A standard fastener low temperature mechanical property testing tool

Abstract

The present application relates to the technical field of detection, and discloses a tool for testing the low-temperature mechanical properties of standard fasteners, comprising a workbench.In the low-temperature ductility detection stage of the standard fastener, the pulling hydraulic push rod drives the positioning cover to move up at the same time, the compression piston is synchronously driven to move in the compression cover, the air in the compression cover is in a closed space and is adiabatically compressed, the internal energy of the air is increased to realize temperature rise; after the detection is completed, the airflow channel of the compression cover and the detection chamber is turned on, the compressed air after temperature rise relies on its own pressure to quickly flow into the detection chamber composed of the sealing cover and the positioning cover, strongly pushes the low-temperature air in the chamber to be discharged from the output pipe, and the rapid temperature rise of the detection chamber is realized; the whole avoids the frostbite risk caused by the direct contact of the operator with the low-temperature components, significantly improves the safety, saves the investment of the additional temperature rise equipment, simplifies the operation process of the post-detection chamber temperature rise, and simultaneously improves the integration and detection efficiency of the testing tool.

Description

Technical Field

[0001] This invention belongs to the field of testing technology, specifically, it relates to a tooling for testing the low-temperature mechanical properties of standard fasteners. Background Technology

[0002] In cryogenic operating scenarios such as aerospace, polar engineering, deep-sea operations, and wind power equipment, the cryogenic mechanical properties (especially ductility) of standard fasteners directly determine the structural stability and operational safety of the equipment. For standard fasteners with high ductility, such as high-strength titanium alloy bolts in aerospace, wind turbine flange connecting pins in wind power equipment, and stainless steel fastening bolts used in deep-sea engineering, cryogenic ductility testing is a crucial step in ensuring the long-term reliable operation of the equipment. In existing technologies, cryogenic mechanical property testing of such ductile standard fasteners typically requires creating a pre-set cryogenic environment by purging liquid nitrogen into a sealed chamber. After the chamber temperature stabilizes, an axial tensile force is applied to the fastener using a pull-out mechanism to complete the ductility test.

[0003] However, after the existing testing fixture is completed, a large amount of low-temperature air remains in the sealed chamber due to the evaporation of liquid nitrogen. The chamber and the ductile workpiece clamped inside are in an extremely low temperature state. In order to avoid frostbite caused by direct contact with the low-temperature components and workpieces, it is necessary to wait for the low-temperature air in the chamber to naturally heat up and evaporate. However, the natural heating time is long, which greatly extends the interval between two tests and seriously reduces the testing efficiency. Alternatively, an independent heating device can be configured to heat the chamber. However, configuring an additional heating device increases the structural complexity of the fixture and the cost of equipment investment. Moreover, the coordinated control of multiple devices is prone to failure, which further affects the stability of the test.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows: A fixture for testing the low-temperature mechanical properties of standard fasteners, including a worktable.

[0006] A pair of base plates are mounted on the worktable. The base plates are symmetrically distributed. Each of the base plates is equipped with a clamping assembly, which is used to clamp the end of a standard fastener. One of the base plates is connected to the surface of the worktable, and the other base plate is connected to a pull-out hydraulic push rod mounted on the worktable. A sealing cover is screwed onto the outer wall of the upper substrate, and a positioning cover is vertically inserted into the outer wall of the bottom substrate. The sealing cover and the positioning cover are compatible with each other. After the clamping assembly is locked with the standard fastener, the sealing cover and the positioning cover are screwed together, and low temperature air is introduced into the inner cavity of the sealing cover and the positioning cover. A compression hood is installed on the workbench, and a connecting pipe is installed between the compression hood and the substrate located below. A compression piston that moves synchronously with the positioning hood slides inside the compression hood. During the testing process, the sealing hood and the positioning hood move upward synchronously, driving the compression piston upward, thereby pressurizing the air inside the compression hood and increasing the air temperature. After the test is completed, compressed air is input into the testing chamber and cold air is discharged.

[0007] In a preferred embodiment of the present invention, four adjusting rods are installed at the bottom corner of the workbench, and the adjusting rods are connected to the workbench by threaded connection. A support is installed at the bottom of the adjusting rod, the cross-sectional area of ​​the support is trapezoidal, and a pad is installed at the bottom of the support. The bottom of the pad is provided with an anti-slip groove.

[0008] In a preferred embodiment of the present invention, a bracket is installed on the top of the workbench, a crossbeam is installed on the bracket, a pulling hydraulic push rod is installed on the crossbeam, and a controller is installed on the outer shell of the workbench, the controller being connected to the pulling hydraulic push rod.

[0009] In a preferred embodiment of the present invention, a positioning frame is installed at the end of the substrate, the positioning frame on the bottom substrate is installed on the surface of the worktable, and the positioning frame on the top substrate is connected to the output end of the pull-out hydraulic push rod.

[0010] In a preferred embodiment of the present invention, the clamping assembly includes a pair of clamping plates, on which a sliding plate is mounted. The sliding plate is slidably disposed in a notch opened in the side wall of the substrate. A positioning platform is mounted on the substrate. A threaded rod is rotatably mounted on the clamping plates. The end of the threaded rod is screwed into the positioning platform. A positioning plate is mounted on the threaded rod. The positioning plate and the end of the threaded rod are used to limit the position of the clamping plates.

[0011] In a preferred embodiment of the present invention, a knob is installed on the outer wall of the sealing cover, an internal thread is provided on the inner wall of the sealing cover, a boss is also installed on the inner wall of the sealing cover, and the boss is used to divide the internal thread and limit the position of the substrate. An external thread is provided on the side wall of the positioning cover, and the external thread is adapted to the internal thread. A limit block is also installed on the side wall of the positioning cover, and the connection position of the limit block sealing cover and the positioning cover is specified.

[0012] In a preferred embodiment of the present invention, an input pipe is installed through the side wall of the boss, one end of the input pipe is connected to the liquid nitrogen rapid intelligent system, and the other end of the input pipe is connected to the inner cavity of the sealing cover. An output pipe is also installed through the side wall of the boss, which is used to discharge gas. Valves are installed on both the input pipe and the output pipe.

[0013] In a preferred embodiment of the present invention, the positioning cover is provided with three pairs of limiting seats, and each pair of limiting seats is provided with a limiting rod. The limiting rod is in a vertical state and is movably connected to the surface of the substrate at the bottom. A return spring is sleeved on the limiting rod. One end of the return spring is engaged with the bottom of the substrate at the bottom, and the other end of the return spring is engaged with the limiting seat.

[0014] In a preferred embodiment of the present invention, an mounting plate is installed on the outer wall of the compression cover, the mounting plate is installed on the workbench, and a communicating hole is also provided on the side wall of the compression cover. When the compression piston passes through the communicating hole, it compresses the internal chamber. A baffle is installed on the compression piston, and a plug rod is installed on the baffle. The plug rod is movably connected to the compression cover, and a socket is installed on the top of the plug rod. The socket is connected to the side wall of the positioning cover.

[0015] In a preferred embodiment of the present invention, a vertical rod is installed on the baffle, and a sealing piston is installed on the vertical rod. The sealing piston is movably connected to the connecting pipe, and the cross-sectional area of ​​the sealing piston is larger than the cross-sectional area of ​​the compression piston.

[0016] Compared with the prior art, the present invention has the following advantages: This invention achieves rapid and safe heating of the testing chamber through the coordinated actions of the testing process. During the low-temperature ductility testing of standard fasteners, pulling the hydraulic push rod moves the positioning cover upwards while simultaneously driving the compression piston to move within the compression cover. The air inside the compression cover is in a closed space and undergoes adiabatic compression, increasing its internal energy and thus raising its temperature. After the test is completed, the airflow channel between the compression cover and the testing chamber is opened. The heated compressed air, under its own pressure, quickly rushes into the testing chamber composed of the sealing cover and the positioning cover, forcefully pushing the low-temperature air inside the chamber out through the output pipe, achieving rapid heating of the testing chamber. This design utilizes the coordinated actions of the testing process to prepare heated compressed air, which not only avoids the risk of frostbite caused by direct contact with low-temperature components by operators, significantly improving operational safety, but also eliminates the need for additional heating equipment, simplifies the post-test chamber heating process, shortens the interval between two tests, and simultaneously improves the integration of the testing fixture and the testing efficiency.

[0017] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0018] In the attached diagram: Figure 1 A front view of a tooling for testing the low-temperature mechanical properties of a standard fastener; Figure 2 A 3D diagram of a tooling for testing the low-temperature mechanical properties of a standard fastener; Figure 3A cross-sectional view of the sealing cover of a tooling for testing the low-temperature mechanical properties of a standard fastener; Figure 4 A tooling for testing the low-temperature mechanical properties of a standard fastener. Figure 3 Enlarged view of point A in the middle; Figure 5 A structural diagram of a positioning cover for a tooling system used for testing the low-temperature mechanical properties of standard fasteners; Figure 6 A bottom view of the positioning cover of a tooling for testing the low-temperature mechanical properties of a standard fastener; Figure 7 A tooling for testing the low-temperature mechanical properties of a standard fastener. Figure 5 Sectional view.

[0019] In the diagram: 1. Workbench; 11. Adjusting rod; 111. Support; 112. Pad; 12. Controller; 13. Bracket; 131. Crossbeam; 132. Pull-out hydraulic push rod; 14. Positioning frame; 141. Base plate; 15. Clamping plate; 151. Slide plate; 152. Notch; 153. Positioning stage; 154. Threaded rod; 155. Positioning plate; 16. Sealing cover; 161. Knob; 162. Boss; 163. Input pipe; 164. Output pipe; 17. Positioning cover; 171. Limiting block; 172. Limiting rod; 173. Limiting seat; 174. Return spring; 2. Compression cover; 21. Mounting plate; 211. Connecting hole; 22. Compression piston; 221. Baffle; 222. Insert rod; 223. Socket; 23. Connecting pipe; 231. Sealing piston; 232. Upright rod. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention. Example

[0021] like Figures 1 to 7 As shown, a fixture for testing the low-temperature mechanical properties of standard fasteners includes a worktable 1. A pair of base plates 141 are mounted on the worktable 1. The base plates 141 are symmetrically distributed. Each of the base plates 141 is equipped with a clamping assembly, which is used to clamp the end of the standard fastener. One base plate 141 is connected to the surface of the worktable 1, and the other base plate 141 is connected to a pull-out hydraulic push rod 132 mounted on the worktable 1. A sealing cover 16 is screwed onto the outer wall of the upper substrate 141, and a positioning cover 17 is vertically inserted into the outer wall of the bottom substrate 141. The sealing cover 16 and the positioning cover 17 are compatible with each other. After the clamping assembly is locked with the standard fastener, the sealing cover 16 and the positioning cover 17 are screwed together, and low temperature air is introduced into the inner cavity of the sealing cover 16 and the positioning cover 17. A compression cover 2 is installed on the workbench 1. A connecting pipe 23 is installed between the compression cover 2 and the base plate 141 located below it. A compression piston 22 slides inside the compression cover 2, moving synchronously with the positioning cover 17. During the test, the sealing cover 16 and the positioning cover 17 move upward synchronously, driving the compression piston 22 upward, thereby pressurizing the air inside the compression cover 2 and raising the air temperature. After the test is completed, compressed air is input into the test chamber, and cold air is discharged. The above structure not only achieves stable clamping of standard fasteners and the construction of a low-temperature test environment, but also provides a structural basis for the subsequent cooling and heating of compressed air after the test, improving the integration level of the tooling. The symmetrically distributed base plate 141 ensures the uniformity of the applied tension, the matching design of the sealing cover 16 and the positioning cover 17 improves the sealing performance of the low-temperature environment, and the synchronous movement design of the compression piston 22 and the positioning cover 17 realizes the linkage between the test and compression actions. like Figures 1 to 7 As shown in the specific embodiment, four adjusting rods 11 are installed at the bottom corner of the workbench 1, and the adjusting rods 11 are connected to the workbench 1 by threaded connection. A support 111 is installed at the bottom of the adjusting rod 11. The cross-sectional area of ​​the support 111 is trapezoidal, and a pad 112 is installed at the bottom of the support 111. The bottom of the pad 112 has an anti-slip groove. By setting the threaded adjusting rods 11, trapezoidal support 111, and anti-slip pad 112, the horizontal state of the workbench 1 can be flexibly adjusted to adapt to placement sites with different flatness. At the same time, the trapezoidal support 111 and anti-slip pad 112 greatly improve the placement stability of the workbench 1, avoid the deviation of the tensile force direction due to the tilt of the workbench during the test, and ensure the accuracy of the test data.

[0022] like Figures 1 to 7 As shown, a bracket 13 is further installed on the top of the workbench 1, a crossbeam 131 is installed on the bracket 13, and a pulling hydraulic push rod 132 is installed on the crossbeam 131. A controller 12 is installed on the outer shell of the workbench 1, and the controller 12 is connected to the pulling hydraulic push rod 132. The bracket 13 and the crossbeam 131 provide a stable mounting support for the pulling hydraulic push rod 132, ensuring the stability and linearity of the pulling force output. At the same time, the connection design between the controller 12 and the pulling hydraulic push rod 132 realizes the automated control of the pulling force action, reduces human operation error, and improves the convenience and accuracy of the testing process.

[0023] like Figures 1 to 7As shown, a positioning frame 14 is mounted on the end of the substrate 141. The positioning frame 14 on the bottom substrate 141 is mounted on the surface of the worktable 1, and the positioning frame 14 on the top substrate 141 is connected to the output end of the pull hydraulic push rod 132. The positioning frame 14 achieves a precise connection between the substrate 141, the worktable 1, and the pull hydraulic push rod 132, ensuring the accuracy of the substrate 141's installation position, providing a guarantee for the stable transmission of subsequent pulling force, and avoiding test errors caused by substrate 141 offset.

[0024] like Figures 1 to 7 As shown, in a specific embodiment, the clamping assembly includes a pair of clamping plates 15, on which a sliding plate 151 is mounted. The sliding plate 151 is slidably disposed in a notch 152 opened in the side wall of the base plate 141. A positioning platform 153 is mounted on the base plate 141. A threaded rod 154 is rotatably mounted on the clamping plate 15, and the end of the threaded rod 154 is screwed into the positioning platform 153. A positioning plate 155 is mounted on the threaded rod 154, and the positioning plate 155 and the end of the threaded rod 154 are used to limit the position of the clamping plate 15. By the screwing engagement of the threaded rod 154 and the positioning platform 153, the sliding plate 151 is driven to slide, realizing the flexible adjustment of the spacing between the clamping plates 15, which can be adapted to standard fasteners of different specifications.

[0025] like Figures 1 to 7 As shown, furthermore, a knob 161 is installed on the outer wall of the sealing cover 16, and an internal thread is formed on the inner wall of the sealing cover 16. A boss 162 is also installed on the inner wall of the sealing cover 16, which is used to divide the internal thread and to limit the position of the substrate 141. An external thread is formed on the side wall of the positioning cover 17, and the external thread is compatible with the internal thread. A limiting block 171 is also installed on the side wall of the positioning cover 17, and the limiting block 171 is the connection position between the sealing cover 16 and the positioning cover 17. Through the threaded connection between the sealing cover 16 and the positioning cover 17 and the knob 161, the two can be quickly disassembled and assembled, which facilitates the removal and placement of fasteners. The design of the boss 162 not only achieves precise positioning of the substrate 141, but also optimizes the force distribution of the threaded connection. The limiting block 171 improves the sealing performance of the connection position, avoids low-temperature air leakage, and ensures the stability of the low-temperature test environment.

[0026] like Figures 1 to 7As shown, furthermore, an input pipe 163 is installed through the side wall of the boss 162. One end of the input pipe 163 is connected to the liquid nitrogen rapid intelligent system, and the other end is connected to the inner cavity of the sealing cover 16. An output pipe 164 is also installed through the side wall of the boss 162. The output pipe 164 is used to discharge gas, and valves are installed on both the input pipe 163 and the output pipe 164. The input pipe 163 achieves precise communication between the liquid nitrogen rapid intelligent system and the detection chamber, allowing for stable input of low-temperature air. The output pipe 164 provides a channel for the discharge of gas from the chamber. Combined with the valve design, the input and discharge of gas can be flexibly controlled, achieving precise regulation of the low-temperature environment and improving the controllability of the testing environment. Example 1

[0027] The difference between the above embodiments and this embodiment is that: Figures 1 to 7 As shown, three pairs of limiting seats 173 are installed on the positioning cover 17. Each pair of limiting seats 173 is equipped with a limiting rod 172. The limiting rod 172 is in a vertical state and movably passes through the surface of the bottom substrate 141. A return spring 174 is sleeved on the limiting rod 172. One end of the return spring 174 is engaged with the bottom of the bottom substrate 141, and the other end is engaged with the limiting seat 173. Through the cooperation of the limiting seats 173 and the limiting rods 172, the precise limiting of the movement direction of the positioning cover 17 is achieved, preventing deviation during its movement. At the same time, the design of the return spring 174 can automatically reset the positioning cover 17 after the test is completed without manual intervention, simplifying the reset operation after the test and improving the test efficiency.

[0028] like Figures 1 to 7 As shown, in a specific embodiment, an mounting plate 21 is installed on the outer wall of the compression cover 2. The mounting plate 21 is mounted on the workbench 1. A connecting hole 211 is also provided on the side wall of the compression cover 2. When the compression piston 22 passes through the connecting hole 211, it compresses the internal chamber. A baffle 221 is installed on the compression piston 22, and a plug rod 222 is installed on the baffle 221. The plug rod 222 is movably inserted into the compression cover 2. A socket 223 is installed on the top of the plug rod 222, and the socket 223 is connected to the side wall of the positioning cover 17. The mounting plate 21 ensures the stable installation of the compression cover 2 on the workbench 1, guaranteeing the stability of the compression process. The design of the connecting hole 211 enables precise switching of the compression state. Effective compression can only be achieved after the compression piston 22 passes through the connecting hole 211, improving the accuracy of compressed air preparation. At the same time, the cooperation between the plug rod 222 and the socket 223 enables the synchronous linkage between the compression piston 22 and the positioning cover 17, ensuring the coordination of the detection action and the compression action.

[0029] like Figures 1 to 7As shown, furthermore, a vertical rod 232 is installed on the baffle 221, and a sealing piston 231 is installed on the vertical rod 232. The sealing piston 231 is movably connected to the connecting pipe 23, and the cross-sectional area of ​​the sealing piston 231 is larger than that of the compression piston 22. By driving the sealing piston 231 and the compression piston 22 to move synchronously, precise on / off control of the connecting pipe 23 is achieved, ensuring the pressure and heating effect of the compressed air and improving the efficiency of subsequent cooling and heating.

[0030] The implementation principle of the tooling for testing the low-temperature mechanical properties of standard fasteners according to the present invention is as follows: Before testing, the workbench 1 is adjusted to a horizontal position using the four adjusting rods 11 at the bottom corner. The trapezoidal cross-sectional support 111 at the bottom of the adjusting rods 11 and the anti-slip groove pad 112 ensure that the workbench 1 is placed stably. Then, the standard fastener to be tested is placed between a pair of symmetrically distributed base plates 141. The threaded rod 154 on the clamping plate 15 in the clamping assembly is rotated. The screwing engagement between the threaded rod 154 and the positioning table 153 causes the slide plate 151 to slide within the notch 152 on the side wall of the base plate 141, so that the pair of clamping plates 15 clamp the end of the fastener. At the same time, the positioning plate 155 on the threaded rod 154 limits the position of the clamping plate 15 to prevent over-clamping or loosening. Next, the sealing cover 16 is screwed into the positioning cover 17 via the internal thread. The inner boss 162 of the sealing cover 16 limits the base plate 141, and the limiting block 171 on the side wall of the positioning cover 17 seals the connection position. Then, the liquid nitrogen rapid intelligent system is connected through the input pipe 163 on the boss 162. The valves of the input pipe 163 and the output pipe 164 are closed to prepare for the injection of cryogenic air.

[0031] Then, the liquid nitrogen rapid intelligent system is activated, and low-temperature air is introduced into the closed inner cavity composed of the sealing cover 16 and the positioning cover 17 through the input pipe 163. The air is continuously injected into the cavity to reach the preset low temperature value. During this period, the valve is kept closed to ensure the stability of the low-temperature environment and to meet the environmental requirements for the low-temperature mechanical performance test of standard fasteners.

[0032] During the testing phase, the controller 12 on the outer shell of the workbench 1 activates the pull-out hydraulic push rod 132 on the crossbeam 131 of the support 13. The output end of the pull-out hydraulic push rod 132 drives the top positioning frame 14 and the corresponding base plate 141 to move upward, simultaneously driving the sealing cover 16 and the positioning cover 17 to move upward. During this process, a relative displacement is formed between the top base plate 141 and the bottom base plate 141, applying axial tension to the clamped and fixed standard fasteners. This allows for the testing of the fasteners' ductility under low-temperature conditions, capturing the degree of deformation of the fasteners under the combined effects of low temperature and tension in real time. The positioning cover 17 drives the insertion rod 222 and the compression piston 22 to move synchronously upward within the compression cover 2, which is fixed to the worktable 1 by the mounting plate 21, via the socket 223. When the compression piston 22 has not passed the connecting hole 211, the air inside the compression cover 2 can circulate with the outside through the connecting hole 211, but cannot form effective compression. When the compression piston 22 passes the connecting hole 211, the air space inside the compression cover 2 is sealed and continuously compressed. Due to the adiabatic compression effect, the air temperature rises, and the compression effect is further enhanced. At the same time, the baffle 221 drives the upright rod 232 and the sealing piston 231 to move synchronously upward within the connecting pipe 23. Because the cross-sectional area of ​​the sealing piston 231 is larger than that of the compression piston 22, the air inside the compression cover 2 is in a compressed state.

[0033] When the hydraulic push rod 132 completes the preset pulling stroke and the inspection is completed, the compression piston 22 has effectively compressed the air inside the compression cover 2, and the baffle 221 drives the sealing piston 231 to move upward in the connecting pipe 23 until it is completely separated from the sealing mating surface of the connecting pipe 23, so that the airflow channel between the compression cover 2 and the inspection chamber is connected. At the same time, the valve on the output pipe 164 is opened, and the compressed air in the compression cover 2 after being heated is naturally input into the inspection chamber composed of the sealing cover 16 and the positioning cover 17 through the connecting pipe 23. The heated compressed air will quickly replace the low-temperature air in the chamber, and blow the low-temperature air out of the output pipe 164 quickly by its own pressure, so as to achieve rapid heating of the inspection chamber, making it convenient for the operator to take out the fasteners after inspection in time.

[0034] After the low-temperature air in the chamber is completely discharged, the controller 12 controls the hydraulic push rod 132 to reset, and the top plate 141 moves downward accordingly. The positioning cover 17 moves downward synchronously under the elastic force of the reset spring 174 on its side wall limit rod 172, thereby driving the compression piston 22 back to the initial position in the compression cover 2, and simultaneously driving the sealing piston 231 back to the initial sealing position in the connecting pipe 23. The entire fixture is restored to its initial state, ready for the next test.

[0035] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fixture for testing the low-temperature mechanical properties of standard fasteners, comprising a worktable (1), characterized in that: A pair of base plates (141) are mounted on the workbench (1). The base plates (141) are symmetrically distributed. Each pair of base plates (141) is equipped with a clamping assembly, which is used to clamp the end of a standard fastener. One of the base plates (141) is connected to the surface of the workbench (1), and the other base plate (141) is connected to the pull-out hydraulic push rod (132) mounted on the workbench (1). A sealing cover (16) is screwed onto the outer wall of the upper substrate (141), and a positioning cover (17) is vertically inserted into the outer wall of the bottom substrate (141). The sealing cover (16) and the positioning cover (17) are adapted to each other. After the clamping assembly is locked with the standard fastener, the sealing cover (16) and the positioning cover (17) are screwed together, and low temperature air is introduced into the inner cavity of the sealing cover (16) and the positioning cover (17). A compression cover (2) is installed on the workbench (1). A connecting pipe (23) is installed between the compression cover (2) and the substrate (141) below. A compression piston (22) moves synchronously with the positioning cover (17) inside the compression cover (2). During the detection process, the sealing cover (16) and the positioning cover (17) move upward synchronously, which drives the compression piston (22) to move upward, thereby pressurizing the air inside the compression cover (2) and increasing the air temperature. After the detection is completed, the compressed air is input into the detection chamber and the cold air is discharged.

2. The tooling for testing the low-temperature mechanical properties of standard fasteners according to claim 1, characterized in that, Four adjusting rods (11) are installed at the bottom corner of the workbench (1), and the adjusting rods (11) are connected to the workbench (1) by screw thread. A support (111) is installed at the bottom of the adjusting rod (11). The cross-sectional area of ​​the support (111) is trapezoidal. A pad (112) is installed at the bottom of the support (111). The bottom of the pad (112) is provided with anti-slip grooves.

3. The tooling for testing the low-temperature mechanical properties of standard fasteners according to claim 1, characterized in that, The workbench (1) is equipped with a bracket (13) on top, a crossbeam (131) is installed on the bracket (13), a pull hydraulic push rod (132) is installed on the crossbeam (131), and a controller (12) is installed on the outer shell of the workbench (1). The controller (12) is connected to the pull hydraulic push rod (132).

4. The tooling for testing the low-temperature mechanical properties of standard fasteners according to claim 1, characterized in that, The base plate (141) is equipped with a positioning frame (14) at its end. The positioning frame (14) on the bottom base plate (141) is mounted on the surface of the workbench (1). The positioning frame (14) on the top base plate (141) is connected to the output end of the pull hydraulic push rod (132).

5. The tooling for testing the low-temperature mechanical properties of standard fasteners according to claim 1, characterized in that, The clamping assembly includes a pair of clamping plates (15), on which a sliding plate (151) is mounted. The sliding plate (151) is slidably disposed in a notch (152) opened in the side wall of the base plate (141). A positioning stage (153) is mounted on the base plate (141). A threaded rod (154) is rotatably mounted on the clamping plate (15). The end of the threaded rod (154) is screwed into the positioning stage (153). A positioning plate (155) is mounted on the threaded rod (154). The positioning plate (155) and the end of the threaded rod (154) are used to limit the position of the clamping plate (15).

6. The fixture for testing the low-temperature mechanical properties of standard fasteners according to claim 1, characterized in that, A knob (161) is installed on the outer wall of the sealing cover (16). An internal thread is provided on the inner wall of the sealing cover (16). A boss (162) is also installed on the inner wall of the sealing cover (16). The boss (162) is used to divide the internal thread and to limit the position of the substrate (141). An external thread is provided on the side wall of the positioning cover (17). The external thread and the internal thread are compatible with each other. A limit block (171) is also installed on the side wall of the positioning cover (17). The limit block (171) is the connection position between the sealing cover (16) and the positioning cover (17).

7. The tooling for testing the low-temperature mechanical properties of standard fasteners according to claim 6, characterized in that, An input pipe (163) is installed through the side wall of the boss (162). One end of the input pipe (163) is connected to the liquid nitrogen rapid intelligent system, and the other end of the input pipe (163) is connected to the inner cavity of the sealing cover (16). An output pipe (164) is also installed through the side wall of the boss (162). The output pipe (164) is used to discharge gas, and valves are installed on both the input pipe (163) and the output pipe (164).

8. The fixture for testing the low-temperature mechanical properties of standard fasteners according to claim 1, characterized in that, The positioning cover (17) is equipped with three pairs of limiting seats (173), and each pair of limiting seats (173) is equipped with a limiting rod (172). The limiting rod (172) is in a vertical state and the limiting rod (172) is movably connected to the surface of the substrate (141) at the bottom. A reset spring (174) is sleeved on the limiting rod (172). One end of the reset spring (174) is engaged with the bottom of the substrate (141) at the bottom, and the other end of the reset spring (174) is engaged with the limiting seat (173).

9. The tooling for testing the low-temperature mechanical properties of standard fasteners according to claim 1, characterized in that, An installation plate (21) is installed on the outer wall of the compression cover (2). The installation plate (21) is installed on the workbench (1). A connecting hole (211) is also provided on the side wall of the compression cover (2). When the compression piston (22) passes through the connecting hole (211), it compresses the internal chamber. A baffle (221) is installed on the compression piston (22). A plug rod (222) is installed on the baffle (221). The plug rod (222) is movably connected to the compression cover (2). A socket (223) is installed on the top of the plug rod (222). The socket (223) is connected to the side wall of the positioning cover (17).

10. The fixture for testing the low-temperature mechanical properties of standard fasteners according to claim 9, characterized in that, A vertical rod (232) is installed on the baffle (221), and a sealing piston (231) is installed on the vertical rod (232). The sealing piston (231) is movably connected to the connecting pipe (23), and the cross-sectional area of ​​the sealing piston (231) is larger than the cross-sectional area of ​​the compression piston (22).

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