Ultrahigh-temperature tensile and tensile creep test clamp applied to bar-shaped sample

Abstract

The invention discloses an ultrahigh-temperature tensile and tensile creep test clamp applied to a bar-shaped sample, and belongs to the field of high-temperature mechanical testing. Comprising force application positioning modules, a testing auxiliary module and a positioning auxiliary module, the force application positioning modules are arranged at the two ends of a rod-shaped sample and used for transmitting loading force of a testing machine loading mechanism to the two ends of the rod-shaped sample, and the rod-shaped sample is subjected to axial tensile deformation; the test auxiliary module is connected to the test section of the rod-shaped sample and is used for transmitting the tensile deformation amount to the deformation measurement equipment; and the positioning auxiliary module is used for assisting the positioning of the rod-shaped sample in the mounting groove of the force application positioning module, so that the uniformity of the clamping force on the rod-shaped sample can be ensured. According to the invention, the problem that the sample and the clamp are easy to adhere at ultrahigh temperature is solved; when damage occurs, only the gasket needs to be replaced generally, so that the test cost is reduced; the two ends of the sample are positioned by being embedded into the grooves of the chucks, thread fixation is not needed, and the problem that the rod-shaped sample is difficult to install is solved.

Description

Technical Field

[0001] The invention belongs to the field of high temperature mechanical testing, and in particular relates to an ultra-high temperature tensile and tensile creep test fixture applied to a bar-shaped sample. Background Art

[0002] When conducting ultra-high temperature tensile and creep performance tests, some materials, especially some ceramics, refractory metals and their alloys, must fully measure their mechanical properties at service temperature, which is mainly done in the high temperature environment of the testing machine. The testing machine has a compact structure and a small internal space. Usually, the specific test method for rod-shaped specimens is to conduct the test by threading the testing machine.

[0003] At present, the clamps for high-temperature tensile and creep tests on specimens use a pressure plate or positioning hole. Usually, the pressure plate positioning is suitable for plate specimens and needs to be positioned with fasteners; for bar specimens, positioning holes are usually used for positioning, which can avoid slippage during the test, and its structure is relatively simple and easy to operate. However, the bar specimen needs to be set with a limit position for installing the ferrule at both ends of the middle test section. Since the outer circumference of the limit position is larger than the test section, the two ends of the bar specimen will be restricted when installed in the positioning hole. Therefore, the design of the clamping part needs to consider many factors, resulting in a more complicated structure and steps during installation and disassembly. When the positioning structure is complex, the problem of uneven clamping force is prone to occur, especially on brittle materials, it is easy to cause the specimen to break in an abnormal position due to excessive local stress, thereby distorting the test results. At the same time, the positioning holes require the specimen to be installed and disassembled outside the testing machine, and the operation process is cumbersome and easy to damage the specimen. In addition, due to the lack of precise alignment and clamping devices, the positioning hole fixture is more likely to "break teeth" or "lock" at high temperatures, making the fixture unable to be reused and the sample test difficult to continue.

[0004] In summary, the most fundamental technical problem of the existing positioning hole method in ultra-high temperature tensile and tensile creep tests is the lack of uniform clamping force, which cannot effectively deal with the thermal deformation and stress concentration of materials in high temperature environments, resulting in insufficient accuracy and reliability of test results. Based on the above problems, it is necessary to develop a new fixture design to meet the ultra-high temperature testing needs of ceramics and refractory metals and their alloys in environments with temperatures of 2000℃ and above. Summary of the invention

[0005] Technical issues to be solved:

[0006] In order to avoid the shortcomings of the prior art, the present invention provides a super-high temperature tensile and tensile creep test fixture for rod-shaped specimens, which can complete high temperature tensile and tensile creep tests at 2000°C and above. The fixture fixes the specimen through grooves and gaskets and transmits the loading force to the specimen. The gap design avoids direct contact between the fixture and the specimen, solving the problem of easy adhesion between the specimen and the fixture at super-high temperatures; when damage occurs, generally only the gasket needs to be replaced, reducing the test cost; the two ends of the specimen are positioned by embedding the grooves of the chuck, and there is no need to use threaded fixation, solving the problem of difficult installation of rod-shaped specimens; because the fixture is clamped by gaskets and bosses, the possibility of the specimen breaking in an abnormal position during the test is avoided, making the data results of the specimen test more accurate and comprehensive, more convenient for widespread promotion and use, and can be applied to a variety of super-high temperature tensile and tensile creep tests of rod-shaped specimens.

[0007] The technical solution of the present invention is: an ultra-high temperature tensile and tensile creep test fixture applied to rod-shaped specimens, comprising a force positioning module, a test auxiliary module and a positioning auxiliary module, wherein the force positioning module is arranged at both ends of the rod-shaped specimen, and is used to transmit the loading force of the loading mechanism of the testing machine to the two ends of the rod-shaped specimen, so that the rod-shaped specimen undergoes axial tensile deformation; the test auxiliary module is connected to the test section of the rod-shaped specimen, and is used to transmit the tensile deformation to the deformation measuring device; the positioning auxiliary module is used to assist the positioning of the rod-shaped specimen in the installation groove of the force positioning module, and can ensure the uniformity of the clamping force on the rod-shaped specimen.

[0008] A further technical solution of the present invention is: the rod-shaped specimen is a stepped shaft structure, with cylindrical bosses symmetrically arranged at both ends, a test section in the middle, and annular bosses respectively arranged at both ends of the test section, and the diameters of the cylindrical boss and the annular boss are both larger than the diameter of the shaft portion therebetween.

[0009] A further technical solution of the present invention is: the force positioning module includes an upper chuck and a lower chuck with the same structure and symmetrical arrangement, which are respectively clamped at the two ends of the rod-shaped specimen; one end of the chuck connected to the loading mechanism of the testing machine is the fixed end, and the other end connected to the rod-shaped specimen is the clamping end; the fixed end is provided with a pin hole, and is connected to the loading mechanism of the testing machine through a pin; the clamping end is provided with a groove along the radial direction of the chuck, and the groove profile is consistent with the axial cross-section of the end of the rod-shaped specimen, and is a clearance fit, and the installation gap is evenly filled by the positioning auxiliary module to achieve uniform clamping.

[0010] A further technical solution of the present invention is that the groove at the clamping end of the chuck includes a rectangular groove for positioning and installing the cylindrical boss at the end of the rod-shaped sample and a limiting groove located at the end surface outlet, and the limiting groove is used to pass through the shaft between the cylindrical boss and the annular boss.

[0011] A further technical solution of the present invention is: the calculation method of the rectangular groove width of the chuck groove is, first, calculating the thermal expansion compensation amount of the positioning auxiliary module according to the linear expansion coefficient of the material used for the positioning auxiliary module and the test target temperature; then, determining the thickness of the positioning auxiliary module according to the thermal expansion compensation amount; finally, increasing the diameter value of the end of the rod-shaped specimen by twice the thickness of the positioning auxiliary module, that is, obtaining the size of the rectangular groove width of the chuck.

[0012] A further technical solution of the present invention is: the test auxiliary module includes a ferrule, the ferrule is a rectangular plate structure, and lugs connected to an extension rod are respectively arranged at both ends of the ferrule, the extension rod is connected between the ferrule and the deformation measuring device, and can transmit the displacement variable generated by the ferrule synchronized with the rod-shaped specimen to the deformation measuring device; a central stepped hole is opened on the end face of the ferrule for passing through the rod-shaped specimen, and the stepped surface of the stepped hole is used to limit the ferrule on the rod-shaped specimen.

[0013] A further technical solution of the present invention is: the two ferrules are respectively mounted on the two annular bosses of the rod-shaped specimen, with their small diameter ends facing the upper chuck and their large diameter ends facing the lower chuck; positioning auxiliary modules are installed on the large diameter ends of the two ferrules, and the positioning of the ferrules on the rod-shaped specimen is completed by cooperating with the annular surface of the annular boss.

[0014] A further technical solution of the present invention is: the positioning auxiliary module is a gasket with a notch, the central hole diameter of the gasket is adapted to the diameter of the test section and the shaft at both ends of the rod-shaped specimen, and can be fitted thereon through the notch; the outer diameter of the gasket is larger than the outer diameter of the circular ring boss of the rod-shaped specimen and the diameter of the small diameter end of the stepped hole of the ferrule.

[0015] A method for preparing a test fixture for ultra-high temperature tensile and tensile creep tests of a bar-shaped specimen, the specific steps of which are as follows:

[0016] Connect the upper chuck to the loading mechanism of the testing machine through a pin;

[0017] Insert gaskets into the two stepped holes of the ferrules on the rod-shaped specimen and fix them above the two circular bosses of the rod-shaped specimen;

[0018] Put the clamping end of the rod-shaped specimen into the groove of the upper clamp, and fix the clamping end of the rod-shaped specimen by inserting a gasket between the rod-shaped specimen and the groove of the upper clamp;

[0019] Place the clamping end of the other side of the rod-shaped specimen into the groove of the lower clamp, and fix the clamping end of the specimen by inserting a gasket between the rod-shaped specimen and the lower clamp;

[0020] The lower chuck is connected to the loading mechanism of the testing machine through a pin.

[0021] The invention discloses an application of an ultra-high temperature tensile and tensile creep test fixture for a rod-shaped sample. The test fixture is suitable for ultra-high temperature tensile and tensile creep tests of alloy rod-shaped samples at 2000°C.

[0022] Beneficial Effects

[0023] The beneficial effects of the present invention are:

[0024] 1. The rod-shaped specimen has a simple structure and can be processed by lathe, which reduces production errors, improves production efficiency and reduces experimental costs.

[0025] 2. The specimen is connected to the testing machine by embedding the specimen into the chuck, which avoids the problem that brittle materials such as ceramics cannot be tested due to the inability to process threads.

[0026] 3. The fixture is fixed with gaskets and transmits the test force to the specimen. It is small in size, easy to disassemble and assemble, and has uniform and reliable clamping force, which reduces the risk of specimen falling off during the test and ensures the smooth progress of the experiment.

[0027] 4. The fixture and the experimental room are protected from direct contact by gaskets, which effectively reduces the adhesion between the fixture and the sample after ultra-high temperature experiments.

[0028] 5. Since the fixture is centered and clamped by gaskets and bosses, the possibility of the test specimen breaking in an abnormal position during the test is avoided, making the data results of the specimen test more accurate and comprehensive, and easier to promote and use.

[0029] 6. The technology of the present invention can not only be used to test rod-shaped specimens, but also can be applied to ultra-high temperature testing of materials such as pipes and wires, and has a good market application prospect.

[0030] The difficulty of the present invention lies mainly in how to effectively test the tensile and creep properties of brittle materials in an ultra-high temperature environment of 2000°C or above, while solving the structural problems and usage limitations of traditional fixtures. Its advantage lies in that through innovative design and material selection, it not only overcomes these technical difficulties, but also expands the scope of test applications and has a good market promotion prospect. The innovation and wide applicability of this design are the core advantages of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of a bar sample according to a specific embodiment of the present invention;

[0032] Figure 2 It is a schematic diagram of a rod clamping sleeve according to a specific embodiment of the present invention;

[0033] Figure 3 It is a schematic diagram of a lower clamping sleeve for a bar according to a specific embodiment of the present invention;

[0034] Figure 4 This is a gasket diagram of the contact portion between the test fixture and the bar sample of a specific embodiment of the present invention;

[0035] Figure 5 It is a schematic diagram of the gasket of the contact part between the upper clamping sleeve of the rod and the lower clamping sleeve of the rod and the rod sample in a specific embodiment of the present invention;

[0036] Figure 6 A schematic diagram of a test tooling for a specific embodiment of the present invention;

[0037] Figure 7 It is a schematic diagram of the parts decomposition of the test tooling according to a specific embodiment of the present invention;

[0038] Figure 8 This is a 2000°C ultra-high temperature tensile curve of a refractory alloy rod sample obtained using a specific embodiment of the present invention.

[0039] Fig. 9 The 2000°C-20MPa ultra-high temperature tensile creep curve of a refractory alloy rod sample obtained by using a specific embodiment of the present invention.

[0040] Explanation of the accompanying reference numerals: 1 - upper chuck of the rod; 2 - rod-shaped specimen; 3 - upper ferrule of the rod; 4 - lower ferrule of the rod; 5, 6 - gaskets; 7 - lower chuck of the rod. DETAILED DESCRIPTION

[0041] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0042] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0043] Based on the problem of obtaining accurate measurement values ​​in high-temperature tensile and tensile creep tests at 2000°C and above in the prior art, the present invention provides an ultra-high temperature tensile and tensile creep test fixture applied to a rod-shaped specimen, comprising a force positioning module, a test auxiliary module and a positioning auxiliary module. The force positioning module is arranged at both ends of the rod-shaped specimen, and is used to transmit the loading force of the loading mechanism of the testing machine to the two ends of the rod-shaped specimen, so that the rod-shaped specimen undergoes axial tensile deformation; the test auxiliary module is connected to the test section of the rod-shaped specimen, and is used to transmit the tensile deformation to the deformation measuring device; the positioning auxiliary module is used to assist the positioning of the rod-shaped specimen in the installation groove of the force positioning module, and can ensure the uniformity of the clamping force on the rod-shaped specimen.

[0044] The above structure is further described below in conjunction with the accompanying drawings:

[0045] Specifically, refer to Figure 1 As shown, the rod-shaped specimen is a stepped shaft structure, with cylindrical bosses symmetrically arranged at both ends, a test section in the middle, and annular bosses respectively arranged at both ends of the test section, and the diameters of the cylindrical boss and the annular boss are both larger than the diameter of the shaft portion therebetween.

[0046] Specifically, refer to Figure 6 , 7 As shown, the force positioning module includes an upper chuck and a lower chuck with the same structure and symmetrical arrangement, which are respectively clamped at the two ends of the rod-shaped specimen; one end of the chuck connected to the loading mechanism of the testing machine is the fixed end, and the other end connected to the rod-shaped specimen is the clamping end; the fixed end is provided with a pin hole, and is connected to the loading mechanism of the testing machine through a pin; the clamping end is provided with a groove along the radial direction of the chuck, and the groove profile is consistent with the axial cross-section of the end of the rod-shaped specimen, and is a clearance fit, and the installation gap is evenly filled by the positioning auxiliary module to achieve uniform clamping.

[0047] Specifically, the groove at the clamping end of the chuck includes a rectangular groove for positioning and installing the cylindrical boss at the end of the rod-shaped sample and a limiting groove located at the end surface outlet, and the limiting groove is used to pass through the shaft between the cylindrical boss and the annular boss.

[0048] Specifically, the calculation method of the rectangular groove width of the chuck groove is as follows: first, the thermal expansion compensation amount of the positioning auxiliary module is calculated according to the linear expansion coefficient of the material used for the positioning auxiliary module and the test target temperature; then, the thickness of the positioning auxiliary module is determined according to the thermal expansion compensation amount; finally, the diameter value of the end of the rod-shaped specimen is increased by twice the thickness of the positioning auxiliary module, so as to obtain the size of the rectangular groove width of the chuck.

[0049] Specifically, refer to Figure 2 and 3As shown, the test auxiliary module includes a ferrule, which is a rectangular plate structure, and has lugs connected to an extension rod at both ends. The extension rod is connected between the ferrule and the deformation measuring device, and can transmit the displacement variable generated by the ferrule in synchronization with the rod-shaped specimen to the deformation measuring device; a central stepped hole is opened on the end face of the ferrule for passing through the rod-shaped specimen, and the stepped surface of the stepped hole is used to limit the ferrule on the rod-shaped specimen.

[0050] Specifically, the two ferrules are respectively mounted on the two annular bosses of the rod-shaped specimen, with their small diameter ends facing the upper chuck and their large diameter ends facing the lower chuck; positioning auxiliary modules are installed on the large diameter ends of the two ferrules, and the positioning of the ferrules on the rod-shaped specimen is completed by the cooperation between the positioning auxiliary modules and the annular surface of the annular boss.

[0051] Specifically, refer to Figure 4 and 5 As shown, the positioning auxiliary module is a gasket with a notch, the central hole diameter of the gasket is adapted to the diameter of the test section and the shaft at both ends of the rod-shaped specimen, and can be fitted thereon through the notch; the outer diameter of the gasket is larger than the outer diameter of the circular ring boss of the rod-shaped specimen and the diameter of the small diameter end of the stepped hole of the ferrule.

[0052] In this embodiment, the specimen adopts a rod-shaped structure, with two ends as clamping and loading sections, and the middle section as a test section. A disc-shaped boss is designed between the test section and the clamping section to place the upper clamping sleeve and the lower clamping sleeve of the rod connecting the extension rod. A gasket is placed on the contact part between the upper clamping sleeve of the rod and the upper clamping sleeve of the rod and the rod specimen. A 120° chamfer transition is adopted between the clamping end and the clamping section, and an arc transition is adopted between the disc-shaped boss and the clamping section and the test end. The coordination between the specimen and the clamping sleeve is shown in FIG. Figure 6 and 7 . The specific embodiments of the present invention are given below:

[0053] The fixture and rod-shaped specimens were used to carry out 2000℃ ultra-high temperature tensile and tensile creep tests on refractory alloy rod-shaped specimens. Figure 1 As shown, the width of the clamping loading section at both ends of the specimen is 6 to 8 mm, the length between the clamping end and the disc-shaped boss is 18 mm, the middle section is the test section, the width is 2.5 mm, the length is 25 mm, the disc-shaped boss and the clamping section and the test end adopt an arc transition, the arc radius is 1 mm, and the total length of the specimen is 77 mm.

[0054] Before the test, install the specimen and the fixture. First, fix the upper ferrule and the lower ferrule of the bar to the upper end of the disc-shaped boss through gaskets, then put the clamping end of the specimen into the groove of the upper chuck, and fix the clamping end of the specimen and the upper chuck through gaskets. Put the clamping end of the other side of the specimen into the groove of the lower chuck, and then fix the clamping end of the other side of the specimen and the lower chuck through gaskets, and finally connect the lower pull rod and the loading mechanism of the testing machine through pins. The diameter of the fixture groove and the diameter of the ferrule through hole are slightly larger than the diameter of the specimen, and the diameter of the pin through hole is slightly larger than the diameter of the pin, which provides space for the thermal expansion of the specimen and the pin at high temperature, and avoids the adhesion of the specimen and the pin to the fixture and ferrule. Apply a certain holding force through the testing machine to ensure that the specimen and the fixture are aligned up and down. After the specimen and the fixture are installed, evacuate or pass an inert atmosphere, and heat up to start the test.

[0055] For detailed calculations, we will use the parameters you provide and the design methods discussed previously to calculate the relevant parameters of the fixture for ultra-high temperature tension and tensile creep tests at 2000℃.

[0056] Basic parameters of the sample

[0057] Width of clamping loading section: w c =6~8mm

[0058] Length L between the clamping end and the disc-shaped boss c =18mm

[0059] Test segment width: w t =2.5mm

[0060] Test section length: L t =25mm

[0061] Arc transition radius: R = 1mm

[0062] Total length of the specimen: L total =77mm

[0063] 1. Calculation of clamping force

[0064] We first calculate the clamping force required to ensure that the specimen does not slip. Since the width is 6 to 8 mm, we take the middle value w c =7mm for calculation.

[0065] Contact area A c :Wc×Lc=7×18=126mm 2

[0066] Assume that the tensile strength of the sample material is t =400MPa (refractory alloys usually have higher tensile strength), then the clamping force F c for:

[0067] F c =σ t ×_A c =400×126=50400N}, (about 50.4kN)

[0068] 2. Thermal expansion compensation calculation

[0069] According to the linear expansion coefficient of the material at high temperature α = 5 × 10 -6 K -1 And the test temperature T = 2000 ° C, calculate the thermal expansion compensation of the gasket δL:

[0070] δL=L c ×α×δT=18×5×10 -6 ×1975=0.17775mm

[0071] Therefore, the thickness of the gasket t p Designed for:

[0072] t p ≥0.18mm

[0073] 3. Calculation of fixture groove width

[0074] Width w of the fixture groove g It should be slightly larger than the width of the clamping section to facilitate the embedding of the specimen and take into account the high temperature expansion. We still take the middle value of the width w c =7mm for calculation:

[0075] w g =w c +2·t p =7+2×0.18=7.36mm

[0076] 4. Stress distribution and local structure optimization

[0077] In order to reduce stress concentration, the chuck at the contact point between the fixture and the specimen should be designed as an arc transition structure. Arc transition radius R g The same 1 mm radius can be used to ensure a reduction in the stress concentration factor.

[0078] 5. Summary and application

[0079] From these calculations we determined the following parameters:

[0080] Clamping force: about 50.4kN

[0081] Thermal expansion compensation: gasket thickness is at least 0.18mm

[0082] Chuck groove width: 7.36mm

[0083] Arc transition radius: 1mm

[0084] These parameters ensure that the specimen can be reliably fixed under high temperature conditions of 2000°C and reduce stress concentration problems caused by thermal expansion. This design will significantly improve the accuracy and repeatability of the test. The specific advantages are analyzed as follows:

[0085] Special design for brittle materials: The present invention avoids the difficulty of traditional thread processing by connecting the sample by embedding the sample into the chuck, so that brittle materials such as ceramics can also be smoothly tested at ultra-high temperatures. This design significantly broadens the scope of application of materials.

[0086] Innovative use of gaskets: The invention uses gaskets between the fixture and the specimen, which not only effectively reduces the risk of adhesion at high temperatures, but also provides uniform clamping force and avoids stress concentration problems. This design ensures the stability of the specimen during the test and the accuracy of the test results.

[0087] Modular and easy-to-disassemble design: The fixture of the present invention has a compact structure and a small size. Through the pin connection and gasket fixation, the fixture can be easily disassembled and reused after high temperature testing. This design avoids the "locking" or "tooth collapse" phenomenon, reduces the experimental cost, and improves the practicality of the fixture.

[0088] Versatility and wide application prospects: The present invention is not only applicable to rod-shaped specimens, but can also be extended to ultra-high temperature testing of materials such as pipes and wires. This versatility makes the present invention have good application prospects in the market and meets the high temperature testing needs of different materials and shapes.

[0089] Improve the accuracy and reliability of test results: Through precise centering design and uniform clamping force, the present invention significantly reduces the possibility of specimen breaking in abnormal positions during the test, thereby improving the accuracy and comprehensiveness of the test data. This advantage enables the present invention to provide more reliable and credible test results.

[0090] This embodiment uses an ultra-high temperature tensile and tensile creep test fixture to perform an ultra-high temperature test, which specifically includes the following steps:

[0091] Step 1: Connect the upper fixture to the loading mechanism of the testing machine through pins.

[0092] Step 2: Place gaskets in the grooves of the upper and lower ferrules of the bar and fix them above the two bosses of the specimen.

[0093] Step 3: Place the specimen gripping end into the upper fixture groove and secure the specimen gripping end by inserting a shim between the specimen and the fixture.

[0094] Step 4: Place the other side of the specimen into the groove of the lower fixture and secure the specimen by inserting a gasket between the specimen and the fixture.

[0095] Step 5: Connect the lower fixture to the loading mechanism of the testing machine through pins.

[0096] The 2000℃ high temperature tensile and tensile creep curves of the refractory alloy rod specimen obtained through the above test process are as follows: Figure 8-9 shown.

[0097] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A fixture for ultra-high temperature tensile and tensile creep tests for bar-shaped specimens, characterized in that: It includes a force positioning module, a test auxiliary module and a positioning auxiliary module. The force positioning module is arranged at both ends of the rod-shaped specimen, and is used to transmit the loading force of the loading mechanism of the testing machine to the two ends of the rod-shaped specimen, so that the rod-shaped specimen undergoes axial tensile deformation; the test auxiliary module is connected to the test section of the rod-shaped specimen, and is used to transmit the tensile deformation to the deformation measuring device; the positioning auxiliary module is used to assist the positioning of the rod-shaped specimen in the installation groove of the force positioning module, and can ensure the uniformity of the clamping force on the rod-shaped specimen.

2. The ultra-high temperature tensile and tensile creep test fixture for bar-shaped specimens according to claim 1, characterized in that: The rod-shaped specimen is a stepped shaft structure, with cylindrical bosses symmetrically arranged at both ends, a test section in the middle, and annular bosses respectively arranged at both ends of the test section. The diameters of the cylindrical boss and the annular boss are both larger than the diameter of the shaft portion therebetween.

3. The ultra-high temperature tensile and tensile creep test fixture for bar-shaped specimens according to claim 2, characterized in that: The force positioning module includes an upper chuck and a lower chuck with the same structure and symmetrical arrangement, which are respectively clamped at the two ends of the rod-shaped specimen; one end of the chuck connected to the loading mechanism of the testing machine is the fixed end, and the other end connected to the rod-shaped specimen is the clamping end; the fixed end is provided with a pin hole, and is connected to the loading mechanism of the testing machine through a pin; the clamping end is provided with a groove along the radial direction of the chuck, the groove profile is consistent with the axial cross-section of the end of the rod-shaped specimen, and is a clearance fit, and the installation gap is evenly filled by the positioning auxiliary module to achieve uniform clamping.

4. The ultra-high temperature tensile and tensile creep test fixture for bar-shaped specimens according to claim 3, characterized in that: The groove at the clamping end of the chuck includes a rectangular groove for positioning and installing the cylindrical boss at the end of the rod-shaped sample and a limiting groove located at the end surface outlet, and the limiting groove is used to pass through the shaft between the cylindrical boss and the annular boss.

5. The ultra-high temperature tensile and tensile creep test fixture for bar-shaped specimens according to claim 4, characterized in that: The calculation method of the rectangular groove width of the chuck groove is as follows: first, the thermal expansion compensation amount of the positioning auxiliary module is calculated according to the linear expansion coefficient of the material used for the positioning auxiliary module and the test target temperature; then, the thickness of the positioning auxiliary module is determined according to the thermal expansion compensation amount; finally, the diameter value of the end of the rod-shaped sample is increased by twice the thickness of the positioning auxiliary module, so as to obtain the size of the rectangular groove width of the chuck.

6. The ultra-high temperature tensile and tensile creep test fixture for bar-shaped specimens according to claim 5, characterized in that: The test auxiliary module includes a ferrule, which is a rectangular plate structure, and has lugs connected to an extension rod at both ends. The extension rod is connected between the ferrule and the deformation measuring device, and can transmit the displacement variable generated by the ferrule in synchronization with the rod-shaped specimen to the deformation measuring device; a central stepped hole is opened on the end face of the ferrule for passing through the rod-shaped specimen, and the stepped surface of the stepped hole is used to limit the ferrule on the rod-shaped specimen.

7. The ultra-high temperature tensile and tensile creep test fixture for bar-shaped specimens according to claim 6, characterized in that: The two ferrules are respectively mounted on the two annular bosses of the rod-shaped specimen, with their small diameter ends facing the upper chuck and their large diameter ends facing the lower chuck; positioning auxiliary modules are installed on the large diameter ends of the two ferrules, and the positioning of the ferrules on the rod-shaped specimen is completed by the cooperation between the positioning auxiliary modules and the annular surface of the annular boss.

8. The ultra-high temperature tensile and tensile creep test fixture for bar-shaped specimens according to claim 7, characterized in that: The positioning auxiliary module is a gasket with a notch. The central hole diameter of the gasket is adapted to the diameter of the test section and the shaft at both ends of the rod-shaped specimen, and can be fitted thereon through the notch; the outer diameter of the gasket is larger than the outer diameter of the circular ring boss of the rod-shaped specimen and the diameter of the small diameter end of the stepped hole of the ferrule.

9. A method for applying the ultra-high temperature tensile and tensile creep test fixture to a bar-shaped specimen as claimed in any one of claims 1 to 8, characterized in that The specific steps are as follows: Connect the upper chuck to the loading mechanism of the testing machine through a pin; Insert gaskets into the two stepped holes of the ferrules on the rod-shaped specimen and fix them above the two circular bosses of the rod-shaped specimen; Put the clamping end of the rod-shaped specimen into the groove of the upper clamp, and fix the clamping end of the rod-shaped specimen by inserting a gasket between the rod-shaped specimen and the groove of the upper clamp; Place the clamping end of the other side of the rod-shaped specimen into the groove of the lower clamp, and fix the clamping end of the specimen by inserting a gasket between the rod-shaped specimen and the lower clamp; The lower chuck is connected to the loading mechanism of the testing machine through a pin.

10. An application of the ultra-high temperature tensile and tensile creep test fixture for bar-shaped specimens according to any one of claims 1 to 8, characterized in that: The test fixture is suitable for 2000°C ultra-high temperature tensile and tensile creep tests of alloy rod-shaped specimens.

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