Thermoplastic FRP rib upset head forming device and rib upset head forming method

Abstract

The invention discloses a thermoplastic FRP rib upset head forming device and a rib upset head forming method. The rib upset head forming device comprises a supporting system, a molding system, a pressurizing device, a split grouting system and a temperature control system, and the supporting system comprises a reaction frame and an anti-bending platform; the molding system comprises a lower mold, an upper mold and an end baffle; the pressurizing device is arranged on the jack base and is used for driving the middle part of the reaction frame to move up and down along the reaction frame upright post; the split grouting system comprises a nozzle with a blade and a push rod device; and the temperature control system is used for realizing uniform heating and softening of the FRP rib at the end part as well as cooling and secondary curing molding after molding. The ribbed upset head formed by compression molding can obviously enhance the contact area, mechanical occlusal force and friction force between the rib and an anchoring material, and can directly improve the anti-pulling performance, thereby improving the anchoring efficiency.

Description

Technical Field

[0001] This invention relates to a method for upsetting and molding ribs of thermoplastic fiber-reinforced polymer (FRP), belonging to the field of thermoplastic FRP rib upsetting and anchoring technology. Background Technology

[0002] Due to its excellent properties such as lightweight, high strength, and corrosion resistance, FRP (fiberglass reinforced plastic) bars are gradually becoming a powerful alternative to traditional steel bars in the field of marine engineering. Compared with thermosetting FRP bars, thermoplastic FRP bars have advantages such as secondary heating and curing, better corrosion resistance, and better fatigue performance.

[0003] However, thermoplastic FRP bars face significant anchoring challenges in practical applications. Due to the chemical inertness of the thermoplastic matrix, they exhibit poor chemical bonding with common anchors (such as metal anchors, which are mostly made of high-strength alloy steel, possessing good mechanical properties and durability; or some anchors made of special engineering plastics, possessing good corrosion resistance and insulation), making effective anchoring difficult. In particular, for smooth round bars, the low coefficient of friction of their smooth surface further exacerbates the risk of slippage in the anchoring system. When the structure is subjected to large tensile forces, the bars are very easy to pull out of the anchors, seriously affecting the safety and stability of the structure.

[0004] The existing methods for end treatment and anchoring of thermoplastic FRP bars mainly include the following: Pre-extrusion-bonding anchoring method: The invention patent of Xian Guijun et al., "A pre-extrusion-bonding anchoring system and anchoring method for thermoplastic resin-based FRP rods", melts the resin at the end of the thermoplastic FRP bar by heating, and extrudes it into a conical corrugated toothed plate using a molding device. Then, a mixed adhesive (such as epoxy resin + iron sand + expansion agent) is filled into the sleeve, and anchoring is achieved through mechanical interlocking and chemical bonding.

[0005] Melt-type anchoring methods, such as the invention patent of Liu Yue et al. entitled "A Melt-type Anchoring Method for a Unidirectional Component of Fiber-Reinforced Thermoplastic Composite Material", heat the end of the FRP bar to above the resin melting point, causing it to melt and fuse with the molten resin injected into the sleeve. After cooling, it forms an integral conical end, which transfers the load through self-anchoring. The invention patent of Wang Bu et al. entitled "An On-site Molding Device and Molding Method for Enlarging the Anchoring End of FRP Bars" places the FRP bar into a mold containing a hot-melt cavity, heats it to the resin melting temperature, removes the resin, leaving only the fiber bundle; then, a fiber dispersion device is used to disperse the fibers circumferentially on the inner wall of the hot-melt cavity; finally, the glue is injected through the injection channel, and after the glue solidifies, the mold is removed, so that the FRP bar forms a structure with enlarged and ribbed ends.

[0006] Fiber winding anchoring methods, such as the invention patent of Wu Zhishen et al. entitled "An Enlarged End for Anchoring FRP Reinforcement, Processing Method and Anchoring Method", involve winding bidirectional fiber cloth impregnated with thermoplastic resin as the inner layer and continuous fiber impregnated with thermosetting resin as the outer layer on a mandrel using a mold. After high-temperature curing, it is formed into an enlarged end with a tapered tightening section. During on-site construction, it is heated to 60~100℃, and the FRP reinforcement is screwed in. After the inner layer resin cools and cures, the FRP reinforcement is efficiently anchored in the concrete through the synergistic effect of the mechanical interlocking of the threads and the bonding of the resin.

[0007] Although many technologies are available to process the ends of thermoplastic FRP bars and enhance their anchoring performance, existing solutions still have certain limitations. There is an urgent need for a processing device and anchoring method that has high anchoring efficiency, strong applicability, smooth stress transition between the anchoring zone and the stress-bearing section, and high processing efficiency. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a thermoplastic FRP bar upsetting device and a forming method for improving anchoring efficiency.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A thermoplastic FRP rib upsetting device, comprising: The support system includes a reaction frame and an anti-bending platform; the reaction frame includes a jack base, a reaction frame middle section, a reaction frame base, and a reaction frame column, the reaction frame middle section is located between the jack base and the reaction frame base and is mounted on the reaction frame column; the anti-bending platform is mounted on the reaction frame base and is provided with a rib fixing groove; The molding system includes a lower mold, an upper mold, and an end baffle; the lower mold and the upper mold are combined to form a cavity inside, the cavity including a circular hole section and an enlarged conical section; the end baffle is disposed on the reaction frame base, and a baffle grouting hole is provided on the end baffle; the end baffle can slide in the horizontal direction to seal the cavity during grouting. The lower mold is fixed on the base of the reaction frame; the upper mold is fixed on the middle part of the reaction frame, and the lower mold and the upper mold are aligned by the column of the reaction frame; the rib fixing groove of the anti-bending platform is concentric with the circular hole section of the cavity and has the same radius; A pressurizing device is installed on the jack base to drive the middle part of the reaction frame to move up and down along the reaction frame column; A split grouting system includes a bladed nozzle and a push rod device; the bladed nozzle has a cutting edge on its surface that can split along the length of the rib, and the top of the bladed nozzle has nozzles on both sides for spraying resin mixture; the push rod device drives the bladed nozzle to enter the cavity from the baffle grouting hole along the length of the rib, and moves it out from the baffle grouting hole after completing the split and grouting. as well as A temperature control system is used to achieve uniform heating and softening of the end FRP ribs, as well as cooling and secondary curing after molding.

[0010] This invention relates to a thermoplastic FRP rib upsetting head forming device. The device involves symmetrically splitting the rib end along its length, filling the interior with a resin mixture containing high-rigidity particles, and then embedding these particles into the rib body through heating and pressurization. The ribbed end is then formed into a ribbed upsetting head using a ribbed conical mold. The splitting process increases the contact area between the rib body and the resin filler (2-3 times greater than non-split ends) and allows the high-rigidity particles to embed within the rib body, improving the overall integrity of the upsetting head. The molded ribbed upsetting head significantly enhances the contact area, mechanical interlocking force, and friction between the rib and the anchoring material, directly improving pull-out resistance and thus increasing anchoring efficiency.

[0011] The above-mentioned upsetting head forming device is used to process the anchorage area of ​​the tendon to form a ribbed upsetting head; it can then be anchored inside the concrete or conventional adhesive anchoring can be used for external prestressed tendon scenarios. The molding system allows for flexible changes in mold type, diameter, quantity, distribution, and rib pattern as needed; Pressurization devices include, but are not limited to, automatic or manual loading devices such as screw presses, hydraulic jacks, and pneumatic presses; The temperature control system includes a heating system and a condensation system; the condensation system is arranged around the lower mold and the upper mold, and the heating system is arranged on the contact surface of the upper mold, the lower mold and the support system.

[0012] The condensation system consists of interconnected condenser tubes, which achieve cooling through the internal circulation of condensate. Heating systems include, but are not limited to, non-contact heating components such as laid heating rods, heating resistance wires, and microwave heating equipment; When the diameter of the reinforcing bar is 6-10mm, the number of symmetrical splits is distributed between 2-4; when the diameter of the reinforcing bar is 12-18mm, the number of symmetrical splits is distributed between 4-6; when the diameter of the reinforcing bar is greater than or equal to 20mm, the number of symmetrical splits is 8. The end baffle is at the same height as the bladed nozzle and is provided with a small hole and a movable baffle; the bladed nozzle can exit the mold cavity through the small hole, and the movable baffle can block the small hole after the nozzle exits; This device can simultaneously meet the end shaping requirements of thermoplastic ribbed FRP bars and plain FRP bars; The components of high-toughness resin mixtures include, but are not limited to, thermoplastic resins, fibers, quartz sand, iron sand, glass microsphere fillers, etc. By adjusting the type and mixing ratio of the mixed materials, they can be adapted to the usage requirements of different working conditions. The contact points between the rib fixing plate and the anti-bending platform and the rib are filled with hard rubber. Beneficial effects

[0013] 1. High anchoring efficiency. Symmetrical splitting of the FRP reinforcement not only expands the contact area between the reinforcement and the high-toughness resin mixture, but also ensures that each segment is evenly dispersed at a certain angle along the length of the reinforcement, further improving anchoring efficiency. The high-toughness resin mixture contains particulate matter, which can be embedded into the reinforcement during molding, increasing the mechanical interlocking force and friction, thus improving overall integrity. Furthermore, the ribbed mold forms rib patterns on the upsetting surface, and the presence of particulate matter roughens the surface, further enhancing anchoring efficiency. Testing shows that the anchoring efficiency of this invention can reach over 95%.

[0014] 2. Near-circular cross-section after molding. The lower mold has an injection section that works in conjunction with the upper mold to effectively mold the FRP reinforcement. The lower and upper molds have the same radius of curvature, ensuring that the unsplit portion of the FRP reinforcement remains near-circular after secondary processing, matching the original cross-sectional height of the reinforcement. This improves the uniformity of stress in the cross-section and reduces the reduction in the mechanical properties of the reinforcement caused by secondary processing. Furthermore, it ensures a smooth stress transition between the anchorage section and the load-bearing section, laying the foundation for reliable anchorage and overall load-bearing capacity of the FRP reinforcement in engineering applications.

[0015] 3. High Design Flexibility. The upsetting head forming device provided by this invention features a highly designable molding system. It not only allows for convenient replacement based on specific production requirements, but its ribs also support functional design. Through targeted structural optimization and parameter adjustment, the ribs can precisely meet the specific requirements of actual application scenarios in terms of load-bearing capacity, durability, and adaptability, further expanding the device's application range. Furthermore, the high-toughness resin mixture can be adapted to different working conditions by adjusting the type and ratio of the mixed materials, demonstrating high design flexibility and a wide range of applications.

[0016] 4. High efficiency in local shaping. Compared with other thermoplastic FRP bar shaping technologies, the upsetting device provided by this invention can simultaneously shape multiple thermoplastic FRP bars locally, and is easy to operate; in addition, the temperature control system can quickly achieve uniform heating and softening of FRP bars and cooling and curing, and the combination of these two aspects significantly improves the overall efficiency. Attached Figure Description

[0017] Figure 1The reaction frame base 14 is the assembled version of Example 1.

[0018] Figure 2 The distribution of the heating system 62 at the bottom of the lower mold mounting groove 16 in Example 1 is shown.

[0019] Figure 3 The reaction frame 12 after the temperature control system 6 is implanted in Example 1.

[0020] Figure 4 This is a schematic diagram of the support system composition in Example 1.

[0021] Figure 5 This is an example of the installation of jack 31 in Example 1.

[0022] Figure 6 Example 1: Split-type grouting system 7.

[0023] Figure 7 The upper mold 4 is from Example 1.

[0024] Figure 8 This is the lower mold 5 of Example 1.

[0025] Figure 9 Example 1 shows the end baffle 8.

[0026] Figure 10 Example 1 shows the upsetting head forming device.

[0027] Figure 11 This is a thermoplastic smooth FRP bar after the end is split in Example 2.

[0028] Figure 12 The thermoplastic smooth FRP bar in Example 2 is processed by an upsetting device.

[0029] Figure 13 This is a load-displacement relationship diagram of the anchorage system after processing of thermoplastic GFRP bars in Example 2.

[0030] The components include: 1. reaction frame; 2. anti-bending platform; 3. jack; 4. upper mold; 5. lower mold; 6. temperature control system; 7. split grouting system; and 8. end baffle. Detailed Implementation

[0031] The technical solution of the present invention will be further explained in detail below with reference to the accompanying drawings. It should be understood that these embodiments are only used to further illustrate the present invention and are not intended to limit the scope of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art fall within the scope defined by the appended claims.

[0032] Example 1 This embodiment provides an upsetting head forming device, including: The support system includes a reaction frame 1 and an anti-bending platform 2. The reaction frame 1 includes a jack base 11, a reaction frame middle section 12, a reaction frame base 14, and a reaction frame column 13. The reaction frame middle section 12 is located between the jack base 11 and the reaction frame base 14 and is mounted on the reaction frame column 13. The anti-bending platform 2 is mounted on the reaction frame base 11 and is provided with a rib fixing groove 21. The molding system includes a lower mold 4, an upper mold 5, and an end baffle 8. After the lower mold 4 and the upper mold 5 are combined, a cavity is formed inside. The cavity includes a circular hole section and an enlarged conical section. The end baffle 8 is set on the reaction frame base 14. A baffle grouting hole 81 is provided on the end baffle 8. The end baffle 8 can slide in the horizontal direction to seal the cavity during grouting. The lower mold 4 is fixed on the reaction frame base 14; the upper mold 5 is fixed on the middle part 12 of the reaction frame, and the lower mold 4 and the upper mold 5 are aligned by the reaction frame column 13; the rib fixing groove 21 of the anti-bending platform 2 is concentric with the circular hole section of the cavity and has the same radius. The pressurization device is installed on the jack base 14 and is used to drive the middle part 12 of the reaction frame to move up and down along the reaction frame column 13. The split grouting system 7 includes a bladed nozzle 71 and a push rod device 72; the bladed nozzle 71 has a cutting blade on its surface that can split along the length of the rib, and the top of the bladed nozzle has nozzles on both sides for spraying resin mixture; the push rod device 72 drives the bladed nozzle 71 to enter the cavity from the baffle grouting hole 81 along the length of the rib, and moves it out from the baffle grouting hole 81 after splitting and grouting. as well as Temperature control system 6 is used to achieve uniform heating and softening of the end FRP ribs, as well as cooling and secondary curing after molding.

[0033] The assembly method of the molding device includes: The first step is to assemble the reaction frame base 14.

[0034] like Figure 1 and Figure 2 As shown, the reaction frame base 14 houses a temperature control system 6, end baffle mounting rods 17, and a matching power unit. Its end also features a split-type grouting system base 18. The temperature control system 6 consists of a heating system 62 and a condensation system 61. The heating system 62 is embedded in the bottom of the lower mold mounting groove 16, and the condensation system 61 is installed around the lower mold mounting groove 16. Furthermore, the end of the reaction frame base 14 has three rows of end baffle mounting rods 17 and a matching power unit; the end baffle mounting rods 17 are used to install end baffles 8, and the power unit controls the horizontal sliding of the end baffles 8 during grouting, ultimately achieving end sealing.

[0035] The second step is to assemble the middle part 12 of the reaction frame.

[0036] like Figure 3 As shown, the reaction frame base 12 also has a temperature control system 6 installed inside. The heating system 62 is embedded in the bottom of the upper mold mounting groove 15, and the condensation system 61 is installed around the upper mold mounting groove 15.

[0037] The third step is to assemble the reaction frame 1 and install the jacks 3 and the split grouting system 7.

[0038] like Figure 4 and Figure 5 As shown, the reaction frame 1 consists of a jack base 11, a reaction frame middle section 12, a reaction frame base 14, and a reaction frame column 13. The bottom dimensions of the jack base 11, the reaction frame middle section 12, and the reaction frame base 14 are equal, but their heights may vary depending on the actual situation. The reaction frame column 13 is fixed to the four corners of the reaction frame base 14; the reaction frame middle section 12 has through holes at corresponding positions at its four corners. The through holes at the four corners of the reaction frame middle section 12 are passed through the reaction frame column 13, with the upper mold mounting groove 15 located below the reaction frame middle section 12. First, the jack base 11 is fixed to the bottom of the jack 3 with bolts. The jack base 11 has through holes at its four corners; these through holes are passed through the reaction frame column 13 and fixed to the top of the reaction frame column 13. Finally, the free end of the jack 3 is fixed to the top of the reaction frame middle section 12. Figure 6 As shown, the split grouting system 7 consists of a bladed nozzle 71 and a push rod device 72. The bladed nozzle 71 can be replaced according to actual requirements, and the push rod device 72 is fixed to the split grouting system base 18 by bolts.

[0039] The fourth step is to assemble the support system.

[0040] like Figure 4 As shown, the anti-bending platform 2 includes a rib fixing groove 21 and a rib fixing plate 22. The rib fixing plate 22 is fixed to the anti-bending platform 2 by bolts. Hard rubber is laid at the contact position between the rib fixing groove 21 and the rib fixing plate 22 and the rib. The anti-bending platform 2 can be placed at the tail of the lower mold mounting groove 16 to form a support system together with the reaction frame 1.

[0041] Step 5: Install the molding system.

[0042] The molding system consists of an upper mold 4 and a lower mold 5. Figure 7 For upper mold 4, Figure 8 The lower mold 5 is installed in the upper mold mounting slot 15 and the lower mold mounting slot 16, respectively. Both the upper mold 4 and the lower mold 5 have through holes at their four corners, and bolts are used to fix them to the mounting slots during installation.

[0043] Step 6: Install end baffle 8.

[0044] like Figure 9As shown, the end baffle 8 includes a baffle injection hole 81, a movable baffle 82, and a mounting hole 83. The bladed nozzle 71 can exit the mold cavity through the baffle injection hole 81; the movable baffle 82 can seal the small hole after the bladed nozzle 71 is exited; when installing the end baffle 8, the end baffle mounting rod 17 passes through the mounting hole 83 and a nut is fitted on the end baffle mounting rod 17 to complete the installation.

[0045] Example 2 This embodiment provides a method for upsetting thermoplastic smooth FRP ribs, including: The first step involves placing the thermoplastic smooth FRP rib into the rib fixing groove 21 of the device described in Example 1, ensuring that the rib end and the lower mold end are in the same vertical plane. The rib is then fixed to the anti-bending platform 2 using the rib fixing plate 22 and bolts. The second step is to start jack 3 to slowly lower the upper mold 4 to the designated position. At this time, the rib is in contact with the upper mold 4 but is not under pressure.

[0046] The third step is to start the temperature control system 6, heat the rib to a certain temperature and maintain that temperature, requiring the resin to soften at that temperature but still maintain its shape.

[0047] The fourth step is to activate the grouting and splitting system 7 to split the ends of the reinforcing bars. After treatment, as shown... Figure 11 As shown.

[0048] Fifth, the grouting and splitting system 7 begins injecting the resin mixture. During grouting, the bladed nozzle 71 gradually moves away from the rib end. Due to the low fluidity of the resin mixture containing high-rigidity particles, it can fix the dispersed state of the split rib and prevent it from immediately flowing out of the mold cavity. At the same time, the end baffles 8 on both sides gradually close as the nozzle moves away. After the end baffles 8 on both sides are completely closed, the nozzle part of the bladed nozzle 71 remains inside the mold cavity through the grouting hole 81 of the baffle. After the mold cavity is filled with a sufficient amount of resin mixture, the bladed nozzle 71 exits the mold cavity, and the movable baffle 82 seals the grouting hole 81 of the baffle.

[0049] Step 6: Adjust the temperature control system 6 to heat the ribs until the preset molding temperature is reached, then restart jack 3 for molding. After molding, adjust the temperature control system 6 to cool the ribs, and finally demold. The finished product should look like this. Figure 12 As shown.

[0050] The treated tendons can be anchored inside the concrete or conventionally bonded anchored for use in external prestressed tendon applications.

[0051] Figure 13High-modulus thermoplastic round GFRP bars with diameters of 7mm and 10mm were used. After the ends were processed by an upsetting device, they were bonded to steel sleeves to form an anchoring system. The corresponding load-displacement curves are shown. Tensile tests were conducted using a 200 kN universal testing machine (WAW-200, Shanghai, China). A displacement-controlled loading method with a loading rate of 2mm / min was used, and the test was terminated after the GFRP bar fractured. The ultimate bearing capacity of the 7mm GFRP bar was 68.47kN, the ultimate bearing capacity of the anchoring system was 67.10kN, and the anchoring efficiency was 98%. The ultimate bearing capacity of the 10mm GFRP bar was 133.94kN, the ultimate bearing capacity of the anchoring system was 128.54kN, and the anchoring efficiency was 96%. The final failure mode of both diameter bars was explosive fracture of the free segment, which is an ideal failure mode, indicating that the anchoring system has high reliability.

Claims

1. A thermoplastic FRP tendon upset forming device, characterized by, include: The support system includes a reaction frame and an anti-bending platform; the reaction frame includes a jack base, a reaction frame middle section, a reaction frame base, and a reaction frame column, the reaction frame middle section is located between the jack base and the reaction frame base and is mounted on the reaction frame column; the anti-bending platform is mounted on the reaction frame base and is provided with a rib fixing groove; The molding system includes a lower mold, an upper mold, and an end baffle; the lower mold and the upper mold are combined to form a cavity inside, the cavity including a circular hole section and an enlarged conical section; the end baffle is disposed on the reaction frame base, and a baffle grouting hole is provided on the end baffle; the end baffle can slide in the horizontal direction to seal the cavity during grouting. The lower mold is fixed on the base of the reaction frame; the upper mold is fixed on the middle part of the reaction frame, and the lower mold and the upper mold are aligned by the column of the reaction frame; the rib fixing groove of the anti-bending platform is concentric with the circular hole section of the cavity and has the same radius; A pressurizing device is installed on the jack base to drive the middle part of the reaction frame to move up and down along the reaction frame column; A split grouting system includes a bladed nozzle and a push rod device; the bladed nozzle has a cutting edge on its surface that can split along the length of the rib, and the top of the bladed nozzle has nozzles on both sides for spraying resin mixture; the push rod device drives the bladed nozzle to enter the cavity from the baffle grouting hole along the length of the rib, and moves it out from the baffle grouting hole after completing the split and grouting. as well as A temperature control system is used to achieve uniform heating and softening of the end FRP ribs, as well as cooling and secondary curing after molding.

2. The thermoplastic FRP tendon heading forming apparatus according to claim 1, characterized by The anti-bending platform is also equipped with a rib fixing plate to prevent the ribs from sliding along their length.

3. The thermoplastic FRP tendon heading forming apparatus according to claim 1, characterized by The lower mold has a vertical injection section, the end of which is a concave semi-cone shape and the rest is a semi-circle; the upper mold has a concave semi-cone shape at the end and the rest is an approximately semi-circular concave arc surface; the corresponding arc radii of the upper and lower molds are equal and the surfaces have ribs.

4. The thermoplastic FRP tendon heading forming apparatus according to claim 1, characterized by The pressurizing device includes, but is not limited to, automatic or manual loading devices such as screw presses, hydraulic jacks, and pneumatic presses.

5. The thermoplastic FRP tendon heading forming apparatus according to claim 1, wherein The temperature control system includes a heating system and a condensation system; the condensation system is arranged around the lower mold and the upper mold, and the heating system is arranged on the contact surface of the upper mold, the lower mold and the support system.

6. The thermoplastic FRP rib upsetting device according to claim 5, characterized in that, The condensation system consists of interconnected condenser tubes, and cooling is achieved through the internal circulation of condensate. The heating system includes, but is not limited to, non-contact heating components such as laid heating rods, heating resistance wires, and microwave heating equipment.

7. A method for forming ribs using the thermoplastic FRP rib upsetting apparatus according to any one of claims 1-6, characterized in that, Place the thermoplastic smooth FRP rib into the cavity of the lower mold, and ensure that the end of the rib and the end of the lower mold are in the same vertical plane; fix the rib to the anti-bending platform using the rib fixing plate; Start the pressurization device to slowly lower the upper mold to the designated position. At this time, the rib is in contact with the upper mold but is not under pressure. Start the temperature control system to heat the rib to the set temperature and maintain that temperature. At this temperature, the resin should soften but retain its shape. The grouting and splitting system was activated to split the ends of the reinforcing bars. The grouting and splitting system begins to inject a resin mixture into the split ribs; Adjust the temperature control system to heat the ribs until the preset molding temperature is reached, then restart the pressurizing device for molding. After molding, adjust the temperature control system to cool the ribs, and finally demold.

8. The method for forming a rib upsetting head according to claim 7, characterized in that, When the diameter of the reinforcing bar is 6-10mm, the number of symmetrical splits is distributed between 2 and 4; when the diameter of the reinforcing bar is 12-18mm, the number of symmetrical splits is distributed between 4 and 6; when the diameter of the reinforcing bar is greater than or equal to 20mm, the number of symmetrical splits is 8.

9. The method for forming a rib upsetting head according to claim 7, characterized in that, During the grouting process, the bladed nozzle gradually moves away from the end of the rib, and the baffles on both sides gradually close as the nozzle moves away. After the baffles on both sides are completely closed, the nozzle part of the bladed nozzle remains inside the mold cavity through the grouting hole of the baffle. After the mold cavity is filled with a sufficient amount of resin mixture, the bladed nozzle exits the mold cavity, and the movable baffle blocks the grouting hole of the baffle.

10. The method for forming a rib upsetting head according to claim 7, characterized in that, The resin mixture includes, but is not limited to, thermoplastic resin, fiber, quartz sand, iron sand, and glass microsphere filler. By adjusting the type and ratio of the mixed materials, it can be adapted to the usage requirements of different working conditions.

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