阅读说明：本技术 带有自锁的螺柱复合连接装置及连接方法 (Stud composite connecting device with self-locking function and connecting method ) 是由 山河 李永兵 马运五 杨炳鑫 雷海洋 于 2020-04-01 设计创作，主要内容包括：一种带有自锁的螺柱复合连接装置,包括：螺柱、驱动头和螺柱配合件,其中：螺柱包括：依次连接的螺柱体和尾部空心结构,该螺柱体的一端设有作为驱动连接部的盲孔；盲孔通过①设置于开口端外表面的对称双平面结构和/或②设置于内表面的呈棱柱结构及设置于螺柱体外部的螺纹以连接驱动头。本发明通过控制螺柱的尾部空心结构张开产生的底切量形成了基于底切量的机械自锁效果,通过控制待连接板材的流动状态形成了基于环形凹槽的机械自锁效果,在自锁机械连接的基础上实现螺柱与工件之间的固相连接,形成了机械-固相复合连接；仅对上层板材预制连接孔,降低了对中性和装卡精度的要求,避免了螺栓连接上下开放式的接头结构,增强了接头的密封性,提高了抗腐蚀性能。(A stud composite connection with self-locking, comprising: stud, drive head and stud fitting, wherein: the stud includes: the tail part of the tail part; the blind hole is connected with the driving head through a symmetrical biplane structure arranged on the outer surface of the opening end and/or a prismatic structure arranged on the inner surface and a thread arranged outside the screw cylinder. According to the invention, the mechanical self-locking effect based on the undercut amount is formed by controlling the undercut amount generated by the opening of the tail hollow structure of the stud, the mechanical self-locking effect based on the annular groove is formed by controlling the flowing state of the plate to be connected, the solid-phase connection between the stud and the workpiece is realized on the basis of the self-locking mechanical connection, and the mechanical-solid-phase composite connection is formed; only the connecting holes are prefabricated on the upper plate, so that the requirements on the neutrality and the clamping precision are reduced, the problem that bolts are connected with an upper-lower open type joint structure is solved, the sealing performance of the joint is enhanced, and the corrosion resistance is improved.)

1. The utility model provides a double-screw bolt composite connection device with auto-lock which characterized in that includes: stud, drive head and stud fitting, wherein: the stud includes: the tail part of the tail part;

the blind hole is connected with the driving head through a symmetrical biplane structure arranged on the outer surface of the opening end and/or a prismatic structure arranged on the inner surface and a thread arranged outside the screw cylinder.

2. The composite stud connector with self-locking function as claimed in claim 1, wherein the driving head is provided with a ball plunger for locking with the stud and driving the stud to be drilled into the lower connecting plate to a predetermined depth, then the prefabricated hole of the upper connecting plate is inserted through the stud and attached to the lower connecting plate, and the stud fitting member is used for pressing the upper connecting plate and the lower connecting plate to form the mechanical-solid-thread composite connector.

3. The composite stud connector as claimed in claim 1, wherein the inner and/or outer wall of the hollow tail structure has multiple sets of self-locking annular grooves.

4. The composite stud connector with self-locking according to claim 1 or 3, wherein the tail hollow structure is provided at its end with a wedge-shaped rounded transition structure to guide the generation of undercut and the flow of plastic material.

5. The composite stud connecting device with self-locking function as claimed in claim 1 or 3, wherein at least two through grooves are formed at the tail end of the tail hollow structure, and the through grooves are uniformly distributed along the circumferential direction at equal angles.

6. The composite stud connecting device with self-locking function as claimed in claim 2, wherein the exposed height of the stud body, the height of the thread structure and the height of the tail hollow structure are matched with the thickness of the upper and lower plates and the size of the nut, specifically:

for an internally threaded stud: h is₁<t₁，h₂＝k·t₂(k<1)，h-h₂＝t₁；

For an externally threaded stud: h is h₁+h₂，h₁≥t₁+h₀，h₂＝k·t₂(k<1) Wherein: h is the total height of the stud; h is₁Is the height of the thread structure; h is₂The height of the tail part hollow structure; h is₀The height of the nut matched with the external thread stud; t is t₁The thickness of the upper plate; t is t₂The thickness of the lower plate; and k is a matching coefficient set according to the plate property.

7. The composite stud connecting device with self-locking function as claimed in claim 3, wherein the cavity formed by the self-locking annular groove is filled with a material which is extruded into the cavity by the tail hollow structure after the mechanical-solid-thread composite connecting joint is formed, and the requirements are met: pi r²·(D-h₂)＝π(R²-r²)·h₂Wherein: d is the depth of the stud cavity; r is the outer diameter of the tail hollow structure; r is the inner diameter of the tail hollow structure; namely, the depth D of the stud cavity is required to satisfy the following conditions:

8. the connecting method of the self-locking stud composite connecting device according to claims 1 to 7, characterized in that a blank holder is preset on a clamped lower-layer connecting plate for pressing, a driving head is matched with a stud and is arranged at a position coaxial with the blank holder, the driving head drives the stud to drill into the lower-layer connecting plate in a high-speed rotation and low-speed feeding mode, friction heat is generated and accumulated through relative friction between the stud rotation and the plate to increase the temperature of a connecting area, meanwhile, the plasticity of the plate is increased, and plastic metal flows into a tail hollow structure of the stud to form mechanical self-locking of the trapped metal; stopping the driving head and driving the stud to rapidly upset downwards to enable the wedge-shaped tail end of the tail hollow structure to open outwards to form mechanical self-locking based on undercut amount, meanwhile, filling a cavity of the lower section of the stud with plastic metal due to upsetting downwards, forming mechanical self-locking based on an annular groove after cooling, additionally installing a prefabricated hole of an upper connecting plate at the riveted stud, and combining the stud matching structure and the stud to tightly press the upper connecting plate and a lower connecting plate to form a mechanical-solid phase-thread composite connecting joint;

the mechanical-solid phase-thread composite connection is as follows: the clearance of each interface of the stud accessory is eliminated, and the close solid-phase connection of materials on two sides of at least one interface is realized:

firstly, an interface between the inner wall of a hollow structure at the tail part of the stud and trapped metal;

and interface between the outer wall of the hollow structure at the tail part of the stud and the board to be connected.

9. The method as claimed in claim 8, wherein the connecting method divides the process according to the specific combination of the plates to be connected, and controls the rotating speed and the feeding rate of the stud in a segmented manner to obtain the personalized connecting effect.

Technical Field

The invention relates to the technology in the field of material connection, in particular to a stud composite connecting device with self-locking and a connecting method.

Background

In the connection of metal plates, for the combination of steel for the upper plate and light alloy plate for the lower plate, the lower light alloy plate is thicker, so that mechanical connection methods suitable for thin plates, such as self-piercing riveting, flow drilling riveting and the like, cannot be adopted. In addition, the steel plate is overlapped under the light alloy, so that solid phase connection processes such as friction stir welding, friction unit welding and the like cannot be applied, and the connection of the plate combination is mainly realized by adopting the traditional bolt connection process of presetting through holes on the upper plate and the lower plate. The existing bolt connection technology is suitable for connecting detachable structural components, and the existing problems include the following points: the connecting plates need to be drilled and tapped in advance, so that the additional processing step of the bolt connecting process is added, and the requirement on the alignment property of the prefabricated screw holes and the tapping of each layer of plate in the clamping process is high; the open structure of the prefabricated through holes of each layer of plate material causes poor joint sealing performance, reduces the corrosion resistance of the joint and limits the service range of the bolt connection joint; the bolts penetrate through the multilayer plates, are long in size and heavy in weight, and meet the requirement of light weight.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a stud composite connecting device with self-locking and a connecting method, which form mechanical-solid phase-thread composite connection and strengthen the static and dynamic mechanical properties of a joint.

The invention is realized by the following technical scheme:

the invention relates to a stud composite connection device with self-locking, comprising: stud, drive head and stud fitting, wherein: the stud includes: the screw cylinder body and the tail part hollow structure are connected in sequence.

One end of the screw cylinder body is provided with a blind hole serving as a driving connecting part.

The blind hole is connected with the driving head through a symmetrical biplane structure arranged on the outer surface of the opening end and/or a prismatic structure arranged on the inner surface and a thread arranged outside the screw cylinder.

The inner wall and/or the outer wall of the tail hollow structure is/are provided with a plurality of groups of self-locking annular grooves; the end of which is provided with a wedge-shaped structure with a circular arc transition to guide the generation of undercut amount and the flow of plastic state material.

The driving head is provided with a ball plunger to be locked with the stud and drive the stud to drill into the lower layer of plates to be connected to a preset depth, then the prefabricated hole of the upper layer of plates to be connected penetrates through the stud and is attached to the lower layer of plates, the upper layer of plates to be connected and the lower layer of plates to be connected are pressed tightly by using a stud fitting piece, and finally the mechanical-solid phase-thread composite connecting joint is formed.

Preferably, when the stud is made of a material with high strength or the wall of the tail hollow structure is thick, in order to ensure that the stud is sufficiently opened and effective mechanical self-locking based on undercut amount is formed, at least two through grooves can be arranged at the tail end of the tail hollow structure, the through grooves are in any geometric shape, the number of the through grooves is at least two, and the through grooves are uniformly distributed along the circumferential direction at equal angles.

The drive head is preferably a magnetic prism.

The stud body of double-screw bolt expose height, helicitic texture height and afterbody hollow structure height, with upper and lower floor's plate thickness and nut size phase-match, specifically:

for an internally threaded stud: h is₁<t₁，h₂＝k·t₂(k<1)，h-h₂＝t₁；

For an externally threaded stud: h is h₁+h₂，h₁≥t₁+h₀，h₂＝k·t₂(k<1) Wherein: h is the total height of the stud; h is₁Is the height of the thread structure; h is₂The height of the tail part hollow structure; h is₀The height of the nut matched with the external thread stud; t is t₁The thickness of the upper plate; t is t₂The thickness of the lower plate; k is a matching coefficient set according to the sheet property, and is generally set to 0.6-0.8.

The cavity that self-locking annular groove produced should be filled up after the technology finishes, and remaining cavity above lower floor's panel is filled up and satisfied by the material that tail hollow structure extrudes into cavity inside promptly after the technology finishes: pi r²·(D-h₂)＝π(R²-r²)·h₂Wherein: d is the depth of the stud cavity; r is the outer diameter of the tail hollow structure; r is the inner diameter of the tail hollow structure; namely, the depth D of the stud cavity is required to satisfy the following conditions:

the lower plate adopts a multi-layer structure composed of light alloys of the same or different types, and t is₂The total thickness of the multilayer board.

The invention relates to a connecting method of a stud composite connecting device with self-locking, which is characterized in that a clamping ring is preset on a clamped lower-layer connecting plate for pressing, a driving head is matched with a stud and is arranged at a position coaxial with the clamping ring, the driving head drives the stud to drill into the lower-layer connecting plate in a high-speed rotation and low-speed feeding mode, friction heat is generated and accumulated through the relative friction between the stud rotation and the plate to enable the temperature of a connecting area to rise, meanwhile, the plasticity of the plate is increased, and plastic metal flows into a tail hollow structure of the stud to form mechanical self-locking of trapped metal; and stopping the driving head and driving the stud to quickly upset downwards to enable the wedge-shaped tail end of the tail hollow structure to open outwards to form mechanical self-locking based on undercut amount, meanwhile, filling a cavity at the lower section of the stud with plastic metal due to upsetting downwards, forming mechanical self-locking based on an annular groove after cooling, additionally installing a prefabricated hole of the upper connecting plate at the riveted stud, and combining the stud matching structure with the stud to compress the upper connecting plate and the lower connecting plate to form the mechanical-solid phase-thread composite connecting joint.

The mechanical-solid phase-thread composite connection is as follows: the clearance of each interface of the stud accessory is eliminated, and the close solid-phase connection of materials on two sides of at least one interface is realized:

firstly, an interface between the inner wall of a hollow structure at the tail part of the stud and trapped metal;

and interface between the outer wall of the hollow structure at the tail part of the stud and the board to be connected.

Technical effects

On the basis of the basic principle of self-piercing friction riveting, the invention creatively designs the semi-hollow stud with the mechanical self-locking function and the thread locking function, solves the problem that the traditional plate point connection process cannot be suitable for plate combination with steel plates above and below light alloy, avoids various disadvantages of the traditional bolt connection process, and realizes a mechanical-solid phase-thread composite connection joint.

The invention adopts a semi-hollow stud structure and a non-penetrating joint form, reduces the size and the weight of a joint stud, meets the requirement of light structure and improves the process application prospect and the flexibility of structural design; only the connecting holes are prefabricated on the upper plate, so that the requirements on the neutrality and the clamping precision are reduced, the connecting and upper-lower open type joint structure of a bolt is avoided, the sealing performance of the joint is enhanced, and the corrosion resistance is improved; the hollow structure at the tail part of the stud provides a space for extruding materials, only friction metal flashes with small sizes relative to the plate and the stud are generated, and accurate installation of the upper-layer prefabricated hole steel plate is guaranteed.

Drawings

FIG. 1 is a schematic structural view of example 1;

in the figure: a is a stud; b is a driving head; c is a bolt;

FIG. 2 is a diagram showing the application procedure of example 1;

in the figure: a is a schematic diagram of step 1); b is a schematic diagram of step 2); c is a schematic diagram of step 3); d is a schematic diagram of step 4);

FIG. 3 is a schematic view of a composite joint formed according to example 1;

FIG. 4 is a schematic structural view of embodiment 2;

in the figure: a is a stud; b is a driving head; c is a nut;

FIG. 5 is a diagram showing the application procedure of example 2;

in the figure: a is a schematic diagram of step 1); b is a schematic diagram of step 2); c is a schematic diagram of step 3); d is a schematic diagram of step 4);

FIG. 6 is a schematic view of a composite joint formed according to example 2;

in the figure: the self-locking device comprises a stud 1, a driving head 2, a blank holder 3, a plate to be connected 4, a flat bottom mold 5, a bolt 6, a nut 7, a stud body 101, a driving connection part 102, threads 103, a self-locking annular groove 104, a tail hollow structure 105, a ball plunger 201, an upper plate 401, a lower plate 402 and an internal self-locking characteristic position 403.

Detailed Description

Example 1

As shown in fig. 1, the present embodiment relates to a stud composite connection device with self-locking, which includes: double-screw bolt 1, drive head 2, bolt 6, blank holder 3 and flat bottom mould 5, wherein: the driving head 2, the stud 1, the blank holder 3 and the flat-bottom mold 5 are coaxially arranged, the driving head 2 drives the stud 1 to be inserted into a to-be-connected plate 4, the blank holder 3 is arranged outside the stud 1 and is in contact with the to-be-connected plate 4, the flat-bottom mold 5 is arranged below the to-be-connected plate 4, and the bolt 6 is matched with the stud 1 and forms a composite connection joint with the to-be-connected plate 4.

The stud 1 comprises the following components in sequence from top to bottom: drive connection 102, stud 101 and tail hollow structure 105, wherein: the upper section of the drive connection 102 and the threaded shank 101 form a cavity and are internally provided with a thread 103.

The driving head 2 is provided with a ball plunger 201 to be in close contact with the stud 1.

The plate 4 to be connected specifically comprises: upper and lower sheet materials 401, 402 with pre-made holes, wherein: the upper sheet 401 is a thermoformed steel sheet and the lower sheet 402 is an aluminum alloy 7a 52.

The diameter of the prefabricated hole is 1.1-1.3 times of the outer diameter of the stud 1.

The height of the screw column body 101, the height of the screw thread 103 and the height of the tail hollow structure 105 are matched with the thickness of the upper plate 401 and the lower plate 402 and the size of the bolt 6,the concrete requirements are as follows: h is₁<t₁，h₂＝k·t₂(k<1)，h-h₂＝t₁Wherein: h is the height of the stud 1, h₁Height, h, of the thread 103₂Is the height, t, of the tail hollow structure 105₁Is the thickness, t, of the upper sheet 401₂K is a matching coefficient (set to 0.6-0.8) set according to the sheet property for the thickness of the lower sheet 402.

The cavity depth of the tail hollow structure 105 is 23.0 mm.

The stud 1 is an M8 internal thread stud 1, is made of 45 steel and has a height of 28.0 mm.

The outer diameter of the screw cylinder 101 is 16.0mm, and the height thereof is 10.0 mm.

Three groups of self-locking annular grooves 104 are arranged on the inner wall of the tail hollow structure 105 at equal intervals.

The shape of the self-locking annular groove 104 is a combination of one or more geometric shapes, the cross section of the groove in the embodiment is rectangular, the height of the groove is 1.0mm, and the depth of the groove is 0.5 mm.

The length of the equal interval is 1.0 mm.

The inner diameter of the tail hollow structure 105 is 9.6mm, the outer diameter of the tail hollow structure is 12.0mm, the height of the tail hollow structure is 15.0mm, the tail end of the tail hollow structure is provided with a smoothly-transited wedge-shaped taper angle, and the outer wall of the tail hollow structure is of a smooth structure.

The inner diameter of the blank holder 3 is larger than the outer diameter of the stud 1.

The size of the flat bottom mould 5 is larger than the outer diameter of the blank holder 3.

The outer side of the upper end of the driving connection part 102 is a symmetrical biplanar structure to match with the inner surface of the driving head 2.

The thickness of the upper plate 401 is 10.0 mm; the diameter of the prefabricated hole is 18.0 mm; the thickness of the lower plate 402 is 20.0 mm.

The bolt 6 is an M8 bolt 6, the size of a nut of the bolt is 20.0mm, and the length of a screw rod of the bolt is 6.0 mm.

The flat bottom die 5 is made of smooth round tool steel.

As shown in fig. 2, the present embodiment relates to a connection method of a stud composite connection device with self-locking, which specifically includes the following steps:

1) and (3) clamping the lower-layer plate 402 right above the flat bottom mold 5, clamping the stud 1 in the driving head 2 and locking the stud by using the ball plunger 201, and then placing the blank holder 3 on the lower-layer plate 402 which is pre-clamped.

2) The driving head 2 drives the stud 1 to penetrate into the lower-layer plate 402 at the rotating speed of 3600rpm and the feeding speed of 1.0mm/s under the driving of the servo motor until the stud is drilled into the depth of 10.0mm, friction heat is generated and accumulated due to the violent friction action between the stud 1 and the lower-layer plate 402 during the process, the temperature of the plate in a region to be connected is increased, the material is softened, the plasticity is enhanced, and when plastic aluminum alloy is filled above the self-locking annular groove 104, the metal mechanical internal self-locking is formed.

3) Then the driving head 2 stops rotating, upsetting is carried out for 4.0mm at the feed speed of 7mm/s, the tail hollow structure 105 is outwards opened under the guiding action of the wedge-shaped end and the axial force, the undercut amount is generated, and the mechanical self-locking of the undercut amount is formed, as shown in an inner self-locking characteristic position 403 in FIG. 3; and eliminating the gap between the stud 1 and the lower-layer plate 402, forming a solid-phase connection area after cooling, and compacting friction metal flash generated at the root part of the outer wall of the stud 1 by a platform between the stud body 101 and the tail hollow structure 105 in the lower heading process.

The internal self-locking characteristic position 403 specifically satisfies the following conditions: pi r²·(D-h₂)＝π(R²-r²)·h₂Wherein: d is the depth of the lower section cavity of the stud 1, and D satisfies the following conditions:r is the outer diameter of the tail hollow structure 105 and R is the inner diameter of the tail hollow structure 105.

4) After sufficient cooling, the upper layer plate 401 with the prefabricated holes is accurately added to the riveted stud 1, the bolt 6 is screwed into the internal thread 103 of the stud 1, and the upper layer plate 401 and the lower layer plate 402 are compacted and locked to form the mechanical-solid phase-thread composite connecting joint, as shown in fig. 3.

Compared with the prior art, the embodiment solves the problem that the bolt connection requires punching of the upper plate 401 and punching and tapping of the lower plate 402 by forming the mechanical-solid phase-thread composite connection joint, and has high requirement on the neutrality during clamping. The embodiment forms effective metal mechanical internal self-locking and undercut mechanical self-locking, and combines the advantages of the traditional threaded connection to tightly assemble the upper plate and the lower plate in the solid-phase welding area, thereby ensuring the static and dynamic mechanical properties of the obtained mechanical-solid-threaded composite connecting joint.

Example 2

As shown in fig. 4, the present embodiment relates to a stud composite connection device with self-locking, which includes: double-screw bolt 1, drive head 2, nut 7, blank holder 3 and flat bottom mould 5, wherein: the driving head 2, the stud 1, the blank holder 3 and the flat-bottom mold 5 are coaxially arranged, the driving head 2 drives the stud 1 to be inserted into a board to be connected 4, the blank holder 3 is arranged outside the stud 1 and is in contact with the board to be connected 4, the flat-bottom mold 5 is arranged below the board to be connected 4, and the nut 7 is matched with the stud 1 and forms a composite connection joint with the board to be connected 4.

The stud 1 comprises the following components in sequence from top to bottom: a barrel 101 and a tail hollow structure 105.

One end of the screw cylinder 101 is provided with a blind hole as a driving connection part 102, and the outer surface thereof is provided with a thread 103.

The plate 4 to be connected specifically comprises: an upper layer of board 401 with pre-holes and two lower layers of board 402, wherein: the upper plate 401 is a hot-formed steel plate, the first lower plate 402 is an aluminum alloy 5083, and the second lower plate 402 is cast aluminum AlSi10 MgMn.

The diameter of the prefabricated hole is 1.1-1.3 times of the outer diameter of the stud 1.

The height of the stud body 101, the height of the thread 103 and the height of the tail hollow structure 105 are matched with the thickness of the upper plate 401 and the lower plate 402 and the size of the nut 7, and the requirements are specifically met: h is h₁+h₂，h₁≥t₁+h₀，h₂＝k·t₂(k<1) Wherein: h is the height of the stud 1, h₁Height, h, of the thread 103₂Height, h, of the tail hollow structure 105₀Is a screw threadHeight of mother 7, t₁Is the thickness, t, of the upper sheet 401₂K is a matching coefficient (set to 0.6-0.8) set according to the sheet property for the thickness of the lower sheet 402.

The stud 1 is an M6 external thread stud 1, is made of 45 steel and has a height of 21.0 mm.

The height of the screw body 101 is 10.0 mm.

Four groups of self-locking annular grooves 104 are arranged on the inner wall of the tail hollow structure 105 at equal intervals, the cross section of each self-locking annular groove 104 is rectangular, the height of each groove is 0.5mm, and the depth of each groove is 0.4 mm.

The length of the equal interval is 0.8 mm.

The inner diameter of the tail hollow structure 105 is 5.0mm, the outer diameter of the tail hollow structure is 6.0mm, the height of the tail hollow structure is 11.0mm, the tail end of the tail hollow structure is provided with a smooth transition wedge-shaped taper angle, and the outer wall of the tail hollow structure is of a smooth structure.

The cavity depth of the tail hollow structure 105 is 15.5 mm.

The surface of the driving connection part 102 is prism-shaped to match with the outer surface of the magnetic prism-shaped driving head 2.

The thickness of the upper plate 401 is 2.0 mm; the diameter of the prefabricated hole is 7.0 mm; the thickness of the first lower-layer plate 402 is 4.0 mm; the thickness of the second lower plate 402 is 10.0 mm.

The nut 7 is an M6 nut 7, the height of the nut is 5.0mm, and the outer diameter of the nut is 10.0 mm.

The flat bottom die 5 is made of smooth round tool steel.

As shown in fig. 5, the present embodiment relates to a connection method of a stud composite connection device with self-locking, which specifically includes the following steps:

1) and (3) clamping the lower-layer plate 402 right above the flat bottom die 5, clamping the driving head 2 in the stud 1, and placing the blank holder 3 in the pre-clamped lower-layer plate 402.

2) The driving head 2 drives the stud 1 to penetrate into the lower-layer plate 402 at the rotation speed of 4000rpm and the feeding speed of 2.0mm/s under the driving of the servo motor until the stud penetrates through the first lower-layer plate 402 at the depth of 4.0mm, then the stud is fed at the rotation speed of 4000rpm and the feeding speed of 1.0mm/s for 4.0mm, the second lower-layer plate 402 is fully rubbed and softened, and after the rotary feeding is finished, the four self-locking annular grooves 104 are fully filled, so that the internal self-locking of the trapped metal machine is formed.

3) The drive head 2 is then stalled and upset at a feed rate of 5.0mm/s for 2.5mm, causing the tail hollow structure 105 to flare outwardly, creating an undercut amount that is mechanically self-locking, as shown by internal self-locking feature 403 in FIG. 6.

The internal self-locking characteristic position 403 specifically satisfies the following conditions: pi r²·(D-h₂)＝π(R²-r²)·h₂Wherein: d is the depth of the lower section cavity of the stud 1, and D satisfies the following conditions:r is the outer diameter of the tail hollow structure 105 and R is the inner diameter of the tail hollow structure 105.

4) After sufficient cooling, the upper plate 401 is compacted and locked by a nut 7, and finally the mechanical-solid-thread composite connection joint is obtained, as shown in fig. 6.

Compared with the embodiment 1, the lower layer plate 402 of the embodiment is formed by overlapping double-layer differential thick plates, and in order to avoid the influence of the gap between the two plates on the self-locking in the trapped metal, the self-locking annular grooves 104 of the embodiment are designed to be distributed in a multi-density and fine manner; the first lower layer plate 402 is an aluminum alloy 5083 which has good plasticity and elongation and increases the feed rate when piercing the first lower layer plate 402, while the second lower layer plate 402 is cast aluminum which has poor elongation and is prone to cracking, and therefore, it is necessary to increase the proportion of the rotary feed stage and reduce the proportion of the upset-down and the upset-down rate.

Preferably, when the plate to be riveted is thick or rigid, the flat bottom die in the above embodiment can be omitted.

Preferably, the driving head in the above embodiment is designed with a matched external/internal driving structure according to different thread structures (internal/external threads) for matching with the stud and transmitting torque, the external driving adopts a sleeve driving mode, a symmetrical biplane driving structure matched with the upper end of the internal threaded stud is arranged in the sleeve and locked by using a ball plunger, and the internal driving adopts a magnetic prism driving structure matched with the upper end of the external threaded stud;

in conclusion, compared with the prior art, the invention solves the problem that the traditional plate point connection process cannot be applied to the plate combination with the steel plate on the upper part and the light alloy plate on the lower part, and avoids a plurality of disadvantages of the traditional bolt connection process. The connection is based on the self-piercing friction riveting basic principle, a semi-hollow stud is creatively designed, the undercut amount generated by opening the hollow structure at the tail part of the stud is controlled to form a mechanical self-locking effect based on the undercut amount, the mechanical self-locking effect based on the annular groove is formed by controlling the flowing state of a plate to be connected, meanwhile, the solid-phase connection between the stud and a workpiece is realized on the basis of the mechanical self-locking, and the mechanical-solid-phase composite connection is formed; only the connecting holes are prefabricated on the upper plate, so that the requirements on the neutrality and the clamping precision are reduced, the connecting and upper-lower open type joint structure of a bolt is avoided, the sealing performance of the joint is enhanced, and the corrosion resistance is improved; the semi-hollow stud structure and the non-penetrating joint form reduce the size and the weight of the joint stud, meet the requirement of light structure and improve the process application prospect and the flexibility of structural design; the hollow structure at the tail part of the stud provides a space for extruding materials, and only friction metal flashes with small sizes relative to the plate and the stud are generated, so that the accurate installation of the upper-layer prefabricated hole steel plate is ensured.

The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.