A fixture for metal fatigue testing in cryogenic environments

Abstract

This utility model discloses a fixture for metal fatigue testing in a cryogenic environment, which has an upper clamp and a lower clamp for clamping metal samples. Both the upper and lower clamps include threaded columns for connecting to a metal creep tester, with a connecting cylinder fixedly attached to the end of the threaded column. A limiting cylinder slides inside the connecting cylinder, and the inner wall of the connecting cylinder has multiple vertically arranged guide grooves, each containing a guide block. The guide groove has a T-shaped cross-section and includes interconnected auxiliary grooves and pre-tightening grooves. The auxiliary grooves are located on the inner wall of the connecting cylinder, and the pre-tightening grooves are inclined, with the inclination angle gradually increasing towards the threaded column. Each guide block includes an auxiliary block that slides with the auxiliary groove, and a pre-tightening block that slides with the pre-tightening groove is fixedly attached to the auxiliary block. A mating block is fixedly connected to the auxiliary block. This design solves the problem in existing fixtures where metal samples cannot be quickly assembled and disassembled for fatigue testing.

Description

Technical Field

[0001] This utility model relates to the field of metal performance testing technology, specifically to a fixture for metal fatigue testing under cryogenic conditions. Background Technology

[0002] In some high-end industrial fields, metallic materials often need to operate for extended periods in cryogenic environments ranging from -100℃ to -273℃. The tensile stress, yield strength, and other fatigue properties under cryogenic conditions directly determine the operational safety and reliability of the equipment. Therefore, performance testing of metallic samples under cryogenic conditions has become a core component of materials research and development, equipment design, and quality verification.

[0003] Currently, liquid nitrogen is widely used in the industry as a cooling medium to simulate cryogenic environments. This method has advantages such as controllable low-temperature gradient, fast cooling rate, relatively low cost, and the ability to stably maintain extreme low-temperature environments, making it the mainstream technical approach for cryogenic fatigue testing of metal samples. During the testing process, the metal sample needs to be fixed to the force loading end of the metal fatigue testing equipment using a special fixture, such as the fixed end and movable end of a metal creep tester. Furthermore, the fixture must be compatible with the liquid nitrogen cooling environment to avoid structural failure or affecting the accuracy of force transmission due to low temperatures. Therefore, the reliability and ease of operation of the fixture directly determine the efficiency of the testing process and the accuracy of the data.

[0004] However, existing metal sample fixtures have significant drawbacks in practical applications: in order to meet the requirements of structural stability and force transmission in cryogenic environments, most fixtures adopt a multi-component rigid connection design, which requires multiple steps such as bolt tightening and buckle locking to fix the sample. When disassembling and assembling the sample, operators need to use special tools such as wrenches and screwdrivers, which further increases the time spent on disassembling and assembling metal samples. Utility Model Content

[0005] The purpose of this invention is to solve the problem that existing fixtures cannot quickly assemble and disassemble metal samples for fatigue testing, and to provide a fixture for metal fatigue testing in a cryogenic environment.

[0006] To address the shortcomings of the aforementioned technical problems, the present invention adopts the following technical solution: a clamp for metal fatigue testing in a cryogenic environment, which has an upper clamp and a lower clamp capable of clamping metal samples. Both the upper and lower chucks include threaded columns that can be connected to a metal creep machine, and a connecting cylinder is fixedly provided at the end of the threaded column; A limiting cylinder is slidably provided inside the connecting cylinder, and multiple vertically arranged guide grooves are provided on the inner wall of the connecting cylinder, with guide blocks slidably provided in each of the multiple guide grooves; The guide groove has a T-shaped cross-section and includes an auxiliary groove and a pre-tightening groove that are interconnected. The auxiliary groove is opened on the inner wall of the connecting cylinder, and the pre-tightening groove is inclined, with the inclination angle of the pre-tightening groove gradually increasing towards the direction of the threaded column. The guide block includes an auxiliary block that slides with the auxiliary groove, and a pre-tightening block that slides with the pre-tightening groove is fixedly provided on the auxiliary block; The auxiliary block is fixedly connected to a docking block. During the reverse movement of the upper and lower chucks, multiple docking blocks are pressed down by the limiting cylinder at the end of the metal sample and come together to clamp the metal sample.

[0007] As a further optimization of the fixture for metal fatigue testing in a cryogenic environment of this utility model: the auxiliary block is fixedly connected to the mating block near the threaded post, and the pre-tightening block is cylindrical, so that when the multiple mating blocks are vertically downward, they are distributed in a trumpet shape with the trumpet opening facing away from the threaded post.

[0008] As a further optimization of the fixture for metal fatigue testing in a cryogenic environment of this utility model: the guide groove passes through the end of the connecting cylinder away from the threaded post, and the through end of the connecting cylinder is detachably connected to a sealing component that blocks the guide groove.

[0009] As a further optimization of the fixture for metal fatigue testing in a cryogenic environment of this utility model: the sealing component includes a threaded cylinder that is threadedly connected to the connecting cylinder.

[0010] As a further optimization of the fixture for metal fatigue testing in a cryogenic environment of this utility model: an elastic sleeve is bonded to the outer periphery of the screw cylinder, and the cross-section of the elastic sleeve is wavy.

[0011] As a further optimization of the fixture for metal fatigue testing in a cryogenic environment of this utility model: a sealing ring is snapped into the outlet of the screw-in cylinder corresponding to the connecting cylinder, and the sealing ring can be fitted onto the metal sample.

[0012] As a further optimization of the fixture for metal fatigue testing in a cryogenic environment of this utility model: the vertical height of the lower clamp connecting cylinder is greater than the vertical height of the upper clamp connecting cylinder.

[0013] As a further optimization of the fixture for metal fatigue testing under cryogenic conditions of this utility model: the limiting cylinder is threadedly connected to the metal sample.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention, by setting guide grooves, allows multiple mating blocks located in the connecting cylinder to move axially along the connecting cylinder. When assembling the clamping cylinder, the gap between these mating blocks can move vertically along the threaded column, thereby increasing or decreasing the gap between the multiple clamping blocks. Based on this, the multiple mating blocks forming the clamping cylinder, under the condition of being in contact with the metal sample restraining cylinder, can move away from the threaded column to reduce the gap between the multiple clamping blocks, thus clamping the metal sample. Furthermore, with the cooperation of the restraining cylinder, the connection stability between the metal sample and the fixture is further ensured. Simultaneously, the displacement can also separate the multiple mating blocks forming the clamping cylinder, even if the gap between the multiple clamping blocks increases, so that the inner diameter of the clamping cylinder formed by the multiple clamping blocks is larger than the outer diameter of the restraining cylinder, thus facilitating quick assembly and disassembly of the metal sample from the fixture by the operator.

[0015] This invention utilizes guide grooves to allow multiple mating blocks within the connecting cylinder to move axially along the connecting cylinder. Furthermore, when assembling the snap-fit ​​cylinder, the gap between these mating blocks can move vertically along the threaded post, thereby increasing or decreasing the gap between the multiple snap-fit ​​blocks. Based on this, in conjunction with the tensile force of a metal creep tester, the limiting cylinder can further displace the multiple snap-fit ​​blocks away from the threaded post, further reducing the gap between the multiple snap-fit ​​blocks. This increases the clamping force of the snap-fit ​​blocks on the metal sample, reducing the probability of the metal sample loosening. Attached Figure Description

[0016] Figure 1 This is a cross-sectional structural diagram of the present invention; Figure 2 This is a schematic diagram of the first cross-sectional structure of the upper clamp of this utility model; Figure 3 This is a schematic diagram of the second cross-sectional structure of the upper clamp of this utility model; The markings in the diagram are: 1. Upper chuck; 2. Lower chuck; 3. Sealing component; 301. Threaded sleeve; 302. Elastic sleeve; 303. Sealing ring; 4. Guide groove; 401. Auxiliary groove; 402. Pre-tightening groove; 5. Guide block; 501. Auxiliary block; 502. Pre-tightening block; 6. Connecting block; 7. Limiting sleeve; 8. Metal sample; 9. Threaded post; 10. Connecting sleeve. Detailed Implementation

[0017] To better understand this utility model, the following embodiments further illustrate the content of this utility model, but the content of this utility model is not limited to the following embodiments.

[0018] like Figure 1-3As shown, a fixture for metal fatigue testing in a cryogenic environment includes an upper clamp 1 and a lower clamp 2 for connecting the two ends of a metal sample 8. Both the upper clamp 1 and the lower clamp 2 include a threaded post 9 and a connecting cylinder 10. The connecting cylinder 10 contains multiple mating blocks 6 that can form a locking sleeve for connecting to the ends of the metal sample 8. Each mating block 6 has a pre-tightening block 502, which is slidably connected to a guide groove 4 formed on the inner wall of the connecting cylinder 10. The guide groove 4 is axially arranged along the connecting cylinder 10 and guides the pre-tightening block 502, causing the gap between the multiple mating blocks 6 to increase when the bolts move vertically towards the threaded post 9, and conversely, to decrease the gap when the bolts move downwards towards the threaded post 9. During the process of the threaded column 9 connecting the corresponding creep machine fixed end and movable end to pull the metal sample 8 to displacement, the two sets of mating blocks 6, guided by the guide groove 4 and restricted by the limiting cylinder 7 located at the threaded connection at the end of the metal sample 8, will reduce the gap between the two sets of mating blocks 6 and compress both ends of the metal sample 8, thereby increasing the preload between the mating blocks 6 and the metal sample 8. When encountering cold contraction, the gap between the two sets of mating blocks 6 will further reduce to compress the metal sample 8, thereby further increasing the preload between the two sets of mating blocks 6. The stability of the connection with the metal sample 8 ensures stable fatigue testing of the metal sample 8 under cryogenic conditions. After the test, the upper chuck 1 or the lower chuck 2 can be inverted to separate the multiple locking blocks of the corresponding group, so that the inner diameter of the locking cylinder composed of the multiple locking blocks of the corresponding group changes to the outer diameter of the limiting cylinder 7. This makes it easier for operators to assemble or disassemble the upper chuck 1, the lower chuck 2 and the metal sample 8 according to their own needs.

[0019] The guide groove 4 has a T-shaped cross-section. The transverse section of the guide groove 4, radiating along the axis of the connecting cylinder 10, is an auxiliary groove 401. An auxiliary block 501, fixed to the docking block 6, is slidably disposed within the auxiliary groove 401 to limit the stability of the vertical displacement of the docking block 6. The vertical section perpendicular to the transverse section is a pre-tightening groove 402. 402 is inclined. Specifically, one end of the pre-tightening groove 402 facing the threaded post 9 is away from the center of the connecting cylinder 10, while the other end of the pre-tightening groove 402 is close to the center of the connecting cylinder 10. A pre-tightening block 502, fixed together with the auxiliary block 501, is slidably arranged inside the pre-tightening groove 402. This causes the gap between the multiple mating blocks 6 that make up the clamping cylinder to increase when moving vertically toward the threaded post 9, and conversely, to decrease the gap between the multiple mating blocks 6. As a result, during use in a cryogenic environment, the upper chuck 1 and the lower chuck 2 are further clamped at the end of the metal sample 8 due to the pull of the metal creep machine, thereby further stabilizing the fatigue test of the metal sample 8 in a cryogenic environment.

[0020] The auxiliary block 501 is located at the end of the mating block 6 near the threaded post 9, and the pre-tightening block 502 is cylindrical, so that when the connecting cylinder 10 is placed vertically, the mating block 6 is positioned away from the end of the threaded post 9. The inclined shape of the inner wall of the connecting cylinder 10 causes the multiple mating blocks 6 that make up the snap-fit ​​cylinder to be flared towards the outlet of the connecting cylinder 10, which facilitates the operator to insert the metal sample 8 and the corresponding limiting cylinder 7 into the multiple mating blocks 6 and connect them together. The pre-tightening block 502 is cylindrical, which makes it easy for the pre-tightening block 502 to not be hard-friction locked with the pre-tightening groove 402 after being stretched, thus making it easier for the operator to separate the metal sample 8 from the mating blocks 6, thereby improving the efficiency of the operator's installation and disassembly. During the installation process, the threaded post 9 and the connecting cylinder 10 are placed vertically, and then the multiple mating blocks 6 that make up the snap-fit ​​cylinder are brought together under the influence of gravity. Then the operator can thread the metal sample 8 to the corresponding multiple mating blocks 6 and pull it down to slide the pre-tightening block 502 away from the threaded post 9 to a certain extent along the pre-tightening groove 402, thereby making the multiple mating blocks 6 and the metal sample 8 stably connected together. Then the above operation can be repeated to connect another clamp to the other end of the metal sample 8. Finally, the two threaded posts 9 are connected to the fixed end and the movable end of the metal creep machine respectively, and the metal sample 8 is placed in the corresponding cryogenic environment to carry out the fatigue test of the metal sample 8 in the corresponding cryogenic environment.

[0021] The guide groove 4 extends out of the connecting cylinder 10 away from the threaded post 9, allowing operators to disassemble and replace the guide block 5 and the mating block 6 for maintenance of the fixture. A sealing element 3 is provided outside the connecting cylinder 10, which can... The separation of guide block 5 and docking block 6 is restricted to maintain structural stability. The sealing component 3 can connect to the containment cylinder that forms a cryogenic environment to seal the containment cylinder, allowing liquid nitrogen to be introduced into the containment cylinder to simulate a cryogenic environment. This allows the metal sample 8 to be placed inside the containment cylinder for fatigue testing under cryogenic conditions. The sealing component 3 includes a threaded sleeve 301 threaded to the connecting cylinder 10. The threaded sleeve 301 has an elastic sleeve 302 on its outer periphery, and the elastic sleeve 302 has a wavy cross-section, allowing it to deform more effectively and fill the gap between the threaded sleeve 301 and the containment cylinder. This stabilizes the seal at the end of the containment cylinder, ensuring that the liquid nitrogen subsequently injected into the containment cylinder is confined and sealed within the containment cylinder to form a cryogenic environment. A sealing ring 303 is snapped into the outlet of the connecting cylinder 10. The sealing ring 303 can fit against the end of the metal sample 8 to seal the internal environment of the connecting cylinder 10, thereby reducing the amount of liquid nitrogen entering the connecting cylinder 10. This reduces the impact of liquid nitrogen on the cooling and contraction of the docking block 6, the guide groove 4, and the pre-tightening block 502, and further reduces the probability of the docking block 6 separating from the metal sample 8.

[0022] Specifically, the vertical height of the connecting cylinder 10 of the upper clamp 1 is less than the vertical height of the connecting cylinder 10 of the lower clamp 2. That is, the upper clamp 1 is connected to the fixed end of the metal creep machine, and the lower clamp 2 is connected to the movable end of the metal creep machine. The fixed end of the metal creep machine does not need to move, so the sealing and receiving cylinder does not need to be too long. However, since the lower clamp 2 and the movable end of the metal creep machine need to be displaced, the lower clamp 2 needs to be displaced within the receiving cylinder based on the sealing and receiving cylinder. Therefore, the connecting cylinder 10 of the lower clamp 2 needs to be longer.

[0023] The sealing ring 303 and the elastic sleeve 302 are made of materials including but not limited to phenyl silicone rubber, polytetrafluoroethylene and polychlorotrifluoroethylene, to adapt to the cryogenic environment simulated by liquid nitrogen.

[0024] The specific embodiments of this utility model have been described above. It should be understood that this utility model is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the substantive content of this utility model.

Claims

1. A clamp for metal fatigue testing under cryogenic environment, characterized by: It has upper clamp head (1) and lower clamp head (2) that can clamp metal sample (8); The upper clamp head (1) and the lower clamp head (2) both include threaded column (9) that can be connected to metal creep machine, and the end of threaded column (9) is fixedly provided with connecting cylinder (10); The connecting cylinder (10) is slidably provided with limiting cylinder (7) inside, and the inner wall of connecting cylinder (10) is provided with a plurality of vertical guide grooves (4), and a plurality of guide blocks (5) are slidably arranged in the plurality of guide grooves (4); The cross section of the guide groove (4) is T-shaped, and the guide groove (4) includes auxiliary groove (401) and pre-tightening groove (402) that are in communication with each other, the auxiliary groove (401) is opened on the inner wall of the connecting cylinder (10), and the pre-tightening groove (402) is inclinedly arranged, and the inclination angle of the pre-tightening groove (402) gradually increases in the direction of the threaded column (9); The guide block (5) includes auxiliary block (501) that is in sliding fit with the auxiliary groove (401), and the auxiliary block (501) is fixedly provided with pre-tightening block (502) that is in sliding fit with the pre-tightening groove (402); The auxiliary block (501) is fixedly connected with butt block (6), and in the reverse movement process of the upper clamp head (1) and the lower clamp head (2), a plurality of butt blocks (6) are pressed from above by the limiting cylinder (7) threaded on the end of the metal sample (8) and are close to each other to clamp the metal sample (8).

2. The clamp for testing fatigue of a metal in a cryogenic environment according to claim 1, wherein: The auxiliary block (501) is fixedly connected to the butt block (6) close to the threaded column (9), and the pre-tightening block (502) is cylindrical, so that a plurality of butt blocks (6) are distributed in a horn shape with the horn mouth away from the threaded column (9) when vertically downward.

3. The clamp for testing fatigue of a metal in a cryogenic environment according to claim 1, wherein: The guide groove (4) penetrates one end of the connecting cylinder (10) away from the threaded column (9), and the penetrating end of the connecting cylinder (10) is detachably connected with a blocking member (3) that blocks the guide groove (4).

4. The clamp for testing fatigue of a metal in a cryogenic environment according to claim 3, wherein: The blocking member (3) includes a threaded sleeve (301) that is in threaded connection with the connecting cylinder (10).

5. The clamp for testing fatigue of a metal in a cryogenic environment according to claim 4, wherein: The threaded sleeve (301) is externally bonded with an elastic sleeve (302), and the cross section of the elastic sleeve (302) is wavy.

6. The clamp for testing fatigue of a metal in a cryogenic environment according to claim 5, wherein: The threaded sleeve (301) is clamped with a sealing ring (303) at the outlet of the connecting cylinder (10), and the sealing ring (303) can be sleeved on the metal sample (8).

7. The clamp for testing fatigue of a metal in a cryogenic environment according to claim 1, wherein: The vertical height of the connecting cylinder (10) of the lower clamp head (2) is greater than that of the connecting cylinder (10) of the upper clamp head (1).

8. The clamp for testing fatigue of a metal in a cryogenic environment according to claim 1, wherein: The limiting cylinder (7) is in threaded connection with the metal sample (8).

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