive wear during subsequent service; the present invention solves the problems of complex process and lengthy cycle in the existing connection process of composite materials and metals, so that the original multi-step integration of hole making, adjustment, drilling, connection, etc. is simplified into a single step, greatly reducing the manufacturing cycle of heterogeneous material structures and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the three-dimensional structure of the hollow rivet in Example 1;

[0015] In the figure: 1 is the wedge-shaped structure of the upper part of the rivet cap, 2 is the countersunk hole in the middle part of the rivet cap, 3 is the cylindrical surface structure of the rivet through hole, 4 is the cross-shaped groove structure distributed along the circumferential direction, 5 is the arc surface structure at the bottom of the rivet leg, 6 is the cross-shaped groove structure at the bottom of the rivet leg;

[0016] Figure 2 is a cross-sectional schematic diagram of the hollow rivet of Example 1;

[0017] Figure 3 for Figure 2 Top view;

[0018] Figure 4 for Figure 2 Bottom view;

[0019] Figure 5 This is a cross-sectional morphology diagram of the riveted joint of Example 1;

[0020] In the figure: 7 hollow rivets, 8 composite material plates, 9 metal plates.

[0021] Figure 6 It is a schematic diagram of the three-dimensional structure of the hollow rivet in Example 2;

[0022] In the figure: 10 rivet through-hole cylindrical structure;

[0023] Figure 7 This is a cross-sectional schematic diagram of the hollow rivet of Example 2;

[0024] Figure 8 This is a cross-sectional morphology diagram of the riveted joint of Example 2;

[0025] In the figure: 11 hollow rivet;

[0026] Fig. 9 This is a riveting welding flow chart of Example 1;

[0027] Fig.10 This is a schematic diagram of the cross-sectional morphology of the joint in the embodiment;

[0028] Fig.11 is a schematic diagram of a load-displacement curve of an embodiment;

[0029] In the figure: 101 driving shaft, 102 edge clamping sleeve, 103 hollow rivet, 104 composite material plate, 105 metal plate, 106 supporting structure, 107 negative pressure device, 108 composite material debris. DETAILED DESCRIPTION Example 1

[0030] like Figure 1-Figure 4 As shown, this embodiment relates to a hollow rivet for connecting composite materials and metals, wherein a plurality of wedge-shaped structures 1 are arranged on the rivet cap, and the rivet body is a hollow structure.

[0031] The wedge-shaped structure 1 on the upper part of the rivet cap transmits torque during the riveting and welding process. In order to ensure that it does not soften and fail during the connection process and can achieve a good solid-phase connection with the underlying plate, the hardness of the rivet material is usually required to be 0.8 to 1.0 times the hardness of the metal plate to be connected.

[0032] The center of the rivet cap is provided with a countersunk hole 2 for accommodating fiber debris and connecting to a vacuum system. The radius R1 of the countersunk hole 2 and the outer diameter R of the rivet cap satisfy: R1≤0.5R.

[0033] The height h of the countersunk hole 2 and the height H of the rivet cap satisfy: 0≤h<0.6H. When the thickness of the composite material plate T1≤2mm, there are fewer chips, and their cleaning and collection work is carried out after the riveting and welding process is completed, and the countersunk hole structure is not required; when the thickness of the composite material plate T1>2mm, a countersunk hole structure is required to avoid excessive chips flowing out between the driving head and the rivet cap, affecting the joint formation.

[0034] A cross-shaped groove structure 4 for discharging fiber debris is provided in the middle of the nail body of the hollow structure along the circumferential direction, and a cylindrical surface structure 3 is provided between adjacent cross-shaped groove structures 4 to further optimize the fiber debris discharging effect and the cutting effect on the composite material.

[0035] The diameter R3 of the cylindrical surface structure satisfies: L4<R3<L3, wherein: L3 is the length from the edge of the groove to the center, and L4 is the width of the cross-shaped groove.

[0036] The length L3 from the edge to the center of the cross-shaped groove structure 4 satisfies: L3≤R2-0.25mm, wherein: the outer diameter R2 of the rivet leg satisfies: R2≤R1.

[0037] The material of the hollow rivet is usually selected from the same type of alloy as the underlying metal sheet to ensure the joint quality and connection effect.

[0038] like Figure 2 As shown, the total length of the rivet body of the hollow rivet in this embodiment is L=L1+L2, where: t i is the thickness of the i-th composite material plate, n is the number of composite material plate layers, and L2 is the length of the conical variable cross-section part.

[0039] The length of the hollow structure is H+L1-h.

[0040] The rivet leg tip opening angle of the conical variable cross-section part Where: K is the material hardness correction factor, and the recommended value range is [-0.4, -0.2]. The value of the opening angle α can usually be selected according to the fiber strength and layering method of the composite material. Generally, the higher the fiber strength and the more complex the layering, the smaller the opening angle α is used.

[0041] The arc surface structure 5 at the bottom of the rivet leg is used to cut the composite material. The angle β between the arc surface projection of the rivet leg and the horizontal direction affects the cutting effect of the rivet on the composite material plate, and its value range is usually [0°, 10°].

[0042] The cross groove structure 6 at the bottom of the rivet leg is used to cut composite materials. The groove width at the bottom of the rivet leg is the same as the cross groove width L4. To ensure the stability of the cutting edge at the bottom of the rivet, its height is usually 0.1-0.5 times the length L2 of the rivet leg, and is adjusted according to the lightweight requirements of the rivet.

[0043] After specific experiments, a carbon fiber composite plate with a grade of T300 and a thickness of 4.0 mm was used as the upper connecting part, and a stainless steel plate with a grade of 301L-HT and a thickness of 3.0 mm was used as the lower connecting part. The contact surface between the carbon fiber composite plate and the stainless steel plate is a smooth surface, and there is no need to clean the surface of the connecting parts before riveting and welding.

[0044] The rivet cap has a height of 2.0 mm and a diameter of 10.0 mm. Six wedge-shaped structures 1 are distributed at equal angles along the outer circumference. The height of the wedge-shaped structure is 1.2 mm, and it meshes with the end of the drive shaft to achieve axial and rotational movement.

[0045] In this embodiment, the thickness T1 of the carbon fiber composite plate is greater than 2 mm. In order to prevent carbon fiber chips from flowing out between the driving head and the nail cap during riveting and welding, a countersunk hole needs to be processed, wherein the diameter of the countersunk hole is 5.0 mm and the depth is 1.0 mm.

[0046] The cylindrical surface of the rivet through hole is coaxial with the countersunk hole and has a diameter of 2.0 mm.

[0047] The total length of the rivet leg is 7.0 mm, of which the upper part of the rivet leg is 4.0 mm, which is consistent with the thickness of the carbon fiber composite plate, and the lower part of the rivet leg is 3.0 mm, which is consumed during the riveting process and forms a solid phase connection with the stainless steel plate. In addition, the outer diameter of the rivet leg is 4.5 mm.

[0048] The rivet tip is connected to the cylindrical surface of the rivet through hole, with an opening angle α=20°, and a fillet radius R=1mm at the connection between the two.

[0049] The inner side of the rivet has 4 through slots evenly distributed along the inner circumference direction, with a length of 2.0 mm and a width of 1 mm. The connection between the rivet through-hole cylindrical surface and the rivet tip acts as a cutting edge to cut the carbon fiber composite material.

[0050] The arc surface included angle β of the rivet leg is 3°, and the width of the groove at the bottom of the rivet leg is 1.0 mm and the height is 0.3 mm.

[0051] The hollow rivet in this embodiment is made of stainless steel with a grade of SUS304. The rivet is cold headed and processed by electrical discharge, and the size tolerance of electrical discharge processing is ±0.05mm, and the other tolerances are ±0.1mm.

[0052] like Fig. 9 As shown, this embodiment relates to a riveting welding process based on the above-mentioned hollow rivet, including:

[0053] In the first stage, the carbon fiber composite plates and stainless steel plates are stacked in sequence, and the upper and lower plates are fixed with a clamping sleeve. The clamping force is controlled by a pair of springs. A hollow annular support is placed in the area coaxial with the driving rod at the bottom of the stainless steel plate to simulate the riveting and welding conditions of the closed profile structure.

[0054] In the second stage, the hollow rivet is engaged with the driving head, fed at a low speed to the upper surface of the carbon fiber composite and in stable contact. At the same time, this point is used as the zero point position of the riveting welding program, the riveting welding process parameters are input, and then the riveting welding is carried out.

[0055] In the third stage, the hollow rivet penetrates the upper carbon fiber composite plate at a rotation speed of 2400rpm and a feed speed of 2mm / s. Under the cutting action of the rivet, the carbon fiber composite plate is cut into carbon fiber debris. The generated carbon fiber debris is sucked away by the vacuum device while avoiding heat accumulation. The feed displacement in this stage is slightly larger than the thickness of the upper carbon fiber composite plate to ensure that the carbon fiber composite plate in the axial projection area of ​​the rivet leg is completely removed.

[0056] In the fourth stage, the hollow rivet is fed downward for 3mm at a rotation speed of 1800rpm and a feed speed of 8mm / s. After the rivet contacts the lower stainless steel plate, the friction between the two generates heat to soften the rivet legs and the upper surface of the plate. Under the combined action of the axial force and the reaction force of the bottom stainless steel plate, the softened material forms flash along the radial direction. The material flowing inward squeezes out the remaining carbon fiber debris and fills the cavity.

[0057] In stage five, the hollow rivet is fed until the lower surface of the rivet cap contacts the upper surface of the carbon fiber composite plate. At this time, the driving rod stops rotating and feeding, and still keeps tight engagement with the rivet. After maintaining a constant axial pressure for 5 seconds, the composite debris is sucked away by the negative pressure device through the hollow structure of the rivet to avoid residue. The driving rod is withdrawn upward, and the riveting is completed.

[0058] Compared with the traditional solid pier riveting and pull riveting processes, this embodiment greatly simplifies the connection process and improves the connection efficiency. The time consumption of single-point connection is shortened from the original 3-5min to 7.4s; in this embodiment, the lower stainless steel plate has no through holes, and the hollow rivet is in close contact with the carbon fiber plate, which greatly improves the sealing of the joint; in this embodiment, a solid-phase connection interface with a microstructure is formed between the hollow rivet and the stainless steel plate, and at the same time, the rivet leg side wall and the nail cap structure mechanically lock the carbon fiber composite plate, and finally a riveted joint with excellent mechanical properties is obtained. A tensile shear test was carried out at room temperature. Compared with the pull-riveted rivet joint with an outer diameter of 4.8mm, the tensile shear peak force of the riveted joint in this embodiment was increased from 5.2kN of the pull-riveted joint to 8.2kN. Example 2

[0059] like Figure 6-Figure 7 As shown, this example relates to a hollow rivet for connecting composite materials and metals. Compared with Example 1, the hollow rivet structure of this embodiment is simpler. A plurality of wedge-shaped structures 1 are provided on the rivet cap, a through hole 10 is provided in the middle of the rivet, and a conical variable cross-section and a groove at the bottom of the rivet leg for circumferential cutting are retained.

[0060] The wedge-shaped structure 1 on the upper part of the rivet cap transmits torque during the riveting and welding process. In order to ensure that it does not soften and fail during the connection process and can achieve a good solid-phase connection with the underlying plate, the hardness of the rivet material is usually required to be 0.8 to 1.0 times the hardness of the metal plate to be connected.

[0061] The rivet through-hole cylindrical surface structure 10 is used as a channel for discharging fiber debris, and the inner diameter R3 of the central part thereof generally satisfies: 0.5R2≤R3<R2.

[0062] The material of the hollow rivet is usually selected from the same type of alloy as the underlying metal sheet to ensure the joint quality and connection effect.

[0063] In this embodiment, the total length of the rivet body of the hollow rivet is L=L1+L2, where L1 satisfies: t i is the thickness of the i-th composite material plate, and n is the number of composite material plate layers.

[0064] The hollow structure comprises: a cross-shaped equal-section portion located at the top, with a length of H+L1-h, and a conical variable-section portion located at the bottom, with a length of L2.

[0065] The opening angle α of the rivet leg tip of the conical variable cross-section portion satisfies, Where K is the material hardness correction factor, and the recommended value range is [-0.4, -0.2]. The value of the opening angle α can usually be selected according to the fiber strength and layering method of the composite material. Generally, the higher the fiber strength and the more complex the layering, the smaller the opening angle α is used.

[0066] The outer diameter R2 of the hollow rivet generally satisfies: 0.5R≤R2<R.

[0067] In this embodiment, the groove width L4 at the bottom of the hollow rivet leg satisfies: 0.2≤L4<0.5R2. To ensure the stability of the cutting edge at the bottom of the rivet, its height is usually 0.1-0.5 times the length L2 of the rivet leg, and is adjusted according to the lightweight requirements of the rivet.

[0068] After specific experiments, a carbon fiber composite plate with a grade of T300 and a thickness of 4.0 mm was used as the upper connecting part, and a stainless steel plate with a grade of 301L-HT and a thickness of 3.0 mm was used as the lower connecting part. The contact surface between the carbon fiber composite plate and the stainless steel plate is a smooth surface, and there is no need to clean the surface of the connecting parts before riveting and welding.

[0069] The rivet cap has a height of 2.0 mm and a diameter of 10.0 mm. Six wedge-shaped structures 1 are distributed at equal angles along the outer circumference. The height of the wedge-shaped structure is 1.2 mm, and it meshes with the end of the drive shaft to achieve axial and rotational movement.

[0070] The cylindrical surface diameter of the rivet through hole is 4.0 mm.

[0071] The total length of the rivet leg is 7.0 mm, of which the upper part of the rivet leg is 4.0 mm, which is consistent with the thickness of the carbon fiber composite plate, and the lower part of the rivet leg is 3.0 mm, which is consumed during the riveting process and forms a solid phase connection with the stainless steel plate. In addition, the outer diameter of the rivet leg is 6.4 mm.

[0072] The rivet conical surface is connected to the rivet through-hole cylindrical surface, with an opening angle α=20°, and a fillet radius R=1mm at the connection between the two.

[0073] The hollow rivet in this embodiment is made of stainless steel with a grade of SUS304. The rivet is cold headed and machined, and the dimensional tolerance is ±0.1 mm.

[0074] like Fig. 9 As shown, the riveting welding process involved in this embodiment is the same as that in the embodiment, including:

[0075] In the first stage, the carbon fiber composite plates and stainless steel plates are stacked in sequence, and the upper and lower plates are fixed with a clamping sleeve. The clamping force is controlled by a pair of springs. A hollow annular support is placed in the area coaxial with the driving rod at the bottom of the stainless steel plate to simulate the riveting and welding conditions of the closed profile structure.

[0076] In the second stage, the hollow rivet is engaged with the driving head, fed at a low speed to the upper surface of the carbon fiber composite and in stable contact. At the same time, this point is used as the zero point position of the riveting welding program, the riveting welding process parameters are input, and then the riveting welding is carried out.

[0077] In the third stage, the hollow rivet penetrates the upper carbon fiber composite plate at a rotation speed of 3600rpm and a feed speed of 1mm / s. Under the cutting action of the rivet, the carbon fiber composite plate is cut into carbon fiber debris. The generated carbon fiber debris is sucked away by the vacuum device while avoiding heat accumulation. The feed displacement in this stage is slightly larger than the thickness of the upper carbon fiber composite plate to ensure that the carbon fiber composite plate in the axial projection area of ​​the rivet leg is completely removed.

[0078] In the fourth stage, the hollow rivet is fed downward for 3mm at a rotation speed of 2400rpm and a feed speed of 6mm / s. After the rivet contacts the lower stainless steel plate, the friction between the two generates heat to soften the rivet legs and the upper surface of the plate. Under the combined action of the axial force and the reaction force of the bottom stainless steel plate, the softened material forms flash along the radial direction. The material flowing inward squeezes out the remaining carbon fiber debris and fills the cavity.

[0079] In stage five, the hollow rivet is fed until the lower surface of the rivet cap contacts the upper surface of the carbon fiber composite plate. At this time, the driving rod stops rotating and feeding, and still keeps tight engagement with the rivet. After maintaining a constant axial pressure for 5 seconds, the composite debris is sucked away by the negative pressure device through the hollow structure of the rivet to avoid residue. The driving rod is withdrawn upward, and the riveting is completed.

[0080] Compared with the traditional solid rivet and pull riveting process, this embodiment greatly simplifies the connection process and improves the connection efficiency. The time consumption of single-point connection is shortened from the original 3-5 minutes to 9.5 seconds; in this embodiment, the lower stainless steel plate has no through holes, and the hollow rivet is in close contact with the carbon fiber plate, which greatly improves the sealing of the joint; in this embodiment, a solid-phase connection interface with a microstructure is formed between the hollow rivet and the stainless steel plate, and at the same time, the rivet leg side wall and the nail cap structure mechanically lock the carbon fiber composite plate, and finally a riveted joint with excellent mechanical properties is obtained. The cross-sectional morphology of the joint is as follows: Fig.10 As shown. The tensile shear test was carried out at room temperature, and the load-displacement curve is shown in Fig.11 As shown, compared with the pull-riveted rivet joint with an outer diameter of 4.8 mm, the peak shear force of the riveted joint in this embodiment is increased from 5.2 kN of the pull-riveted joint to 10.6 kN.

[0081] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A hollow rivet for connecting composite materials and metals, characterized in that: The nail cap is provided with a number of wedge-shaped structures, and the nail body is a hollow structure; The hollow structure comprises: a portion with a constant cross section located at the top and a portion with a variable cross section located at the bottom.

2. The hollow rivet for connecting composite materials and metals according to claim 1, characterized in that: The center of the wedge-shaped structure is provided with a countersunk hole for accommodating debris and connecting a vacuum system.

3. The hollow rivet for connecting composite materials and metals according to claim 1, characterized in that: The equal cross-section part is circular or cross-shaped.

4. The hollow rivet for connecting composite materials and metals according to claim 1, characterized in that: The variable cross-section portion is in the shape of a cone that gradually expands outwards; The conical rivet leg tip opening angle α=KL 2 2+60, where: K is the material hardness correction factor, L2 is the length of the conical variable cross-section part.

5. The hollow rivet for connecting composite materials and metals according to claim 1, characterized in that: The rivet tail is provided with a cross-shaped groove structure.

6. The hollow rivet for connecting composite materials and metals according to claim 2, characterized in that: The radius R1 of the countersunk hole and the outer diameter R of the rivet cap satisfy: R1≤0.5R; the height h of the countersunk hole and the height H of the rivet cap satisfy: 0≤h<0.6H.

7. The hollow rivet for connecting composite materials and metals according to claim 5, characterized in that: A cylindrical surface structure is provided between adjacent cross-shaped groove structures to further optimize the fiber debris discharge effect and the cutting effect on the composite material. The diameter R3 of the cylindrical surface structure satisfies: L4<R3<L3, where: L3 is the length from the groove edge to the center, and L4 is the width of the cross-shaped groove; The length L3 from the edge to the center of the cross-shaped groove structure satisfies: L3≤R2-0.25mm, wherein: the outer diameter R2 of the rivet leg satisfies: R2≤R1.

8. A riveting welding device based on the hollow rivet according to any one of claims 1 to 7, characterized in that: include: A rivet driving device and a negative pressure device for in-situ suction and removal of debris, wherein: the rivet driving device contacts the wedge-shaped structure of the hollow rivet, and the negative pressure device is connected to the inside of the rivet driving device, the inside of the hollow rivet and the cavity formed by the plate to be processed, and the debris is sucked out of the riveted joint by generating negative pressure.

9. A riveting welding process based on the hollow rivet according to any one of claims 1 to 7, characterized in that: include: In the first stage, the carbon fiber composite plate and the stainless steel plate are stacked in sequence, and the upper and lower plates are fixed with a clamping sleeve. The clamping force is controlled by a pair of springs. A hollow annular support is placed in the area coaxial with the driving rod at the bottom of the stainless steel plate to simulate the riveting welding condition of the closed profile structure. In the second stage, the hollow rivet is engaged with the driving head, fed at a low speed to the upper surface of the carbon fiber composite and stably contacted; at the same time, this point is used as the zero point position of the riveting welding program, the riveting welding process parameters are input, and then the riveting welding is carried out; In the third stage, the hollow rivet penetrates the upper carbon fiber composite plate at a rotation speed of 3600rpm and a feed speed of 1mm / s. Under the cutting action of the rivet, the carbon fiber composite plate is cut into carbon fiber debris. The generated carbon fiber debris is sucked away by the vacuum device to avoid heat accumulation. The feed displacement in this stage is slightly larger than the thickness of the upper carbon fiber composite plate to ensure that the carbon fiber composite plate in the axial projection area of ​​the rivet leg is completely removed. In the fourth stage, the hollow rivet is fed downward for 3 mm at a rotation speed of 2400 rpm and a feed speed of 6 mm / s. After the rivet contacts the lower stainless steel plate, the friction between the two generates heat to soften the rivet legs and the upper surface of the plate. Under the combined action of the axial force and the reaction force of the bottom stainless steel plate, the softened material forms flash along the radial direction. The material flowing inward squeezes out the remaining carbon fiber debris and fills the cavity. In stage five, the hollow rivet is fed until the lower surface of the rivet cap contacts the upper surface of the carbon fiber composite plate. At this time, the driving rod stops rotating and feeding, and still maintains tight engagement with the rivet. After maintaining a constant axial pressure for 5 seconds, the composite debris is sucked away by the negative pressure device through the hollow structure of the rivet to avoid residue; the driving rod is withdrawn upward, and the riveting is completed.

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