High-shear-resistance slotless titanium alloy threaded self-plugging rivet and preparation process thereof

Abstract

The invention relates to the technical field of fastening connection of aerospace, and particularly discloses a high-shear-resistance slotless titanium alloy threaded self-plugging rivet and a preparation process thereof.The self-plugging rivet comprises a core rod, a pipe body, a rivet body and a driving nut, the driving nut, the rivet body and the pipe body are sequentially arranged on the core rod in a sleeving mode, and the rivet body is divided into a head part, a middle part and a tail part; the end face of the end, close to the driving nut, of the nail body head is flat, the driving nut abuts against the end face, a threaded groove allowing the core rod to penetrate through is formed in the center of the end face, the surface roughness of the end face is 1.6-2.2 micrometers, and the diameter of the outer circle of the end face is larger than that of the circumcircle of the driving nut. The end face of the head of the rivet body is flat, the center of the end face is only provided with the threaded groove allowing the core rod to penetrate through, after the core rod is broken, the core rod can completely shield the threaded groove in the center of the end face, and the structure can reduce the radar reflection area and improve the stealth performance of an airplane.

Description

Technical Field

[0001] This invention relates to the field of fastening technology in aerospace, specifically to a high shear resistance grooveless titanium alloy threaded blind rivet and its manufacturing process. Background Technology

[0002] Threaded blind rivets (also known as pull rivets) are quick-connect fasteners that can be applied from one side only, and are widely used in structural connections that require operation in enclosed spaces or are accessible from only one side. In the manufacturing of aerospace vehicles, due to strict weight control requirements, situations often arise where installation space is limited, making installation impossible for workers. In such cases, blind rivets, which can be used for single-sided riveting, are typically employed to achieve assembly. To improve the locking strength of blind rivets, Chinese Patent No. CN212407248U discloses a high-preload locking blind rivet, comprising a mandrel, an elastic washer, a tube, a rivet body, and a drive nut. One end of the mandrel has a protruding head, and the other end has a clamping portion. The drive nut, rivet body, tube, and elastic washer are sequentially fitted onto the mandrel near the head. A standard threaded portion is provided on the mandrel near the head, and the rivet body is threadedly connected to the standard threaded portion. A modified threaded portion is provided on the mandrel near the clamping portion, and the drive nut is threadedly connected to the modified threaded portion. The major diameter of the standard threaded portion is larger than that of the modified threaded portion. An annular necking groove is provided between the standard threaded portion and the modified threaded portion. When installing the blind rivet, the drive nut is fixed, and rotating the mandrel causes the drive nut and rivet body to advance towards the head of the mandrel. The rivet body deforms by compressing the tube, and the tube deforms by compressing the elastic washer. When the drive nut reaches the necking groove, the mandrel is stopped at the necking groove. During installation and use, the elastic washer deforms and generates a large axial force, which increases the preload during product installation and use. This axial force increases the friction between the threaded parts, thereby increasing the locking force and improving the product's anti-loosening performance and reliability. The threaded blind rivet has a tapered surface near the drive nut, with a groove circumferentially arranged around its central axis. The drive nut also has a tapered section extending from the end near the rivet, with raised stripes circumferentially arranged around its central axis. The tapered surface and grooves work together to prevent relative rotation between the drive nut and the rivet, facilitating the blocking of the mandrel. However, after the mandrel is blocked within the rivet, the tapered surface is not completely covered, leaving a portion exposed. This exposed surface increases the radar cross-section, negatively impacting the aircraft's stealth performance. Summary of the Invention

[0003] The purpose of this invention is to provide a high shear resistance grooveless titanium alloy threaded blind rivet and its manufacturing process, in order to solve the problem that the conical surface of the rivet body of the existing threaded blind rivet is not completely covered by the blocked core rod, and part of the conical surface is exposed, which increases the radar reflection area and leads to poor aircraft stealth performance.

[0004] To address the above issues, the following technical solution is provided: A high shear resistance grooveless titanium alloy threaded blind rivet includes a core rod, a tube body, a rivet body, and a drive nut. The drive nut, rivet body, and tube body are sequentially fitted onto the core rod. The rivet body is divided into a head, a middle section, and a tail section. The end face of the head section near the drive nut is flat, with the drive nut abutting against the end face. A threaded groove for the core rod to pass through is provided in the center of the end face. The surface roughness of the end face is 1.6-2.2μm, and the diameter of the outer circle of the end face is larger than the diameter of the outer circle of the drive nut. The middle section is cylindrical, with three evenly distributed concave points on the outer wall of the middle section. The concave points are arc-shaped recesses that indent into the rivet body. The tail section, away from the drive nut, is conical.

[0005] The basic principle of the above technical solution is as follows: a rivet gun is used to fix and drive the nut to rotate. The nut and the nail body are locked together by the surface friction of the cross section, so that the nut and the nail body are relatively stationary. At the same time, the rivet gun head holds the tail of the core rod and drives the core rod clockwise. The clockwise rotating core rod generates axial displacement under the axial action of the rivet thread pair. The head of the core rod pulls the tube body, and after the tube body contacts the sandwich plate, a bulge occurs, thus forming an upsetting head. The core rod exposed outside the end face is broken off, and the riveting is completed, so that two or more parts that need to be connected are fastened together.

[0006] The beneficial effects of the above technical solution are as follows: 1. The head end face of the nail body is flat, and the center of the end face only has a threaded groove for the core rod to pass through. When the core rod breaks, the core rod can completely block the threaded groove in the center of the end face. This structure can reduce the radar reflection area and improve the stealth performance of the aircraft. 2. By forming three symmetrically distributed contraction deformation areas on the rivet body, the three-point uniform force characteristics are utilized to reduce local stress concentration and provide a self-locking function, thereby improving the fatigue resistance of the connection parts, extending service life, and achieving reliable locking of the connected parts. This effectively prevents the blind rivet from loosening and falling off due to vibration, load, or environmental factors.

[0007] Furthermore, the head is a countersunk head that expands outward by 100-130°, and the end of the countersunk head abuts against the drive nut. The nail body with the countersunk head can be used on the surface of equipment with high pneumatic requirements. A corresponding countersunk is made on the surface of the sandwich panel according to the shape of the nail head, ensuring that the surface of the sandwich panel is flat and smooth after installation.

[0008] Furthermore, the head can be either convex or flat. Nails with convex or flat heads can be used in areas requiring high connection strength or in locations where the interlayer thickness is thin and does not meet the requirements for denting.

[0009] Furthermore, one end of the core rod has a protruding head, and the other end of the core rod has a clamping part with a flat opening. The core rod has a reinforcing thread near the head, and the nail body is threadedly connected to the reinforcing thread. The core rod has a flattened major diameter thread near the clamping part, and the drive nut is threadedly connected to the flattened major diameter thread. The major diameter of the flattened major diameter thread is larger than that of the reinforcing thread, and an annular necking groove is provided between the flattened major diameter thread and the reinforcing thread.

[0010] Furthermore, the reinforcing thread is a UNJF or MJ reinforcing thread.

[0011] Furthermore, the inner wall of the tube near the nail is stepped, and a ring is embedded within the stepped inner wall of the tube near the nail. The stepped shape creates a certain strength difference in the tube as a whole, which is beneficial for the upsetting head to form a locking mechanism.

[0012] A manufacturing process for a high shear resistance grooveless titanium alloy threaded blind rivet includes the following steps: S1: Core rod manufacturing: The core rod is made of GH2132 material and is formed by hot forging to form a protruding head and a flat mouth at the tail. Then, it is finely processed to form the outer circle of the head. The outer circle is polished smooth and then subjected to strong heat treatment after thread rolling. Finally, it is machined into an annular neck groove through multiple turnings. S2: Pipe body manufacturing: The pipe body is made of austenitic stainless steel heat-resistant steel, which is processed by two machining processes, then cleaned, solution treated and surface treated, and then molybdenum disulfide is added to the pipe body for lubrication. S3: Nail Body Manufacturing: The nail body is made of titanium alloy TC4 material. After the nail head shape is formed by hot forging, it is cleaned by ultrasonic cleaning machine. At the same time, alkaline cleaning agent is used to remove oil and oxides from the surface of the nail body. Then, it is machined by the first CNC turning. The first CNC turning uses carbide tools to complete the basic shaping of the outer circle and inner hole of the nail body. Then, the nail body is precision turned by the second CNC turning to ensure that the overall length is consistent and that the key dimensions meet the final requirements. After that, tapping is performed. After tapping, the nail body is machined by the third CNC turning. The third CNC turning produces three evenly distributed circumferential tapping points on the outer wall of the middle of the nail body. After the third CNC turning, aging is performed. The aging process involves placing the nail body in an environment of 480℃~600℃ for 2~6 hours. After aging, a fluorinated modified phosphate coating is applied to the surface of the nail body. After the coating, cetyl alcohol is applied to the threads and mating parts of the nail body for lubrication. S4: Ring manufacturing: The ring is made of polyoxymethylene material through two machining processes; S5: Drive nut manufacturing: The drive nut is made of No. 45 hexagonal bar material, which is processed by two machining operations and one tapping, then cleaned, and then quenched and tempered to a hardness of HRC40-45 to complete the manufacturing of the drive nut. S5: Assembly of threaded blind rivets: First, fit the ring into the inner wall step of the tube. Then, assemble the assembled tube onto the mandrel until one end of the tube abuts against the protruding head of the mandrel. Next, assemble the rivet onto the mandrel and install the drive nut. After the rivet is circumferentially closed at three points using a three-point closing machine, the assembly of the product is completed. Attached Figure Description

[0013] Figure 1 Structural diagram of a high shear resistance grooveless titanium alloy threaded blind rivet; Figure 2 This is a structural diagram of a 100° countersunk nail body; Figure 3 This is a schematic diagram of the core rod structure; Figure 4 This is a schematic diagram of the tube structure; Figure 5 This is a schematic diagram of the process of riveting sandwich panels with blind rivets.

[0014] The reference numerals in the accompanying drawings include: core rod 1, head 11, clamping part 12, reinforcing thread 13, flattened major diameter thread 14, necking groove 15, tube body 2, step 21, nail body 3, head 31, middle part 32, closing point 321, tail part 33, drive nut 4, ring 5, bulge 6, sandwich plate 7. Detailed Implementation

[0015] The following detailed description illustrates the specific implementation method: The basic implementation examples are as follows: Figure 1-5 As shown: A high-shear-resistant, slotless titanium alloy threaded blind rivet, such as Figure 1 As shown, it includes a core rod 1, a tube 2, a nail 3, and a drive nut 4. The drive nut 4, nail 3, and tube 2 are sequentially fitted onto the core rod 1, as shown. Figure 2 As shown, the nail body 3 is divided into a head 11, a middle section 32, and a tail 33. The end face of the head 11 near the drive nut is flat, and the drive nut 4 abuts against the end face. A threaded groove for the core rod to pass through is provided in the center of the end face. The surface roughness of the end face is 2.2μm, and the diameter of the outer circle of the end face is larger than the diameter of the outer circle of the drive nut. The middle section 32 is cylindrical, and three evenly distributed constriction points 321 are provided on the outer wall of the middle section 32. The constriction points 321 are arc-shaped recesses that are recessed into the nail body 3. The end of the tail 33 away from the drive nut 4 is set into a conical shape. Figure 1As shown, the head 11 is a countersunk head that expands outward by 100°. The head 11 can also be a countersunk head that expands outward by 130°. The end of the countersunk head abuts against the drive nut 4. The head 11 can also be a convex head.

[0016] like Figure 3 As shown, one end of the core rod 1 has a protruding head 11, and the other end of the core rod 1 has a clamping part 12. The clamping part 12 is a flat opening. The core rod 1 has a reinforcing thread 13 near the head 11. The reinforcing thread 13 is a UNJF thread. The nail body 3 is threadedly connected to the reinforcing thread 13. The core rod 1 has a flattened major diameter thread 14 near the clamping part 12. The drive nut 4 is threadedly connected to the flattened major diameter thread 14. The major diameter of the flattened major diameter thread 14 is larger than the major diameter of the reinforcing thread 13. An annular necking groove 15 is provided between the flattened major diameter thread 14 and the reinforcing thread 13.

[0017] like Figure 4 As shown, the inner wall of the tube 2 near the nail 3 is set in the shape of a step 21, as... Figure 1 As shown, a ring 5 is embedded in the stepped inner wall of the tube body 2 near the nail body 3.

[0018] The specific implementation process is as follows: like Figure 5 As shown, taking the connection of the sandwich panel 7 as an example, the assembled blind rivet is passed through the sandwich panel 7, and the drive nut 4 is rotated using a rivet gun. The drive nut 4 and the rivet body 3 are locked together by the surface friction of the cross section, so that the drive nut 4 and the rivet body 3 are relatively stationary. At the same time, the head of the rivet gun clamps the tail 33 of the core rod 1 and drives the core rod 1 clockwise. The core rod 1, which rotates clockwise, generates axial displacement under the axial action of the blind rivet thread pair. The head 11 of the core rod 1 pulls the tube body 2, so that after the tube body 2 contacts the sandwich panel 7, a bulge 6 occurs, thus forming an upsetting head. Finally, the core rod 1 is broken off from the neck groove 15, and the riveting is completed, so that the two or more sandwich panels 7 that need to be connected are fastened together.

[0019] The head of the rivet is flat, with a threaded groove in the center for the mandrel to pass through. When the mandrel breaks, it completely blocks the threaded groove in the center of the head, reducing radar cross-section and improving aircraft stealth performance. Three symmetrically distributed tapering deformation areas are formed on the rivet, utilizing the uniform force distribution at three points to reduce local stress concentration and provide a self-locking function. This enhances the fatigue resistance of the connection, extends service life, and ensures reliable locking of the connected parts, effectively preventing the rivet from loosening or falling off due to vibration, load, or environmental factors.

[0020] A manufacturing process for a high shear resistance grooveless titanium alloy threaded blind rivet includes the following steps: S1: Core rod manufacturing: The core rod is made of GH2132 material and is formed by hot forging to form a protruding head and a flat mouth at the tail. Then, it is finely processed to form the outer circle of the head. The outer circle is polished smooth and then subjected to strong heat treatment after thread rolling. Finally, it is machined into an annular neck groove through multiple turnings. S2: Pipe body manufacturing: The pipe body is made of austenitic stainless steel heat-resistant steel, which is processed by two machining processes, then cleaned, solution treated and surface treated, and then molybdenum disulfide is added to the pipe body for lubrication. S3: Nail Body Manufacturing: The nail body is made of titanium alloy TC4 material. After the nail head shape is formed by hot forging, it is cleaned by ultrasonic cleaning machine. At the same time, alkaline cleaning agent is used to remove oil and oxides from the surface of the nail body. Then, it is machined by the first CNC turning. The first CNC turning uses carbide tools to complete the basic shaping of the outer circle and inner hole of the nail body. Then, the nail body is precision turned by the second CNC turning to ensure that the overall length is consistent and that the key dimensions meet the final requirements. After that, tapping is performed. After tapping, the nail body is machined by the third CNC turning. The third CNC turning produces three evenly distributed circumferential tapping points on the outer wall of the middle of the nail body. After the third CNC turning, aging is performed. The aging process involves placing the nail body in an environment of 480℃~600℃ for 2~6 hours. After aging, a fluorinated modified phosphate coating is applied to the surface of the nail body. After the coating, cetyl alcohol is applied to the threads and mating parts of the nail body for lubrication. S4: Ring manufacturing: The ring is made of polyoxymethylene material through two machining processes; S5: Drive nut manufacturing: The drive nut is made of No. 45 hexagonal bar material, which is processed by two machining operations and one tapping, then cleaned, and then quenched and tempered to a hardness of HRC40-45 to complete the manufacturing of the drive nut. S5: Assembly of threaded blind rivets: First, fit the ring into the inner wall step of the tube. Then, assemble the assembled tube onto the mandrel until one end of the tube abuts against the protruding head of the mandrel. Next, assemble the rivet onto the mandrel and install the drive nut. After the rivet is circumferentially closed at three points using a three-point closing machine, the assembly of the product is completed.

[0021] The above descriptions are merely embodiments of the invention, and common knowledge regarding specific structures and characteristics of the solutions is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the scope of this invention, and these should also be considered within the protection scope of this invention. These modifications and improvements will not affect the effectiveness of the invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A high shear resistance grooveless titanium alloy threaded blind rivet, comprising a core rod, a tube body, a rivet body, and a drive nut, wherein the drive nut, rivet body, and tube body are sequentially fitted onto the core rod, characterized in that: The nail body is divided into a head, a middle section, and a tail section. The end face of the head section near the drive nut is flat, with the drive nut abutting against the end face. A threaded groove for the core rod to pass through is provided in the center of the end face. The surface roughness of the end face is 1.6-2.2μm. The diameter of the outer circle of the end face is larger than the diameter of the outer circle of the drive nut. The middle section is cylindrical, with three evenly distributed circumferential taps on the outer wall of the middle section. The taps are arc-shaped pits that are recessed into the nail body. The tail section is conical at the end away from the drive nut.

2. The high shear resistance grooveless titanium alloy threaded blind rivet according to claim 1, characterized in that: The head is a countersunk head that expands outward by 100-130°, and the end of the countersunk head abuts against the drive nut.

3. The high shear resistance grooveless titanium alloy threaded blind rivet according to claim 1, characterized in that: The head is either convex or flat.

4. The high shear resistance grooveless titanium alloy threaded blind rivet according to claim 1, characterized in that: One end of the core rod has a protruding head, and the other end of the core rod has a clamping part with a flat opening. The core rod has a reinforcing thread near the head, and the nail body is threadedly connected to the reinforcing thread. The core rod has a flattened major diameter thread near the clamping part, and the drive nut is threadedly connected to the flattened major diameter thread. The major diameter of the flattened major diameter thread is larger than that of the reinforcing thread. An annular necking groove is provided between the flattened major diameter thread and the reinforcing thread.

5. A high shear resistance grooveless titanium alloy threaded blind rivet according to claim 4, characterized in that: The reinforcing thread is UNJF or MJ reinforcing thread.

6. A high shear resistance grooveless titanium alloy threaded blind rivet according to claim 1, characterized in that, The inner wall of the tube near the nail is stepped, and a ring is embedded in the stepped inner wall of the tube near the nail.

7. A manufacturing process for a threaded blind rivet according to claims 1-6, characterized in that, Includes the following steps: S1: Core rod manufacturing: The core rod is made of GH2132 material and is formed by hot forging to form a protruding head and a flat mouth at the tail. Then, it is finely processed to form the outer circle of the head. The outer circle is polished smooth and then subjected to strong heat treatment after thread rolling. Finally, it is machined into an annular neck groove through multiple turnings. S2: Pipe body manufacturing: The pipe body is made of austenitic stainless steel heat-resistant steel, which is processed by two machining processes, then cleaned, solution treated and surface treated, and then molybdenum disulfide is added to the pipe body for lubrication. S3: Nail Body Manufacturing: The nail body is made of titanium alloy TC4 material. After the nail head shape is formed by hot forging, it is cleaned by ultrasonic cleaning machine. At the same time, alkaline cleaning agent is used to remove oil and oxides from the surface of the nail body. Then, it is machined by the first CNC turning. The first CNC turning uses carbide tools to complete the basic shaping of the outer circle and inner hole of the nail body. Then, the nail body is precision turned by the second CNC turning to ensure that the overall length is consistent and that the key dimensions meet the final requirements. After that, tapping is performed. After tapping, the nail body is machined by the third CNC turning. The third CNC turning produces three evenly distributed circumferential tapping points on the outer wall of the middle of the nail body. After the third CNC turning, aging is performed. The aging process involves placing the nail body in an environment of 480℃~600℃ for 2~6 hours. After aging, a fluorinated modified phosphate coating is applied to the surface of the nail body. After the coating, cetyl alcohol is applied to the threads and mating parts of the nail body for lubrication. S4: Ring manufacturing: The ring is made of polyoxymethylene material through two machining processes; S5: Drive nut manufacturing: The drive nut is made of No. 45 hexagonal bar material, which is processed by two machining operations and one tapping, then cleaned, and then quenched and tempered to a hardness of HRC40-45 to complete the manufacturing of the drive nut. S5: Assembly of threaded blind rivets: First, fit the ring into the step inside the inner wall of the tube. Then, assemble the assembled tube onto the mandrel until one end of the tube abuts against the protruding head of the mandrel. Next, assemble the rivet onto the mandrel and install the drive nut. Then, use a special equipment to perform a three-point circumferential closing machine on the rivet and the tube according to the technical requirements to complete the assembly of the product.

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